MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps14824

ABSTRACT: Increases in jellyfish abundance have coincided with changing conditions associated with climate change, such as higher temperatures and salinity, in several areas of the world. Jellyfish are voracious predators of zooplankton, a prey source that is also utilized by juvenile fish and forage fishes. Moon jellyfish (Aurelia labiata) medusae can form large blooms or aggregations in estuaries including Puget Sound, WA, but the impacts of these aggregations on the surrounding ecosystem are not well understood. This study used mesocosm experiments and in situ field sampling to examine A. labiata predation on zooplankton and other environmental impacts of jellyfish in Puget Sound, providing novel insight into how predator-prey dynamics observed in experiments translate to the natural environment and estimating clearance rates for taxa that have not yet been reported elsewhere. In mesocosm experiments, A. labiata at high treatment densities were able to consume a large proportion of available natural zooplankton in just two hours. In the field, copepod densities were significantly lower inside of jellyfish aggregations. Jellyfish biomass was the primary predictor of copepod abundance in jellyfish-inhabited inlets. Chlorophyll was also higher inside of aggregations, indicating the presence of a potential trophic cascade. Our results suggest that jellyfish can consume a significant amount of zooplankton prey when present in dense aggregations, and future increases in jellyfish abundance may limit prey availability for fish in the immediate area.