The alteration of food web dynamics through addition or removal of species can have major impacts on the size-structure and abundance of other species. Changes in the size-structure and abundance of zooplankton, whose rapid life-histories allow for swift responses to food web changes, can readily impact prey quality and availability for fishes. Utah Lake has been the site of intensive common carp (Cyprinus carpio) removal efforts since 2009, experiencing a biomass reduction of over 75% at one point. Our previous research has linked reduction in carp biomass to changes in zooplankton species composition, but the impact on size-structure of individual taxa had not been examined. Here, we analyzed the body length of five common taxa, Calanoid and Cyclopoid copepods, Daphnia, Diaphanosoma, and Ceriodaphnia, from 2013-2020 using zooplankton monitoring data to examine their response to carp removal in Utah Lake. We found that all five taxa increased in size during periods of low carp biomass. Additionally, all taxa except Daphnia demonstrated a negative trend across years, suggesting other factors (e.g. lake level, temperature) are influencing zooplankton body size. Increased size during periods of lower carp biomass suggests a release from predation pressure by carp. Since zooplankton size can have important positive effects across different trophic levels, other zooplanktivorous fishes in Utah Lake, including the endemic June sucker (Chasmistes liorus), will benefit from the increased availability of energy-dense, larger zooplankton. Further, larger zooplankton are generally more efficient grazers of phytoplankton and thus may help limit the severity of harmful algal blooms. Future analyses will examine the relationship between zooplankton size and algal bloom severity in Utah Lake.
University / Institution: Utah State University
Format: In Person
SESSION A (9:00-10:30AM)
Area of Research: Science & Technology
Faculty Mentor: Timothy Walsworth
Location: Alumni House, SORENSON ROOM (9:20am)