Tributary Phosphorus Research Articles

Connecting past, present, and future trends of hydraulic and phosphorus loading in the Bay of Quinte tributaries, Ontario, Canada

Study regionThe Bay of Quinte watershed, located on the northeastern shore of Lake Ontario, Canada. Special focus is placed on the Napanee River and Wilton Creek catchments, where the presence of a subterranean network of conduits that facilitate groundwater-surface water interactions is conducive to an increase in the delivery of nutrients during storm events and can exacerbate the risk of eutrophication. Study focusDevelopment of a rigorous modelling framework that can advance our understanding of past and present trends of streamflow and tributary phosphorus (P) concentration and loads. We also analyze future streamflow rates and P export trends in order to guide the long-term watershed management in the area. Our analysis is carried out through a comprehensive combination of data-driven and process-based models. Novel hydrological insights for the regionRetrospective analysis provides evidence of a recent increase in the impact of nonpoint-source P pollution. General Circulation Models suggest a future increase in both temperature minima and maxima relative to present conditions (2002–2018). Precipitation projections are indicative of increased frequency of occurrence of high extreme precipitation events during the summer and mid-fall, when the Bay of Quinte is more susceptible to undesirable ecological shifts. Our study predicts a seasonality shift in the streamflow, with the spring freshet occurring earlier in the year accompanied by higher flow rates in the local creeks for the winter and early spring. We also examined the relationship between precipitation and streamflow across varying levels of flow regulation. Our analysis indicates that our predictive capacity declines with increased flow regulation as well as when streamflow rates are predicted by contemporaneous precipitation values.

A New Approach to Predict Tributary Phosphorus Loads Using Machine Learning- and Physics-Based Modeling Systems.

Tributary phosphorus (P) loads are one of the main drivers of eutrophication problems in freshwater lakes. Being able to predict P loads can aid in understanding subsequent load patterns and elucidate potential degraded water quality conditions in downstream surface waters. We demonstrate the development and performance of an integrated multimedia modeling system that uses machine learning (ML) to assess and predict monthly total P (TP) and dissolved reactive P (DRP) loads. Meteorological variables from the Weather Research and Forecasting (WRF) Model, hydrologic variables from the Variable Infiltration Capacity model, and agricultural management practice variables from the Environmental Policy Integrated Climate agroecosystem model are utilized to train the ML models to predict P loads. Our study presents a new modeling methodology using as testbeds the Maumee, Sandusky, Portage, and Raisin watersheds, which discharge into Lake Erie and contribute to significant P loads to the lake. Two models were built, one for TP loads using 10 environmental variables and one for DRP loads using nine environmental variables. Both models ranked streamflow as the most important predictive variable. In comparison with observations, TP and DRP loads were predicted very well temporally and spatially. Modeling results of TP loads are within the ranges of those obtained from other studies and on some occasions more accurate. Modeling results of DRP loads exceed performance measures from other studies. We explore the ability of both ML-based models to further improve as more data become available over time. This integrated multimedia approach is recommended for studying other freshwater systems and water quality variables using available decadal data from physics-based model simulations.

Modeling the interactive effects of nutrient loads, meteorology, and invasive mussels on suitable habitat for Bighead and Silver Carp in Lake Michigan

Anthropogenic stressors that affect ecological processes in the Laurentian Great Lakes can impact their susceptibility to bioinvasions. Bighead Hypophthalmichthys nobilis and Silver Carp H. molitrix, collectively ‘bigheaded carps’ (BHC), are planktivorous fishes threatening to invade Lake Michigan. While previous studies indicate the lake contains habitat suitable for BHC growth, there is a need to understand how anthropogenic-driven changes to the abiotic and biotic environment could alter its vulnerability to BHC. We applied a spatially explicit model of BHC growth rate potential (GRP; g g−1 d−1) to nine biophysical model scenarios to evaluate changes in habitat suitability in Lake Michigan. Scenarios differed in meteorology (cool, reference, warm), annual tributary phosphorus loads (0, 3300, and 5600 MTA), and the presence/absence of invasive dreissenid mussels. Mussel effects on BHC GRP relied on their contact with the surface mixed layer (SML), the depth of which was affected by meteorology. The warm year advanced the expansion of Bighead Carp habitat by increasing temperature-dependent foraging rates and lessening the time of competitive interaction with mussels due to earlier stratification separating mussels from the SML. Phosphorus loads were the most influential driver of the lake’s suitability. Compared to present conditions, we estimate BHC could have grown an additional 8–40% annually in the 1980s when mussels were not in the lake and phosphorus loads were higher. Our study demonstrates how climate change and nutrient enrichment can increase Lake Michigan’s vulnerability to BHC by affecting thermal regime and productivity, thereby limiting negative effects of dreissenid mussels on BHC growth.

Spatial and temporal patterns in macronutrient concentrations and stoichiometry of tributaries draining the lower Great Lakes-St. Lawrence basin

Nutrient management in the Great Lakes-St. Lawrence basin has focused on the reduction of tributary phosphorus inputs to control lake eutrophication. However, the regional implications of nutrient enrichment on stream eutrophication and management remain understudied. We compared nutrient concentrations and stoichiometric ratios of carbon, nitrogen, and phosphorus to evaluate spatial and temporal patterns in the potential for nutrient limitation in streams of the lower Great Lakes-St. Lawrence basin in Ontario, Canada. Monitoring data from 127 streams was used to describe macronutrient concentrations and stoichiometry over a 10-year period (2007–2016). Nutrient enrichment was widespread as 65% and 68% of studied streams had nitrogen and phosphorus concentrations above regional guidelines, respectively. Macronutrient stoichiometry indicated that 35% of streams were depleted for phosphorus and 65% were co-depleted for nitrogen and phosphorus relative to the Redfield ratio. However, algal production in most streams was likely nutrient saturated such that only 2% of streams showed the potential for phosphorus limitation and 21% for nitrogen and phosphorus co-limitation. Temporal assessment of individual nutrients that were depleted indicated minimal variation within most streams. In contrast, macronutrient stoichiometry was associated with spatial patterns in catchment land-cover whereby a shift from nitrogen and phosphorus co-depletion to phosphorus depletion occurred with increasing agriculture and decreasing natural and wetland cover. Our results suggest that phosphorus reductions alone may be insufficient to manage stream eutrophication in the Great Lakes-St. Lawrence basin and that dual nutrient reductions needed to improve stream conditions may be achievable through land-cover management.

Long-Term Phosphorus Loading and Springtime Temperatures Explain Interannual Variability of Hypoxia in a Large Temperate Lake.

Anthropogenic eutrophication has led to the increased occurrence of hypoxia in inland and coastal waters around the globe. While low dissolved oxygen conditions are known to be driven primarily by nutrient loading and water column stratification, the relative importance of these factors and their associated time scales are not well understood. Here, we explore these questions for Lake Erie, a large temperate lake that experiences widespread annual summertime hypoxia. We leverage a three-decade data set of summertime hypoxic extent (1985-2015) and examine the role of seasonal and long-term nutrient loading, as well as hydrometeorological conditions. We find that a linear combination of decadal total phosphorus loading from tributaries and springtime air temperatures explains a high proportion of the interannual variability in average summertime hypoxic extent (R2 = 0.71). This result suggests that the lake responds primarily to long-term variations in phosphorus inputs, rather than springtime or annual loading as previously assumed, which is consistent with internal phosphorus loading from lake sediments likely being an important contributing mechanism. This result also demonstrates that springtime temperatures have a substantial impact on summertime hypoxia, likely by impacting the timing of onset of thermal stratification. These findings imply that management strategies based on reducing tributary phosphorus loading would take several years to reap full benefits, and that projected future increases in temperatures are likely to exacerbate hypoxia in Lake Erie and other temperate lakes.

Influence of invasive quagga mussels, phosphorus loads, and climate on spatial and temporal patterns of productivity in Lake Michigan: A biophysical modeling study

AbstractWe applied a three‐dimensional biophysical model to Lake Michigan for the years 2000, 2005, and 2010 to consider the mechanisms controlling spatial and temporal patterns of phytoplankton abundance (chlorophyll a) and lake‐wide productivity. Model skill was assessed by comparison to satellite‐derived Chl a and field‐measured water quality variables. We evaluated model sensitivity to scenarios of varying mussel filter feeding intensity, tributary phosphorus loads, and warm vs. cool winter‐spring climate scenarios. During the winter‐spring phytoplankton bloom, spatial patterns of Chl a were controlled by variables that influenced surface mixed layer depth: deep mixing reduced net phytoplankton growth through light limitation and by exposing the full water column to mussel filter feeding. Onset of summer and winter stratification promoted higher surface Chl a initially by increasing mean light exposure and by separating the euphotic zone from mussels. During the summer stratified period, areas of relatively high Chl a were associated with coastal plumes influenced by tributary‐derived nutrients and coastal upwelling‐downwelling. While mussels influenced spatial and temporal distribution of Chl a, lake‐wide, annual mean primary production was more sensitive to phosphorus and warm/cool meteorology scenarios than to mussel filter feeding scenarios. Although Chl a and primary production declined over the quagga mussel invasion, our results suggest that increased nutrient loads would increase lake‐wide productivity even in the presence of mussels; however, altered spatial and temporal patterns of productivity caused by mussel filter feeding would likely persist.

Tributary phosphorus monitoring in the U.S. portion of the Laurentian Great Lake Basin: Drivers and challenges

This paper examines the tributary monitoring network currently in place for sampling the amount of phosphorus entering the U.S. Great Lakes, focusing on the challenges faced by the agencies and organizations responsible for maintaining the network. The tributaries that are monitored vary in terms of flow, the size and terrain of the watershed being drained, and patterns of land use. Data generated by this network are used by researchers to compute lake-wide phosphorus loads. In this work, the primary drivers and challenges associated with operating an effective phosphorus tributary monitoring program were investigated through interviews with stakeholders responsible for managing a portion of the existing network. Based on these interviews, the authors identify three recommendations that policy makers interested in maintaining an effective phosphorus monitoring network in the Great Lakes should consider. The first is to provide states with incentives to support the long-term monitoring that is required to estimate phosphorus loads in tributaries to the Great Lakes; currently, most states design their programs to meet the requirements of the Clean Water Act, which results in patterns of sampling that are not necessarily useful for computing loads. The second recommendation is to facilitate the creation of a monitoring protocol that generates enough samples to identify trends and quantify loads at a level of certainty necessary for use in statistical models and load control programs. Finally, funding mechanisms capable of supporting long-term monitoring programs need to be established, with programs in Michigan and Minnesota serving as potential models.

Tributary phosphorus loading to Lake Ontario

Tributary phosphorus (P) loading was estimated for 145 Canadian and American streams entering Lake Ontario and was compared with historical P loads of the Niagara River. The 145 Lake Ontario tributaries contributed 2606mT/year of P, with the U.S. tributaries contributing 1411mT/year and the Canadian tributaries contributing 1195mT/year. In New York, the largest tributary sources of total phosphorus (TP) were from the Genesee River (417mT/year), followed by the Oswego River (336mT/year) and the Black River (135mT/year). In Ontario, the largest tributary sources of TP were from the Trent River (200mT/year), the Humber River (93.0mT/year), and the Welland Canal (80.8mT/year). Phosphorus loading from both Canadian and American wastewater treatment plants was 781mT in 2008. The total P load of tributaries (2606mT/year) to Lake Ontario was 234% higher than that of wastewater treatment plants and was 67.5% of the 1982 Niagara River P load and 50.3 to 70.6% of the 1999 and 2004 Niagara River P loads. While the P load from the Niagara River connecting channel is important to the overall trophic status of the offshore of Lake Ontario, the impact of tributaries on water chemistry and ecology of the nearshore and embayments of Lake Ontario is potentially great and is being increasingly recognized as a driver of nearshore conditions.

Dedication

Tributary phosphorus (P) loading was estimated for 145 Canadian and American streams entering Lake Ontario and was compared with historical P loads of the Niagara River. The 145 Lake Ontario tributaries contributed 2606 mT/year of P, with the U.S. tributaries contributing 1411 mT/year and the Canadian tributaries contributing 1195 mT/year. In New York, the largest tributary sources of total phosphorus (TP) were from the Genesee River (417 mT/year), followed by the Oswego River (336 mT/year) and the Black River (135 mT/year). In Ontario, the largest tributary sources of TP were from the Trent River (200 mT/year), the Humber River (93.0 mT/year), and the Welland Canal (80.8 mT/year). Phosphorus loading from both Canadian and American wastewater treatment plants was 781 mT in 2008. The total P load of tributaries (2606 mT/year) to Lake Ontario was 234% higher than that of wastewater treatment plants and was 67.5% of the 1982 Niagara River P load and 50.3 to 70.6% of the 1999 and 2004 Niagara River P loads. While the P load from the Niagara River connecting channel is important to the overall trophic status of the offshore of Lake Ontario, the impact of tributaries on water chemistry and ecology of the nearshore and embayments of Lake Ontario is potentially great and is being increasingly recognized as a driver of nearshore conditions.

Do Invasive Mussels Restrict Offshore Phosphorus Transport in Lake Huron?

Dreissenid mussels were first documented in the Laurentian Great Lakes in the late 1980s. Zebra mussels (Dreissena polymorpha) spread quickly into shallow, hard-substrate areas; quagga mussels (Dreissena rostriformis bugensis) spread more slowly and are currently colonizing deep, offshore areas. These mussels occur at high densities, filter large water volumes while feeding on suspended materials, and deposit particulate waste on the lake bottom. This filtering activity has been hypothesized to sequester tributary phosphorus in nearshore regions reducing offshore primary productivity. We used a mass balance model to estimate the phosphorus sedimentation rate in Saginaw Bay, a shallow embayment of Lake Huron, before and after the mussel invasion. Our results indicate that the proportion of tributary phosphorus retained in Saginaw Bay increased from approximately 46-70% when dreissenids appeared, reducing phosphorus export to the main body of Lake Huron. The combined effects of increased phosphorus retention and decreased phosphorus loading have caused an approximate 60% decrease in phosphorus export from Saginaw Bay to Lake Huron. Our results support the hypothesis that the ongoing decline of preyfish and secondary producers including diporeia (Diporeia spp.) in Lake Huron is a bottom-up phenomenon associated with decreased phosphorus availability in the offshore to support primary production.

Factors that Influence Phosphorus, Filamentous Cyanobacteria and Odor in McDaniel Lake, a Southwest Missouri Water Supply Reservoir, 1983–2002

McDaniel Lake is a 1.12 km2 water supply reservoir subject to occasional taste and odor problems. This paper reviews data for 1983–2002, with a focus on summer, and uses regression analysis to identify predictors of lake phosphorus concentration, cyanobacteria filament concentration and odor production. Cattle were identified as the main source of excess tributary phosphorus, but lake phosphorus was significantly influenced by factors other than tributary phosphorus, including lake level, lake bottom temperature and wind. Likewise, cyanobacteria filament concentration was significantly influenced by factors other than lake phosphorus, including sunshine, air temperature and lake-bottom temperature. Odor (methylisoborneol plus geosmin) production was most strongly associated with high cyanobacteria filament counts and abundant sunshine.

Reducing Sediment and Phosphorus in Tributary Waters with Alum and Polyacrylamide

The Salton Sea is the largest inland water body in California, covering an area of 980 km(2). Inflow to the Salton Sea (1.6 km(3) yr(-1)) is predominately nutrient-rich agricultural wastewater, which has led to eutrophication. Because internal phosphorus release from the bottom sediments is comparatively low and external phosphorus loading to the Salton Sea is high, reduction of tributary phosphorus is expected to reduce algal blooms, increase dissolved oxygen, and reduce odors. Removing both dissolved phosphorus and phosphorus-laden sediment from agricultural drainage water (ADW) should decrease eutrophication. Both alum and polyacrylamide (PAM) are commonly used in wastewater treatment to remove phosphorus and sediment and were tested for use in tributary waters. Laboratory jar tests determined PAM effectiveness (2 mg L(-1)) for turbidity reduction as cationic > anionic = nonionic. Although cationic PAM was the most effective at reducing turbidity at higher speeds, there was no observed difference between the neutral and anionic PAMs at velocity gradients of 18 to 45 s(-1). Alum (4 mg L(-1) Al) reduced turbidity in low energy systems (velocity gradients < 10 s(-1)) by 95% and was necessary to reduce soluble phosphorus, which comprises 47 to 100% of the total P concentration in the tributaries. When PAM was added with alum, the anionic PAM became ineffective in aiding flocculation. The nonionic PAM (2 mg L(-1)) + alum (4 mg L(-1) Al) is recommended to reduce suspended solids in higher energy systems and reduce soluble P by 93%.

A preliminary modeling analysis of water quality in Lake Okeechobee, Florida: Diagnostic and sensitivity analyses

A deterministic mass balance model for nutrient and phytoplankton dynamics was previously developed and calibrated to a comprehensive set of field data for Lake Okeechobee. In the present study, diagnostic and sensitivity analyses were conducted with the calibrated model to better understand factors controlling phytoplankton and load-response dynamics in the lake. Phytoplankton growth rate limitation due to underwater light attenuation appears to be substantially greater than growth rate limitation due to non-optimal phosphorus concentrations. Phytoplankton biomass appears strongly controlled by the supply rate of dissolved available phosphorus to the water column. The dynamics of total phosphorus and chlorophyll a concentrations in the lake are strongly influenced by sediment-water phosphorus fluxes. There is a wide range of uncertainty in responses of total phosphorus and cholorophyll a concentrations to changes in tributary phosphorus loadings. Much of this uncertainty is due to a lack of quantitative understanding of sediment responses to changes in tributary loadings. Other important factors are inter-annual variability in hydrometeorological conditions and the potential influence of wind-induced resuspension of particulate phosphorus. Responses of total phosphorus and chlorophyll a concentrations for a given change in tributary loading depend not only on the magnitide of the loading change, but also on the time frame after the loading change due to a lag in sediment response. Load-response predictions for Lake Okeechobee must take into account changes in available phosphorus loadings to the water column, and must be premised on assumptions for changes in internal phosphorus loadings from the sediments. Results from this preliminary modeling analysis are provisional in that they do not include potential nitrogen limitation, potential interactions between phosphorus and nitrogen, or phytoplankton responses to potential nitrogen fixation.

Alternative Methods for Estimation of Phosphorus Loadings

There exists an assortment of methods for estimating tributary phosphorus mass loadings. The methods vary widely in complexity and sophistication. Selection of an appropriate methodology should be based upon the nature and extent of the available data sets, computational requirements, and the intended application. Several methods were employed for estimating annual phosphorus loadings from the Colorado River to Lake Buchanan, the uppermost reservoir in the chain of Highland Lakes in Central Texas. The historical data set is examined for relationships between flow and phosphorus loading. Loads derived from the various methods are compared for the period 1968–1982. The load-flow relationship developed from the available data set is selected to represent the long-term historical phosphorus loads.