Dangerous relations in the Arctic marine food web: Interactions between toxin producing Pseudo-nitzschia diatoms and Calanus copepodites

Sara Hardardottir, Marina Pancic, Anna Tammilehto, Bernd Krock, Eva Friis Møller, Torkel Gissel Nielsen, Nina Lundholm

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Abstract

Diatoms of the genus Pseudo-nitzschia produce domoic acid (DA), a toxin that
is vectored in the marine food web, thus causing serious problems for marine organisms and humans. In spite of this, knowledge of interactions between grazing zooplankton and diatoms is restricted. In this study, we examined the interactions between Calanus copepodites and toxin producing Pseudo-nitzschia. The copepodites were fed with different concentrations of toxic P. seriata and a strain of P. obtusa that previously was tested to be non-toxic. The
ingestion rates did not differ among the diets (P. seriata, P. obtusa, a mixture of both species), and they accumulated 6%–16% of ingested DA (up to 420 μg per dry weight copepodite). When P. seriata was exposed to the copepodites, either through physical contact with the grazers or separated by a membrane, the toxicity of P. seriata increased (up to 3300%) suggesting the response to be chemically mediated. The induced response was also triggered when copepodites grazed on another diatom, supporting the hypothesis that the cues originate from the copepodite. Neither pH nor nutrient concentrations
explained the induced DA production. Unexpectedly, P. obtusa also produced DA when exposed to grazing copepodites, thus representing the second reported toxic polar diatom
Original languageEnglish
JournalMarine Drugs
Volume13
Issue number6
Pages (from-to)3809-3835
ISSN1660-3397
DOIs
Publication statusPublished - 2015

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