Aquatic Sciences Meeting, Albuquerque 2001

SS22 Strategies To Reduce Mortality in Marine and Freshwater Phytoplankton

Date: Wednesday, February 14, 2001, Time: 11:30:00 AM

Location: Acoma/Zuni/Tesuque

Colin, S, P, University of Connecticut, Groton, USA, sean.colin@uconn.edu

Dam, H, G, University of Connecticut, Groton, USA, hgdam@uconn.edu

TOXIC OR JUST NUTRITIONALLY DEFICIENT? THE EFFECTS OF SEVERAL 'TOXIC' ALGAE ON THE COSMOPOLITAN CALANOID COPEPOD ACARTIA TONSA

Reductions in grazer rate processes could be the result of toxic effects or nutritional deficiency of the grazer diet. Using the framework established by Jónasdóttir et al. (1998), we tested for toxic effects on copepods of 5 phytoplankton species that have been considered to be toxic in the literature: Alexandrium sp. (dinoflagellate), Heterosigma akashiwo (flagellate), Phaeodactylum tricornutum (diatom), Prorocentrum minimum (dinoflagellate), Thalassiosira rotula (diatom). We measured the ingestion, egg production and hatching rates of the copepod Acartia tonsa fed mixtures, based on algal carbon concentration, of the 'toxic' and the control species (100%, 75%, 50%, 25% toxic alga, and 100% control alga). Experiments were run at 250microgramC/l, a concentration limiting to ingestion and egg production, using Tetraselmis sp. (a green alga) as the control diet. In most cases A. tonsa produced fewer eggs on the 'toxic' diet than on the Tetraselmis sp. diet. However, egg production with the mixed diet was not reduced relative to the control diet. Additionally, hatching rates were not significantly decreased by any of the diets. Accordingly, the prescribed diets were not toxic, but rather nutritionally deficient.

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Aquatic Sciences Meeting, Albuquerque 2001

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