SFS Annual Meeting

6/04/2024  |   13:30 - 13:45   |  Philadelphia Ballroom

Effects of agricultural land use types and intensities on river biodiversity and ecosystem health: A large-scale analysis River health, as indicated by riverine biota, can be strongly impacted by agricultural land use of catchments. However, most large-scale studies do not reflect differences in crop types and cultivation intensities, although case studies highlight clear differences. We aggregated Europe´s agricultural activities into 20 Areas of Farming related Freshwater Impacts, based on biomass output and freshwater stress: nutrient surplus, pesticides toxicity, water abstraction, hydromorphological alteration; and derived agricultural pressure profiles for more than 50,000 European catchments. Accounting for the different pressure profiles could nearly double the correlation between agriculture and biota response compared to sheer agriculture. For more in-depth analysis, we used a Germany-wide dataset of about 7,700 sites with information on macroinvertebrates, macrophytes, and diatoms and related it to the adjacent land use. For all organism groups, effects of agriculture were stronger than those of urban land use. Pesticides have been identified most important for macroinvertebrates and macrophytes, while diatoms appear more sensitive to nutrients, which was reflected by crop specific effects. Hence, incorporating crop-specific pesticide- and nutrient application rates could slightly increase the correlative strength of agriculture (up to an increase of explanatory power of R² by 0.14 for diatoms). Strong differences were found among ecoregions with strongest explanatory power of agriculture in small mountain streams of up to R² = 0.43 for macroinvertebrates. These differential effects show that agriculture clearly impairs river biota displaying strong associations with agrochemicals. Consequently, to protect river biota, a shift to more sustainable agricultural practices like reducing pesticide application is urgently required.

Christian Schürings (Primary Presenter/Author), University of Duisburg-Essen, Faculty of Biology Aquatic Ecology Universitätsstrasse 5 D-45141 Essen Germany, christian.schuerings@uni-due.de;

Sebastian Birk (Co-Presenter/Co-Author), University of Duisburg-Essen, Faculty of Biology Aquatic Ecology Universitätsstrasse 5 D-45141 Essen Germany, sebastian.birk@uni-due.de;

Jochem Kail (Co-Presenter/Co-Author), University of Duisburg-Essen, Faculty of Biology Aquatic Ecology Universitätsstrasse 5 D-45141 Essen Germany, jochem.kail@uni-due.de;

Willem Kaijser (Co-Presenter/Co-Author), University of Duisburg-Essen, Faculty of Biology Aquatic Ecology Universitätsstrasse 5 D-45141 Essen Germany, willem.kaijser@uni-due.de;

Nele Markert (Co-Presenter/Co-Author), University of Duisburg-Essen, Faculty of Biology Aquatic Ecology Universitätsstrasse 5 D-45141 Essen Germany, nele.markert@stud.uni-due.de;

Daniel Hering (Co-Presenter/Co-Author), University of Duisburg-Essen, Faculty of Biology Aquatic Ecology Universitätsstrasse 5 D-45141 Essen Germany, daniel.hering@uni-due.de;

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6/04/2024  |   13:45 - 14:00   |  Philadelphia Ballroom

PREDICTIVE MODELING REVEALS ELEVATED CONDUCTIVITY RELATIVE TO BACKGROUND LEVELS IN FRESHWATER TRIBUTARIES WITHIN THE CHESAPEAKE BAY WATERSHED, USA Anthropogenic salinization profoundly impacts freshwater ecosystems. Elevated conductivity (e.g., specific conductance or SC) causes osmotic stress in aquatic organisms and may increase the toxicity of other contaminants. Indices of benthic macroinvertebrate integrity are declining in urban areas across the Chesapeake Bay watershed (CBW), and more information is needed about whether these declines may be due to elevated conductivity. A predictive SC model was developed using existing monitoring data from the National Water Quality Portal. Predictor variables representing SC sources were compiled for all non-tidal reaches in the NHDPlus Version 2.1 stream network across the CBW. Random forests modeling was conducted to predict SC at four time periods for which land use information was available (2001, 2006, 2011, and 2016). A national dataset of background SC was then compared to predicted SC values to quantify departures from background SC. Carbonate geology, impervious and forest cover, and snow depth were the most important variables driving SC in the model. Observations and modeled results showed that snow depth amplified the effect of impervious cover on SC. Elevated SC was predicted in nearly two-thirds of stream reaches in the CBW, and these elevated conditions persisted over time in many areas. Spatial and temporal patterns varied among ecoregions, with the highest SC predicted in northern part of the watershed with high urban land use. These results can be used in stressor identification assessments, to prioritize future monitoring needs, and to determine where management activities could be implemented to reduce elevated conductivity in the region.

Rosemary Fanelli (Primary Presenter/Author), USGS South Atlantic Water Science Center, rfanelli@usgs.gov;

Joel Moore (Co-Presenter/Co-Author), Towson University, moore@towson.edu;

Charles Stillwell (Co-Presenter/Co-Author), USGS South Atlantic Water Science Center, cstillwell@usgs.gov;

Andrew Sekellick (Co-Presenter/Co-Author), USGS MD-DE-DC Water Science Center, ajsekell@usgs.gov;

Richard Walker (Co-Presenter/Co-Author), Upper Iowa University, walkerr03@uiu.edu;

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6/04/2024  |   14:00 - 14:15   |  Philadelphia Ballroom

Estimates of lake nitrogen, phosphorus, and chlorophyll-a concentrations to characterize harmful algal bloom risk across the United States Excess nutrient pollution contributes to the formation of harmful algal blooms (HABs) that compromise fisheries and recreation and that can directly endanger human and animal health via cyanotoxins. Efforts to quantify the occurrence, drivers, and severity of HABs across large areas is difficult due to the resource-intensive nature of field monitoring for lake nutrient and chlorophyll-a concentrations. To better characterize how nutrients interact with other environmental factors to produce algal blooms in freshwater systems, we used spatially explicit and temporally matched climate, landscape, in-lake characteristic, and nutrient inventory datasets to predict nutrients and chlorophyll-a across the conterminous United States (CONUS). Using a nested modeling approach, three random forest (RF) models were trained to explain the spatiotemporal variation in total nitrogen (TN), total phosphorus (TP), and chlorophyll-a concentrations across US EPA’s National Lakes Assessment (n=2000 lakes). Concentrations of TN and TP were the most important predictors and, with other variables, the RF model accounted for 68% of variation in chlorophyll-a. We then used these RF models to extrapolate lake TN and TP predictions to lakes without nutrient observations and predict chlorophyll-a for ~70,000 lakes across the CONUS. Risk for high chlorophyll-a concentrations is highest in the agriculturally dominated Midwest, but other areas of risk emerge in nutrient pollution hot spots across the country. These catchment and lake-specific results can help managers identify potential nutrient pollution and chlorophyll-a hot spots that may fuel blooms, prioritize at-risk lakes for additional monitoring, and optimize management to protect human health and other environmental end goals.

Meredith Brehob (Primary Presenter/Author), ORISE at EPA, meredithbrehob@gmail.com;

Michael Pennino (Co-Presenter/Co-Author), EPA, pennino.michael@epa.gov;

Amalia Handler (Co-Presenter/Co-Author), EPA, Handler.Amalia@epa.gov;

Jana Compton (Co-Presenter/Co-Author), US EPA, Pacific Ecological Systems Division, Corvallis, OR, compton.jana@epa.gov;

Sylvia Lee (Co-Presenter/Co-Author), U.S. Environmental Protection Agency, lee.sylvia@epa.gov;

Robert Sabo (Co-Presenter/Co-Author), US EPA, Sabo.Robert@epa.gov;

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6/04/2024  |   14:15 - 14:30   |  Philadelphia Ballroom

Contextualizing long-term effects of land use on nutrient pollution and benthic macroinvertebrate assemblages in Michigan streams (USA) Nutrient pollution in surface waters negatively affects biota, water quality, and aquatic industries such as tourism, impacting both natural and socioeconomic structures. Despite efforts to improve water quality, excess nitrogen (N) and phosphorus (P) inputs have steadily increased because of agriculture, deforestation, human population growth, and urbanization. Benthic macroinvertebrates are essential in nutrient cycling and are often used in water quality monitoring due to their wide range of pollution tolerance. We examined long-term median concentrations of N/P constituents and relationships among land use and macroinvertebrate diversity from historical records for Michigan streams (2002-2021). Records were retrieved from the Water Quality Portal, synthesized, and partitioned by land-use dominance such as agricultural and developed (>45% dominance), undeveloped (<5% developed/<25% agriculture), and mixed. The percent of agricultural/developed land use (0-10%, 10-20%, 20-30%, 30-40%, >40%) was also correlated with nutrient loading. Statewide, median concentrations of total N ranged between 0.53-1.44 mg/L with no variation among land use. Total P slightly differed as median concentrations in agricultural/developed sites were 2.3 times higher than in undeveloped areas. Inorganic nitrogen was 2 to 10 times higher in agricultural/developed areas, with a substantial increase at 40% of agricultural/developed dominance. Collector-gatherers were the dominant macroinvertebrate feeding guild overall; however, stream sites with agricultural/developed dominance had fewer collector-filterers and more predators, likely associated with higher secondary production stimulated by land disturbance. This research highlights the impact nutrients can have on benthic communities in rivers and identifies how land use influences macroinvertebrate diversity.

Héctor Esparra-Escalera (Primary Presenter/Author), Wayne State University, hector.esparra@wayne.edu;

Kishore Gopalakrishnan (Co-Presenter/Co-Author), Wayne State University, kishore.gopalakrishnan@wayne.edu;

Donna Kashian (Co-Presenter/Co-Author), Wayne State University, dkashian@wayne.edu;

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6/04/2024  |   14:30 - 14:45   |  Philadelphia Ballroom

TEMPORAL VARIATIONS OF DISSOLVED ORGANIC CARBON CONCENTRATIONS IN RIVERS: CAN LAND USE AND GEOMORPHOLOGY EXPLAIN REGIONAL VARIABILITY In the last decades, recovery from acidification and climate change have caused a widespread dissolved organic carbon (DOC) increase in boreal rivers with impacts on water usages such as compromising drinking water supply. However, there are regional differences in this increase, but the patterns and drivers remain unclear. We hypothesized that due to carbon rich soils, forested watershed would show a stable increase of DOC over time and for the opposite reasons, agricultural and urbanized watersheds would show a decrease of DOC over time. To address these differences, we examined the effects of land uses and geomorphology on shaping DOC historical trends (1985-2019) in the St. Lawrence watershed over 91 stations in 54 different rivers selected from the Réseau-rivières monitoring program (Government of Québec, Canada) We used agriculture to forest gradients along with a generalized linear model to include geomorphology factors. We measured a widespread but stable increase, particularly in forested regions. However, agricultural areas showed or no variation or instable decreases in DOC in the last decades. Urban developments were found to have no impacts on historical DOC variations. When adding geomorphological factors, none were found to be a driver of DOC trends. Instead, agriculture, along with wetlands and grassland areas were found to promote DOC increases, emphasizing the importance of acknowledging land uses in a watershed when optimizing water treatment plant facilities to remove DOC from water, along with other suitable treatments.

Jade Dormoy-Boulanger (Primary Presenter/Author), University of Quebec at Trois-Rivières, jade.dormoy-boulanger@uqtr.ca;

Jean Francois Lapierre (Co-Presenter/Co-Author), University of Montreal, jfrancoislapierre@gmail.com;

François Guillemette (Co-Presenter/Co-Author), University of Quebec at Trois-Rivières, Francois.Guillemette3@uqtr.ca;

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