IDENTIFYING B-VITAMIN REQUIREMENTS AND PHYCOSPHERE INTERACTIONS FOR THE HAB FORMING DINOFLAGELLATE, PYRODINIUM BAHAMENSE VAR. BAHAMENSE

Pyrodinium bahamense is a saxitoxin-producing dinoflagellate in tropical and subtropical estuarine waters. Pyrodinium is an emerging HAB species in Florida estuaries, with blooms yet to be reliably forecast. Thus, factors not currently included in prediction models, such as micronutrient (i.e., vitamin) availability and biological interactions, may influence Pyrodinium bloom occurrence and intensity. As many HAB-forming dinoflagellates are auxotrophic for at least one B vitamin, we first evaluated which B vitamins Pyrodinium requires for growth and determined that Pyrodinium is a vitamin-B₁₂ auxotroph. Next, since bacteria in the phycosphere are often able to fulfill algal B₁₂ requirements, we co-cultured Pyrodinium with bacterial communities isolated from estuaries where Pyrodinium often blooms (Old Tampa Bay and Indian River Lagoon). Nanopore full-length 16S rRNA metabarcode sequencing confirmed that inoculated Pyrodinium cultures contained diverse and distinct bacterial communities representative of each estuary. The bacterial community from Indian River Lagoon restored some growth when B₁₂ limitation was induced in Pyrodinium but neither inoculum restored growth to the same levels as media including B₁₂, despite both inoculum bacterial communities containing putative B₁₂-producing bacteria. Our results demonstrate that Pyrodinium bahamense must attain vitamin B₁₂ from the environment to reach bloom levels but bacteria in the surrounding seawater may not provide this critical resource, hence implicating other B₁₂ sources in estuaries where Pyrodinium blooms. 

Presentation Preference: Oral

Primary Presenter: Lydia Ruggles, University of South Florida (lruggles@usf.edu)

Authors:

Lydia Ruggles, University of South Florida College of Marine Science  (lruggles@usf.edu)

Lauren D'Amore, University of South Florida College of Marine Science  (Damore24@usf.edu)

Cary Lopez, Florida Fish and Wildlife Research Institute  (cary.lopez@myfwc.com)

Margaret Mars Brisbin, University of South Florida College of Marine Science  (mmarsbrisbin@usf.edu)