Abstract
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 chron~atography (HPLC) was used to measure the concentrations of chlorophylls a and c (and derived phaeopigments), fucoxanthin and dladinoxanthin 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 diadinoxanthn. The degree of destruction for the 3 pigments vdned in parallel and when it was relatively low the only fluorescent components found in faecal pellets, in appreciable amounts, were chlorophylls a and cand 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.
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