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-Relations between maximum depth, maximum effective length, and proportion of unstratified profiles during May–Aug. (a) Maximum depth versus maximum effective length (n = 231). The reference line was found by Gorham and Boyce (1989) to separate north-temperate natural lakes with and without stable stratification. (b) Mean mixed depth vs. maximum effective length (n = 229). (c) Mean thermocline depth vs. maximum depth (n = 229).
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Vertical profiles of water temperature (n = 7193) and dissolved oxygen (n = 6516) were collected from 235 Missouri reservoirs during 1989–2007; most data were collected during May–August and provide a regional summary of summer conditions. Collectively, surface water temperature ranged from a mean of ∼22 C in May to ∼28 C in July, and individual su...
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... summer. In the shallowest basins (<3 m), however, strat- ification was rare or ephemeral; 13 (including 7 oxbows) had homothermal profiles in >75% of the collections. Mor- phology varied among reservoirs, and a combination of maximum depth and maximum effective length (MEL) ex- plained 52% of variation in the frequency of homothermal conditions (Fig. 2a). These, and other standard dimensions (surface area, maximum length, maximum effective width), are strongly intercorrelated, and alternate combinations ex- plained similar variation in mixing frequency. Interestingly, while most Missouri reservoirs stably stratify, the analysis by Gorham and Boyce (1989) shows that natural lakes with ...
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... maximum length, maximum effective width), are strongly intercorrelated, and alternate combinations ex- plained similar variation in mixing frequency. Interestingly, while most Missouri reservoirs stably stratify, the analysis by Gorham and Boyce (1989) shows that natural lakes with similar depth and length would not stratify (reference line in Fig. 2a). ...
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... mixed depths and thermocline depths (Table 1) were strongly correlated with reservoir dimensions, and the fit was improved by limiting data to reservoirs that were stratified in >75% of profiles (stably stratified dataset). Variation in mixed depth was ex- plained by both MEL (57% in the full dataset, and 68% in the stably stratified dataset; Fig. 2b) and by maximum depth (Z max , >72% of variation in both datasets; Fig. ...
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... with reservoir dimensions, and the fit was improved by limiting data to reservoirs that were stratified in >75% of profiles (stably stratified dataset). Variation in mixed depth was ex- plained by both MEL (57% in the full dataset, and 68% in the stably stratified dataset; Fig. 2b) and by maximum depth (Z max , >72% of variation in both datasets; Fig. ...
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... natural lakes that are shallow relative to their sur- face area and with similar dimensions to Missouri reservoirs would not stratify ( Fig. 2a; Gorham and Boyce 1989). An explanation for this difference is that Missouri reservoirs are impounded in the valleys of erosional topography, and many are located in public lands with forested riparian zones; both features potentially reduce wind exposure and favor strati- fication of shallow water bodies (Demers and Kalff 1993, France ...
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... Studies have shown that thermal stratification is a common characteristic of deep-water lakes and reservoirs, significantly affecting the vertical distribution of dissolved oxygen concentration and plankton populations (Jones et al. 2011, Zhang et al. 2015, Niu et al. 2016, Qiu et al. 2016, Novais et al. 2019. The formation of thermal stratification can deteriorate water quality and accelerate the consumption of dissolved oxygen in the bottom water (Lu & Li 2014). ...
Few studies have explored the relationship between benthic and planktonic assemblages in reservoirs, despite their role in food chains and maintaining ecological functions. Macroinvertebrates play a crucial role in food webs and contribute about 42% of whole-lake secondary productivity. Therefore, their status is vital for maintaining good ecological functions. In this study, we selected Nanwan Reservoir, a eutrophic thermally stratified reservoir in China, to evaluate the community of macroinvertebrates in different seasons and explore the relationships between macroinvertebrate assemblages and different planktonic groups, including phytoplankton, protozoans, rotifers, and planktonic crustaceans. Cyanophyta and Bacillariophyta dominated the phytoplankton assemblages, and their proportions varied with seasons. The bad community of macroinvertebrates in summer, autumn, and winter could be attributed to the excessive growth of Cyanophyta or other phytoplankton. Based on the results of partial least squares regression, an algorithm used for prediction, we determined that the excessive growth of algae, crustaceans, protozoans, and Cyanophyta was detrimental to the development of macroinvertebrates, and was indicative of high nutrient loads in the reservoir. However, the growth of Bacillariophyta, Chrysophyta, and Euglenophyta was advantageous to macroinvertebrate assemblages and indicated a better ecological condition of the reservoir. The results of partial least squares structural equation modeling demonstrated close associations between phytoplankton and both zooplankton and macroinvertebrates, indicating their interdependence in this reservoir system. Our study results imply that the status of macroinvertebrates can be predicted by the abundance of some planktonic assemblages, and cost savings from selecting one of the planktonic groups to monitor ecological conditions could be accomplished in future studies.
... Epilimnetic temperature and dissolved oxygen were determined for each pro le by taking the mean of these parameters above the mixing depth. The depth where anoxia began, or anoxia depth, was considered to be the rst depth where dissolved oxygen concentrations were ≤ 1 mg L − 1 (Jones et al. 2011). Annual means of mixing depth, anoxia depth, epilimnetic temperature, and epilimnetic dissolved oxygen were used for statistical analyses. ...
... Water Temperature and Water Levels Warm water temperatures could limit zebra mussels from reaching high densities in Missouri reservoirs. Between May and August, surface water temperatures in most Missouri reservoirs are greater than 25°C, while mean surface water temperatures in a quarter of reservoirs is ≥ 30°C (Jones et al. 2011). Zebra mussel ltration rates begin to decline above 22°C; above 25°C, zebra mussel growth rates decline (Thorp et al. 1998 . ...
Invasive, filter feeding zebra mussels (Dreissena polymorpha) typically cause an increase in water clarity shortly after their establishment. The purpose of this study is to evaluate whether this occurred in Midwest reservoirs, near the southern edge of their North American expansion, using a 40 + year dataset. We look for regime shifts and long-term trends in annual water clarity and compare these to the estimated zebra mussel invasion date for 7 invaded reservoirs in Missouri, USA. We also look at water clarity in 26 non-invaded, reference reservoirs to evaluate if zebra mussel impacts are being masked by changes in environmental factors. Collectively, our analyses provide a weight of evidence showing that zebra mussel establishment did not increase water clarity, likely because densities are too low to result in a noticeable impact. The highest zebra mussel density we observe is 65 mussels m − 2 , an order of magnitude less than in systems where they have had a sustained impact. Low densities could be due to a combination of sublethal environmental conditions. We identified common characteristics of invaded reservoirs, including reduced particulate inorganic material and water temperatures.
... Studies have shown that, in the thermal stratification period, the penetration of dissolved oxygen and nutrients in the water will be blocked by the thermocline, resulting in the oxycline and bottom hypoxia phenomena, and, at the same time, nutrients will also form a stratification phenomenon [38,39]. In this study, the number of species showed a gradually decreasing trend from the I-VI layers (Figure 4), which was related to the existence of the thermocline. ...
In order to study the vertical distribution characteristics of phytoplankton in the Danjiangkou Reservoir, the water source of the Middle Route Project of the South-North Water Diversion, seven sampling sites were set up in the Reservoir for quarterly sampling from 2017 to 2019, and water environment surveys were conducted simultaneously. The results showed that 157 species (including varieties) were identified, belonging to 9 phyla and 88 genera. In terms of species richness, Chlorophyta had the largest number of species, accounting for 39.49% of the total species. The Bacillariophyta and Cyanobacteria accounted for 28.03% and 13.38% of the total species, respectively. From the whole Danjiangkou Reservoir, the total phytoplankton abundance varied from 0.09 × 102 to 20.01 × 106 cells/L. In the vertical distribution, phytoplankton were mainly observed in the surface–thermospheric layer (I–II layer) and the bottom layer, while the Shannon–Wiener index showed a trend of gradually decreasing from the I–V layer. The Surfer model analysis showed that there was no significant stratification in the Q site’s water temperature (WT) and dissolved oxygen (DO) levels in the water diversion area during the dynamic water diversion process. A canonical correspondence analysis (CCA) showed that DO, WT, pH, electrical conductivity (Cond), chemical oxygen demand (CODMn), total phosphorus (TP), ammonia nitrogen (NH4+-N), and total nitrogen (TN) had significant effects on the vertical distribution of phytoplankton (p < 0.05). A partial Mantel analysis showed that the vertical distribution of the phytoplankton community was related to WT, and the phytoplankton community structure at the other sites, except for Heijizui (H) and Langhekou (L), was affected by DO. This study has positive significance for exploring the vertical distribution characteristics of a phytoplankton community in a deep-water dynamic water diversion reservoir.
... Temperature was a significant parameter in most of the models we fit to the data, however temperature explained only a modest percentage of the variance. This dampened response to temperature could be due to the large range of temperatures throughout the year that golden shiners experience in the Missouri region (Jones et al. 2011, Knouft et al. 2021. Despite this large range in temperature tolerance we still found a significant effect of temperature, suggesting that temperature could have a stronger effect on fish species with tolerance to a smaller range of temperature. ...
Temperature is highly influential on the physiology and behaviour of ectotherms. In fish, temperature affects social interactions such as schooling behaviour, a common defence against predation. However, the effect of temperature on the ability of schooling fish to collectively respond to a predator is unknown. Here we used a loom stimulus to simulate an approaching predator that elicited a fleeing response in schooling fish over a range of water temperatures (9–29°C) and group sizes (1–16 fish). While speed and acceleration always exhibited a positive curvilinear response to temperature, the optimal temperature at which performance peaked was different during the predation threat versus when they were unperturbed. Similarly, group‐level metrics were sensitive to temperature immediately after a loom stimulus but showed no response to temperature during unperturbed swimming. The time taken for fish to respond to the loom stimulus was minimal at 20°C. The proportion of fish that startled, during a loom, peaked at 13°C – around the same temperature at which speed, and acceleration was maximum. Taken together, our results suggest that ectothermic fish may be able to compensate for their slower swim speeds at lower temperatures during unperturbed swimming by increasing their sensitivity to startle in response to a predation threat. More generally, we show that in ectotherms the qualitative and quantitative effect of temperature on a behavioural trait may be dependent on the context.
... Water samples with DO > 2 mg/L at most sampling sites (Table S3) were not conducive to denitrification. The presence of the thermocline (Fu 2020) impeded energy exchange and material cycling in the upper and lower water layers (Jones et al. 2011;Zhang et al. 2015b), resulting in a small proportion of bottom water samples with DO < 2 mg/L and T < 5 °C (Table S3). Temperature indirectly affects denitrification rates by influencing molecular dynamics, physiological adaptation of microbial strains, and changes in microbial assemblages (Hall et al. 2010). ...
Human activities and climate change input more reactive nitrogen into alpine lakes. Alpine saline lakes are usually located in endorheic watersheds at high-altitude areas, with no other drainage methods than evaporation, and are prone to accumulate nutrients. Meanwhile, alpine saline lakes are usually oligotrophic and sensitive to reactive nitrogen inputs, and even modest reactive nitrogen inputs may have significant effects on them, such as eutrophication. Nitrate is the main form of reactive nitrogen in lakes; therefore, clarifying the sources and transformations of nitrate in alpine saline lakes is important to prevent or mitigate eutrophication in alpine saline lakes. In this study, the sources and transformations of nitrate in Qixiangcuo Lake and its inflow rivers in the northern Tibetan Plateau were identified using dual nitrate isotopes and hydrochemistry. The results show that (1) the ranges of NO3− concentrations, δ15N−NO3− , and δ18O−NO3− values were 3.6 ~ 26.1 μg/L, −10.5 to +6.0‰, and −10.4 to +9.2‰ in Qixiangcuo Lake and 194.4 ~ 728.1 μg/L, +5.8 ~ +8.8‰, and −1.9 to +2.4‰ in its inflow rivers, respectively. The NO3− concentrations and δ15N−NO3− values were significantly lower in Qixiangcuo Lake than in its inflow rivers (P < 0.05). (2) The main sources of nitrate in both surface water and bottom water of Qixiangcuo Lake were ammonium in atmospheric deposition (mean probability estimate (MPE) 41.0% and 32.2%, respectively) and livestock manure (MPE 28.9% and 21.7%, respectively). The main sources of nitrate in the inflow rivers of Qixiangcuo Lake were domestic sewage (MPE 35.7%) and livestock manure (MPE 29.6%). (3) The main nitrogen transformation process in Qixiangcuo Lake was nitrification. The conservative mixing of multiple sources controlled the nitrate concentration and isotopic composition of Qixiangcuo Lake. Improvement in grazing area planning and the installation of sewage treatment facilities are effective measures to prevent eutrophication in Qixiangcuo Lake and its inflow rivers.
... As for the process of production and mitigation of N 2 O in wastewater treatment plant, the mechanism of N 2 O production have been investigated (Chen et al. , 2021Ni and Yuan 2015), however, when it referred to stratified reservoirs, thermal and dissolved oxygen (DO) stratification may have great effects on N 2 O production (Deemer et al., 2011;Jones et al., 2011). Research on thermal and DO stratification has examined the spatiotemporal variation mechanism in N 2 O production Liu et al., 2017), N 2 O dynamics in water layers (Beaulieu et al. 2014(Beaulieu et al. , 2015, the impact of reservoir management on N 2 O production (Bao et al., 2015;Yu et al., 2018). ...
Reservoirs are hotspots of greenhouse gas (GHG) emission, and the global warming potential of nitrous oxide (N2O) is higher than that of CO2 and CH4. To promote our understanding of the relationship of biotic and abiotic environments with the mechanism of N2O production in a quintessential karst reservoir, water samples were collected in a weak thermal stratification period (WTSP) and a strong thermal stratification period (STSP) in 2019 in the Longtan (LT) Reservoir. In the LT Reservoir, higher N2O concentrations and functional gene abundances (nitrification and denitrification genes) were found in the STSP than in the WTSP. In detail, the N2O concentrations were 10.45 ± 6.99 nmol L⁻¹ and 23.77 ± 7.06 nmol L⁻¹ in the WTSP and STSP, respectively; the functional gene abundances were higher in the STSP than in the WTSP in each water layer. During the STSP, the nitrification gene abundances were higher at a 30 m depth than at a 100 m depth, while denitrification gene abundances were higher at 100 m than at 30 m. Along the river, N2O flux was significantly higher in the LT Reservoir’s released water than in upstream water in the STSP, while it exhibited no significant difference in whole river-reservoir system in the WTSP. In conclusion, stratification and nitrogen (N) loading facilitated higher N2O production in STSP than in WTSP; different N transformation processes and sources of N2O were present between the water layers above and below the thermocline (in deep water); finally, the river-reservoir system here acted as a source of N2O release to the atmosphere in the STSP, while it exhibited different emission patterns in the WTSP. This work highlights the mechanism of N2O production and functional gene abundances in water layers during different thermal stratification periods, which will help to elucidate the biotic and abiotic environment in a karst deep-water reservoir and will help to inform N2O production mechanisms in other reservoirs worldwide. More sampling campaigns and the denitrification potential of sediment were worthy of conducting to comprehend the mechanisms of N2O production from stratification to turnover period in the reservoir.
... High eutrophication rates in the agriculturally dominated Midwest (Mitsch et al., 2001;Jones et al., 2008a) make these reservoirs precursors of future surface water quality, as ∼94% of reservoirs in the study region are classified as mesotrophic, eutrophic, or hypertrophic (Jones et al., 2008b). Moreover, since Midwestern reservoirs regularly experience hypolimnetic anoxia during summer stratification (Jones et al., 2011), they may also forewarn how future light and nutrient dynamics will affect phytoplankton biomass and primary productivity. ...
... ( Table 5). Hypolimnetic anoxia is common in Missouri reservoirs during summer stratification (Jones et al., 2011). We observed this in both summers, wherein every warm monomictic reservoir (n = 31) experienced hypolimnetic anoxia with DO concentrations < 0.5 mg L −1 . ...
In lakes and reservoirs, climate change increases surface water temperatures, promotes thermal stability, and decreases hypolimnetic oxygen. Increased anthropogenic land-use and precipitation enhance nutrient and sediment supply. Together, these effects alter the light and nutrient dynamics constraining phytoplankton biomass and productivity. Given that lake and reservoir processes differ, and that globally, reservoir numbers are increasing to meet water demands, reservoir-centric studies remain underrepresented. In the agricultural Midwest (United States), ubiquitous reservoirs experience eutrophy and hypolimnetic anoxia. Here, we explore influences of eutrophication and land-use on the proximate light and nutrient status of phytoplankton communities in 32 Missouri reservoirs. Light and nutrient status indicators include mixed layer irradiance, phosphorus (P) and nitrogen (N) stoichiometry/debts, photosynthetic efficiency, and photosynthetic-irradiance parameters. Contributing to the ongoing P vs. N and P management debate, we evaluate if phytoplankton biomass and productivity are constrained by light, P, N, or a combination thereof, across gradients of trophic status and land-use during two contrasting wet and dry summers. Despite agricultural prevalence, P-deficiency is more prominent than either N- or light-deficiency. In 2018, ∼46% of samples were P-deficient with ∼36% indicating neither light nor nutrient deficiency. Gross primary productivity per unit chlorophyll-a (GPPB) demonstrates negative relationships with nutrients, biomass, and turbidity, and positive relationships with light availability. GPPB is highest in oligotrophic reservoirs where light utilization efficiency is also highest. Overall, phytoplankton biomass and productivity appear constrained by P and light, respectively. If Midwestern reservoirs are precursors of future inland waters affected by climate change and eutrophication, our crystal ball indicates that both P and light will be important regulators of phytoplankton dynamics and subsequent water quality.
... Reservoir study at the University of Missouri started in 1975 and continues to the present; emphasis has been on quantifying how morphology, hydrology, and edaphic factors account for trophic state and particulate inorganic matter, and determining the variation of these metrics, within and among impoundments, over time (Jones and Knowlton 1993, 2008b, 2011a, 2011b. This information adds to our understanding of processes in artificial lakes, informs management efforts, and provides a basis to predict water quality in proposed impoundments. ...
... Most reservoirs stably stratify by mid May, but few are sufficiently deep to have hypolimnia with near-uniform temperatures (Jones et al. 2011a). showing mean long-term total phosphorus concentrations (mg/L) for each reservoir. ...
... Cross-system variation in mixed depth and thermocline depth was largely accounted for by maximum length and maximum depth of these basins. Most natural lakes with similar features would not stratify; less wind exposure in impounded valleys and modest water clarity likely account for this difference (Jones et al. 2011a). Surface temperatures are usually >28 C by midsummer, and values >30 C occur (12% of 8008 measurements). ...
Jones JR, Thorpe AP, Obrecht DV. 2020. Limnological characteristics of Missouri reservoirs: synthesis of a long-term assessment. Lake Reserv Manage. XX:XX–XX.
Missouri reservoirs reflect their edaphic location in the midcontinent ecotone between historic prairies and forests. Most are small (median surface area of 28 ha) but provide essential services in a region with few natural lakes. Long-term summer monitoring data (1978–2016) show that they span the full trophic state range, with oligotrophic reservoirs in deep, forested valleys and eutrophic–hypereutrophic impoundments in agricultural regions. In regression analysis, row crop (a surrogate for agricultural nutrient loss) along with depth and flushing rate accounted for some two-thirds of variation among reservoir nutrients. Hydrology is a strong influence; total phosphorus (TP) effectively doubles between flushing rates of 0.25/yr and 2/yr when holding land cover and depth constant. Temporal variation characterizes these impoundments; many show >3-fold range in mean summer trophic state metrics, which is influenced by the volume and timing of annual inflow. This variation may mask gradual nutrient-driven changes in trophic state; based on simulation, doubling chlorophyll (Chl) in a given lake over 20 yr could be undetectable with routine summer monitoring. Some two-thirds of cross-system variation in mean Chl was explained by TP, and inorganic solids further reduced variation (negative coefficient). On average, Chl:TP ratios increased from 0.28 to 0.48 during summer, coincident with a decline in inorganic solids. Inorganic particulates largely determine Secchi transparency and can result in light limitation of phytoplankton. Small reservoirs cover nearly double the area of major impoundments worldwide and are known for an intensity of ecological processes, making this information relevant beyond the region.
... Obrecht, personal communication). The hypolimnion of deep reservoirs can become anoxic during a large part of summer, and the anoxic volume and mixing time is expected to differ among reservoirs (Jones et al. 2011). In the reservoirs examined, mean reservoir depth was not significantly related to tHg variability among reservoirs, because depth was strongly correlated with both surface area and water volume. ...
Large-bodied predatory sportfish from Missouri reservoirs can contain elevated methylmercury concentrations that are of concern to the health of consumers. The concentration of total mercury (tHg) in the muscle (which > 95% is in the methylated-Hg form) of harvestable-sized largemouth bass (Micropterus salmoides; LMB) was examined to determine which factors contributed to the variability of tHg concentration in sportfish populations among Missouri reservoirs. Mean tHg concentrations in LMB from each reservoir were compared to physical and chemical characteristics of the reservoir and to biological attributes of each LMB population. Low concentrations of tHg (70–170 ng/g wet weight) in LMB from large reservoirs (surface area ≥ 35,680 acres) were likely related to the dilution of chemical Hg forms with water volume and depth. The highest tHg concentrations in LMB (268–542 ng/g) were from reservoirs with low particulate inorganic material (< 1.5 mg/L) and chlorophyll a concentrations (< 14.6 μg/L), and from LMB populations with a low proportion of large fish (proportional size distribution of LMB > 12 inches was < 33%). These relationships suggest that resource competition among LMB likely contributed to tHg bioaccumulation in reservoirs < 930 acres. Small reservoirs located in northern Missouri also may have greater methylation potential due to warmer water temperatures and anoxic conditions, but more data are needed to confirm these interactions. Fish consumption advisories for reservoirs with large surface area and volume could be reduced from one fish meal per month to one per week. To improve Missouri fisheries and protect consumers, management strategies to limit methylation and improve fish growth should be considered to reduce methylmercury bioaccumulation in small- and medium-sized reservoirs.
... Anthropogenic nutrient loads have increased phytoplankton growth and the subsequent decomposition of the associated organic material has increased hypolimnetic hypoxia in lakes since the 1850s (Jenny et al. 2016). Cold water fish require access to cool water refugia, and these areas are rendered uninhabitable by hypoxia (Coutant 1985;Müller and Stadelmann 2004;Plumb and Blanchfield 2009;Jones et al. 2011;Arend et al. 2011). Warm-water fish generally tolerate hypoxia but hypoxia, coupled with a warm epilimnion, can cause fish species that require cooler temperatures to experience a 'thermal-dissolved oxygen squeeze' (after Coutant 1985) requiring them to select between suboptimal temperatures or oxygen (Arend et al. 2011). ...
... Specifically, managers should have tools to determine how a reduction in nutrient loads and associated changes in observed phytoplankton abundance would improve dissolved oxygen concentrations. Relationships between nutrient concentrations and chlorophyll (Chl) are readily available (Jones and Bachmann 1976) but empirical relationships between Chl and dissolved oxygen concentrations are rarely reported (Jones et al. 2011). ...
... This estimate of DO m necessarily includes some measurements in the metalimnion, which may increase our estimates of DO m relative to studies that can focus only on the hypolimnion. However, many lakes in the MO and NLA datasets were too shallow to maintain a hypolimnion with small vertical temperature gradients (Jones et al. 2011), and therefore, an approach for consistently defining the hypolimnion for all lakes was not available (Quinlan et al. 2005), and we opted to include all depths below the thermocline in our calculation of DO m . The depth of the lake below the thermocline was also computed as the difference between the maximum depth recorded for each lake and the mean depth of the upper boundary of the metalimnion as defined above. ...
Eutrophication increases hypoxia in lakes and reservoirs, causing deleterious effects on biological communities. Quantitative models would help managers develop effective strategies to address hypoxia issues, but most existing models are limited in their applicability to lakes with temporally resolved dissolved oxygen data. We describe a hierarchical Bayesian model that predicts dissolved oxygen in lakes based on a mechanistic understanding of the factors that influence the development of hypoxia during summer stratification. These factors include the days elapsed since stratification, dissolved organic carbon concentration, lake depth, and chlorophyll concentration. We demonstrate that the model can be fit to two datasets: one in which temporally resolved dissolved oxygen profiles were collected from 20 lakes in a single state and one in which single profiles were collected from 381 lakes across the United States. Analyses of these two datasets yielded similar relationships between volumetric oxygen demand and chlorophyll concentration, suggesting that the model structure appropriately represented the effects of eutrophication on oxygen depletion. Combining both datasets in a single model further improved the precision of predictions.
