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
04:30 PM
Stratification onset and dissipation influences gelatinous zooplankton abundance and diversity (9302)
Primary Presenter: Adam Greer, University of Georgia, Skidaway Institute of Oceanography (atgreer@uga.edu)
Shelf seas are biologically productive and can oscillate between vertically mixed (fall/winter) and stratified conditions (spring/summer). The latter scenario, often driven by solar heating and relatively low wind speeds, favors aggregations that are especially relevant to consumers that rely on concentrated prey resources. Gelatinous zooplankton are an abundant group of consumers that encompass a wide range of feeding strategies, from grazers to predators, suggesting their responses to stratification and mixed conditions may differ among genera or functional groups. Resolving these dynamics is critical for understanding the diversity of trophic pathways and broader properties of shelf food webs. Using in situ imaging systems, we measured the fine-scale abundances of gelatinous zooplankton in well-mixed and stratified conditions from both the South Atlantic Bight and Gulf of Mexico. A 50-km transect in the northern Gulf of Mexico, just south of Perdido Bay (Florida, USA), showed that the diversity of gelatinous zooplankton increased with more intense stratification in the summer. Many groups of hydromedusae and siphonophores (identified to the genus level) displayed low spatial overlap, even when associated with similar water mass properties. Doliolids were one of the only groups to consistently occupy the pycnocline - an area often associated with high concentrations of marine snow. Future work will determine if aggregations are consistent among years and how these distributions of gelatinous zooplankton influence diets and trophic structure in shelf food webs.
04:45 PM
SPECIES-SPECIFIC REPRODUCTIVE STRATEGIES IN SALPS: IMPLICATIONS FOR BLOOM FORMATION (9064)
Primary Presenter: Farzana Yesmin, University of Oregon (fyesmin@uoregon.edu)
Salps, pelagic tunicates with alternating sexual and asexual generations, can rapidly form large blooms under favorable conditions, significantly impacting marine biogeochemical cycles through their high filtration efficiency. Although salp blooms are well-studied for their ecological impact, the influence of species-specific reproductive strategies on salp bloom formation and magnitude remains poorly understood. In this study, we compare sexual and asexual reproductive outputs across salp species, with a focus on their asexual budding strategies and their implications for bloom formation. Salp specimens used in this study were imaged in situ or hand-collected in 1-liter jars via untethered "blue water" diving off the coast of Kailua-Kona, Hawaii, a region with high salp diversity. After collection, the specimens were photographed in the lab using a DSLR camera. Morphometric measurements, and reproductive traits were analyzed from images. By comparing the reproductive traits across a variety of salp species, this research will shed light on the ecological and evolutionary factors driving reproductive success in salps. The findings will also enhance our understanding of how species-specific reproductive strategies contribute to salp bloom dynamics and their broader role in marine pelagic ecosystems.
05:00 PM
ASSESSING GELATINOUS ZOOPLANKTON TROPHIC FLEXIBILITY IN A COASTAL UPWELLING SYSTEM USING STABLE ISOTOPES (8794)
Primary Presenter: Elizabeth Wallace, University of Oregon (ewal@uoregon.edu)
Gelatinous zooplankton are abundant and diverse members of marine communities, yet their role in food webs has often been overlooked. Though gelatinous organisms all have large watery bodies compared to carbon content, they have a variety of taxonomic identities, life histories, and feeding strategies. These varied characteristics suggest that gelatinous zooplankton taxa may occupy distinct roles in the food web and may respond in different ways to changes in environmental conditions, nuances which are not yet accounted for in current conceptions of marine food webs and food web models. Using nitrogen and carbon stable isotope analysis, we examined seasonal and spatial shifts in the trophic niche of 33 taxa of gelatinous and semi-gelatinous zooplankton and fish larvae in the Northern California Current (NCC). The NCC experiences strong seasonal upwelling which allows for comparisons across temperature and productivity gradients. Taxa varied in carbon and nitrogen stable isotope ratios and in C:N ratios, suggesting unique trophic roles. Additionally, comparisons across seasons and space revealed that gelatinous zooplankton taxa may respond uniquely to changes in environmental parameters including temperature and primary production. This study highlights the complexity of gelatinous zooplankton trophic dynamics in an eastern boundary current. It suggests that variations between taxa are essential for accurate modelling of gelatinous zooplankton food webs especially when considering human-induced changes in temperature and nutrient levels.
05:15 PM
DIETARY PLASTICITY DIFFERENTIATIES TROPHIC NICHES OF DOLIOLIDS AND SALPS (8941)
Primary Presenter: Emily Gipson, University of Georgia (emily.gipson@uga.edu)
Filter feeding by pelagic tunicates links them to both the grazing and microbial food webs, thus influencing the quantity and form of particulate organic matter (POM) in the water column. On the South Atlantic Bight (SAB) continental shelf, the doliolid Dolioletta gegenbauri populations persist year-round and occasionally form dense blooms in response to favorable conditions. SAB primary productivity fluctuates seasonally and interannually, and we hypothesize that trophic niche breadth in doliolids, but not co-occurring salps, varies following these fluctuations in food availability and quality. In August of 2021, 2022, and 2023, we sampled several parameters to quantify the microbial and phytoplankton communities on the SAB shelf, including bacterial production rates, POC:Chl-a ratios, and Chl-a:Phaeopigment ratios. We also measured the δ13C and δ15N composition of POM and representative zooplankton samples, including doliolids and salps. Doliolid trophic niche breadth differed appreciably from year to year, whereas the niche breadth of salps was less variable. Understanding the factors that modulate trophic strategy among pelagic tunicates and other gelatinous organisms is key for resolving different trophic pathways for carbon in shelf systems.
05:30 PM
Pyrosoma atlanticum fecal pellet production in the California Current: implications for grazing and carbon export dynamics (9110)
Primary Presenter: Grace Cawley, University of California: San Diego (gcawley@ucsd.edu)
Pyrosoma atlanticum, a colonial pelagic tunicate, has exhibited significant increases in abundance in the California Current Ecosystem (CCE) since anomalously warm temperatures emerged following the 2014-2016 Northeast Pacific heatwave. This study investigates the ecological role of pyrosomes in the Southern California Current region. We investigated the role of pyrosome fecal pellets by quantifying their production, morphology, sinking rates, and carbon, nitrogen and biogenic silica content. Shipboard experiments were conducted during the California Current Ecosystem Long-Term Ecological Research 2021 process cruise, across upwelling-influenced coastal and oligotrophic offshore waters. We conducted a total of 32 experiments, which showed pyrosomes produced small pellets (354 ± 111 µm), at high rates (19 ± 19 pellets min-1), which resulted in the production of up to 500,000 pellets m-2 d-1 in locations with high densities. Fecal pellets had slow sinking rates: freshly produced pellets had average sinking rates of 47 ± 38 m d-1, and pellets aged for 1-2 days h sank even slower (31 ± 28 m d-1), suggesting that a large portion could be remineralized within the upper water column. We estimated their removal of primary production using an assimilation efficiency of 0.6, which indicated that ~20-90 of the stock could be grazed depending on the location. Finally, we present novel results based on our biogenic silica measurements to estimate their impact on diatom standing stocks. Our study indicates that P. atlanticum can play an important role in carbon cycling and food-web pathways and that their role might be enhanced in offshore oligotrophic waters.
05:45 PM
REFINING FECAL PELLET CARBON DENSITY ESTIMATES OF KEY ZOOPLANKTON TAXA IN THE SARGASSO SEA (9553)
Primary Presenter: Yuuki Niimi, Arizona State University (yniimi@asu.edu)
Zooplankton play a fundamental role in marine ecosystems, facilitating carbon export by producing fecal pellets that transport organic carbon from surface waters to the deep ocean. This process significantly impacts carbon sequestration and oceanic carbon cycling. Global models that estimate carbon flux using the carbon density of zooplankton fecal pellets often overlook regional variability, potentially leading to inaccurate predictions of carbon export. This study seeks to improve the accuracy of these models by quantifying the carbon density of key zooplankton taxa in the Sargasso Sea, an oligotrophic region with diverse zooplankton communities. Zooplankton were collected in March 2023 during both day and night MOCNESS tows conducted at the Bermuda Atlantic Time Series (BATS) site. The sampling focused on important taxa such as euphausiids, salps, pteropods, and the copepod Pleuromamma xiphias. After sorting, animals were allowed to excrete and fecal pellets were sampled for a combination of image-based methods and CHN elemental analysis. Results revealed substantial discrepancies between experimental carbon density values and predictions from global models. These variations substantially alter the prediction of carbon flux inferred from either zooplankton abundance or image based analysis of trap particles. This study underscores the critical importance of integrating localized, taxa-specific data into biogeochemical models to enhance our understanding of midwater carbon flux and its broader implications for the global carbon cycle.
SS44C - Ocean and Freshwater Zooplankton Ecology
Description
Time: 4:30 PM
Date: 29/3/2025
Room: W207AB