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
02:30 PM
DETERMINING THE HOST-ASSOCIATED MICROBIOME OF DAPHNIA DENTIFERA IN EXPERIMENTAL AND NATURAL POPULATIONS (9697)
Primary Presenter: Carla Caceres, University of Illinois Urbana - Champaign (carla.e.caceres@gmail.com)
We sampled lakes and conducted a series of laboratory experiments to determine the structure of the host-associated microbiome in experimental and natural populations of Daphnia dentifera. In the laboratory, Daphnia were raised in several environments, including exposure to the virulent pathogenic fungus, Metschnikowia bicuspidata. In addition, we sampled individuals from the hypolimnion and epilimnion of three lakes created by strip mining in Vermilion County, IL, USA. We now have short-read 16s sequencing of 200 samples across a series of environments. Analysis is ongoing, but our preliminary analysis has found that Metschnikowia bicuspidata infection alters the microbial composition of the Daphnia. This difference was driven by differences in the relative abundance of Limnohabitans, which was the only taxa that showed a significant difference between exposed and control animals. When our analysis is complete, we will be able to determine which (if any) taxa are present across all environments and which are associated with particular conditions.
02:45 PM
TEMPERATURE AND SESTON STOICHIOMETRY DRIVE SEASONAL SHIFTS IN ZOOPLANKTON ELEMENTAL COMPOSITION AND BIOMASS (9290)
Primary Presenter: Hailee Mersino, Oakland University (hmersino@oakland.edu)
Seston elemental composition and temperature interact to shape the elemental composition, population dynamics, and biomass of zooplankton communities. However, the nature of these interactions are poorly understood in natural environments, particularly during early spring and with multiple zooplankton taxa. Here, we investigate seasonal shifts in seston and zooplankton elemental composition and biomass. Beginning in March, we conducted weekly sampling in a eutrophic, dimictic, small lake in southeast Michigan, USA. Seston samples were collected from the photic zone to measure elemental composition and chlorophyll a concentration. Additionally, we assessed zooplankton biomass and analyzed elemental composition and abundance of two zooplankton taxa: Daphnia and copepods. Our findings reveal that Daphnia exhibited higher phosphorus (P) content than copepods, consistent with the growth rate hypothesis. However, both Daphnia and copepods had a rapid decline in their %P and carbon (C) body composition during early spring as temperatures increased. Cyclopoid copepods dominated early spring biomass but by May, the biomass of Daphnia and cyclopoid copepods biomass began to converge. These results highlight the temperature-dependency of zooplankton elemental composition among taxa and the role of seston stoichiometry in shaping elemental dynamics within zooplankton communities.
03:00 PM
Development of a custom-built stereo-imaging system for in situ zooplankton studies (9184)
Primary Presenter: Aditya Nayak, Florida Atlantic University (aditya.nayak@gmail.com)
In aquatic ecosystems, zooplankton serve as critical intermediaries between different food web trophic levels and regulate nutrient cycling. In situ behavioral observations of zooplankton and their connections with the environment they inhabit, e.g., prey capture/avoidance, aggregation/swarming dynamics and interactions with flow at different scales, are crucial to gain better insights into their ecology. However, this is a relatively underexplored area due to inherent challenges in capturing accurate in situ data. Here, we present a custom-built stereo-imaging system that facilitates characterization of meso- and macro-zooplankton communities in their natural habitats, including abundance, distribution and behavioral patterns. The system uses high-resolution monochrome cameras with Power over Ethernet (PoE) that allow for live observations and adaptive sampling in diverse aquatic environments. Laboratory validation confirmed that the overall coefficients of variation (CV) are less than 2%, indicating consistent and reliable depth measurement performance. Sample results from different field observations will highlight the capabilities of the system in providing individual and group metrics, including but not limited to, swimming speeds and acceleration, swarm density, nearest neighbor distances (NND), orientation and polarization order. This framework offers valuable insights into complex behavioral patterns, social interactions, and predator-prey dynamics, highlighting how future applications in targeted studies could enhance our understanding of zooplankton ecology.
03:15 PM
A closer look into copepod’s morphology: in situ imaging reveals links with environment and marine heat waves (8772)
Primary Presenter: Rubén Tournier-Broer, Laboratoire d’Océanologie et Géosciences (LOG ) - Université du Littoral Côte d'Opale (ULCO) (ruben.tournier-broer@univ-littoral.fr)
Within marine mesozooplankton communities, copepods are a key group both in terms of abundance and biomass, hence contributing to central ecological functions of aquatic ecosystems. Analyzing their morphological traits can provide valuable insight into ecosystem processes and relation with the environment that might otherwise go unnoticed. Imaging techniques are an increasingly used tool to sample the traits of mesozooplankton, and especially of copepods. In this study, we use in situ imaging from the Underwater Vision Profiler (UVP) to explore the relationship between copepod’s morphology and environmental conditions in the upwelling of the California Current Ecosystem (CCE). Over 4 years, from 2008 to 2016, morphological traits such as size, complexity, and transparency were measured from copepod’s images captured by the UVP deployed as part of the CCE-Long-Term Ecosystem Research. Our findings reveal that copepod’s size is linked with environmental seasonal variations, with larger copepods in fall, smaller in summer/spring and even smaller during a summer marine heatwave. Change of transparency also occurs during seasons, especially between spring and fall showing a significant relationship between copepod transparency and seasonal productivity. Interestingly, our results indicate more transparent copepods in the CCE are associated with higher carbon flux. By uncovering these morphological-environmental patterns, our study contributes to a better understanding of copepods’ roles in aquatic ecosystem functioning and consequences of environmental change on this group.
03:30 PM
THE EFFECT OF THE EL NIÑO SOUTHERN OSCILLATION ON ZOOPLANKTON PHENOLOGY IN THE CALIFORNIA COAST (9463)
Primary Presenter: Fiona Madsen, McGill University (fionacmadsen@gmail.com)
The El Niño Southern Oscillation (ENSO) is the most dominant interannual climatic phenomenon globally. However, the ways in which ENSO impacts the phenology of zooplankton, the primary consumers in the majority of marine food webs, is poorly understood. While ENSO comprises three phases (El Niño, La Niña, and neutral periods), much of the research focuses on El Niño events and changes in zooplankton biomass only. This is despite evidence that La Niña influences nutrient upwelling, and that different zooplankton taxa respond differently to ENSO events. Here, we examine how both El Niño and La Niña events, as well as their affected environmental variables, impact zooplankton taxa phenology using empirical data spanning two decades. Using data sampled within the California Coastal System (CCS), we assessed the timing of peak biomass to determine phenological differences between taxa during different ENSO phases. Our results demonstrate that phenological shifts vary greatly between taxa. Our results also show that there is a regional pattern in that Eastern Pacific (EP) El Niño and La Niña events are associated with delayed peaks in the majority of taxa examined, while Central Pacific (CP) El Niño and La Niña events are associated with earlier peaks in most taxa. We also found environmental variables that were strongly associated with phenological disruptions during different ENSO events. Our work furthers the understanding of how ENSO impacts zooplankton and gives insight into how these effects will respond to ongoing climate change leading to the disruption of ENSO events.
03:45 PM
INSIGHTS INTO YEAR-ROUND MERCURY CONCENTRATIONS IN ANTARCTIC KRILL AND ITS RELATIONSHIP WITH BIOLOGICAL AND ENVIRONMENTAL PARAMETERS (8978)
Primary Presenter: Rita Franco-Santos, CSIRO (rita.franco-santos@outlook.com)
Long-range atmospheric transport and deposition processes have resulted in mercury (Hg) being widely available in the oceans, even in areas away from major urban settlements, such as Antarctica. In polar zones, Hg can be deposited onto sea-ice and snow and potentially transferred to the ocean upon thawing. Phytoplankton take up Hg within the photic zone from the surrounding water, which can then bioaccumulate through the food web. Antarctic krill (Euphausia superba) are an important link in the Antarctic food web, as they transfer energy generated by primary producers to higher trophic levels. They can, however, also transfer contaminants. Evaluating the impacts and associated risks of Hg to top predators in Southern Ocean food webs is of high ecological and economic importance, especially under the context of climate change. To do so, it is crucial to first understand how Hg concentration in lower trophic levels (in this case, krill) varies spatially and temporally. In this presentation, we provide a baseline of total Hg concentrations in sexed krill individuals obtained fortnightly from December 2013 until August 2019 (except for the October and November months) from a commercial fishing vessel that operates in three Southern Ocean locations: South Georgia, the South Orkney Islands, and the West Antarctic Peninsula. We also present and discuss the results of generalised linear models which tested the importance of biotic (length, dry mass, sex, and stage) and abiotic (location and time of sampling) parameters in explaining Hg concentrations in krill.
SS44B - Ocean and Freshwater Zooplankton Ecology
Description
Time: 2:30 PM
Date: 29/3/2025
Room: W207AB