With global warming and increased erratic and severe weather events, our world is changing. Understanding aquatic ecosystem health, e.g., the mechanisms that sustain biodiversity and ecosystem functions, in a world with which we are familiar is difficult, let alone in a constantly changing world. Generations of aquatic ecologists have produced knowledge showing linkages between inflows (hydraulic displacement and resource loading), temperature, stratification, irradiance, conductivity, biodiversity, and ecosystem functions. With this understanding, our power to predict ecosystem health remains limited and our ability to manage aquatic ecosystems tenuous. In an unfamiliar and changing world, other processes that are currently not considered in management decisions are likely to become more important. For example, increased propagule pressure on the early-season plankton community from the previous year’s late-season plankton community will likely occur with milder winters. It is possible that less palatable assemblages will occur earlier in the season, which might sequester resources and prevent them from moving up the food web at a time when many organisms are spawning. In addition, microbially-driven ecosystem processes and interactions between microbes and other plankton taxa are likely to change. Erratic weather might lead to greater stochasticity and magnitude in disturbances causing local extinctions of rare species, thereby decreasing richness and destabilizing ecosystem functions. In this session, we welcome presentations that explore the issue of how to better understand aquatic ecosystem health (including, but not limited to, microbes and plankton) in a changing world with which we are unfamiliar. Presentations that are based on patterns observed across environmental gradients (e.g., latitudinal, precipitation, temperature, disturbance frequency, etc.) are particularly welcome.
Lead Organizer: Daniel Roelke, Texas A&M University Galveston (droelke@tamu.edu)
Co-organizers:
Jessica Labonte, Texas A&M University Galveston, USA (labontej@tamug.edu)
Simon Mitrovic, University of Technology Sydney, Australia (Simon.Mitrovic@dnr.nsw.gov.au)
Robert Ptacnik, WasserCluster Lunz, Austria (Robert.Ptacnik@wcl.ac.at)
Sierra Cagle, Texas A&M University Galveston (sec1414@tamu.edu)
Presentations
09:00 AM
MULTIPLE MECHANISMS DRIVE WIDESPREAD EUTROPHICATION OF CANADIAN PRAIRIE LAKES ALONG BROAD ENVIRONMENTAL GRADIENTS AND SPATIAL AND TEMPORAL SCALES (7750)
Primary Presenter: Cale Gushulak, University of Madison-Wisconsin (gushulak@wisc.edu)
Canadian Prairie lakes exist along broad climatic and hydrological gradients, and exhibit a wide range of physical, chemical, and biological characteristics. Similarly, these lakes are subject to diverse environmental stressors including agricultural intensification (crops, livestock), urbanization, industrial water extraction, exposure to novel pollutants, and shoreline development. The effects of these stressors vary with proximity to the basin, hydrological connectivity, management strategy, climate variability, and disturbance history. Despite this diversity, many prairie lakes are experiencing symptoms of water quality degradation, including increased blooms of toxic cyanobacteria, deep-water anoxia, macrophyte loss, and sudden fish mortality. Through the use of multiple lines of investigation including paleolimnology, long-term environmental monitoring, experiments, and remote sensing, this talk highlights how varying environmental mechanisms, antecedent lake conditions, and climatic milieu conspire to degrade water quality across prairie lakes that vary greatly in morphology, trophic status, landscape connectivity, and disturbance history. Results of these studies call attention to the difficulty in forecasting unique responses of individual lakes to multiple changing stressors, particularly under unequal management scenarios. We highlight that strategies to protect or improve focal ecosystems can have unanticipated consequences for other lakes, and that landscape-scale management is likely needed to protect aquatic ecosystems on the northern Great Plains.
09:15 AM
What causes metalimnetic hypoxia in Green Lake, Wisconsin, and why have they gotten worse? (7821)
Primary Presenter: Dale Robertson, U.S. Geological Survey (dzrobert@usgs.gov)
In the early 1900’s, Green Lake, the deepest natural lake in Wisconsin, was oligotrophic with hypoxia only occurring in the deepest part of its hypolimnion. Increased nutrient (phosphorus) loading caused the lake to become mesotrophic, with increased algal production and hypoxia also occurring in its metalimnion (referred to as a metalimnetic oxygen minimum - MOM). Statistical and hydrodynamic water-quality modeling with the General Lake Model (GLM-AED) were used to describe the factors affecting MOMs and what could be done to reduce their extent. Model results indicated that worse MOMs occurred in years with increased productivity (higher chlorophyll a), poorer water clarity, and warmer water. Since 1905, MOMs increased in mean severity from ~ 7 mg/L to ~2 mg/L, and in recent years have a range of ~5 mg/L. Empirical relations developed from correlation analyses indicate that the recent variability in MOMs was about equally caused by variations in summer productivity and water temperatures. Climatic change may have caused stratification to develop earlier and the mean MOM to become more severe by ~0.6–2.1 mg/L. The remaining long-term change in mean MOM severity (2.9–4.4 mg/L) may have been caused by increased productivity caused by increased nutrient loading. Hydrodynamic water-quality modeling with incremental changes in phosphorus loading indicated that relative to 2014–18, a 57% decrease in controllable external phosphorus sources was needed to eliminate MOMs <5 mg/L in over 75% of the years, the target set by the Wisconsin Department of Natural Resources.
09:30 AM
USING IN SITU SENSORS TO EXPLORE PATTERNS OF CARBON CYCLING AND METABOLISM IN RIVERS IMPACTED BY AGRICULTURAL AND URBAN LAND USE (8308)
Primary Presenter: Ilyanna Janvier, University of Lethbridge (ilyanna.janvier@uleth.ca)
Despite decades of research, major gaps remain in our understanding of human impacts on river ecosystems. For southern Alberta, one of Canada’s most heavily impacted agricultural landscapes, riverine metabolism and carbon cycling are not well quantified. We explored sub-hourly trends in pH, pCO2, temperature, and O2 using sensor deployments at two locations (Mosquito Creek (MCR) and Little Bow River (LBR)). Both rivers are heavily regulated for irrigation, and we hypothesized that upstream effluent inputs and agricultural impacts would enhance organic matter processing and CO2 production at our sites. From spring to fall, we estimated whole-river metabolism (gross primary production, GPP, and ecosystem respiration, ER) and metabolic contributions to CO2 dynamics. MCR and LBR both had low daily discharge rates (1.15 m3 s-1 vs. 2.38 m3 s-1 respectively). Yet we observed large differences in mean net ecosystem production (NEP = GPP-ER), which was more balanced for MCR (-2.07 g O2 m-2 d-1 ) and more heterotrophic for LBR (-12.03 g O2 m-2 d-1). These metabolic differences had important consequences for CO2 cycling, since mean pCO2 was lower for MCR (721 ppm) than LBR (1174 ppm). In both cases, mean pCO2 was well below average values for global rivers. Our preliminary results indicate that while metabolic patterns differ between rivers, the intense flow regulation and other factors may limit the processing of externally-derived carbon and overall CO2 production in these ecosystems.
09:45 AM
PARTICULATE MATTER VECTORS- KEY PARTICLES SERVING AS SPONGE-LIKE CARRIERS OF TOP-PRIORITY POLLUTANTS (7888)
Primary Presenter: Peleg Astrahan, IOLR (peleg.astrahan@ocean.org.il)
Aquatic environments are in many cases sinks of many pollutants. Yet, they may also serve as a source. Organic pollutants are considered toxic to various populations including humans, fish, phytoplankton, and zooplankton. The distribution of organic pollutants in aquatic environments is frequently studied in the water phase, where their solubility is limited. However, many of these molecules tend to adhere to specific and yet poorly described particulate matter. In our latest studies in Lake Kinneret, Israel, we identified a few sources of top-priority pollutants such as persistent PAHs and Pesticides, in urban runoff, rivers, and atmospheric depositions. Interestingly, apart from phytoplankton cells, these contributors are a few of the dominant sources of the lake’s particulate matter. When considering sediments as the sink of many particles, while routine water monitoring shows pollutants general concentrations <0.1 ppb, sediment concentrations are extremely high. Despite their high volatility, the most dominant pollutant analyzed was the BTEX group, reaching 6000µg/Kg. An inhomogeneous distribution of highly polluted sediment particles was found in the lake, resulting in “hot spots”. In the presented study, we crosslink physical and chemical analyses with the pollutants’ particulate adsorption, and specific characteristics of the “key particles” acting as pollutant sponges, in addition to modeling their potential translocation in the lake. The fingerprint of these specific particles bearing a potentially hazardous impact may be followed in other water bodies elsewhere in the world.
10:00 AM
BIOACCUMULATION AND TRANSPORT OF POLYFLUOROALKYL-SUBSTANCES IN ESTUARINE COPEPODS (ACARTIA TONSA, EUTERPINA ACUTIFRONS) OFF THE CAPE FEAR REGION, NC FRESHWATER-SALTWATER FRONTIERS: THE IMPACTS OF POLYFLUOROALKYL-SUBSTANCES ON ESTUARINE PLANKTONIC ECOSYSTEM (8040)
Primary Presenter: Gena Leib, University of North Carolina Wilmington (gml5089@uncw.edu)
As rivers discharge into the ocean, they can be vectors for the transport of contaminants accumulated from large basins, especially those with intense human activity. Such contaminants include Polyfluoroalkyl-Substances (PFAS), whose strong and stable carbon-fluorine bonds, can have deleterious lasting effects on natural ecosystems. The Cape Fear River, NC is a natural system impacted by these toxic chemicals. Although accumulation of these substances has been studied in aquatic systems, research is limited in biota. To understand the drivers of transport and accumulation of these chemicals locally, we are investigating the presence and potential bioaccumulation of PFAS in copepod species that occupy different water column habitats. We hypothesize higher concentrations in benthic species compared to pelagic ones due to differential exposure. Similarly, river-transported species are expected to have higher concentrations than oceanic ones, reflecting sources. Preliminary data identified PFAS compounds PFBA, PFHxA, PFOA, PFBS, PFOS and HFPO-DA in copepods within the river-influenced Intracoastal Waterway off the UNCW Center for Marine Sciences. Concentrations were highest in PFBA (93 ng/g), PFOA (93 ng/g), and HFPO-DA (known as GenX; 130ng/g). Understanding the spatial (river, estuary, coastal and offshore) variability of contaminants within a dynamic system will allow us to further understand transportation pathways in natural ecosystems especially where hydrographic regimes changes are expected to exert significant pressure on planktonic assemblages due to global change.
10:15 AM
EXPLORING SULFATE CYCLING IN A MINERAL-SOIL WETLAND RESTORED WITH WASTEWATER (8155)
Primary Presenter: Mariya Denny, University of Lethbridge (avemaria9513@gmail.com)
Sulfate pollution is contributing to the salinization of surface waters worldwide. Wetlands are natural filters on the landscape that remediate surface water by retaining and processing various pollutants. However, the capacity for wetlands to process excess sulfate from wastewater is poorly understood, especially for natural (as opposed to constructed) wetlands. Here, we explore the sulfate remediation capacity of Frank Lake, a restored, multi-basin wetland complex in southern Alberta, Canada, that is used to treat effluents from municipal and beef slaughterhouse sources. Using a combination of approaches, we show limited sulfate processing throughout the wetland. Mass balances constructed for two distinct hydrologic periods showed that Frank Lake shifted from a sulfate source during wet years (2013 - 2015) to a sink during drought years (2021 - 2022). Yet we found little evidence of active sulfate processing in surveys conducted during drought years. Stable isotope (34S and 18O) analysis showed limited enrichment across the basins of the wetland, implying limited transformation of sulfate via microbial reduction. Sediment incubations confirmed the patterns observed for stable isotopes. We hypothesize that the preferential reduction of nitrate and other more energetically favourable constituents of effluent may restrict the rate of microbial sulfate reduction. The limited extent of emergent and submerged vegetation may also limit sulfate uptake by plants. Given the limited sulfate processing in Frank Lake, and the headwater position of this wetland complex in the broader watershed, our work provides context on previous reports of increasing salt concentrations documented in rivers throughout the South Saskatchewan River watershed.
SS16A - Understanding Aquatic Ecosystem Health in a Changing World
Description
Time: 9:00 AM
Date: 6/6/2024
Room: Hall of Ideas I