Aquatic Sciences Meeting, Albuquerque 2001

SS22 Strategies To Reduce Mortality in Marine and Freshwater Phytoplankton

Date: Wednesday, February 14, 2001, Time: 10:30:00 AM

Location: Acoma/Zuni/Tesuque

Rengefors, K, , Woods Hole Oceanographic Institution, Woods Hole, USA, krengefors@whoi.edu

Legrand, C, , University of Kalmar, Kalmar, Sweden, Catherine.Legrand@ng.hik.se

TOXICITY IN PERIDINIUM ACICULIFERUM - AN ADAPTIVE STRATEGY TO OUTCOMPETE OTHER WINTER PHYTOPLANKTON?

Freshwater dinoflagellates may form dense blooms during winter in ice-covered lakes. Unlike their marine counterparts freshwater dinoflagellates are rarely considered to be potential toxin producers. Here we tested if the winter species Peridinium aciculiferum produces toxin(s) and investigated the potential adaptive function of that toxin - i.e. predator defense or inhibition of competitors (allelopathy). P. aciculiferum produces a toxin(s). Using traditional toxicity bioassays (Artemia toxicity test and haemolytic activity assay), we detected the production of a toxic substance by P. aciculiferum cells from both the field and from laboratory cultures. Only cultures deprived of phosphorus showed toxicity. Potential predators, such as Daphnia galeata (Cladocera) and Eudiaptomus graciloides (Copepoda), were apparently not harmed by P. aciculiferum toxicity. However, a competitor, the flagellate Rhodomonas lacustris (Cryptophyceae), which co-occurs with P. aciculiferum was killed (allelopathy) by the P.aciculiferum toxin. The toxin(s) caused the cells of R. lacustris to swell and burst. We concluded that allelopathy may be an adaptive strategy of winter dinoflagellates, allowing them to outcompete other phytoplankton species, and thereby dominate the algal biomass.

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Aquatic Sciences Meeting, Albuquerque 2001

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