Impact of a Trichodesmium Bloom on Zooplankton Distribution and Available Nitrogen in Tampa Bay

Zooplankton serve as an important link within marine food webs – between abundant phytoplankton primary producers and a diversity of consumers. Trichodesmium is an important warm-water cyanobacteria capable of fixing nitrogen in oligotrophic environments and a potential food source for zooplankton predators. Along the Southwest Florida coastline, the toxic dinoflagellate Karenia brevis is notable for creating harmful algal blooms (HABs) on a near annual basis. Nitrogen cycling in Tampa Bay, linked to the nitrogen fixing cyanobacteria Trichodesmium, has been identified as an amplifier of K. brevis blooms. To assess the impacts of ambient nitrogen variation on K. brevis appearance and subsequent impacts on zooplankton community dynamics, sampling took place weekly at three locations within Tampa Bay. Nutrient samples were collected leading up to Trichodesmium bloom events and analyzed for inorganic nitrogen (nitrate, nitrite, and ammonia) and dissolved organic nitrogen using absorption-based spectrophotometry. Zooplankton tows were performed and preserved for quantification and identification. The measured uptake of inorganic nitrogen and release of organic amines during the Trichodesmium bloom provide insight into the nutrient dynamics facilitating K. brevis blooms in estuarine environments. Synergistic analysis of zooplankton further indicated impacts on the community composition, particularly the dominant calanoid copepod species as well as changes in total zooplankton abundance suggesting a bottom-up effect of Trichodesmium produced nitrogen within marine ecosystems.

Presentation Preference: Poster

Primary Presenter: Rebecca Waggett, The University of Tampa (rwaggett@ut.edu)

Authors:

Alyssa Meyers, The University of Tampa  (alyssa.meyers@spartans.ut.edu)

Rebecca Waggett, The University of Tampa  (rwaggett@ut.edu)

Rob Masserini, The University of Tampa  (rmasserini@ut.edu)