Zooplankton are fundamental to aquatic ecosystems, influencing not only biogeochemical cycles but also broader ecological dynamics. As primary consumers, they link lower trophic levels, such as phytoplankton, to higher trophic levels, including fish and other predators, thereby shaping food web structures. This session will delve into the ecological roles of zooplankton across aquatic environments, with a focus on their contributions to biogeochemical cycles and their adaptive responses to environmental changes.
In both marine and freshwater systems, zooplankton contribute to carbon cycling through the biological pump. They graze on phytoplankton, respire carbon dioxide, and repackage organic matter into fecal pellets that can sink to deeper waters or sediments, a process crucial for sequestering atmospheric carbon dioxide. Additionally, zooplankton excrete dissolved inorganic nutrients that are rapidly assimilated by phytoplankton, sustaining primary production in nutrient-depleted areas.
We invite contributions on the latest findings in zooplankton ecology, including their distribution, behavior, and interactions with other organisms in both marine and freshwater ecosystems. The session will also encompass studies on zooplankton-mediated carbon and nutrient cycling, examining factors that influence export efficiency, such as species traits, community dynamics, and environmental changes like climate change, ocean acidification, and deoxygenation.
The session will also highlight cutting-edge methodologies advancing our understanding of zooplankton ecology. Innovations in imaging, molecular tools, and biogeochemical modeling are providing new insights into zooplankton distributions, behaviors, and ecological roles. We encourage presentations showcasing these technologies and their applications in contemporary research.
This session aims to synthesize current knowledge, identify research gaps, and prioritize future studies in zooplankton biogeochemistry. We will explore how these small but ecologically vital organisms can be integrated into global biogeochemical models, with implications for climate predictions and resource management.
By bringing together experts in aquatic biology, ecology, limnology, oceanography, and biogeochemistry to foster interdisciplinary collaboration. It is designed to attract researchers, educators, policymakers, and students focused on the ecological and biogeochemical roles of zooplankton and their responses to environmental change. Through this exchange, we aim to deepen our understanding of the ecological importance of zooplankton and their role in maintaining healthy aquatic ecosystems.
The session’s importance lies in its potential to advance our understanding of the critical roles zooplankton as ecological keystones in aquatic environments. As we face unprecedented environmental challenges, it is crucial to integrate zooplankton ecology into broader scientific frameworks to preserve aquatic biodiversity and ensure the sustainability of global biogeochemical cycles.
Lead Organizer: Yuuki Niimi, Arizona State University (yniimi@asu.edu)
Co-organizers:
Leocadio Blanco-Bercial, Arizona State University/Bermuda Institute of Ocean Science (leocadio@asu.edu)
Susanne Neuer, Arizona State University (Susanne.Neuer@asu.edu)
Presentations
09:00 AM
PREY ENCOUNTER AND CAPTURE BEHAVIOR OF THE MYSID NEOMYSIS AMERICANA IN THE WATER LAYER ADJACENT TO THE BOTTOM (9076)
Primary Presenter: Houshuo Jiang, Woods Hole Oceanographic Institution (hsjiang@whoi.edu)
Mysids are small crustaceans that contribute significantly to both the abundance and biomass of zooplankton communities in shallow coastal and estuarine waters. They are typically found in the water layer immediately above the sediment, feeding omnivorously on small zooplankton, algae, and detritus, and serving as important prey for fish. Neomysis americana, a key species in the coastal and estuarine food webs of the northwest Atlantic, was the focus of this study. Using high-speed videographic observations, we investigated the prey encounter and capture behavior of N. americana. Mysids were freshly collected from the Damariscotta River estuary, Maine, and offered copepods, copepod nauplii, and polychaete larvae as prey. Observations were conducted in darkness under infrared illumination. Rather than relying on a suspension feeding current, N. americana detected and attacked zooplankton prey individually. The capture success rate of adult copepods was extremely low because they overwhelmingly evaded mysid attacks by escape jumping. In contrast, N. americana captured copepod nauplii and polychaete larvae with extremely high success rates, curving its body with precise maneuvers to avoid displacing prey. Additionally, mysids demonstrated significantly greater reaction distances than those of their prey reacting to them, highlighting their specialized predatory strategies.
09:15 AM
POPULATION DYNAMICS, LIFE HISTORY CHARACTERISTICS, AND ENVIRONMENTAL DRIVERS OF NEOMYSIS AMERICANA IN THE DAMARISCOTTA RIVER ESTUARY (9176)
Primary Presenter: Allison Fogg, University of Southern Maine (allison.fogg1@maine.edu)
Mysid shrimp (Neomysis americana) play a pivotal role in estuarine food webs by linking primary producers to higher trophic levels and serving as an important food source for commercially valuable fish. Despite their ecological significance, mysids are often undersampled, leading to gaps in our understanding of their population dynamics and life history traits. This study investigated N. americana over a full year (June 2023 to May 2024) in the temperate Damariscotta River Estuary in Maine. The research focused on how environmental factors such as temperature, turbidity, salinity, chlorophyll a, and zooplankton biomass affect mysid density and reproduction. Temperature emerged as a key factor, with warmer temperatures leading to higher mysid density. Our results also indicated distinct overwintering cohorts, highlighting that at least a portion of the population remains in the estuary year round, with seasonal shifts in size distribution. These findings enhance our understanding of N. americana's ecological role in temperate estuaries, building on previous research of this important species.
09:30 AM
Testing diel vertical migration cues in fish and Mysis with surface drones in Lake Superior (9297)
Primary Presenter: Thomas Evans, Cornell University (tme33@cornell.edu)
Numerous organisms participate in diel vertical migrations (DVM) in pelagic waters in lakes and oceans. In the Laurentian Great Lakes, the omnivorous crustacean Mysis diluviana (hereafter Mysis) are a key food web component and prey item for fish. Mysis migrate upwards at night to feed on other plankton and then retreat to deeper water at day with predatory fish paralleling these movements. Studying this DVM cycle in the Great Lakes has often been limited either temporally or spatially because of logistical challenges. However, high endurance surface drones are now available that allow DVM patterns to be studied over large spatial and temporal scales. We deployed two uncrewed surface vessels equipped with 120 kHz Simrad EK80 transducers in western Lake Superior from August to September of 2022 to measure fish and Mysis vertical distributions in the water column. We utilized existing laboratory-derived mechanistic models of Mysis preferred depth to predict their location within the water column across the sampling period and compared this to in situ distributions observed in Lake Superior to understand drivers of this species’ diel migrations. Mysis were highly responsive to light (even changes in moonlight), choosing to descend as light levels rose. Further, we observed that Mysis generally remained suspended above the bottom of the lake, weakening benthic-pelagic coupling by these organisms. Fish were often found under the Mysis during the night, and amongst the Mysis during the day. The use of autonomous drones equipped with acoustics instrumentation facilitates fish and Mysis observations across large spatial scales and opens new opportunities to answer questions about the ecological role of vertical migrations in lake food webs.
09:45 AM
Beyond Oxygenation: The impact of aerator installation on the chemical and biological recovery of Frame Lake, Yellowknife (9288)
Primary Presenter: Madeline Patenall, Wilfrid Laurier University (madelinepatenall55@gmail.com)
The contamination of freshwater resources from nutrient and metal(loid) pollution is a global concern. Recent interest has been placed on the influence of legacy pollutants, which can remobilize in anoxic conditions and have lasting effects on the recovery of aquatic systems. In the Northwest Territories, Frame Lake provides an excellent case study for investigating legacy contaminant dynamics. Urbanization and mining in the region have led to the deposition of over half a century of nutrient and arsenic-bearing atmospheric emissions, resulting in eutrophication, contamination, winter anoxia, and reduced recreational value. However, efforts to rehabilitate Frame Lake have begun. The primary rehabilitation intervention injects oxygenated water into the deep region of the lake (hypolimnetic aeration), increasing winter oxygen concentrations. It is hypothesized that increasing oxygen concentrations will prevent winter anoxia, mitigating the remobilization of legacy elements, such as the nutrient phosphorus and the metal(loid) arsenic, to the overlying water. Additionally, increased oxygen concentrations may promote the biological recovery of the lake by creating habitable overwintering conditions and improved water quality for organisms of the lower food web (zooplankton). With the projected effects of climate change in the Arctic, the prevalence and severity of anoxia in lakes are anticipated to increase in the coming decades. Identifying effective rehabilitation methods mitigating the remobilization of contaminants while promoting biological recovery is paramount.
10:00 AM
EFFECTS OF RESERVOIR TYPE (RUN OF RIVER VS. STORAGE) ON NATIVE AND INVASIVE ZOOPLANKTON ASSEMBLAGES (9435)
Primary Presenter: Jess Mitchell, Washington State University (jess.mtchell@gmail.com)
Impoundments (dams and their resulting reservoirs) hydrologically alter riverine systems by lengthening water residence time and altering water quality. Zooplankton are vital primary and secondary consumers in these systems and are an important prey base for the economically and ecologically important salmonids of the Pacific Northwest. The NSF (DISES-DAMS) project aims to determine the ways in which run of river (ROR) and storage reservoirs differ ecologically, including how zooplankton i) assemblage structure, ii) seasonal abundance, and iii) occurrence of invasive species differ between reservoir type. We undertook a two-year field study of four impoundments within the Columbia River Basin, including two ROR (Bonneville, The Dalles) and two storage (Cougar, Detroit) reservoirs. Replicate zooplankton and associated environmental samples were collected at each site bimonthly. We found zooplankton absolute abundances to be higher in storage reservoirs than in ROR reservoirs (with marked seasonal variability). Additionally, relative abundance was also different between storage and ROR reservoirs, with taxa more evenly distributed in ROR systems and dominated by copepods in storage systems. Temperature and conductivity were found to be significant factors associated with zooplankton assemblage structure, which may be due to their effects on phytoplankton productivity. Lastly, invasives (e.g., the copepod Pseudodiaptomus forbesi) were only found in the ROR sites, likely due to the mainstem Columbia fostering invasive introductions via shipping.
10:15 AM
Cumulative stressors shape elevated zooplankton populations in eutrophic Hamilton Harbour, Ontario. (9580)
Primary Presenter: Kelly Bowen, Fisheries and Oceans Canada (kelly.bowen@dfo-mpo.gc.ca)
Hamilton Harbour at the west end of Lake Ontario has historically been regarded as one of the most polluted areas of the Laurentian Great Lakes due to its intense industrial past and urbanization. This eutrophic Area of Concern experiences regular harmful algal blooms and severe hypolimnetic hypoxia due to high nutrient loadings and internal phosphorus cycling. Despite these impacts, lower food web monitoring by Fisheries and Oceans Canada (DFO) since 2002 has found some of the highest levels of zooplankton production the Great Lakes, typically an order of magnitude higher than nearshore Lake Ontario. The most dominant taxa include the cladoceans Daphnia retrocurva, D. galeata, Bosmina and the cyclopoids Diacyclops and Mesocyclops. Unlike planktivorous fishes, zooplankton appear to be largely unaffected by hypoxia, and their excessively high biomass levels are largely due to the lack of top-down control by forage fishes. However, in recent years, cladocerans and cyclopoids periodically show dramatic late summer population declines, coupled with increases in diaptomid copepods. Cumulative stressors appear to be responsible, including blooms of unpalatable filamentous algae and/or the dinoflagellate Ceratium, combined with predation by the spiny water flea Bythotrephes. This invader was virtually absent in the harbour prior to 2016. Proposed remedial actions to improve trophic transfer of zooplankton to fishes include further reductions in nutrient loadings, leading to reduced hypoxia, improvements in pelagic fish habitat and fewer undesirable algal blooms.
SS44A - Ocean and Freshwater Zooplankton Ecology
Description
Time: 9:00 AM
Date: 29/3/2025
Room: W207AB