RELATIONSHIP BETWEEN THE QUALITATIVE NATURE OF PARTICLES AND COPEPOD FECES IN THE IRISH SEA

The biochemical composition (carbon, nitrogen, free amino acids, fatty acids, chlorophylls, carotenoids) of copepod faecal pellets was measured and compared with that of the particulate matter collected from three sites, of differing hydrographic regimes, in the Irish Sea during May/June 1988. The sites were: coastal weakly thermally stratified, central strongly thermally stratified and a central mixed isothermal site. Food was not limiting for copepods at the sites, as shown by the maximum concentration of the chlorophyll a which ranged from 4 to 7.5 mug l-1. There were marked differences in the composition and quality of particulates at these three sites. Site I was dominated by diatoms, site II was characterized by a diverse phytoplankton population, while site III was dominated by senescent diatoms and detritus. These differences were reflected in the biochemical composition of copepod faecal pellets. No significant bacterial enrichment occurred in facecal pellets as shown by the level of bacterial biomarkers. The fate of faecal pellets in the water column is discussed in relation to the use of biomarkers.