Hambright, K. DavidWitt, Brenda2016-03-162016-03-162016-05-13http://hdl.handle.net/11244/33093Harmful algae blooms (HABs) have the ability to produce profound changes to aquatic communities through a variety of factors, most commonly their propensity to produce toxins that can harm co-existing organisms. Many zooplankton species are particularly susceptible due to their close trophic relationship as grazers and shifts in zooplankton community structure may result due to species-specific responses such as selective feeding. I hypothesized that selective feeding would alter zooplankton community structure, with overall zooplankton densities decreasing and non-selective grazers dropping out of the community. My study investigated how the toxigenic haptophyte alga Prymnesium parvum affects a natural zooplankton community under controlled laboratory conditions. I found that species responses varied, with significant reductions in two taxa known to be non-selective feeders, D. menodotae and Keratella sp. A predatory species, Asplanchna sp., also experienced a significant reduction, possibly due to reductions in prey sources. These reductions drove an overall shift in community structure. In addition, Prymnesium cell density had a significant effect on the abundances of all three zooplankton taxa, although this was the result of reductions in specific species and not overall reductions. My study resolves the more intricate relationships related to selective feeding among zooplankton species and provides solid evidence that Prymnesium blooms can have detrimental effects on zooplankton community composition and may lead to long-term community changes that can have a profound influence on the affected ecosystem.Prymnesium parvum, zooplankton, communitiesinvasive species