CHLOROPHYLL AND CAROTENOID TRANSFORMATION AND DESTRUCTION BY CALANUS SPP GRAZING ON DIATOMS

Copepods and seawater were collected during spring bloom conditions off southwest Nova Scotia and the east coast of Newfoundland, Canada. The copepods were starved for 12 or 24 h and then fed with screened seawater. High pressure liquid chromatography (HPLC) was used to measure the concentrations of chlorophylls a and c (and derived phaeopigments), fucoxanthin and diadinoxanthin in the incubation medium both before and after grazing, and in purified samples of faecal pellets collected after grazing. Close to 100 % of ingested chlorophylls a and c did not survive digestion by copepods. Virtually no phaeophorbide a or phaeophytin a were produced but instead one or both of their pyrolised derivatives. A pyrolised phaeoporphyrin c derivative was apparently also produced. Fucoxanthin was completely broken down during digestion, but some or all may have been converted to a less polar unidentified derivative. Some ingested diadinoxanthin sometimes appeared intact in faecal pellets. The conversion efficiency of chlorophyll a to pyrophaeopigment a was not usually 100 %, but ingested chlorophyll a was less extensively destroyed than either chlorophyll c or diadinoxanthin. The degree of destruction for the 3 pigments varied in parallel and when it was relatively low the only fluorescent components found in faecal pellets, in appreciable amounts, were chlorophylls a and c and the 3 pyrophaeopigments. When the degree of pigment destruction was high, a number of unidentified fluorescent components were also present in faecal pellets, which were probably the products of more extensive chlorophyll degradation.