Aquatic Sciences Meeting, Albuquerque 2001

SS22 Strategies To Reduce Mortality in Marine and Freshwater Phytoplankton

Date: Wednesday, February 14, 2001, Time: 11:15:00 AM

Location: Acoma/Zuni/Tesuque

Wolfe, G, V, California State University, Chico, Chico, USA, gwolfe2@csuchico.edu

Radzio, T, A, Longwood College, Farmville, USA, tradzio@longwood.lwc.edu

Strom, S, L, Western Washington University, Anacortes, USA, stroms@cc.wwu.edu

PHYSICAL AND CHEMICAL ACTIVATION OF IN VIVO DMSP CLEAVAGE IN MARINE PHYTOPLANKTON

We examined bloom-forming haptophytes (Emiliania huxleyi, Isochrysis galbana, Phaeocystis globosa) and autotrophic dinoflagellates (Alexandrium sp., Amphidinium carterae) containing high intracellular dimethylsulfoniopropionate (DMSP) and varying DMSP lyase activities. We found evidence for in vivo DMSP cleavage in response to environmental cues, including continuous darkness, mechanical (shear) stress produced by sparging live cells, and treatment with polyamino compounds, known chemical triggers of exocytosis or stimulated secretion. There was considerable intraspecific variation in algal response to these external signals, but in general, dinoflagellates were the most sensitive to physical (shear) stress, while haptophytes showed greater response to darkness and chemical triggers. Therefore, these algae can clearly respond to environmental triggers by releasing or cleaving DMSP. Although it is not yet clear if physical or chemical signals from herbivorous protist grazers stimulate DMSP cleavage or release, these algal responses appear to function for grazing deterrence, and likely constitute an activated defense system. We propose that triggered exocytosis (stimulated secretion), known only in a few specialized cases, may be a general defense mechanism among unicellular eukaryotes.

This Session Listing

Aquatic Sciences Meeting, Albuquerque 2001

Quicklinks