Aquatic Sciences Meeting, Albuquerque 2001

PC01 Harmful Algal Blooms

Date: Tuesday, February 13, 2001

Location: Southwest Hall

Hamasaki, K, , Scripps Institution of Oceanography, La Jolla, USA, khamasaki@ucsd.edu

Takahashi, T, , Hiroshima University, Higashi-Hiroshima, Japan,

Uye, S, , Hiroshima University, Higashi-Hiroshima, Japan, suye@hiroshima-u.ac.jp

RETENTION AND EXCRETION OF PARALYTIC SHELLFISH POISONING (PSP) TOXINS IN MARINE COPEPODS DURING THE GRAZING OF A TOXIC DINOFLAGELLATE, ALEXANDRIUM TAMARENSE

Laboratory grazing experiments using the copepod, Acartia omorii, and the dinoflagellate, A. tamarense, demonstrated that the PSP toxin was retained in both the gut content and the tissue of the copepod. After the copepods were transferred into a starved condition, 87% of the toxin incorporated into a copepod during the feeding period was excreted (72%) or decomposed (15%) and 13% was retained. During the bloom of A. tamarense in Hiroshima Bay, Japan, the average toxin content of an individual copepod increased with an increase in ambient phytoplankton toxin levels, but saturated at much lower levels than those expected from laboratory experiments. These results suggest that copepods exhibit a self-regulation mechanism by controlling their ingestion of toxic dinoflagellates. Therefore, the flux of PSP toxins from herbivorous copepods to planktivorous fish is not as large as those predicted using laboratory feeding experiments. Also, while the role of copepods as toxic vectors in pelagic food webs has been emphasized, excretion of toxin contaminated fecal pellets should also be considered as an important mechanism for the delivery of PSP toxins to benthic environments.

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Aquatic Sciences Meeting, Albuquerque 2001

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