Thematic session.
Lead Organizer: Nandini Sarma, FES Iztacala, UNAM (nandini@unam.mx)
Co-organizers:
S. S. S. Sarma, FES Iztacala, UNAM (sarma@unam.mx)
Presentations
11:00 AM
BODY SIZE AND GEOMETRY PREDICT ZOOPLANKTON SURVIVAL TO AIR EXPOSURE (10150)
Primary Presenter: Donn Branstrator, University of Minnesota Duluth (dbranstr@d.umn.edu)
Dormant life stages of freshwater zooplankton are typically resistant to environmental exposure, and this facilitates overland dispersal. However, environmental exposure and overland dispersal are less well understood for active life stages. To characterize empirically the longevity of active life stages out of water, survival time to air exposure was measured in the laboratory for eight cladoceran species using heartbeat cessation to signify survival time. Survival time increased with body dry weight with an allometric scaling exponent near 2/3 for a multispecies model with six bivalved species including Bosmina longirostris, Acroperus harpae, Ceriodaphnia dubia, Daphnia mendotae, Daphnia pulex, and Daphnia magna. The 2/3 scaling exponent is consistent with Euclidean geometry and points to water loss across the surface of a spherical body as the cause. Survival time of a seventh species, Holopedium gibberum, was 571% longer than predictions based on the multispecies model, likely due to its gelatinous mantle. Survival time of an eighth species, Bythotrephes cederströmii, was 68-94% shorter than predictions based on the multispecies model, likely due to its lack of a bivalved carapace. The longest survival time of an individual was 225 min (H. gibberum). We share a conceptual model of how body size may predict overland dispersal potential of zooplankton active life stages.
11:00 AM
ZOOPLANKTON COMMUNITY COMPOSITION IN WAQUOIT BAY, A SHALLOW, TEMPERATE ESTUARY (10722)
Primary Presenter: Sierra Brown, Woods Hole Oceanographic Institution (brown_sierra@outlook.com)
We sought to characterize the zooplankton community within Waquoit Bay, a shallow, tidally-mixed estuary on the south shore of Cape Cod, Massachusetts. As a National Estuarine Research Reserve, Waquoit Bay has been the site of diverse research studies and a long-term water quality monitoring program that is supported by volunteers. Despite the wealth of information about the Bay, the mesozooplankton community is not routinely monitored. We collected mesozooplankton via net tows from four stations within the Bay at four monthly intervals between March and July 2025. Over this time the temperature ranged from 6.6-26 C, and salinity ranged from 28-31 ppt. Samples were preserved in formalin and imaged using a FlowCam Macro. Debris and particles <350 um were filtered using Visual Spreadsheet software, and zooplankton images are being classified within EcoTaxa. Consistent with previous observations, the community was dominated by calanoid copepods, including Acartia spp, Eurytemora affinis, and Centropages hamatus. Zooplankton abundance was highest in March and decreased over the summer. Qualitatively, the decrease in zooplankton abundance coincided with increases in gelatinous zooplankton, suggesting top-down control. Analysis is ongoing to quantify calorimetric content of zooplankton samples and assess zooplankton community composition in the context of nutrient and chlorophyll measurements. Semi-automated image analysis provides a relatively rapid means of zooplankton community assessment and could facilitate sustained monitoring of this coastal ecosystem. *This research was developed with funding from the Defense Advanced Research Projects Agency (DARPA). The views, opinions and/or findings expressed are those of the author and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government.
11:00 AM
ZOOPLANKTON COMMUNITY DISTRIBUTION AND COMPOSITION IN RELATION TO SUBSURFACE PRODUCTIVITY IN AN ARCTIC MARGINAL SEA (10757)
Primary Presenter: Matoska Silva, Oregon State University (matoska.silva@gmail.com)
The significant climate change-associated loss of sea ice in the Arctic Ocean and its marginal seas is supporting increased phytoplankton primary productivity due to reduced obstruction of sunlight by sea ice cover. Subsurface phytoplankton productivity during the late open water season has been recently estimated to contribute a substantial portion of total primary productivity in the Chukchi Sea, and climate-related increases in productivity may be driving a shift in trophic dynamics in this ecosystem. The purpose of this study was to expand on prior biogeochemical profiling of the Chukchi shelf to determine if subsurface productivity plays a role in shaping the species composition, energy density, and distribution of zooplankton communities. We present the results of taxonomic classification and caloric value quantification of zooplankton communities in the Hanna Shoal and Barrow Canyon region of the NE Chukchi shelf in summer 2017. These results aid in further quantifying the contributions of subsurface productivity to the Chukchi Sea food web, with implications for better understanding this ecosystem’s response to ongoing warming.
11:00 AM
Zooplankton in Transition: Biodiversity and Turnover Patterns in the Chilean Oxygen Minimum Zone under contrasting ENSO states (10914)
Primary Presenter: Carolina Gonzalez, Universidad de Antofagasta (carolina.gonzalez@imo-chile.cl)
Las Zonas de Mínimo Oxígeno (ZMO) son regiones oceánicas críticas donde la baja disponibilidad de oxígeno limita la biodiversidad y altera el funcionamiento de la red trófica. Estos sistemas son altamente sensibles a la variabilidad climática, como los fenómenos de El Niño y La Niña, que modifican la estructura fisicoquímica de la columna de agua. Comprender cómo dicha variabilidad ambiental influye en la diversidad y la composición de la comunidad del zooplancton es esencial para anticipar los impactos futuros del cambio climático. Durante las campañas oceanográficas realizadas en 2023 (condiciones de El Niño) y 2024 (La Niña/condiciones neutrales), se evaluó la diversidad del zooplancton a través de gradientes de oxígeno en la ZMO chilena utilizando ARNr 18S y metabarcoding COI. Los principales grupos detectados fueron Copepoda, Euteleostemi y Thaliacea. Los perfiles oceanográficos revelaron diferencias interanuales en los 200 m superiores, con menor oxígeno, temperatura y salinidad, y mayores concentraciones de clorofila durante las condiciones de La Niña (2024), en relación con las condiciones de El Niño (2023). Entre las especies de zooplancton identificadas, Subeucalanus subtenuis dominó durante El Niño, mientras que Pseudosagitta maxima prevaleció bajo condiciones neutrales/de La Niña. La riqueza de especies fue mayor en las capas oxigenadas y alcanzó un mínimo en el núcleo de la ZMO tanto para el ARNr 18S como para el COI. A lo largo del gradiente de oxígeno, la diversidad beta estuvo dominada por la rotación de especies en lugar de la anidación entre la ZMO y las capas más profundas, lo que indica un alto dinamismo ecológico impulsado por el reemplazo de especies. Los modelos de aprendizaje automático confirmaron que la concentración de oxígeno es el principal factor que modula la estructura de la comunidad en la ZMO, mientras que la temperatura actúa como la variable estructurante primaria tanto en las capas superficiales como profundas. Estos hallazgos resaltan la influencia combinada de los gradientes de oxígeno y la variabilidad de ENSO en la estructura de la comunidad de zooplancton, lo que sugiere que las oxiclinas actúan como una barrera ecológica.
11:00 AM
MULTIGENERATIONAL EFFECTS OF L-BMAA ON THE LIFE TABLE TRAITS OF CERIODAPHNIA DUBIA (CLADOCERA) (10938)
Primary Presenter: Cesar Zamora Barrios, Universidad Nacional Autónoma de México (zamoracesaralejandro@iztacala.unam.mx)
Secondary metabolites produced by CyanoHABs (Cyanobacterial Harmful Algal Blooms) in inland aquatic systems are often toxic to various members of the zooplankton community. However, there are still controversial and inconsistent reports regarding their effects, particularly for understudied metabolites such as the amino acid L-BMAA (L-β-N-methylamino-L-alanine). This study aimed to evaluate the multigenerational effects of L-BMAA on the survival and fecundity of Ceriodaphnia dubia, exposed to three concentrations (12.5, 25, and 50% of the LC50) and a toxin-free control. Cladocerans were exposed for five consecutive generations. The results showed a progressive decline in all life-table variables (life expectancy, net reproductive rate, gross reproductive rate, generation time, and intrinsic rate of increase) across generations. At the 12.5% concentration, the toxic effects were moderate, and organisms partially compensated in the F1 generation; however, life expectancy was drastically reduced compared to the control. In contrast, higher concentrations markedly reduced survival, especially in later generations, suggesting accumulation and generational transfer of the toxin.
11:00 AM
THE EFFECTS OF GUT MICROBIOME ON FUNGAL INFECTION IN DAPHNIA DENTIFERA (11368)
Primary Presenter: Michelle Villalobos, University of Illinois Urbana-Champaign (mvill31@illinois.edu)
The host-associated gut microbiome communities are involved in a wide range of processes within the host, from metabolic regulation and developmental signaling to behavioral and social interactions. These symbionts aid the host through a range of functions, such as digestion, nutrient acquisition, and regulating the host immune system. Disrupting the host’s microbiome, may alter susceptibility to pathogens and negatively impact the host’s life history traits. To understand the effects of the gut microbiome in host-parasite exposure, a series of laboratory experiments were conducted with the parthenogenetic species Daphnia dentifera and the pathogenic fungus Astrolozyma monospora (formerly known as Metschnikowia bicuspidata). A transmission assay was performed in which two genotypes of Daphnia (Clear-1 and IL-16) were exposed to the fungus after either being raised in the presence (microbiome-reduced) or absence (control) of antibiotics. Then, we conducted a microbiome re-exposure experiment with Daphnia to rear healthy, unhealthy, and microbiome-reduced individuals, who were then exposed to the fungus. Infection rate and life-history traits were recorded to understand the role of the host’s gut-microbiome on host fitness and susceptibility to infection. We observed that infection rate between the two treatments indicated that “microbiome-reduced” Daphnia were less susceptible to the fungus. The 16S rRNA data showed differences in microbial composition and relative abundance of the microbial species in both treatments. These studies will provide more understanding of the factors that influence pathogenic transmission rate and the role of the host’s microbiome in these interactions.
11:00 AM
WHERE THE WIND BLOWS: THE ZOOPLANKTON WILL BE (11447)
Primary Presenter: Jumana Tanner, Center For Limnology (jumanatanner13@gmail.com)
Strong winds, high precipitation, and energetic storms are most common during spring months in temperate regions and are becoming more extreme and more frequent as the climate changes. These weather events can change long and short-term species distributions and trophic interactions in lake ecosystems. We hypothesize that weather events during spring and early summer months will change the horizontal and vertical distribution of zooplankton taxa, especially for larger species and larger-sized individuals. Additionally, we hypothesize that spring weather events and water column remixing will result in higher spatial variability in zooplankton distribution compared to stratified summer periods. To test our hypotheses, we sampled vertical temperature, dissolved oxygen, and chlorophyll-a. Zooplankton were also collected weekly from three sites in Escanaba Lake, Boulder Junction, WI, USA, using a Schindler-Patalas trap during the open water season of 2024. Zooplankton taxa were enumerated, and a subsample of Daphnia was measured from each sampling event to determine the size and species distributions. Early season weather events led to larger zooplankton species and larger-sized individuals accumulating on downwind shorelines. However, the type and duration of weather events interacts with migration behaviors to generate variable distributions of zooplankton. Seasonal patterns will be discussed within the context of overall seasonal plankton community changes and both vertical and horizontal zooplankton movement.
11:00 AM
THERMAL CONSTRAINTS AND PREDATION RISK SHAPE SPATIO-TEMPORAL DYNAMICS OF ZOOPLANKTON TAXA IN STRATIFIED LAKES (11600)
Primary Presenter: Andrea Bertolo, Université du Québec � Trois-Rivières (andrea.bertolo@uqtr.ca)
Predation risk and thermal structure jointly shape the spatio-temporal dynamics of fish and zooplankton in stratified lakes. Using in situ imagery (Underwater Vision Profiler) and acoustic telemetry of brook charr, we examined how 3D fine scale habitat variability, thermal barriers, and behavioral differences modulate predator prey relationships. During summer, zooplankton communities exhibited pronounced within lake heterogeneity, both in terms of contrasting species dominance and of strong variation in size spectra that matched differences typically observed among distinct lakes. As the lake cooled, fish redistributed across depths, initiating shifts in zooplankton size structure and composition that pointed to a cascading effect of predator movements. Thermal constraints restricted fish access to epilimnetic zones in summer, limiting overlap with large cladocerans except for a subset of individuals that consistently selected resource rich areas. When the thermal barrier weakened, fish entered littoral and upper layers, increasing spatial overlap with their prey. Zooplankton diel vertical migration also responded to these seasonal changes in predation risk, with large cladocerans remaining in the epilimnion during summer while avoiding the metalimnion where fish aggregated. Together, these patterns illustrate how thermal fragmentation and selective predation determine the spatio- temporal overlap between fish and zooplankton, but ultimately among zooplankton taxa, shaping their resource use across vertical and horizontal gradients in temperate lakes.
11:00 AM
The One Piece in the Biological Pump: Krill as Model Organisms for Spatial Variability in Zooplankton-Mediated Carbon Export (11877)
Primary Presenter: Yuuki Niimi, Arizona State University/BIOS (yniimi@asu.edu)
Krill (euphausiids) are a dominant zooplankton group and serve as model organisms for understanding zooplankton-mediated carbon export, as many species are cosmopolitan and inhabit multiple ocean basins. Through the production of fecal pellets, euphausiids contribute substantially to the biological carbon pump, yet genus- and species-specific roles, as well as the relative contributions of resident versus migratory communities, remain poorly quantified across regions. This study examines spatial differences in euphausiid-mediated carbon export between the northwest Atlantic and northeast Pacific, two regions with distinct hydrographic conditions, community compositions, and proportions of resident and vertically migrating taxa. Zooplankton samples were collected with diel MOCNESS tows during NSF Ocean Acidification cruises in 2011 (Atlantic) and 2012 (Pacific). Euphausiids are being processed with ZooScan and Ecotaxa to obtain genus-level identifications, size distributions, biovolumes, and abundance estimates. Carbon content and fecal pellet production are calculated by integrating these data with experimentally derived carbon density values and R-based modeling approaches. Depth-specific fecal pellet production will be compared across basins and taxa to assess variability in export magnitude. Preliminary results suggest that differences in euphausiid assemblages, particularly in the relative abundance of migratory (e.g. Euphausia sp.) versus resident (e.g. Stylocheiron sp.) taxa, drive distinct patterns of midwater carbon flux in each region. By leveraging euphausiids as a model group, this study provides new insight into the mechanisms controlling regional carbon export and underscores the importance of incorporating taxon-specific and behavioral traits into biogeochemical and climate models to better predict ecosystem responses to environmental change.
11:00 AM
SPECIES CO-OCCURRENCE PATTERNS OF ZOOPLANKTON IN A NEOTROPICAL FLOODPLAIN (11893)
Primary Presenter: Érica Lima, Universidade Estadual de Maringá (erika22schmoeller@gmail.com)
In tropical floodplains such as the Pantanal, hydrological variation is a major driver of zooplankton distribution and species co-occurrence patterns. We investigated how seasonal shifts between flood and drought phases structure positive and negative species associations, and whether environmental variables mediate these patterns. Specifically, we tested whether rotifers and cladocerans co-occur more or less often than expected by chance and whether functional similarity shapes these associations. Co-occurrence patterns were estimated using probabilistic models, and their relationships with environmental gradients were assessed through multivariate analyses and latent-variable models. Overall, positive associations predominated, indicating that many species respond similarly to environmental conditions. During the flood, positive co-occurrences were concentrated among functionally similar species, consistent with environmental filtering. In contrast, drought conditions led to an increase in negative associations, particularly among functionally distinct species, suggesting stronger niche differentiation under hydrological isolation. Environmental gradients related to water quality were the main predictors of co-occurrence structure. Together, these results show that the alternation between flood and drought regulates the balance between environmental filtering and niche differentiation, shaping zooplankton coexistence through time and contributing to biodiversity maintenance in tropical wetlands.
CS007P Zooplankton Ecology and Physiology
Description
Time: 11:00 AM
Date: 15/5/2026
Room: 517C