Copepod feeding behaviour and egg production during a dinoflagellate bloom in the North Sea

Abstract

Feeding strategies of copepods were studied during a dinoflagellate-dominated bloom in the North Sea in August 2001. The aim of this study was to evaluate the importance of mesozooplankton grazing as a biological loss factor of harmful algal blooms under natural conditions. Therefore, ingestion, egestion and egg production experiments were performed with the most abundant copepod species Calanus helgolandicus, Temora longicornis and Acartia sp. feeding on the natural phytoplankton community. Dinophysis norvegica and Ceratium furca were the most abundant dinoflagellate species at the time of the experiments. Grazing experiments as well as examination of fecal pellet content revealed C. helgolandicus fed efficiently on D. norvegica. Ingestion rates up to 47 cells female À1 h À1 were measured and a large proportion of the C. helgolandicus fecal pellets contained intact D. norvegica cells. Dinophysis cells were rarely seen in fecal pellets produced by T. longicornis, and never observed in pellets produced by Acartia sp. The ingestion rate of C. furca, which was the dominating Ceratium species, mimicked that of D. norvegica. C. helgolandicus grazed significantly on C. furca (16 cells female À1 h À1 ), while the ingestion rate of T. longicornis was low and Acartia sp. was not able to graze on C. furca. Egg production experiments revealed that 92% of the C. helgolandicus females produced eggs. The specific egg production rate and the proportion of females producing eggs among T. longicornis were low. This field experiment clearly shows that some copepod species feed efficiently on D. norvegica and C. furca under natural conditions, which may affect the bloom development of these dinoflagellates. #

Distribution of Dinophysis species and their association with lipophilic phycotoxins in plankton from the Argentine Sea

“…The latter species might be confused with Dinophysis acuta, which is known to occur in Chilean waters (Balech, 2002), but D. acuta is typically larger in size (54-100 mm) and the maximum width is below the mid-line of the cell, which was never the case for the cells found in this study. Records of Dinophysis norvegica cells in this study were almost restricted to the southern and cooler waters, which agrees with its wide distribution in cold-temperate waters of the northern hemisphere, including the Baltic, Norwegian, North and Arctic Seas (Okolodkov and Dodge, 1996;Meyer-Harms and Pollenhe, 1998;Edvardsen et al, 2003;Jansen et al, 2006). Although D. norvegica is known to be frequently toxigenic around the world, our results do not allow a clear association between D. norvegica and particular lipophilic toxins, as this species was always found at lower cell densities than other putatively toxigenic species from the genus in samples that contained toxins.…”

Copepods grazing on Coscinodiscus wailesii: a question of size?

“…Analyses of gut or faecal pellet contents can give a qualitative insight in what have been grazed by a copepod, but can rarely provide quantitative results (but see Wexels Riser et al 2003;Jansen et al 2006). In cases where copepods do not ingest whole cells, interpretation of stomach or faecal pellet contents may be diYcult or even impossible as only a few pieces of evidence of the diatom prey may be found.…”

Growth limitation due to high pH and low inorganic carbon concentrations in temperate species of the dinoflagellate genus Ceratium

“…Dinoflagellates belonging to the genus Ceratium are common in temperate waters, especially in the late summer and fall (Smetacek 1981, Jansen et al 2006. In Scandinavian coastal waters, Ceratium spp.…”