Global change biology often involves “ecological surprises” arising from unexpected responses to extreme or novel environmental changes (i.e. stressors). The inability to predict such typically non-linear responses stems from our lack of knowledge concerning the nature of ecological interactions that can mediate the direct effects of individual stressors and the difficulties in predicting outcomes when multiple stressors exist. We seek presentations that will stimulate exchange of methodologies (e.g., ecological modeling, experiments, meta-analysis, paleolimnology) used to generate mechanistic insights into the cumulative impacts of multiple stressors across various scales of biological organization (e.g., organismal, population, community, trophic interactions) in freshwater and marine ecosystems. Also, presentations are encouraged that place multiple aquatic stressors in an applied conservation context to better connect scientists with stakeholders and indigenous knowledge keepers in codesigning mitigation strategies and restoration of stressed ecosystems. We anticipate the session will provide a clearer approach to forecasting the cumulative socio-ecological impacts of multiple stressors, and a deeper understanding of the underlying mechanisms.
Lead Organizer: Rolf Vinebrooke, University of Alberta (rolf@ualberta.ca)
Co-organizers:
Shelley Arnott, Queen's University (arnotts@queensu.ca)
James Rusak, Government of Ontario (jim.rusak@ontario.ca)
Presentations
09:00 AM
Mapping threats to the world's freshwater biodiversity (10807)
Primary Presenter: Christophe Brabant, McGill University (christophe.brabant@mail.mcgill.ca)
Earth has entered an era of unparalleled human activities, resulting in dramatic biodiversity loss worldwide. Nowhere is this more true than in freshwater ecosystems, which are both the richest habitats on Earth as well as the most threatened globally. Although the major anthropogenic pressures in freshwater ecosystems have been studied, effective conservation action remains limited due to the lack of spatial data on threats to freshwater species. Here, we use comprehensive data from the International Union for the Conservation of Nature to map the impact of 45 threats to all assessed freshwater amphibians, reptiles, fish, mammals, dragonflies. Using a novel threat mapping method, we create maps that illustrate the impact of threats to species, globally. Our results highlight the most acute overlap of threats occurring in Europe and the Permanent Maghreb, with pollution and agriculture as the major threats to freshwater biodiversity. We find three threats that impact on average close to one-fourth of freshwater species anywhere on Earth. Additionally, we find an association between threat intensity and extinction risk, particularly for the impact of pollutants. Finally, we provide evidence that freshwater species are nearly universally more impacted than terrestrial ones, for any threat anywhere on Earth. Our assessment reports global evidence of the far-reaching and dramatic impacts of anthropogenic activities. We hope the resulting threat maps can provide the baseline knowledge needed for future mitigation actions and conservation initiative in freshwater systems.
09:15 AM
Losing our breath: The causes and consequences of aquatic deoxygenation (11917)
Primary Presenter: Kevin Rose, Rensselaer Polytechnic Institute (rosek4@rpi.edu)
Dissolved oxygen losses are occurring in many waterbodies globally, including rivers, lakes and reservoirs, and marine ecosystems. Despite a large variation in deoxygenation rates among waterbodies, the causes of deoxygenation can be grouped into just a few categories, including reductions in solubility associated with warming temperatures, stronger and longer stratification that reduces deep-water ventilation, and increases in biological and chemical oxygen demand. Among these drivers, warming temperatures and stratification changes are global drivers affecting most regions, while changes in oxygen demand are often associated with local waterbody and landscape drivers. This talk will also briefly discuss some examples of research and monitoring programs actively seeking to understand the causes and consequences of aquatic deoxygenation. SCALE, A Survey of Climate and Adirondack Lake Ecosystems, is an example program focused on waterbodies in the Adirondack Park, New York State, USA. Deoxygenation impacts are diverse and can include the initiation of regime shifts resulting in a rapid transition to a less desirable state associated with lower water quality including the presence of harmful algal blooms. The loss of dissolved oxygen can harm biodiversity, contribute to release of phosphorus and dissolved organic matter from lake sediments, and regulate other processes such as mercury methylation and methane production. Given its global pervasiveness and widespread impacts aquatic deoxygenation can arguably be considered a Planetary Boundary process.
09:30 AM
ECOLOGICAL RESPONSES TO MULTIPLE STRESSORS IN A SALINE LAKE AND IMPLICATIONS FOR CONSERVATION (10227)
Primary Presenter: John Melack, University of California, Santa Barbara (melack@bren.ucsb.edu)
Saline lakes throughout the world are threatened by decreasing water levels and increasing salinity due to climate changes and diversions of inflows. At Mono Lake, California, stream diversions led to an elevation decline and doubling of salinity. Since 1981, periods with large snowmelt runoff, followed by periods with low runoff and continued water diversions, have led to six episodes of strong year-round stratification followed by eventual winter mixing. During periods of persistent stratification, vertical mixing of nutrients and algal abundance were reduced and influenced Artemia monica, a critical food source for breeding gulls and migratory grebes and phalaropes. The variations in stratification of varying duration have compounded ecological variability due to climatic variation and changing management regimes. Measurements from 1980 to the present, combined with statistical analyses, experimental studies and modeling provide the basis for interpretation of ecological changes over 45 years. Adult Artemia abundance has large interannual variability and can include a large second generation associated with a very low spring hatch, years of high abundance associated with the breakdown of long periods of stratification, and a 42% decline in abundance-weighted fecundity. Recent high phytoplankton abundance during summer, not previously observed, indicate a significant shift in the balance between growth and loss of phytoplankton. These scientific results have contributed to revised regulation of water diversions and continue to guide adaptive management of the lake.
09:45 AM
INDIVIDUAL AND CUMULATIVE EFFECTS OF FRESHWATER SALINIZATION AND HEATWAVES ON ZOOPLANKTON STRUCTURE AND FUNCTION (10745)
Primary Presenter: Adebukola Aborigho, University of Vermont (saseyiadebukola@gmail.com)
Zooplankton play a crucial role in freshwater food webs, linking primary producers and higher trophic levels. However, co-occurrence of stressors may compromise zooplankton ecological functions. Many studies have examined the individual effects of stressors, but few have assessed the cumulative effects of co-stressors on zooplankton community structure and function. We conducted a 6-wk mesocosm experiment to test how crustacean zooplankton community structure and function respond to heatwave (HW) pulses and chloride (Cl-) press disturbances. We measured structural (biomass, diversity) and functional (respiration) responses. We hypothesized that co-occurring stressors would amplify community disruptions and increase metabolic demand. Community structure showed no individual or interactive effects of either stressor, although diversity increased under the combined stressors. Copepod biomass declined upon the first HW pulse only, suggesting greater resistance upon subsequent HW exposure. Compositional changes suggest a shift toward tolerant taxa under both elevated Cl- and heatwave treatments. Metabolic responses were similarly limited, with respiration showing no effects of HW, Cl-, or their interaction, indicating that zooplankton metabolism remained stable despite modest structural change. Overall, HW and Cl- disturbances resulted in detectable but limited impacts on zooplankton community structure while community function remained comparatively resistant.
10:00 AM
Transgenerational Plasticity and Maternal Effects in Daphnia magna Across Multiple Stressors and (Mis)Matching Environmental Conditions (10324)
Primary Presenter: Charlotte Carrier-Belleau, Laval University, University College Dublin (carrierc@tcd.ie)
Anthropogenic activities are increasing the number and intensity of environmental stressors, with major consequences for how organisms adapt and evolve. Because stressor–response relationships are not consistent through time, past environmental conditions can shape future ecological responses through parental effects. These non-genetic influences can either enhance or impair offspring performance, yet most research on transgenerational plasticity has focused on single stressors. In contrast, substantial knowledge gaps remain in multiple-stressor contexts, particularly when offspring experience environments that match or mismatch those of their parents. To address this, we conducted a factorial experiment using three genotypes of Daphnia magna, exposing mothers to elevated temperature, elevated salinity, or both combined. Offspring were then reared under all possible stressor combinations, creating matched and mismatched environmental conditions across generations. We quantified key fitness traits, including survival, reproductive output, and time to first reproduction and show strong stresor-specific adaptive transgenerational effects. This work underscores the importance of incorporating temporal dynamics into multiple-stressor research, as organisms increasingly face variable and unpredictable environments where stressor legacies may shape ecological and evolutionary responses across generations.
10:15 AM
TRACKING LONG-TERM CHANGES IN FOOD WEB DYNAMICS LINKED TO PAST SEABIRD INPUTS AT CAPE ST. MARY’S, NEWFOUNDLAND (11246)
Primary Presenter: Zoe Kane, Queen's University (16zak2@queensu.ca)
Cape St. Mary’s Ecological Reserve (Newfoundland and Labrador, Canada) hosts the third-largest and southernmost Northern Gannet (Morus bassanus) colony in North America. The colony occupies ‘Bird Rock,’ a 100m offshore sea stack, and the adjacent mainland cliffs, collectively supporting tens of thousands of breeding birds. Wind-driven transport of ornithogenic material from Bird Rock has previously been shown to enrich a freshwater pond approximately 240m inland, generating nutrient accumulation and ecological restructuring that paralleled the gannet colony’s twentieth-century expansion. This project integrates sub-fossil cladoceran analysis into the existing multi-proxy paleolimnological framework to examine how primary consumers responded to seabird-derived nutrient inputs. Cladocerans, as bioindicators, reveal shifts in food quality, ionic composition, and habitat structure resulting from seabird activity that primary producer proxies alone cannot resolve. By implementing cladocerans as response variables, we can quantify the timing and magnitude of past aquatic community and food web changes in relation to a historically increasing seabird population, which is now considered stable. This approach also helps establish a framework for predicting ecological responses to long-term changes in seabird activity, thereby enhancing our understanding of seabird-driven ecosystem processes in coastal freshwater systems.
SS047A Towards a Convergence of Current Knowledge and Application of Multiple Stressor Ecology Across Aquatic Habitats
Description
Time: 9:00 AM
Date: 13/5/2026
Room: 520CF