DWQ-2024-004889

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Final Report: Utah Lake Littoral Sediment
Study: An Assessment of Carbon,
Nitrogen, and Phosphorus Dynamics in the
Utah Lake Littoral Zone

Version 1 July 2022

Prepared by the Littoral Sediment Team

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List of Contributors
PI: Dr. Erin Rivers, Utah State University
Co-PI: Dr. Zachary Aanderud, Western States Water and Soil & Brigham Young University
Co-PI: Dr. Greg Carling, Western States Water and Soil & Brigham Young University

Revision History
July 14, 2022 Initial release to the Utah Department of Environmental Quality-Division of Water
Quality

Acknowledgements
The work was supported by the Utah Department of Environmental Quality-Water Quality. Any
recommendations expressed here are those of the author(s) and do not necessarily reflect the
views of the Utah Department of Environmental Quality.

Acronyms/Abbreviations
USU Utah State University
BYU Brigham Young University
DWQ Division of Water Quality
CUWCD Central Utah Water Conservancy District
ULWQS Utah Lake Water Quality Study
SAP Sampling and Analysis Plan
P Phosphorus
N Nitrogen
PAR Photosynthetically active radiation
SOP Standard operating procedures
DIN Dissolved inorganic nitrogen
SRP Soluble reactive phosphorus or orthophosphate
TN Total nitrogen (mg/L)
TP Total phosphorus (mg/L)
DEA Denitrification enzyme activity

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Contents
1. Introduction ............................................................................................................................. 5
2. Background .............................................................................................................................. 6
2.1 Problem Statement .......................................................................................................... 7
2.2 Study Objectives ............................................................................................................. 8
3. Task 1 – Frequency and Duration of Sediment Drying-Rewetting on Nutrient Release and
Oxygen Demand ............................................................................................................................. 9
3.1 Materials and Methods .................................................................................................... 9
3.1.1 Study Design ............................................................................................................... 9
3.1.2 Sediment Continuous Control and Drying and Re-wetting Procedure ..................... 10
3.1.3 Water Chemistry and Nutrient Analyses .................................................................. 11
3.1.4 Sediment and Sediment Chemistry Analyses ........................................................... 12
3.1.5 Sample Transport and Storage .................................................................................. 13
3.1.6 Nutrient Release Rates and Statistics ........................................................................ 13
3.2 Results ........................................................................................................................... 13
3.2.1 Initial Water Nutrient Concentrations ....................................................................... 13
3.2.2 Water Chemistry During Control and Drying and Re-wetting ................................. 13
3.2.3 Nutrient Release Rates from Sediments ................................................................... 14
3.2.4 P Release During Control and Drying and Re-wetting ............................................. 14
3.2.5 N Release During Control and Drying and Re-wetting ............................................ 14
3.2.6 DOC Release During Control and Drying and Re-wetting ...................................... 15
3.2.7 Potential P adsorption from Sediments ..................................................................... 15
4. Task 2 – Rate and Magnitude of C, N, and P Fluxes from Drying, Dry, and Rewetting
Sediments ...................................................................................................................................... 16
4.1 Study Design ................................................................................................................. 16
4.1.1 Benthic Nitrogen Cycling ......................................................................................... 16
4.1.2 Microbial P Release .................................................................................................. 17
4.1.3 Sediment Chemistry .................................................................................................. 18
4.1.4 Statistical Analyses ................................................................................................... 18
4.1.5 Sediment Core Sampling Locations and Sampling Schedule ................................... 18
4.1.6 Sample Transport and Storage .................................................................................. 19
4.2 Results ........................................................................................................................... 19
4.2.1 Sediment C, N, and P ................................................................................................ 19

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4.2.2 Benthic Nitrogen Cycling ......................................................................................... 20
4.2.3 Benthic Carbon Cycling ............................................................................................ 22
4.2.4 Key Findings ............................................................................................................. 22
5. References ............................................................................................................................. 23
Appendix 1A. Task 1 Tables ........................................................................................................ 25
Appendix 1B. Task 1 Figures ....................................................................................................... 32
Appendix 2A. Task 2 Mass Rate Tables ....................................................................................... 42
Appendix 2B: Task 2 Areal Rates Tables ..................................................................................... 45
Appendix 2C: Task 2 Figures ....................................................................................................... 49

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1. Introduction
With the large variations in lake levels and shallow depth, large expanses of Utah Lake’s littoral
sediments are subject to wetting and drying cycles of varying durations and frequencies. As
littoral sediments go through periods of desiccation and inundation, it changes sediment
properties and alters the duration of oxic and anoxic conditions, which in turn affects sediment
oxygen demand, C, N and P release as well as microbial activity and composition (Weise et al.,
2016). A number of studies have found that sediment drying and re-wetting promotes the release
of potentially significant amounts of bio-available N and P on re-wetting (the so-called “Birch
effect”; Baldwin and Mitchell, 2000; Birch, 1960; McComb and Qiu, 1998; Scholz et al., 2002).
This occurs as a result of numerous interacting processes, including enhanced aerobic microbial
mineralization of organic matter (OM) and the reduction of nitrate, leading to an accumulation of
ammonium N in the sediment; a decreased capacity of the sediments to adsorb nutrients such as
P (Baldwin, 1996); and the release of cell-bound nitrogen (ammonium) and filterable reactive
phosphorus from sediment bacteria as they are killed during drying (Qiu and McComb, 1995).
Although both N and P may be released by these processes, they may respond differently, since
the re-wetted sediments may have a reduced capacity to release P under anoxic conditions
(which suggests that more N than P could be released into the water column on lake filling)
(Mitchell and Baldwin, 1998). The degree and duration of drying before rewetting has been
shown to affect nutrient release. Schönbrunner et al. (2012) performed an internal phosphorus
loading study in which floodplain sediments were exposed to different dry/wet treatments. They
found that total phosphorus (TP) release from sediments into the water column increased with
increasing duration of dry periods prior to rewetting and that repeated drying and wetting
resulted in elevated phosphorus release. This effect was more pronounced when drying periods
led to an 80% reduction in water content.
Sediment characteristics also affect nutrient releases. Shaughnessy et al. (2019) found that spatial
distributions of lakebed nutrients in an agricultural reservoir in Illinois were predominantly
controlled by sediment depositional patterns. The largest proportion of clay‐sized particles and
highest concentrations of OM were deposited near the dam wall and the highest proportion of
(heavier) sand‐sized particles were deposited near the river mouth. They found a significant and
positive correlation between TP, TN, and TC with OM. Shaughnessy et al. (2019) also found that
seasonal factors were important to consider. Nitrogen species varied seasonally at the sediment‐
water interface and were significantly higher during warmer weather/the growing season. The
warmer conditions may enhance the release of nutrients from the sediments to the water column
due to higher decomposition rates, higher pH due to photosynthetic activities, and low DO near
the sediment‐water interface that can change redox conditions so that reduced iron (Fe) might
liberate P.
Little is currently known about the effects of water level fluctuations/wet and dry phases on C,
N, and P loading from littoral sediments in Utah Lake. As the Science Panel works to respond to
charge questions and nutrient criteria are being developed, it is important that this knowledge
gap be addressed. More specifically, the Science Panel needs to better understand whether
littoral sediments act as nutrient sinks (e.g., through denitrification, respiration and
sedimentation) or sources (e.g., decomposition/mineralization and release upon rewetting), to
what magnitude, and whether they reduce or enhance nutrient loads and impact the overall
nutrient budget of the lake. The Science Panel also needs quantitative relationships between the

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duration and frequency on wetting and drying on nutrient loading in order to evaluate
relationships between external and internal loads to Utah Lake. A comprehensive understanding
of the influence of fluctuating hydrological conditions on internal nutrient loading within Utah
Lake is critical in developing restoration and management plans, and this study will inform these
solutions.
2. Background
The Utah Department of Environmental Quality, Division of Water Quality (DWQ) contracted
with Utah State University to conduct a littoral sediment study to help understand effects of
drying/wetting on Carbon (C), Nitrogen (N) and Phosphorus (P) flux from littoral sediments in
Utah Lake. This study was prioritized by the Utah Lake Water Quality Study (ULWQS) Science
Panel..
The Utah Division of Water Quality (DWQ) is in Phase 2 of the Utah Lake Water Quality Study
(ULWQS) to evaluate the effect of excess nutrients on the lake’s recreational, aquatic life, and
agricultural designated uses and to develop site-specific nitrogen and phosphorus water quality
criteria to protect these uses. The ULWQS is guided by the Stakeholder Process developed
during Phase 1, which established a 16-member interest-based Steering Committee and a 10-
member disciplinary-based Science Panel. The Steering Committee charged the Science Panel
with developing and answering key questions to characterize historic, current, and future nutrient
conditions in Utah Lake. Responses to the key questions will be used by the Steering Committee
to establish management goals for the lake and by the Science Panel to guide development of
nutrient criteria to support those goals.
Water level data have been collected in Utah Lake since the late 1800’s (Figure 1; CUWCD and
Thurin 2007). A probability distribution of fluctuations in lake area using data from 2004-2018
Figure 1. Annual and five-year average within-year variation in Utah Lake level from 1884 to 2006
showing generally increasing variation (doubling) over the historical period from 1884 to the 1930s to
1940 (from CUWCD and Thurin 2007; Figure 11).

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estimated that the 5 to 95th percentile in lake area varied by 30 mi2 from an average of 130 mi2
(J. Martin, pers. comm).
Based on other estimates, approximately 10-15%
of the area is littoral. The extent of the areas of
wetting and drying can also be illustrated by the
Utah Lake bathymetry (Figure 2) comparing areas
that were always wet to those that were
periodically dry. In either case, the amount of lake
area potentially affected by wetting and drying is
substantial. The duration of dry and wet phases
can also be inferred from lake level data and can
range from months to years.
Other existing, complementary studies include a
project recently completed by Goel and Carling on
sediment–water-nutrient interactions in Utah
Lake1 (Goel et al., 2020). Results include
calculations of sediment fluxes over a range of
water column P concentrations and an exploration
of the potential effects of changing pH, alkalinity,
and redox. Equilibrium P concentration, the water
column concentration at which the sediment
switches from a sink to a source of P, were
estimated from this study as well. The study also
estimated sediment oxygen demand and provided
information on the role of sediment resuspension on nutrient releases or removal, primarily via
calcite scavenging. The experiments were performed on wet cores collected from two sites —one
site in Provo Bay and one site in the main body of the lake at an established DWQ monitoring
site. These data could be contrasted with the results from this work, but also provide information
on wet core nutrient content and flux rates. Aside from that, little is known about nutrient release
from littoral sediments in Utah Lake, thus the need for this work.
2.1 Problem Statement
There is a high degree of annual variability in water levels in Utah Lake, resulting from a
combination of natural and anthropogenic factors. Variability in precipitation patterns,
evaporation, upstream water use, and managed outflow contribute to the hydrologic fluctuations
that result in 3-4 feet variability in lake levels throughout the year. Due to the shallow nature of
the lake, fluctuations in water levels cause major changes in water-edge location and lake
characteristics. Water level fluctuations that cause sediments to transition between dry and wet
affects sediment redox potential and Currently, little is known about the effects of dry and wet
phases resulting from water level fluctuations in Utah Lake.

Figure 2. Areas of Utah Lake that were continuously wet
for the period of 2010 – 2020 (light blue) versus those that
were periodically dry (dark blue bands). Stars indicate
sampling locations.

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2.2 Study Objectives
The objective of this research is to address the following question identified by the ULWQS as
critical to understanding the current state of Utah Lake with respect to nutrients and littoral
sediment: What is the sediment oxygen demand of, and nutrient releases from, sediments in Utah
Lake under current conditions? (Science Panel charge 2.4.ii)
Additionally, this research will help inform the following charge question: If there are linkages
between changes in nutrient regime and Harmful Algal Blooms (HABs), what role if any does
lake elevation change play? (Science Panel charge 2.3.iii)

The study is designed to address the following tasks:
1. Task 1 – Frequency and Duration of Sediment Drying-Rewetting on Nutrient Release and
Oxygen Demand
Quantify the relationships (for Utah Lake) between the frequency and duration of dry
periods on the subsequent nutrient releases and oxygen demand following re-wetting
through field and laboratory studies.
2. Task 2 – Rate and Magnitude of C, N, and P Fluxes from Drying-Rewetting Sediments
Quantify the rate and magnitude of nutrient (C, N, and P) fluxes following drying and re-
wetting over a range of sediment characteristics and wetting/drying phases from littoral
sediments.
3. Task 3 – Spatial and Temporal Model on Impact of Drying-Rewetting Sediments
Determine the spatial and temporal extent (duration and frequency) of wetting and drying
patterns in littoral areas through Geographic Information System (GIS) analysis and
evaluation of daily lake elevation data. Develop quantitative relationships for estimating
the oxygen demand and nutrient fluxes of re-wetted sediments as a function of the
frequency and duration of periods of wetting and drying. These objectives will be
completed by DWQ in consultation with the Littoral Sediment Team.

Task 1 will allow for determination of the mass fluxes of C, N, and P associated with wetting and
drying in Utah Lake’s littoral zone, while Task 2 will provide valuable mechanistic insights into
how microbial activity at the sediment-water interface may influence the overall mass fluxes
being measured, and the potential reactivity of N being loaded into the water column upon
inundation. Such mechanistic insights are valuable both for upscaling our mass flux
measurements to the full lake area and may additionally provide management implications for
ways to reduce C, N, and P fluxes from the sediments. USU Research Team will work directly
with the Division of Water Quality to upscale our measurements to the full lake area in Task 3.

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3. Task 1 – Frequency and Duration of Sediment Drying-Rewetting on
Nutrient Release and Oxygen Demand
3.1 Materials and Methods
3.1.1 Study Design
To determine N, and P fluxes from drying-rewetting sediments, we performed experiments using
intact sediment cores collected along sediment transects in the Utah Lake littoral zone. To allow
the sediments to dry in a timely fashion and to capture the N and P release rates with the most
interactive sediment-water interface, we restricted cores to contain approximately 10 cm of
sediment. At four lake sites, detailed below, we extracted cores from three sediment locations
experiencing different lake water fluctuations and frequencies of drying and re-inundation. The
sediment locations included: lake location–in the lake that does not experience drying and re-
inundation, lake margin location–the water margin that may experience periodic drying and re-
inundation that is currently under water at the edge of the lake surface, and upland lake sediment
location–sediment that is now exposed but as the lake level rises may be re-inundated with water
in the future. At each of the four lake sites and the three drying and re-inundation locations, we
extracted two sets of cores that were experimentally manipulated. The first set of cores were
continually wetted or flooded for the duration of the experiment (control cores) to simulate an
absence of drying and re-inundation. The other set of cores experienced a dried and re-inundated
period (drying and re-wetting cores). The core tubes are composed of clear acrylic plastic with
dimensions of 50 cm length  5 cm diameter.
For the experiment, we had four lake sites  three sediment locations  two experiment
manipulations (control, drying and re-inundation cores)  three replicates  repeated
measurements through time (control n = 4, drying and re-wetting n = 6) for a total of 72 cores
and 360 total samples for nutrient analyses. We also incorporated a final time measurement to
assess the potential P sequestration by sediments for another 72 samples for nutrient analyses.
Last, we analyzed the nutrient concentrations in sediments and sediment chemistry on 12 cores
from the four sites and three sediment locations.
The four lake sites covered a range of nutrient concentrations and sediment types across Utah
Lake to provide a weighted average of sediment nutrient conditions across the littoral zone.
Based on a map of sediment P concentrations from a published study (Randall et al., 2019) and a
map of the littoral zone in the lake (Figure 2), we have selected the following sites to collect
sediment cores: 1. Provo Bay (high P concentrations, 2. East Lake (moderate P concentrations),
3. West Lake near Goshen Bay (moderate P concentrations); and 4. Sandy Beach (low P
concentrations).

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3.1.2 Sediment Continuous Control and Drying and Re-wetting Procedure
The drying and re-inundation experiment consisted of a control and two drying and rewetting
periods. The control and drying and re-wetting manipulation were performed as follows.
3.1.2.1 Continuous Control
1) We removed all the residual water from the cores and immediately add 500 mL of lake
water collected from each of the lake sites. Water was removed and added carefully to
prevent disturbing the sediment surface with a peristaltic pump. Water for the
experiments was collected at the same lake location as the sediment cores at each lake
site. Thus, the water in each core was site-specific and contained the bacteria and lake
chemistry local to the site. The volume of water added to each core made a water column
height of ~30 cm above the sediment. All water was collected from the top 20 cm of the
water column pooled into one 200 L plastic drum. Before adding the water to the cores
all water was passed through a Wisconsin net (153 m mesh size) at the time of sampling
to remove zooplankton potentially disturbing the sediments.
2) We bubbled air/oxygen into the water column of all 72 cores to maintain the oxygen
supersaturated conditions common in Utah Lake. Filtered air was bubbled into cores with
aquarium bubblers.
3) All cores were capped to prevent evaporation via a small hole in the cap to allow gas
exchange.
4) We incubated all cores in the dark to prevent the growth of phototrophs in the water
column. The dark incubation discouraged cyanobacteria and total algae growth that may
foul the tubes and act as a significant sink for N and P being released. The manipulation
still allowed bacteria in the water column to utilize the N and P being released from the
sediments.
5) We analyzed water for changes in nutrient and water chemistry 1, 7, and 14 days
following the initial water addition. For each sampling time, we carefully removed 200
mL of water with an automatic serological pipette and replaced the sampled water with
200 mL of water, by location, used to initiate the experiment. We analyzed the nutrient
concentrations in the lake water by site to calculate initial release rates by accounting for
the N and P at time zero.
6) After the final time point, we pulsed the water in the cores with orthophosphate and
sampled nutrient and water chemistry after a 7-day incubation. The experiment was to
quantify P binding by sediments. We added orthophosphate at a concentration of 10 mg-P
L-1 as K2HPO4 to saturate the water column with available P.

3.1.2.2 Drying and Re-inundated
1. We followed the procedure outlined in the control procedure but with several differences
to create the drying and re-wetting experiment. We allowed drying and re-inundated
cores to dry down for three weeks at room temperature until the sediments reached a
constant mass. We expected the sediments to become oxic over time and bacteria to
become inactive. The drying cores were uncapped and air/oxygen was allowed to

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continually be pumped in the column. With the cores slightly uncapped, we most likely
prevent foreign bacteria and fungi from entering the cores.
2. We analyzed water for changes in nutrient and water chemistry following two drying and
rewetting periods. We sampled water chemistry during the first rewetting period 1, 7, and
14 days following the initial rewetting addition. After 14 days, we dried the sediments for
another 21 days. After 21 days, we sampled water chemistry during the second rewetting
period 1 and 7 days following the second rewetting addition.
3. When the cores are wet, we will analyze water chemistry on control and re-inundated
cores periodically over a three-week rewetting period, specifically at days 1, 5, and 21.
4. Just like the continuous cores, we performed the P binding experiment to quantify P
uptake in the sediments following the same procedure.
3.1.3 Water Chemistry and Nutrient Analyses
3.1.3.1 Water Chemistry Analyses
We measured water in-situ physicochemical characteristics in all cores each time before the
water was sampled for nutrients. Specifically, we used the Mettler Toledo Seven Excellence
S470 Benchtop meter (Mettler Toledo, Columbus, OH) Yellow Springs Instrumentation, USA)
to measure pH (accuracy = ± 0.002), electrical conductivity (range 0.001 µS/cm-200 mS/cm and
accuracy = ±0.5% of the reading), and oxygen reduction potential (accuracy = ±0.1 mV) of
water.
3.1.3.2 Water N and P Analyses During Control and Drying and Re-wetting
Nutrient analyses included five forms of P (i.e., TP, PP, TDP, SRP, and DOP), four forms of N
(TN, NO3—N, NH4+–N, and DON), and DOC analyzed using standard methods at the
Environmental Analytical Laboratory (EAL) at BYU or the USU Aquatic Biochemistry
Laboratory (USU ABL). We analyzed the initial lake water used in the experiment by location as
well as multiple times during the two treatments. Specifically, we analyzed four forms of P and
three forms of N to evaluate nutrient release from sediments. The five forms of P vary in
reactivity and potential bacterial use, with the forms including TP, a conglomerate measurement
of P in both organic and inorganic forms; TDP, a conglomerate measurement of dissolved
organic and inorganic P; PP, P bound to colloids or assimilated within other organisms and
presumed to be relatively unavailable to bacteria; and SRP, an inorganic form of P, mostly
orthophosphate, that is the most bioavailable to bacteria. Briefly, we analyzed: TP concentrations
(unfiltered sample) with the persulfate oxidation digestion and ascorbic acid method at the USU
ABL; SRP with the ascorbic acid method (4500-P.F.) (Koenig et al., 2014); and TDP (filtered
sample though a 0.40 m filter) on a Thermo Scientific ICP-OES (iCAP 7400, Thermo Electron,
Madison, WI, USA). We calculated PP using the formula TP – TDP. The limit of detection for
all P forms is < 0.005 mg/L. We evaluated TN with the persulfate oxidation digestion and
cadmium reduction method and NH4+–N (EPA 350.1) and NO3-–N (EPA 353.2) on a FIAlyzer-
2000 system using a flow injection analysis on a rapid flow analyzer (FIAlab Instruments, Inc.,
Bellevue, WA). The detection limits for all three N forms are as follows: NH4+–N = 0.03 mg/L /
NO3-–N = 0.02 mg/L, and TN = 0.02 mg/L.

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We also measured DOC and TDON on a TOC-L series total C analyzer following standard
methods on a Shimadzu TOC analyzer (TOC/TN-L, Shimadzu Scientific, Kyoto, Kyoto
Prefecture, Japan). Total dissolved nitrogen (TDN) was evaluated using the catalytic thermal
decomposition/chemiluminescence method, were determined using the Shimadzu TOC analyzer.
The concentration of dissolved organic N (DON) by difference (TDN – (NH4+–N + NO3-–N).
3.1.4 Sediment and Sediment Chemistry Analyses
We characterized differences in sediment nutrient, chemical, and physical properties across our
lake sites to determine the potential for chemical form and potential, sequential release of P from
sediments. To evaluate the sediments, one extra core was collected from each of the lake sites 
three sediment locations (12 sediment cores) for a suite of analyses. All analyses were performed
on homogenized samples of the 10 cm of sediment from each core. We measured sediment bulk
density, water content after oven drying, and organic matter content by loss on ignition. We also
measured TOC, TN (combustion), TP (ICP-OES), and metals (ICP-OES) using similar protocols
as described above for water samples.
3.1.4.1 P Speciation in Sediments
We estimated P speciation by sequential extractions following a protocol optimized for use in
calcite-rich lake sediments (Hupfer et al., 2009). The extraction steps included: 1) 1 M NH4Cl
(deoxygenated –N2 purged) shaken for 0.5h to extract P in pore water and loosely adsorbed to
surfaces; 2) 0.11 M BD (bicarbonate/dithionite-buffered to a pH 7 using NaHCO3) shaken for 1 h
to remove redox-sensitive P mainly bound to oxidized Fe and Mn compounds; 3) 1M NaOH
shaken for 16 h to remove P exchangeable against OH- ions and P in organic matter; 4) 0.5 HCl
shaken for 16 h to remove P in calcium phosphate minerals and acid-soluble organic P; and 5) 1
M boiling HCl for 0.25 h after a 550°C ignition for 2 h to evaluate the refractory organic P and
nonextractable mineral P. The sediment was rinsed with 1 M NH4Cl between each extraction
steps. After each extraction step, the supernatant (including the 1 M NH4Cl rinse) was filtered
through a 0.45-μm nylon filter and analyzed for TP by ICP-OES.
3.1.4.2 P Sediment Minerology
Sediment mineralogy was analyzed using a Rigaku MiniFlex Benchtop X-Ray Diffractometer
(Rigaku, Tokyo, Japan). XRD patterns were evaluated using Rietveld methods in the Rigaku
PDXL2 software using crystallographic information files obtained from the American
Mineralogist Crystal Structure Database. Minerals with <3% abundance were excluded, and
mineral abundances were normalized to 100% after adding organic matter from LOI
measurements.

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3.1.5 Sample Transport and Storage
All cores were transported to the lab on ice prior to starting the drying-rewetting regimes. The
drying and re-inundation events were initiated within 6 hours of core extraction and
manipulations were conducted at room temperature 20C in the dark.
3.1.6 Nutrient Release Rates and Statistics
We calculated the release rates or fluxes between sediment and the water column of all N and P
chemical forms with the following equation:

nutrient flux (g m-2 day-1) = dCe/dt  V/A  1000 mg g-1  day-1 (equation 1)

where, dCe = change in nutrient concentrations in the water column (mg L-1 = g m-3)
dCe/dt = change in nutrient concentrations over time (g m-3 day-1)
V = volume of overlying water in the core (m3)
A = sediment surface area in the core (m2).

3.2 Results
3.2.1 Initial Water Nutrient Concentrations
Of the ten nutrient characteristics, TP, TDP, SRP, TN, and DOC varied in the initial water from
the four lake sites (i.e., East Lake, Provo Bay, West Lake near Goshen Bay, and Sandy Beach).
East relative to Sandy and West water contained higher levels of TP (one-way ANOVA F = 50,
P < 0.001, df = 3), TDP (one-way ANOVA F = 9.3, P < 0.001, df = 3), and SRP (one-way
ANOVA F = 4.2, P = 0.01, df = 3; Figures 1.1A, 1.1B, and 1.1C). East and Provo water
contained similar levels of TDP and SRP. TN was also higher in East and Provo than Sandy and
West water (one-way ANOVA F = 45, P < 0.001, df = 3; Figures 1.1D). Provo waters contained
the highest levels of DOC (one-way ANOVA F = 5.2, P = 0.008, df = 3; Figures 1.1E). The
remaining nutrient concentrations were similar among the four lake sites with mean
concentrations (mg / L) and  standard errors as follows: DOP = 0.01 0; NO3-–N = 0.69 0.11;
NH4+–N = 0.19 0.05; TDN = 0.64 0.05; TDON 0.06 0.02. Again, the initial water was used
to start all treatments and to replace the water after sampling.
3.2.2 Water Chemistry During Control and Drying and Re-wetting
During the experiment, all waters were well oxygenated (RM-ANOVA F = 1.1, P = 0.36, df = 7)
with an overall mean DO of 9.5 mg / L 0.06 (Figure 1.2A) most likely due to the continual
bubbling of air into the water columns. Water in the West treatments relative to all other waters
possessed a lower pH (8.4 0.01; RM-ANOVA F = 68, P < 0.001, df = 7) and higher electrical
conductivity (4083 59 S / cm; RM-ANOVA F = 187, P < 0.001, df = 7; Figure 1.2C and
1.2D). Oxidation-reduction potential, measured in mV, only slightly varied among the treatments

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(RM-ANOVA F = 4.7, P < 0.001, df = 7) with the lowest (control 213 6.77) and highest mean
(DR 245 4.38) present in West waters.
3.2.3 Nutrient Release Rates from Sediments

Release rates are presented for nutrient form as mg nutrient / L / day in the water column in
Figures 1.3-1.7 and as grams nutrient / m2 sediment / day in Tables 1.1, 1.3, and 1.4. In the
control treatment under the continuous water conditions, most nutrient concentrations were
slightly elevated after the first day, but the increase was most likely an artefact of transporting
the sediments back to the lab and adding the initial waster. Therefore, the first time point was
removed when calculating release rates on a m2 sediment basis.
3.2.4 P Release During Control and Drying and Re-wetting
Exposing sediments, regardless of location, to drying and rewetting increased the release of TP,
and TP was ultimately converted to DOP. TP release rates (g P / m2 sediment / day) ranged from
-0.001 0.001 (West, lake) to 0.005 0.003 (East, margin) in the control; 0.001 0.000 (Sandy,
margin) to 0.117 0.210 (Sandy, upland) following the first drying-rewetting; and 0.008 0.005
(Sandy, margin) to 0.068 0.022 (East, margin) following the second drying-rewetting (Table 1).
In general, TP release rates were positive following both drying and rewetting cycles, while
continuous water conditions lead to almost negligible release levels. The release rates of TP,
measured in the water column, was consistently higher following drying-rewetting than the
control in East (treatment RM-ANOVA F = 7.6, P = 0.008, df = 1; Figure 1.3A). Additionally in
Sandy and West waters, TP release rates were elevated after the second DR relative to the first
DR and the control (treatment  time RM-ANOVA Sandy: F = 11.6, P < 0.001, df = 1 [Figure
1.3C]; West: F = 4.1, P = 0.05, df = 1 [Figures 1.3D]. The P chemical form that accounted for the
increases in TP was DOP instead of SRP. The rate of DOP release was elevated, especially
during the first day of the second drying and rewetting event in all waters except West waters
(treatment RM-ANOVA Provo: F = 4.2, P = 0.05, df = 1 [Figure 1.6B]; East: F = 6.6, P = 0.01,
df = 1 [Figure 1.7B]; and Sandy: F = 6.8, P = 0.01, df = 1 [Figure 1.8B]). Conversely, SRP
release rates were highly variable, but rates were negative in Sandy waters (treatment  time
RM-ANOVA Sandy: F = 8.9, P = 0.004, df = 1, Figure 1.8A) slightly elevated in Provo Bay
margin waters (treatment  time RM-ANOVA F = 40, P < 0.001, df = 1, Figure 1.7A) and
elevated in East waters (treatment  time RM-ANOVA F = 41, P < 0.001, df = 1, Figure 1.6A).
3.2.5 N Release During Control and Drying and Re-wetting
Sediment drying and rewetting elevated the release of TN, predominantly as NO3- –N in all
sediment locations. TN release rates (g N / m2 sediment / day) ranged from -0.009 0.006 (West,
lake) to 0.009 0.008 (West, margin) in the control; -0.019 0.016 (Sandy, upland) to 0.375
0.275 (Provo Bay, upland) following the first drying-rewetting; and 0.047 0.033 (Sandy,
margin) to 0.373 0.217 (Provo Bay, upland; Table 2) following the second drying-rewetting
event. All TN release rates were positive after the second rewetting cycle, but there was no
consistent trend of the first or second drying-rewetting cycle releasing more TN. The release

15

rates of TN were often elevated following drying-rewetting events relative to the control in
Provo (treatment RM-ANOVA F = 7.2, P = 0.009, df = 1 [Figure 1.3B]) and West waters
(treatment RM-ANOVA F = 4.1, P = 0.05, df = 1 [Figure 1.3C]). The second DR instead of the
first DR generated higher TN release rates in Sandy waters (treatment  time RM-ANOVA F =
4.7, P = 0.03, df = 1 [Figure 1.3D]). In East (treatment  time RM-ANOVA F = 9.55, P = 0.003,
df = 1; Figure 1.6C) and Provo Bay (treatment  time RM-ANOVA F = 5.22, P = 0.023, df = 1;
Figure 1.7D) waters, drying-rewetting lead to pulses of NO3- –N in the first day.
3.2.6 DOC Release During Control and Drying and Re-wetting
DOC release rates from sediments were an order of magnitude higher than the control with the
second DR elevating DOC rates to the highest level. DOC release rates (g C / m2 sediment / day)
ranged from 0.001 0.032 (West, lake) to 0.058 0.016 (Provo Bay, margin) in the control;
0.116 0.050 (West, lake) to 0.205 0.102 (East, margin) following DR1; and 0.196 0.086
(West, upland) to 0.914 0.359 (East, margin; Table 3). In all locations, the treatments elevated
the release of DOC into the water column with second DR generating the largest pulse of C
during the first day (treatment RM-ANOVA East: F = 4.6, P = 0.04, df = 1 [Figure 1.5A]; Provo
Bay: F = 3.3, P = 0.07, df = 1 [Figure 1.5B]; Sandy: F = 5.5, P = 0.02, df = 1 [Figure 1.5C];
West: F = 6.2, P = 0.02, df = 1 [Figure 1.5D]).
3.2.7 Potential P adsorption from Sediments
The four lake sites and sediment locations demonstrated varying potential to adsorb SRP from
the water column. For example, regardless of treatment, in the East the margin compared to the
other two locations adsorbed the most SRP (sediment two-way ANOVA F = 7.9, P = 0.007 df =
2, Figure 1.8A), while in Sandy SRP adsorption was most pronounced in the lake sediments
under continuous water (treatment  sediment two-way ANOVA F = 4.2, P = 0.04 df = 2, Figure
1.8C). Provo Bay possessed the highest overall adsorption rates for each sediment location
reaching upwards of 65% SRP adsorption (Table 4) with the lake sediments under DR capable of
adsorbing less SRP than the lake control, upland control, and upland DR (treatment  sediment
two-way ANOVA F = 9.1, P = 0.04 df = 2, Figure 1.8B).

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4. Task 2 – Rate and Magnitude of C, N, and P Fluxes from Drying,
Dry, and Rewetting Sediments
4.1 Study Design
To determine mechanisms of C, N, and P release from sediments with various hydrologic
histories under dry and wet conditions and undergoing wet-to-dry and dry-to-wet transitions, we
will examine the rate and magnitude of several biogeochemical processes that regulate the
production and consumption of C, N, and P under various hydrologic conditions. We will
evaluate sediment metabolic function under experimental drying and inundation scenarios and
measure in situ fluxes of C and N gases.
For this experimental task, Rivers and students completed four field sampling campaigns, during
which lake sediment C and N fluxes were assessed during dry summer conditions and
transitional fall conditions. This part of the project did not experimentally manipulate moisture
content but assessed in situ conditions during a dry to wet period to understand the mechanistic
partitioning of production and consumption processes under variable hydrologic conditions. In
this phase, C and N fluxes were measured along a dry to wet gradient of in situ Utah Lake
sediments.
Sediment cores were collected along the same dry to wet gradient of in situ Utah lake sediments
as in Task 1 (inundated lakebed, intermittent littoral, and perennially dry sediment locations)
within the 4 transects around the lake. Four sampling events occurred at Utah Lake from August
to December 2021. Four cores were extracted at each sampling location and were composited
and homogenized for subsampling for N and P analyses, sediment composition, organic matter
content, porosity, bulk density, and C/N/P content. If water was present, three water samples
were collected and filtered on site. Samples were put on ice and transported back to the
laboratory for analysis. Sediment nitrogen cycling (denitrification, net nitrification, net
mineralization, N release from microbial biomass) were measured in sediments collected from
each lake sampling location.
4.1.1 Benthic Nitrogen Cycling
We evaluated how rewetting events that cause sediments to go from dry to flooded conditions
affects dissolved N pulses that may lead to significant release of reactive N from the sediment
microbial biomass. As N fluxes may play an important role in Utah Lake productivity, and N
cycling dynamics are more complex than those of P, we plan to further assess detailed N
dynamics with inundation. The following analyses measured the potential for N removal via
denitrification, and microbial contributions to reactive N.
Homogenized sediment samples at each lake location were subsampled for analysis of ambient
denitrification rates, denitrification enzyme activity, net mineralization rates, net nitrification
rates, and microbial biomass N. Ambient denitrification rates and denitrification enzyme activity
(DEA) were analyzed to estimate in situ sediment denitrification rates and determine potential
sediment denitrification rates, respectively. The chloramphenicol-amended acetylene-block

17

method (Smith and Tiedje, 1979). Triplicate soil slurries of 10 g sediment and 10 mL lake water
were added to 125 mL glass flasks capped with septa. The DEA set was amended with NO3 (as
KNO3) and organic carbon (as dextrose), and the ambient denitrification set did not receive any
amendments. We added chloramphenicol, an antibiotic that inhibits the production of new
enzymes, allowing for denitrification rates measured in bottle assays to be more representative of
denitrification activity at the time of sampling (Smith and Tiedje, 1979). The flasks were purged
with helium to remove oxygen and force anaerobiosis. We injected 5 mL of acetylene gas into
the sealed, anoxic microcosms through septa caps using a syringe. Acetylene inhibits the
conversion of nitrous oxide (N2O) to dinitrogen (N2) by blocking the activity of nitrous oxide
reductase, allowing the measurement of N2O accumulation to estimate denitrification rates.
Slurries were incubated at room temperature (22oC) for 3 hours, and three 5-mL gas samples
were extracted from the bottle headspaces at 45-minute intervals during the incubation to
measure N2O production over time. Flasks were continually mixed on a shaker table set at 125
rpm between measurements to equilibrate N2O between the gas and aqueous phases. Gas
samples were analyzed immediately by gas chromatography by manually injecting each sample
directly into a Shimadzu GC-2014 equipped with a 2 m Porapak Q column and a 63Ni electron
capture detector. Concentrations are corrected for N2O solubility in the aqueous phase using the
temperature-dependent Bunsen coefficient based on ambient laboratory temperature (Knowles,
1982). The linear rate of N2O production was used to determine the rate of denitrification within
each flask. Only time periods representing linear production of N2O are used for calculations due
to potential interference of bottle effects (Groffman and Tiedje, 1989). DEA rates are scaled to
soil dry-mass (mg-N g-soil-1 h-1) to determine the flux of N per unit mass of soil, allowing
comparisons across soils of contrasting physical properties.
Microbial biomass N was measured using the chloroform fumigation incubation method
(Jenkinson and Powlson, 1976). Samples are fumigated with chloroform to kill and lyse
microbial cells (releasing cellular N), and fumigated soils are inoculated with fresh 0.2 g soil. All
fumigated and unfumigated control samples are incubated at 25oC in the dark for 10 days.
During the incubation, microorganisms lysed by chloroform are mineralized to NH4. Prior to and
following incubation, extractable NH4 and NO3 were measured in fumigated and control
sediments by incubating soil with 2.0M KCl solution on a shaker table at 125 rpm for one hour
to release bound ions into solution. The supernatant is filtered through 2.5 µm Whatman filters
using gravimetric filtration. Sediment extracts were analyzed for NH4 and NO3 on a SEAL
AQ300 Discrete Analyzer (SEAL Analytical, Inc, Mequon, WI)2. Dissolved inorganic N (NH4
and NO3) in pre- and post-incubation control soils was used to calculate net nitrogen
mineralization (production of inorganic N) and net nitrification (transformation of NH4 to NO3-
via net change in NO3). We will determine soil moisture using measuring gravimetric water
content and drying subsamples at 105oC for 24 hours.
4.1.2 Microbial P Release
The release of P from sediment microbial biomass turnover and cell lysis during hydrologic
shifts is a potential source of P to the water column upon rewetting desiccated sediments. The
sampled sediments were analyzed for the P content of the microbial biomass in a similar manner

2 Method detection limits: NH4 – 0.004 mg N L-1; NO3 – 0.004 mg N L-1

18

to microbial biomass N described above. Microbial biomass P is calculated from the difference
between the amount of inorganic P that is extracted by 2M KCl from fresh soil fumigated with
chloroform and unfumigated soil (Brookes et al., 1982).
4.1.3 Sediment Chemistry
Subsamples were taken from homogenized, composite samples for sediment organic matter,
extractable NO3-N, NH4-N, and PO4-P and were analyzed using standard methods (Eaton et al.,
2012).
4.1.4 Statistical Analyses
Measured parameters did not meet assumptions of linear statistics. Non-normality and non-
homogeneity within the datasets were addressed by transforming variables to reach normal
distributions among each parameter. All variables were log-transforming except net N
mineralization and nitrification. These two variables contained negative and positive values, and
a cube root transformation was used. The nature of the study design was nested due to the spatial
and temporal non-independence among sampling locations and times. Specifically, locations
(East Beach, Provo Bay, Sandy Beach, West Beach) were selected to represent the variability of
conditions around the lakeshore, and sites were selected with regard to proximity to the lake to
represent the gradient from saturated to perennially dry sediments. As a result, each site was
nested within a location. Samples were collected at each site within each location thrice at ~45-
day increments. To account for the spatial and temporal non-homogeneity, nested mixed effect
models were used to analyze all parameters using the restricted log-likelihood method in the
nlme package in R statistical programming (R Core Team, 2022). Three nested mixed effect
models were performed on each variable to determine effects of site, location, and season:

Model Fixed effect Random effects
Effect of site Site ~ 1 | location/time
Effect of location Location ~ 1 | site/time
Effect of season Season ~ 1 | site/location

Post-hoc pairwise comparisons were performed on significant effects using least-squares means
(emmeans R package). All statistical tests considered significance at  = 0.05.
4.1.5 Sediment Core Sampling Locations and Sampling Schedule
We collected sediment cores at the same locations as in Task 1. Sediment cores were taken from
the same four locations as in Task 1 (Provo Bay, West Beach, East Beach, and Sandy Beach;
Figure 1.2). Subsites at each lake location included one in-lake site that was perennially
saturated, one margin site in areas with intermittent drying and wetting cycles, and one
perennially dry upland site to represent a gradient of proximity to lake edge. We sampled all
cores and water used in the experiment thrice during the study period at ~45 day intervals.
Sampling events occurred September 9, 2021 when the lake levels are at or near the lowest levels
of the season, October 29, 2021, and December 14, 2021 3 to capture the seasonal heterogeneity

19

and hydrologic fluctuations. Prior measurements of lake processes have not quantified N, P, or C
flux rates during the non-growing season.
4.1.6 Sample Transport and Storage
All cores were transported to the lab on ice. The mechanistic laboratory analyses were initiated
within 24 hours of core extraction and manipulations were conducted at room temperature 20C.
4.2 Results
4.2.1 Sediment C, N, and P
4.2.1.1 Sediment Organic Matter
Sediment organic matter content was measured to provide an estimate of the relative availability
of sources of organic carbon in the sediments. Sediment organic matter (sed-OM) was highly
variable across the lake locations, ranging 11-202 g-OM kg-1 (or 0.6-20.5% by mass; Table 2A.3,
see Table2B.3 for areal rates). There was not a significant effect of proximity to lake edge (lake,
margin, upland) on sed-OM, (Figure 2.1A; p=0.06), nor was there an observed seasonal effect
(Figure 2.1C) due to the spatial variability across lake locations. There was a significant effect of
location on sed-OM. Provo Bay sed-OM was highest among sampling locations (Figure 2.1B; p
< 0.01), and sed-OM was similar at East Beach, Sandy Beach, and West Beach.

Results indicate that lake-wide, sed-OM does not differ due to proximity to the lake edge,
however, there was high variability of sed-OM around the lake. Provo Bay sed-OM was an order
of magnitude higher than other locations, likely resulting from high watershed inputs of organic
matter to the bay, resulting from dense urban land use and wastewater inputs. It is not expected
to see a dramatic short-term shift in organic matter content over the course of four months, and
the observed higher sed-OM at some locations and sites during winter are a result of sediment
heterogeneity and the limited sampling extent.
4.2.1.2 Sediment Nitrogen
Dissolved inorganic nitrogen measurements showed high spatial and temporal variability in N
availability across sites, locations, and seasons. Sediment extractable nitrogen (NO3-N) ranged
from below detection to 4.95 mg-N kg-1. There was a significant effect of site on sediment NO3-
N, with the highest concentrations in upland sediments (Figure 2.2A; p<0.01) but no effect of
location or season on NO3-N was observed (Figure 2.2B-C). Sediment extractable ammonium
(NH4-N) ranged 3 orders of magnitude from 0.005-2.08 mg-N kg-1 with site and season
significantly affecting concentrations. Sediment NH4-N showed contrasting trends of NO3-N:
NH4-N was highest in lake and margin sediments and lowest in upland sediments (Figure 2.3A;
p<0.01). Sediment NH4-N was highest in winter and lowest in summer (Figure 2.3C; p<0.05).
There was no effect of location on NH4-N (Figure 2.3B).

20

Sediment NO3-N and NH4-N showed contrasting seasonal patterns. Sediment NO3-N was higher
during fall and lower NO3-N in winter and summer, whereas NH4-N was higher in winter and
lower in fall and summer. This pattern suggests that availability of dissolved inorganic nitrogen
(DIN) in sediments was more limited during late September when biotic activity is high and
increased during October and December when uptake becomes slower and biotic turnover
occurs.
4.2.1.3 Sediment Phosphorus
Sediment orthophosphate (PO4-P) concentrations ranged from below detection to 0.60 mg-P kg-1.
Despite the high range, there was not a significant effect of proximity to lake edge (lake, margin,
upland) on PO4-P, (Figure 2.4A), nor was there an observed effect of location (Figure 2.4B) or
seasonal effect (Figure 2.1C) due to the variability in PO4-P across the lake. It was expected that
the highest PO4-P would be measured in Provo Bay due to the high sed-OM and high sediment
total phosphorus reported by previous studies, however, sediment PO4-P in Provo Bay was
similar sediment PO4-P in East Beach, Sandy Beach, and West Beach. PO4-P did not appear to
correspond to other measured variables.
4.2.2 Benthic Nitrogen Cycling
The nitrogen (N) cycle is a highly complex process with many microbially-mediated pools and
fluxes. In this study, we quantified potential sources and sinks of inorganic N to provide insights
into the patterns of N flux observed in Task 1. Sediment N cycling parameters were quantified
over the duration of the seasonal transition from late summer to winter conditions in order to
capture the seasonality of these processes. To date, most mechanistic studies of nutrient controls
in Utah Lake have been performed during the growing season (Apr-Oct). An estimate of non-
growing season process rates informs whether these processes are active enough to provide a
seasonal contribution during cold weather months.
4.2.2.1 Net N Mineralization and Nitrification
Net N mineralization rates ranged from -0.8-2.1 mg-N kg-1 d-1, indicating that immobilization
(negative values) and mineralization (positive values) are occurring. Immobilization dominated
during summer and winter months, whereas fall was dominated by mineralization (Figure 2.4C;
p<0.05). This seasonal pattern indicated that immobilization in summer led to net consumption
of DIN during the growing season while the fall led to net production of DIN. Microbial turnover
during the transition from summer to fall, in which the microbial biomass releases bioavailable N
upon senescence, likely stimulated mineralization to occur. This sequence of events poses the
most likely source of N to the water column upon the transition from late growing season into
the fall.

Net nitrification rates ranged from -0.30-2.12 mg-N kg-1 d-1, indicating that net NO3-N
consumption (negative values) and nitrification (positive values) are occurring. Consumption of
sediment NO3-N can be driven by multiple processes, including denitrification and dissimilatory
reduction of nitrate to ammonium. No effect of site, location, or season was observed for net
nitrification rates (Figures 2.4A-C). This may suggest a tightly coupled nitrification-

21

denitrification process and may account for the inconclusive denitrification results presented
below.
4.2.2.2 Microbial Biomass Nitrogen
Microbial biomass nitrogen (MBN) indicates the amount of labile N within the microbial
biomass that is available upon turnover of the microbial community. Sediment MBN ranged 5
orders of magnitude across all samples, from 0.005-224 g-N kg-1. There was a significant effect
of site, with the highest MBN occurring in lake sediments (Figure 2.7A; p<0.05). There was also
a significant effect of location on MBN, with the highest MBN occurring at East Beach and
Provo Bay (Figure 2.7B; p<0.01). No seasonal effects on MBN were observed (Figure 2.7C).

High microbial biomass N corresponded to low DIN, indicated high microbial uptake rates
contributing to low sediment DIN. Although a net effect of season on MBN was not observed,
seasonal average decrease by an order of magnitude from summer to fall, indicating that the
microbial biomass is likely not a large pool of potential DIN release following in the growing
season.
4.2.2.3 Sediment Denitrification
Sediment denitrification activity measurements were inconclusive. Many measured rates of
ambient denitrification were negative, suggesting potential net uptake of N2O in benthic
sediments. Net N2O uptake (i.e. negative rates of denitrification) can occur in sediments
depending on environmental conditions and substrate availability (Murray et al., 2015; Zumft
and Kroneck, 2006). High concentrations of dissolved inorganic nitrogen (DIN) are a primary
driver of benthic N2O production and consumption. Denitrification is enhanced with higher NH4
and NO3 due to the provision of the primary energy supply to the process. At low concentrations
of DIN and O2, N2O can be consumed through reduction processes – dissimilatory reduction of
ammonium to nitrate, and in some cases, in the denitrification process itself – and is influenced
by the quantity and quality of organic matter (Foster and Fulweiler, 2016). However, N2O
consumption in freshwater sediments is not well documented. Due to these considerations, we
will take additional steps to conduct data quality control and perform replicated experiments to
ensure that rates are representative of in situ conditions in Utah Lake Littoral sediments.

Diverging patterns of sediment NO3-N and NH4-N availability suggests spatial and seasonal
variations of DIN flux. Between summer and fall sampling, there was an accumulation of NO3-N
in the sediments, with average concentrations increasing from 0.36-1.10 mg-N kg-1 between
September and October sampling events. Low summer NO3-N may have resulted from
intensified denitrification during periods of high algal production that reduced water column
oxygen content. The fall NO3-N accumulation may have resulted from algal turnover, returning
labile DIN to the water column, progressively oxidizing sediments, and high mineralization and
nitrification rates. In contrast, sediment NH4-N decreased from 0.33-0.12 mg-N kg-1 between
September and October sampling events. The simultaneous accumulation of NO3-N and
reduction in NH4-N availability is also underpinned by the highest nitrification rates occurring
during the fall. Therefore, during the transition from summer to fall, the data suggest that high
nitrification rates are converting NH4-N to NO3-N concurrently with algal biomass turnover and

22

sediment oxidation, leading to increasing sediment NO3-N availability. Sediment DIN
availability is highest during winter at 6.41 mg-N kg-1 and is predominately NH4-N.
4.2.3 Benthic Carbon Cycling
4.2.3.1 Sediment Respiration
Sediment potential respiration (R) rates ranged from 1.42-53.26 mg-C kg-1 d-1. There was a
significant effect of site on potential R rates, with the highest rates occurring in lake sediments
and lowest rates occurring in upland sediments (Figure 2.8A; p<0.05). There was a significant
effect of location on potential R rates, with highest rates occurring in Provo Bay and lowest rates
in Sandy Beach and West Beach (Figure 2.8B; p<0.05). A seasonal effect was also observed,
with the highest potential R rates occurring in summer and lowest rates in winter (Figure 2.8C;
p<0.01). Respiration rates were highly correlated with MBC (r=0.67, p<0.0001), and there was
likely a feedback between microbial biomass turnover and pulses of CO2 from respiration
processes.
4.2.3.2 Microbial Biomass Carbon
Sediment microbial biomass carbon (MBC) ranged from 0.02-2.69 g-C kg-1. A significant effect
of location was observed, with high MBC occurring at Provo Bay and lowest MBC at Sandy
Beach (Figure 2.9A; p<0.05). No significant effects of site or season were observed for MBC.
Sediment MBC was highly correlated with MBN (r=0.73, p<0.0001) and sed-OM (r=0.53,
p<0.001).
4.2.4 Key Findings
Sediments in Utah Lake were found to be highly variable in terms of sediment chemistry and
benthic N and C cycling. Provo Bay sediments were found to host high sediment microbial
biomass which has the potential to become a source of labile C and N upon rewetting of dry
sediments during transitional periods. Sediment microbial biomass N was 1-3 orders of
magnitude lower in other locations, indicated less sensitivity of other sites to microbial bursts of
labile nutrients to the water column upon rewetting. Net mineralization was observed to be
dominant only in the fall during simultaneous microbial biomass turnover and oxidation of the
sediments. High immobilization rates during the summer and fall indicate a high microbial
capacity for N consumption and thus, may provide an offset during nutrient pulses following
sediment rewetting during those seasons. Determination of the magnitude of denitrification will
provide a critical understanding of N removal processes to further understand potential nutrient
offsets following sediment rewetting.

23

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K., Knezevic-Jaric, J., Premke, K., 2016. Water level changes affect carbon turnover and
microbial community composition in lake sediments. FEMS Microbiol. Ecol. 92, fiw035.
Zumft, W.G., Kroneck, P.M., 2006. Respiratory transformation of nitrous oxide (N2O) to
dinitrogen by Bacteria and Archaea. Adv. Microb. Physiol. 52, 107–227.

25

Appendix 1A. Task 1 Tables
Table 1. P species release rates (grams P / m2 sediment / day) from four Utah Lake sites across three sediment locations under continuous water conditions
(control) and exposed to two drying and rewetting cycles (DR 1 and DR 2). Values are means (n: control = 6, DR 1 = 9, and DR 2 = 6) with standard error.
location sediment treatment TP TDP PP SRP DOP
mean sterr mean sterr mean sterr mean sterr mean sterr
east beach upland control 0.002 0.000 0.004 0.000 -0.002 0.001 0.001 0.000 0.003 0.000
east beach margin control 0.005 0.003 0.009 0.001 -0.003 0.002 0.005 0.001 0.004 0.001
east beach lake control 0.000 0.001 0.002 0.001 -0.002 0.001 0.000 0.000 0.001 0.000
provo bay upland control 0.002 0.001 0.004 0.001 -0.002 0.001 0.002 0.000 0.001 0.000
provo bay margin control -0.001 0.002 0.020 0.019 -0.021 0.019 0.001 0.000 0.019 0.019
provo bay lake control 0.000 0.001 0.002 0.001 -0.002 0.000 0.001 0.000 0.001 0.000
sandy beach upland control 0.000 0.001 0.001 0.000 -0.001 0.000 0.000 0.000 0.001 0.000
sandy beach margin control 0.000 0.000 0.001 0.000 -0.001 0.000 0.000 0.000 0.001 0.000
sandy beach lake control 0.001 0.001 0.002 0.001 -0.001 0.000 0.000 0.000 0.001 0.001
west beach upland control -0.001 0.000 0.000 0.000 -0.001 0.000 0.000 0.000 0.000 0.000
west beach margin control 0.000 0.001 0.001 0.000 -0.001 0.001 0.000 0.000 0.001 0.000
west beach lake control -0.001 0.001 0.000 0.000 -0.001 0.000 0.000 0.000 0.000 0.000
east beach lake DR 1 0.010 0.006 0.011 0.007 -0.001 0.002 -0.001 0.005 0.008 0.005
east beach margin DR 1 0.029 0.011 0.031 0.012 -0.002 0.001 0.012 0.003 0.014 0.010
east beach upland DR 1 0.009 0.005 0.012 0.007 -0.003 0.002 -0.007 0.004 0.014 0.008
east beach lake DR 2 0.026 0.015 0.018 0.012 0.008 0.004 -0.001 0.001 0.012 0.008
east beach margin DR 2 0.068 0.022 0.045 0.010 0.024 0.012 0.021 0.009 0.016 0.011
east beach upland DR 2 0.023 0.013 0.015 0.008 0.009 0.006 -0.007 0.004 0.014 0.007
provo bay lake DR 1 0.011 0.006 0.011 0.006 0.000 0.000 -0.002 0.002 0.012 0.006
provo bay margin DR 1 0.022 0.012 0.017 0.010 0.005 0.003 0.004 0.004 0.011 0.007
provo bay upland DR 1 0.009 0.006 0.012 0.006 0.000 0.000 -0.003 0.002 0.011 0.006
provo bay lake DR 2 0.014 0.008 0.015 0.009 0.001 0.003 -0.007 0.003 0.018 0.011
provo bay margin DR 2 0.024 0.016 0.016 0.009 0.008 0.009 -0.002 0.004 0.015 0.008
provo bay upland DR 2 0.039 0.022 0.015 0.011 0.014 0.010 -0.007 0.004 0.029 0.018
sandy beach lake DR 1 0.004 0.002 0.004 0.002 0.000 0.001 -0.006 0.003 0.008 0.004
sandy beach margin DR 1 0.001 0.000 0.001 0.001 -0.001 0.001 -0.006 0.003 0.006 0.003
sandy beach upland DR 1 0.177 0.210 0.003 0.002 0.174 0.210 -0.006 0.003 0.007 0.004
sandy beach lake DR 2 0.012 0.007 0.007 0.004 0.005 0.003 -0.006 0.003 0.010 0.006
sandy beach margin DR 2 0.008 0.005 0.008 0.006 0.001 0.002 -0.006 0.003 0.011 0.007
sandy beach upland DR 2 0.008 0.005 0.006 0.004 0.002 0.001 -0.007 0.003 0.011 0.006
west beach lake DR 1 0.002 0.001 0.003 0.002 0.000 0.001 -0.002 0.002 0.005 0.003
west beach margin DR 1 0.004 0.003 0.005 0.003 0.000 0.001 -0.003 0.002 0.007 0.004
west beach upland DR 1 0.011 0.007 0.012 0.008 -0.001 0.001 0.004 0.004 0.007 0.004
west beach lake DR 2 0.010 0.006 0.004 0.003 0.006 0.004 -0.002 0.002 0.006 0.004
west beach margin DR 2 0.010 0.007 0.001 0.001 0.009 0.006 -0.001 0.004 0.004 0.003
west beach upland DR 2 0.014 0.006 0.011 0.005 0.002 0.002 0.005 0.001 0.007 0.004

26

27

Table 2. N species release rates (grams N / m2 sediment / day) from four Utah Lake sites across three sediment locations under control, DR 1, and DR 2). Values
are means (n: control = 6, DR 1 = 9, and DR 2 = 6) with standard error.
location sediment treatment TN NO3-N NH4-N TDN TDON
mean sterr mean sterr mean sterr mean sterr mean sterr
east beach upland control -0.002 0.003 0.000 0.000 -0.001 0.000 0.002 0.002 0.003 0.002
east beach margin control -0.016 0.008 0.000 0.000 0.000 0.000 0.005 0.001 0.005 0.001
east beach lake control -0.007 0.003 0.001 0.000 0.000 0.000 0.003 0.001 0.002 0.002
provo bay upland control -0.015 0.005 0.000 0.000 0.000 0.000 0.004 0.001 0.004 0.001
provo bay margin control -0.012 0.008 0.000 0.000 -0.002 0.001 0.003 0.001 0.005 0.001
provo bay lake control -0.015 0.003 0.000 0.000 0.000 0.000 0.003 0.000 0.003 0.001
sandy beach upland control -0.005 0.004 0.000 0.000 0.000 0.000 0.004 0.001 0.005 0.001
sandy beach margin control -0.003 0.002 0.000 0.000 -0.001 0.000 0.005 0.001 0.006 0.001
sandy beach lake control -0.004 0.004 0.000 0.000 0.000 0.000 0.004 0.001 0.004 0.001
west beach upland control -0.003 0.007 0.002 0.002 0.001 0.005 0.004 0.004 0.002 0.001
west beach margin control 0.009 0.008 0.001 0.000 0.006 0.006 0.005 0.003 -0.001 0.003
west beach lake control -0.009 0.006 0.001 0.000 0.000 0.002 0.001 0.003 0.000 0.001
east beach lake DR 1 0.021 0.021 0.037 0.035 -0.018 0.010 0.013 0.011 0.003 0.004
east beach margin DR 1 -0.009 0.004 -0.026 0.012 -0.012 0.005 -0.006 0.003 0.008 0.004
east beach upland DR 1 0.032 0.033 0.024 0.026 -0.001 0.004 0.018 0.014 0.003 0.005
east beach lake DR 2 0.161 0.094 0.091 0.058 -0.004 0.010 0.076 0.043 0.003 0.004
east beach margin DR 2 0.298 0.169 0.095 0.059 0.008 0.028 0.106 0.055 0.010 0.008
east beach upland DR 2 0.100 0.061 0.043 0.028 -0.012 0.018 0.045 0.029 0.004 0.005
provo bay lake DR 1 0.071 0.061 0.067 0.058 -0.003 0.002 0.037 0.027 -0.002 0.006
provo bay margin DR 1 0.170 0.159 0.154 0.154 -0.004 0.002 0.076 0.070 -0.002 0.005
provo bay upland DR 1 0.375 0.275 0.380 0.284 -0.004 0.002 0.173 0.125 -0.002 0.006
provo bay lake DR 2 0.061 0.055 0.023 0.028 -0.007 0.003 0.043 0.024 0.004 0.008
provo bay margin DR 2 0.151 0.196 0.037 0.061 0.022 0.034 0.070 0.054 0.016 0.010
provo bay upland DR 2 0.373 0.217 0.063 0.045 0.066 0.053 0.132 0.073 0.004 0.011
sandy beach lake DR 1 0.023 0.021 -0.016 0.014 -0.006 0.004 0.005 0.004 0.002 0.004
sandy beach margin DR 1 -0.015 0.008 -0.047 0.023 -0.006 0.003 -0.006 0.004 0.017 0.008
sandy beach upland DR 1 -0.019 0.016 -0.039 0.019 -0.003 0.001 0.000 0.002 0.012 0.005
sandy beach lake DR 2 0.081 0.054 -0.036 0.013 0.022 0.016 0.043 0.023 0.010 0.003
sandy beach margin DR 2 0.047 0.033 -0.027 0.009 0.007 0.006 0.037 0.020 0.014 0.004
sandy beach upland DR 2 0.055 0.034 -0.026 0.007 0.007 0.007 0.032 0.014 0.006 0.007
west beach lake DR 1 0.125 0.083 0.125 0.085 -0.003 0.005 0.053 0.034 -0.001 0.002
west beach margin DR 1 0.373 0.240 0.377 0.243 -0.016 0.008 0.153 0.098 0.000 0.002
west beach upland DR 1 0.112 0.126 0.077 0.123 -0.012 0.007 0.044 0.048 0.024 0.024

28

location sediment treatment TN NO3-N NH4-N TDN TDON
mean sterr mean sterr mean sterr mean sterr mean sterr
west beach lake DR 2 0.101 0.063 0.020 0.008 0.035 0.024 0.053 0.031 -0.004 0.002
west beach margin DR 2 0.095 0.098 0.042 0.030 0.002 0.029 0.039 0.035 -0.001 0.002
west beach upland DR 2 0.011 0.017 0.016 0.014 -0.025 0.011 0.012 0.007 0.003 0.003

29

Table 3. C species release rates (grams C / m2 sediment/day) from four Utah Lake locations across three sediment types
under continuous water conditions (control) and exposed to two drying and rewetting cycles (DR 1 and DR 2). Values are
means (n: control = 6, DR 1 = 9, and DR 2 = 6) with standard error.
location sediment treatment DOC
mean sterr
east beach upland control 0.001 0.032
east beach margin control 0.031 0.014
east beach lake control 0.009 0.009
provo bay upland control 0.049 0.014
provo bay margin control 0.058 0.016
provo bay lake control 0.041 0.013
sandy beach upland control 0.040 0.012
sandy beach margin control 0.049 0.028
sandy beach lake control 0.031 0.011
west beach upland control 0.029 0.009
west beach margin control 0.016 0.007
west beach lake control 0.016 0.005
east beach lake DR 1 0.161 0.061
east beach margin DR 1 0.205 0.102
east beach upland DR 1 0.187 0.089
east beach lake DR 2 0.551 0.265
east beach margin DR 2 0.914 0.359
east beach upland DR 2 0.614 0.314
provo bay lake DR 1 0.115 0.046
provo bay margin DR 1 0.149 0.075
provo bay upland DR 1 0.202 0.100
provo bay lake DR 2 0.348 0.187
provo bay margin DR 2 0.640 0.374
provo bay upland DR 2 0.852 0.411
sandy beach lake DR 1 0.150 0.068
sandy beach margin DR 1 0.150 0.072
sandy beach upland DR 1 0.159 0.077
sandy beach lake DR 2 0.445 0.205
sandy beach margin DR 2 0.520 0.286
sandy beach upland DR 2 0.332 0.120
west beach lake DR 1 0.116 0.050
west beach margin DR 1 0.134 0.060
west beach upland DR 1 0.135 0.071
west beach lake DR 2 0.279 0.128
west beach margin DR 2 0.285 0.142
west beach upland DR 2 0.196 0.086

30

31

Table 4. SRP adsorption rate by sediments (grams P / m2 sediment / day) and % SRP adsorbed by sediments from four
Utah Lake sites across three sediment locations under control and exposed to DR cycles. Values are means (n: control = 3
and DR = 6) with standard error (sterr).
location sediment treatment rate SRP adsorbed by sediments % adsorbed by sediments
mean sterr mean sterr
east beach upland control 0.033 0.020 10.54 6.35
east beach margin control 0.065 0.014 20.96 4.63
east beach lake control 0.007 0.007 2.31 2.31
provo bay upland control 0.203 0.006 65.31 1.95
provo bay margin control 0.146 0.006 46.92 2.06
provo bay lake control 0.183 0.025 58.89 8.08
sandy beach upland control 0.000 0.000 0.00 0.00
sandy beach margin control 0.056 0.004 18.00 1.25
sandy beach lake control 0.122 0.030 39.27 9.55
west beach upland control 0.101 0.015 32.66 4.87
west beach margin control 0.091 0.017 29.31 5.50
west beach lake control 0.109 0.017 35.19 5.62
east beach upland DR 0.022 0.020 6.98 6.31
east beach margin DR 0.062 0.007 20.10 2.29
east beach lake DR 0.016 0.003 5.03 1.11
provo bay upland DR 0.187 0.016 60.30 5.20
provo bay margin DR 0.140 0.011 45.13 3.44
provo bay lake DR 0.098 0.013 31.69 4.10
sandy beach upland DR 0.006 0.005 1.93 1.50
sandy beach margin DR 0.005 0.005 1.76 1.76
sandy beach lake DR 0.041 0.020 13.34 6.57
west beach upland DR 0.089 0.025 28.62 7.94
west beach margin DR 0.080 0.024 25.85 7.63
west beach lake DR 0.073 0.007 23.36 2.21

32

Appendix 1B. Task 1 Figures
Figure 1.1 Total P (TP, 1A), Total dissolved P (TDP, 1.1B), soluble reactive P (SRP, 1.1C), Total N
(TN, 1.1D, and dissolved organic C (DOC, 1.1E) in the initial water from the four lake sites (i.e., East
Lake, Provo Bay, West Lake near Goshen Bay, and Sandy Beach). The initial water was used to start all
treatments and during the treatments to replace the water that for nutrient sampling. Values by lake sites
are presented in boxplots with letters indicating differences (P < 0.05) based on one-way ANOVA (n =
6).
1A) 1B)

East Provo Sandy West
0.05
0.10
0.15
0.20
0.25
Location
Total P (mg/L)
A
B
C C
East Provo Sandy West
0.05
0.10
0.15
0.20
0.25
Location
Total Dissolved P (mg/L)
A
A
B
B

33

1C) 1D)

1E)

East Provo Sandy West
3
4
5
6
7
Location
DOC (mg/L)
A
AB
B B
East Provo Sandy West
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Location
SRP (mg/L)
East Provo Sandy West
1.6
1.8
2.0
2.2
2.4
Location
Total N (mg/L)
A
B
A
B
AB
A
C
B

34

Figure 1.2 Dissolved oxygen (1.2 A), oxidation-reduction potential (1.2B), pH (1.2C), and electrical
conductivity (1.2D) in control (C) and drying rewetting (DR) sediment cores from the four lake sites.
Values by treatment  lake sites are presented in boxplots with letters indicating differences (P < 0.05)
based on one-way ANOVA (n = 12 control n = 18 DR treatments). 2A) 2B)
2C) 2D)

35

Figure 1.3 TP release rates from the four lake sites (i.e., East Lake, 1.3A; Provo Bay 1.3B; Sandy Beach
1.3C; West Lake near Goshen Bay, 1.3D) and three sediment locations by the C and DR treatments. Rates
are expressed as TP mg/L/day for each treatment and time point (n = 3) during the incubation.

3A) East Lake 3B) Provo Bay
3C) Sandy Beach 3D) West Lake
0.0
0.2
0.4
1 7 14 21 28Time
TP release rate (mg/L/day)
lake
lake
marginupland
treatment
CDR
0.0
0.1
0.2
0.3
0.4
1 7 14 21 28Time
TP release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR
0.00
0.04
0.08
0.12
1 7 14 21 28Time
TP release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR
0.0
0.1
0.2
1 7 14 21 28Time
TP release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR

36

Figure 1.4 TN release rates from the four lake sites (i.e., East Lake, 1.4A; Provo Bay 1.4B; Sandy Beach
1.4C; West Lake near Goshen Bay, 1.4D) and three sediment locations by C and DR treatments. Rates are
expressed as TN mg / L / day (n = 3) for each treatment and time point (n = 3) during the incubation.

4A) East Lake 4B) Provo Bay

4C) Sandy Beach 4D) West Beach

0
2
4
6
8
1 7 14 21 28Time
TN release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR
0
1
2
3
1 7 14 21 28Time
TN release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR
−0.5
0.0
0.5
1.0
1 7 14 21 28Time
TN release rate (mg/L/day)
lake
lakemarginupland
treatment
C
DR
0
2
4
6
1 7 14 21 28Time
TN release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR

37

Figure 1.5 DOC release rates from the four lake sites (i.e., East Lake, 1.5A; Provo Bay 1.5B; Sandy
Beach 1.5C; West Lake near Goshen Bay, 1.5D) and three sediment locations by C and DR treatments.
Rates are expressed as mg C / L / day for each treatment and time point (n = 3) during the incubation.

5A) East Lake 5B) Provo Bay
5C) Sandy Beach 5D) West Lake
0
2
4
6
8
1 7 14 21 28Time
DOC release rate (mg/L/day)
lake
lakemargin
upland
treatment
CDR
0.0
2.5
5.0
7.5
1 7 14 21 28Time
DOC release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR
0.0
2.5
5.0
1 7 14 21 28Time
DOC release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR
0
1
2
3
1 7 14 21 28Time
DOC release rate (mg/L/day)
lake
lake
marginupland
treatment
CDR

38

Figure 1.6 East Release rates of other nutrient chemical forms (SRP, 1.6A; DOP, 1.6B; NO3- –N 1.6C;
and TDON, 1.6D) that were significantly different among the three sediment locations by C and DR
treatments. Rates are expressed as mg / L / day for each treatment and time point (n = 3) during the
incubation.
6A) 6B)

6C) 6D)
−0.2
−0.1
0.0
0.1
1 7 14 21 28Time
SRP release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR
−0.1
0.0
0.1
0.2
1 7 14 21 28Time
DOP release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR
−0.5
0.0
0.5
1.0
1 7 14 21 28Time
NO3−N release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR
0.00
0.05
0.10
0.15
0.20
1 7 14 21 28Time
TDON release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR

39

Figure 1.7 Provo Bay release rates of other nutrient chemical forms (SRP, 1.7A; DOP, 1.7B; PP 1.7C;
and NO3- –N 1.7D) that were significantly different among the three sediment locations by C and DR
treatments. Values are rates (n = 3) during the incubation.

7A) 7B)
7C) 7D)

0.0
0.1
0.2
0.3
1 7 14 21 28Time
DOP release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR
−0.2
0.0
0.2
1 7 14 21 28Time
PP release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR
0
2
4
6
8
1 7 14 21 28Time
NO3−N release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR
−0.10
−0.05
0.00
0.05
0.10
1 7 14 21 28Time
SRP release rate (mg/L/day)
lake
lakemargin
upland
treatment
CDR

40

Figure 1.8 Sandy Beach release rates of SRP and DOP from the three sediment locations by C and DR
treatments. Values are rates (n = 3) during the incubation.
8A) 8B)

−0.075
−0.050
−0.025
0.000
1 7 14 21 28Time
SRP release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR
0.00
0.05
0.10
0.15
1 7 14 21 28Time
DOP release rate (mg/L/day)
lake
lakemarginupland
treatment
CDR

41

Figure 1.9 Potential SRP sequestration by the three sediment locations for the four lake sites after
receiving a pulse of 10 mg SRP / L. Rates are expressed as mg SRP / L / day for each treatment and time
point (n = 3) after a 7-day incubation. Values by sediment location and treatment (i.e., C and DR) are
presented in boxplots with letters indicating differences (P < 0.05) based on two-way ANOVA (n = 3).

8A) East Lake 8B) Provo Bay
8C) Sandy Beach 8D) West Lake

lake.C
margin.C
upland.C
lake.DR
margin.DR
upland.DR
0.0
0.5
1.0
1.5
2.0
2.5
3.0
East
SRP absorbed by sediment (mg/L)
lake.C
margin.C
upland.C
lake.DR
margin.DR
upland.DR
3
4
5
6
7
Provo
SRP absorbed by sediments (mg/L)
lake.C
margin.C
upland.C
lake.DR
margin.DR
upland.DR
0
1
2
3
4
5
6
Sandy
SRP absorbed by sediments (mg/L)
lake.C
margin.C
upland.C
lake.DR
margin.DR
upland.DR
1.5
2.0
2.5
3.0
3.5
4.0
4.5
West
SRP absorbed by sediments (mg/L)
A
A
B B
AB
AB
A
B
B
AB
B B
A
AB
A A
B
AB

42

Appendix 2A. Task 2 Mass Rate Tables
Table 2A.1. Microbial biomass measured in Utah Lake during late summer, fall, and winter.
Mean values and standard error derived from duplicate laboratory measurements.
Date Site Location
Microbial Biomass
Carbon
g-C kg-1
Nitrogen
g-N kg-1
Mean SE Mean SE
9/13/2021 East Beach Margin 1.00 0.22 2.37 1.22
Upland 0.15 0.06 0.38 0.09
Lake 0.51 0.26 224.03 151.44
Provo Bay Margin 1.73 0.20 3.35 0.34
Upland 0.91 0.09 2.23 0.37
Lake 2.69 0.13 23.06 2.31
Sandy Beach Upland 0.41 0.17 0.37 0.09
Margin 0.03 0.00 0.02 0.01
Lake 0.39 0.18 3.32 0.53
West Beach Margin 0.28 0.15 0.84 0.20
Upland 0.02 0.00 0.01 0.00
Lake 1.69 0.06 13.37 5.29
10/29/2021 East Beach Margin 0.83 0.16 0.71 0.15
Upland 0.66 0.23 0.28 0.12
Lake 0.78 0.30 9.81 6.13
Provo Bay Margin 0.63 0.13 0.67 0.02
Upland 1.32 0.08 2.44 0.51
Lake 0.89 0.22 6.04 0.06
Sandy Beach Upland 0.33 0.08 0.05 0.00
Margin 0.17 0.02 0.13 0.08
Lake 0.66 0.07 1.90 0.59
West Beach Margin 0.26 0.11 0.18 0.12
Upland 0.25 0.17 0.04 0.03
Lake 0.18 0.13 2.19 1.55
12/14/2021 East Beach Margin 1.28 0.04 1.30 0.28
Upland 1.55 0.05 2.01 0.71
Lake 0.83 0.03 0.47 0.03
Provo Bay Margin 0.90 0.04 0.81 0.18
Upland 1.82 0.05 4.22 1.83
Lake 1.15 0.16 2.95 1.83
Sandy Beach Upland 0.43 0.03 0.20 0.12
Margin 0.11 0.02 0.04 0.02
Lake 0.53 0.02 0.22 0.09
West Beach Margin 0.42 0.00 0.52 0.08
Upland 0.42 0.07 0.21 0.11
Lake 0.23 0.05 0.04 0.03

43

Table 2A.2. Microbial metabolic rates measured in Utah Lake during late summer, fall, and
winter. Mean values and standard error derived from duplicate laboratory measurements.
Date Site Location
Microbial Rates
Respiration
mg-C kg-1 d-1
Net N Mineralization
mg-N kg-1 d-1
Net Nitrification
mg-N kg-1 d-1
Mean SE Mean SE Mean SE
9/13/2021 East Beach Margin 53.26 5.80 0.010 0.280 0.062 0.043
Upland 3.58 0.76 -0.002 0.013 0.000 0.002
Lake 11.58 3.12 -0.192 0.087 -0.037 0.008
Provo Bay Margin 17.51 0.66 -0.163 0.113 0.143 0.123
Upland 8.48 0.02 -0.027 0.013 -0.033 0.013
Lake 20.23 2.90 -0.014 0.028 0.003 0.001
Sandy Beach Upland 9.87 1.26 0.001 0.019 0.029 0.027
Margin 1.51 0.66 -0.032 0.067 0.019 0.031
Lake 12.29 0.37 -0.615 0.194 0.007 0.000
West Beach Margin 10.20 2.60 -0.004 0.045 0.001 0.001
Upland 1.42 0.38 0.255 0.064 0.237 0.070
Lake 21.09 2.79 -0.213 0.128 0.018 0.015
10/29/2021 East Beach Margin 3.86 1.01 0.123 0.007 0.126 0.009
Upland 3.20 1.01 0.001 0.007 0.002 0.008
Lake 16.57 5.12 0.069 0.045 0.223 0.027
Provo Bay Margin 9.81 3.09 0.078 0.003 0.086 0.006
Upland 8.32 0.22 0.085 0.003 0.089 0.003
Lake 9.84 0.54 -0.072 0.027 -0.017 0.015
Sandy Beach Upland 3.85 0.50 0.100 0.061 0.064 0.035
Margin 3.00 0.73 0.025 0.028 0.038 0.023
Lake 10.99 5.12 -0.095 0.015 0.061 0.045
West Beach Margin 4.60 0.18 -0.391 0.095 -0.302 0.088
Upland 1.57 0.06 2.111 0.109 2.124 0.118
Lake 8.51 3.40 -0.233 0.095 0.015 0.033
12/14/2021 East Beach Margin 4.53 1.12 0.201 0.081 0.069 0.012
Upland 5.16 1.33 -0.075 0.053 0.217 0.170
Lake 5.54 0.81 0.042 0.001 0.058 0.046
Provo Bay Margin 5.72 0.10 0.040 0.112 0.022 0.000
Upland 10.15 0.15 -0.002 0.045 0.022 0.005
Lake 8.62 1.13 -0.150 0.509 0.077 0.018
Sandy Beach Upland 3.63 0.27 -0.016 0.714 0.007 0.021
Margin 1.98 0.05 -0.818 0.036 0.038 0.022
Lake 3.63 0.06 -0.530 0.501 0.036 0.014
West Beach Margin 3.81 0.87 -0.779 0.174 0.044 0.005
Upland 2.07 0.23 0.307 0.465 0.562 0.265
Lake 2.70 0.28 -0.461 0.307 0.040 0.008

44

Table 2A.3. Sediment carbon, nitrogen, and phosphorus measured in Utah Lake during late summer, fall, and winter. Mean values and standard error
derived from duplicate laboratory measurements.
Date Site Location
Sediment C, N, P
NO3-N
mg-N kg-1
NH4-N
mg-N kg-1
DIN
mg-N kg-1
PO4-P
mg-P kg-1
Organic Matter Content
g-OM kg-1
Mean SE Mean SE Mean SE Mean SE Mean SE
9/13/2021 East Beach Margin 0.126 0.089 0.828 0.081 3.92 1.06 0.018 0.013 29.02 11.10
Upland 0.029 0.021 0.027 0.009 0.13 0.07 0.004 0.003 12.96 2.22
Lake 0.396 0.058 0.400 0.036 2.27 0.62 0.029 0.011 18.24 1.62
Provo Bay Margin 0.334 0.024 0.395 0.279 3.71 2.41 0.069 0.033 102.13 1.58
Upland 0.399 0.170 0.030 0.021 0.57 0.29 0.000 0.000 79.69 1.95
Lake 0.043 0.013 0.045 0.032 0.55 0.37 0.081 0.050 64.02 0.98
Sandy Beach Upland 0.150 0.024 0.108 0.029 0.57 0.04 0.020 0.005 27.23 10.43
Margin 0.321 0.177 0.212 0.052 1.06 0.49 0.105 0.034 21.78 2.43
Lake 0.023 0.016 1.473 0.094 6.40 1.85 0.098 0.069 21.12 1.48
West Beach Margin 0.038 0.027 0.119 0.084 0.40 0.23 0.000 0.000 12.30 4.55
Upland 2.472 0.637 0.025 0.001 2.56 0.66 0.049 0.019 54.90 0.50
Lake 0.015 0.011 0.337 0.144 2.53 1.36 0.000 0.000 17.69 2.05
10/29/2021 East Beach Margin 0.083 0.059 0.031 0.014 0.27 0.15 0.054 0.002 41.48 0.15
Upland 0.357 0.096 0.005 0.001 0.38 0.09 0.038 0.005 32.38 11.69
Lake 0.020 0.014 0.199 0.008 1.93 0.04 0.266 0.038 55.06 1.72
Provo Bay Margin 0.055 0.021 0.030 0.017 0.28 0.15 0.022 0.003 80.74 7.70
Upland 0.742 0.132 0.029 0.007 0.94 0.18 0.048 0.006 129.50 0.78
Lake 0.444 0.314 0.098 0.005 1.13 0.34 0.026 0.002 56.85 0.18
Sandy Beach Upland 1.548 0.086 0.005 0.003 1.57 0.07 0.060 0.002 11.21 4.65
Margin 0.914 0.023 0.035 0.007 1.08 0.06 0.174 0.043 13.41 0.64
Lake 0.082 0.058 0.333 0.083 2.09 0.37 0.039 0.007 60.44 14.84
West Beach Margin 3.674 0.583 0.180 0.014 4.57 0.65 0.026 0.007 17.29 0.83
Upland 4.947 1.738 0.026 0.018 5.08 1.83 0.031 0.004 37.92 1.54
Lake 0.379 0.177 0.430 0.072 3.16 0.65 0.021 0.015 26.58 1.57
12/14/2021 East Beach Margin 0.000 0.000 0.231 0.130 1.67 0.94 0.054 0.038 64.13 2.35
Upland 1.835 0.015 0.483 0.132 5.61 1.07 0.608 0.227 133.63 6.61
Lake 0.140 0.083 0.736 0.395 4.72 2.52 0.059 0.031 29.13 2.78
Provo Bay Margin 0.540 0.320 0.579 0.270 4.69 1.63 0.081 0.004 66.04 2.49
Upland 0.010 0.002 0.340 0.231 2.88 1.95 0.030 0.003 202.33 1.60
Lake 0.017 0.012 0.737 0.350 5.91 2.80 0.023 0.016 70.28 1.44
Sandy Beach Upland 0.365 0.258 0.957 0.645 5.50 3.72 0.050 0.003 19.10 2.67
Margin 0.336 0.238 2.005 0.003 9.27 0.21 0.093 0.059 15.85 2.31
Lake 0.076 0.054 1.965 0.153 11.23 1.04 0.033 0.015 15.89 0.79
West Beach Margin 0.024 0.005 2.083 0.006 10.72 0.05 0.013 0.009 24.91 0.91
Upland 3.783 0.698 1.065 0.029 9.32 0.53 0.223 0.041 49.25 1.05
Lake 0.081 0.001 1.055 0.671 5.45 3.41 0.038 0.018 27.45 2.66

45

Appendix 2B: Task 2 Areal Rates Tables
Table 2B.1. Microbial biomass measured in Utah Lake during late summer, fall, and winter.
Mean values and standard error derived from duplicate laboratory measurements.
Date Site Location
Microbial Biomass
Carbon
g-C m-2
Nitrogen
g-N m-2
Mean SE Mean SE
9/13/2021 East Beach Margin 166.78 37.00 395.37 204.40
Upland 18.26 7.22 46.16 11.03
Lake 112.47 58.21 49647.62 33560.49
Provo Bay Margin 291.27 33.62 563.42 56.84
Upland 88.59 8.60 217.82 36.12
Lake 404.15 19.30 3470.29 348.01
Sandy Beach Upland 133.48 54.43 120.04 30.32
Margin 8.55 0.51 6.98 3.32
Lake 118.72 54.83 1013.51 161.15
West Beach Margin 76.23 42.30 232.81 54.22
Upland 3.93 0.32 0.84 0.09
Lake 433.86 15.91 3421.37 1353.81
10/29/2021 East Beach Margin 139.39 27.02 119.19 25.70
Upland 79.12 27.07 34.17 14.95
Lake 172.77 67.24 2174.41 1358.42
Provo Bay Margin 106.12 21.83 112.25 3.86
Upland 129.42 8.26 238.85 49.49
Lake 134.65 33.10 909.25 8.49
Sandy Beach Upland 107.30 26.17 17.53 1.46
Margin 53.32 7.29 41.06 23.64
Lake 201.87 20.90 579.47 178.78
West Beach Margin 71.65 30.03 50.56 33.04
Upland 38.76 27.41 5.91 4.17
Lake 46.17 32.65 560.56 396.36
12/14/2021 East Beach Margin 214.19 6.57 216.53 46.95
Upland 186.74 6.36 241.81 85.28
Lake 185.04 6.60 104.27 7.66
Provo Bay Margin 151.13 7.40 136.76 30.53
Upland 177.47 4.55 412.68 179.19
Lake 172.70 23.76 444.51 274.69
Sandy Beach Upland 137.38 8.47 65.50 38.22
Margin 33.14 6.33 11.61 4.76
Lake 162.54 5.40 67.47 27.06
West Beach Margin 116.49 1.32 145.17 21.65
Upland 66.22 10.36 33.26 16.66
Lake 58.98 12.13 9.41 6.64

46

Table 2B.2. Microbial metabolic rates measured in Utah Lake during late summer, fall, and
winter. Mean values and standard error derived from duplicate laboratory measurements.
Date Site Location
Microbial Rates
Respiration
g-C m-2 d-1
Net N Mineralization
g-N m-2 d-1
Net Nitrification
g-N m-2 d-1
Mean SE Mean SE Mean SE
9/13/2021 East Beach Margin 8.89 0.97 0.002 0.047 0.010 0.007
Upland 3.58 0.76 -0.002 0.013 0.000 0.002
Lake 11.58 3.12 -0.192 0.087 -0.037 0.008
Provo Bay Margin 17.51 0.66 -0.163 0.113 0.143 0.123
Upland 8.48 0.02 -0.027 0.013 -0.033 0.013
Lake 20.23 2.90 -0.014 0.028 0.003 0.001
Sandy Beach Upland 9.87 1.26 0.001 0.019 0.029 0.027
Margin 1.51 0.66 -0.032 0.067 0.019 0.031
Lake 12.29 0.37 -0.615 0.194 0.007 0.000
West Beach Margin 10.20 2.60 -0.004 0.045 0.001 0.001
Upland 1.42 0.38 0.255 0.064 0.237 0.070
Lake 21.09 2.79 -0.213 0.128 0.018 0.015
10/29/2021 East Beach Margin 3.86 1.01 0.123 0.007 0.126 0.009
Upland 3.20 1.01 0.001 0.007 0.002 0.008
Lake 16.57 5.12 0.069 0.045 0.223 0.027
Provo Bay Margin 9.81 3.09 0.078 0.003 0.086 0.006
Upland 8.32 0.22 0.085 0.003 0.089 0.003
Lake 9.84 0.54 -0.072 0.027 -0.017 0.015
Sandy Beach Upland 3.85 0.50 0.100 0.061 0.064 0.035
Margin 3.00 0.73 0.025 0.028 0.038 0.023
Lake 10.99 5.12 -0.095 0.015 0.061 0.045
West Beach Margin 4.60 0.18 -0.391 0.095 -0.302 0.088
Upland 1.57 0.06 2.111 0.109 2.124 0.118
Lake 8.51 3.40 -0.233 0.095 0.015 0.033
12/14/2021 East Beach Margin 4.53 1.12 0.201 0.081 0.069 0.012
Upland 5.16 1.33 -0.075 0.053 0.217 0.170
Lake 5.54 0.81 0.042 0.001 0.058 0.046
Provo Bay Margin 5.72 0.10 0.040 0.112 0.022 0.000
Upland 10.15 0.15 -0.002 0.045 0.022 0.005
Lake 8.62 1.13 -0.150 0.509 0.077 0.018
Sandy Beach Upland 3.63 0.27 -0.016 0.714 0.007 0.021
Margin 1.98 0.05 -0.818 0.036 0.038 0.022
Lake 3.63 0.06 -0.530 0.501 0.036 0.014
West Beach Margin 3.81 0.87 -0.779 0.174 0.044 0.005
Upland 2.07 0.23 0.307 0.465 0.562 0.265
Lake 2.70 0.28 -0.461 0.307 0.040 0.008

47

Table 2B.3. Sediment carbon, nitrogen, and phosphorus measured in Utah Lake during late summer, fall, and winter. Mean values and standard error
derived from duplicate laboratory measurements.
Date Site Location
Sediment C, N, P
NO3-N
g-N m-2
NH4-N
g-N m-2
DIN
g-N m-2
PO4-P
g-P m-2
Organic Matter
Content
kg-OM m-2
Mean SE Mean SE Mean SE Mean SE Mean SE
9/13/2021 East Beach Margin 0.021 0.015 0.138 0.014 0.654 0.177 0.003 0.002 4.84 1.85
Upland 0.029 0.021 0.027 0.009 0.132 0.070 0.004 0.003 1.56 0.27
Lake 0.396 0.058 0.400 0.036 2.268 0.620 0.029 0.011 4.04 0.36
Provo Bay Margin 0.334 0.024 0.395 0.279 3.713 2.414 0.069 0.033 17.19 0.27
Upland 0.399 0.170 0.030 0.021 0.569 0.291 0.000 0.000 7.79 0.19
Lake 0.043 0.013 0.045 0.032 0.550 0.372 0.081 0.050 9.63 0.15
Sandy Beach Upland 0.150 0.024 0.108 0.029 0.565 0.035 0.020 0.005 8.78 3.36
Margin 0.321 0.177 0.212 0.052 1.062 0.492 0.105 0.034 6.79 0.76
Lake 0.023 0.016 1.473 0.094 6.404 1.845 0.098 0.069 6.45 0.45
West Beach Margin 0.038 0.027 0.119 0.084 0.399 0.228 0.000 0.000 3.41 1.26
Upland 2.472 0.637 0.025 0.001 2.557 0.658 0.049 0.019 8.66 0.08
Lake 0.015 0.011 0.337 0.144 2.531 1.356 0.000 0.000 4.53 0.52
10/29/2021 East Beach Margin 0.083 0.059 0.031 0.014 0.273 0.147 0.054 0.002 6.92 0.02
Upland 0.357 0.096 0.005 0.001 0.382 0.090 0.038 0.005 3.89 1.41
Lake 0.020 0.014 0.199 0.008 1.926 0.038 0.266 0.038 12.20 0.38
Provo Bay Margin 0.055 0.021 0.030 0.017 0.282 0.153 0.022 0.003 13.59 1.30
Upland 0.742 0.132 0.029 0.007 0.939 0.181 0.048 0.006 12.66 0.08
Lake 0.444 0.314 0.098 0.005 1.135 0.342 0.026 0.002 8.55 0.03
Sandy Beach Upland 1.548 0.086 0.005 0.003 1.571 0.069 0.060 0.002 1.50 1.50
Margin 0.914 0.023 0.035 0.007 1.076 0.057 0.174 0.043 4.18 0.20
Lake 0.082 0.058 0.333 0.083 2.094 0.374 0.039 0.007 18.45 4.53
West Beach Margin 3.674 0.583 0.180 0.014 4.565 0.655 0.026 0.007 4.79 0.23
Upland 4.947 1.738 0.026 0.018 5.077 1.829 0.031 0.004 5.98 0.24
Lake 0.379 0.177 0.430 0.072 3.161 0.653 0.021 0.015 6.81 0.40
12/14/2021 East Beach Margin 0.000 0.000 0.231 0.130 1.670 0.943 0.054 0.038 10.71 0.39
Upland 1.835 0.015 0.483 0.132 5.610 1.070 0.608 0.227 16.07 0.79
Lake 0.140 0.083 0.736 0.395 4.718 2.524 0.059 0.031 6.45 0.62
Provo Bay Margin 0.540 0.320 0.579 0.270 4.693 1.627 0.081 0.004 11.12 0.42
Upland 0.010 0.002 0.340 0.231 2.875 1.950 0.030 0.003 19.77 0.16
Lake 0.017 0.012 0.737 0.350 5.910 2.801 0.023 0.016 10.58 0.22
Sandy Beach Upland 0.365 0.258 0.957 0.645 5.502 3.724 0.050 0.003 6.16 0.86
Margin 0.336 0.238 2.005 0.003 9.267 0.214 0.093 0.059 4.95 0.72
Lake 0.076 0.054 1.965 0.153 11.227 1.040 0.033 0.015 4.85 0.24
West Beach Margin 0.024 0.005 2.083 0.006 10.716 0.049 0.013 0.009 6.90 0.25
Upland 3.783 0.698 1.065 0.029 9.321 0.526 0.223 0.041 7.77 0.17
Lake 0.081 0.001 1.055 0.671 5.454 3.412 0.038 0.018 7.03 0.68

48

49

Appendix 2C: Task 2 Figures
Figure 2.1. Sediment organic matter content: A) Lake, Margin, and Upland sites, B) East Beach,
Provo Bay, Sandy Beach, and West Beach locations, C) Seasonal late summer (13 Sep 2021),
fall (29 Oct 2021), and winter (14 Dec 2021). Units are mass based, see Appendix 2B for areal
rates. Letters indicate significant differences among means (mixed effect ANOVA, p<0.05).

B B B
A

50

Figure 2.2. Sediment extractable nitrate-N concentrations: A) Lake, Margin, and Upland sites, B)
East Beach, Provo Bay, Sandy Beach, and West Beach locations, C) Seasonal late summer (13
Sep 2021), fall (29 Oct 2021), and winter (14 Dec 2021). Units are mass based, see Appendix 2B
for areal rates. Letters indicate significant differences among means (mixed effect ANOVA,
p<0.05).

B
AB A B

51

Figure 2.3. Sediment extractable ammonium-N concentrations: A) Lake, Margin, and Upland
sites, B) East Beach, Provo Bay, Sandy Beach, and West Beach locations, C) Seasonal late
summer (13 Sep 2021), fall (29 Oct 2021), and winter (14 Dec 2021). Units are mass based, see
Appendix 2B for areal rates. Letters indicate significant differences among means (mixed effect
ANOVA, p<0.05). Note that letters in panel 2.3C indicate significant lake-wide differences
among seasons.

B A
A
B C A

52

Figure 2.4. Sediment extractable phosphate-P concentrations: A) Lake, Margin, and Upland sites,
B) East Beach, Provo Bay, Sandy Beach, and West Beach locations, C) Seasonal late summer
(13 Sep 2021), fall (29 Oct 2021), and winter (14 Dec 2021). Units are mass based, see
Appendix 2B for areal rates. Significant effects of site, location, and season were not observed.

53

Figure 2.5. Sediment net N mineralization rates: A) Lake, Margin, and Upland sites, B) East
Beach, Provo Bay, Sandy Beach, and West Beach locations, C) Seasonal late summer (13 Sep
2021), fall (29 Oct 2021), and winter (14 Dec 2021). Units are mass based, see Appendix 2B for
areal rates. Letters indicate significant differences among means (mixed effect ANOVA,
p<0.05). Note that letters in panel 2.3C indicate significant lake-wide differences among seasons.
B AB A
B
B
B
A
B
B
B

54

Figure 2.6. Sediment net nitrification rates: A) Lake, Margin, and Upland sites, B) East Beach,
Provo Bay, Sandy Beach, and West Beach locations, C) Seasonal late summer (13 Sep 2021),
fall (29 Oct 2021), and winter (14 Dec 2021). Units are mass based, see Appendix 2B for areal
rates. Significant effects of site, location, and season were not observed.

55

Figure 2.7. Sediment net nitrification rates: A) Lake, Margin, and Upland sites, B) East Beach,
Provo Bay, Sandy Beach, and West Beach locations, C) Seasonal late summer (13 Sep 2021),
fall (29 Oct 2021), and winter (14 Dec 2021). Units are mass based, see Appendix 2B for areal
rates. Letters indicate significant differences among means (mixed effect ANOVA, p<0.05).
Note that letters in panel 2.3C indicate significant lake-wide differences among seasons.

A A
B B B

56

Figure 2.8. Sediment respiration rates: A) Lake, Margin, and Upland sites, B) East Beach, Provo
Bay, Sandy Beach, and West Beach locations, C) Seasonal late summer (13 Sep 2021), fall (29
Oct 2021), and winter (14 Dec 2021). Units are mass based, see Appendix 2B for areal rates.
Letters indicate significant differences among means (mixed effect ANOVA, p<0.05). Note that
letters in panel 2.3C indicate significant lake-wide differences among seasons.

A
B AB
B
AB A
B C B
A
B
AB B

57

Figure 2.9. Sediment microbial biomass carbon: A) Lake, Margin, and Upland sites, B) East
Beach, Provo Bay, Sandy Beach, and West Beach locations, C) Seasonal late summer (13 Sep
2021), fall (29 Oct 2021), and winter (14 Dec 2021). Units are mass based, see Appendix 2B for
areal rates. Letters indicate significant differences among means (mixed effect ANOVA,
p<0.05). Note that letters in panel 2.3C indicate significant lake-wide differences among seasons.

AB A
B
C
BC