Skip to main content
2023 ESA Annual Meeting Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.
Back

Contributed Talk

Session: : Communities: Spatial Patterns And Environmental Gradients 1

COS 10-2 - High variability in zooplankton community structure across space and time in an anoxic reservoir due to changing patterns of migration behavior

Monday, August 7, 2023
1:45 PM – 2:00 PM PDT
Location: B119
Abstract: Zooplankton are integral components of freshwater food webs, serving as both food sources for fish and grazers of phytoplankton. Zooplankton commonly exhibit diel vertical or horizontal migration (DVM or DHM), in which they avoid predation and UV radiation in surface waters by migrating to deeper waters (DVM) or near-shore habitat (DHM) during the day, and return to pelagic surface waters at night to feed. Most, but not all, taxa exhibit these migratory behaviors, resulting in variable community structure in pelagic surface waters over 24-hours. Preference for DVM vs. DHM may occur due to factors like summer bottom-water anoxia (< 0.5 mg/L dissolved oxygen). Consequently, as the intensity of anoxia varies throughout a summer, there is likely substantial variability in zooplankton migration dynamics, affecting community structure across spatial (sites) and temporal (hourly and yearly) scales. To understand how zooplankton community structure changes over space and time in response to bottom-water anoxia, we conducted five 24-hour sampling campaigns over three summers at Beaverdam Reservoir, a eutrophic reservoir in southwestern Virginia, USA. We collected zooplankton from a deep and near-shore site every 2-6 hours, identified all individuals to order, and used Euclidean distance to quantify community variability among spatial and temporal scales.


Across all five sampling campaigns, we found that zooplankton community structure was more variable at hourly timescales within 24-hour campaigns than yearly or spatially (between surface water sites). This diel variability in zooplankton community structure is likely driven by zooplankton diel migration behavior to both deep water and near-shore refugia. Within the zooplankton community, we found that cyclopoids were more likely to exhibit DVM and rotifers were more likely to exhibit DHM. Additionally, hourly rotifer variability was 9% - 48% greater than cladoceran and copepod variability, suggesting that zooplankton taxa respond to diel environmental stimuli differently. Specifically, cyclopoids may be more tolerant to anoxia than rotifers, explaining the preference of DVM for cyclopoids and DHM for rotifers. Our work suggests that current zooplankton monitoring approaches, which typically occur once a day around noon, likely underestimate much of the variability in zooplankton community structure. Importantly, this short-term variability in zooplankton densities can have implications on fish communities that feed on zooplankton, as well as algal biomass and water quality. Ultimately, identifying the dominant spatial and temporal scales of variability in zooplankton community structure can elucidate taxa-specific patterns that may be crucial to understanding freshwater ecosystem functioning in the face of global change.



Designed by Cadmium |Technical Support |Give Feedback
© Copyright 2024 Cadmium. All Rights Reserved.