SUSPENDED PARTICULATES IN THE IRISH SEA AND FEEDING CONDITIONS FOR FISH LARVAE

The size distributions (2 to 160 mum equivalent spherical diameter) of suspended particulate material sampled on two cruises along a transec t in the Irish Sea in 1988 are described in relation to hydrographic c onditions, chlorophyll a concentration and carbon to nitrogen ratios. Particulates were more abundant and larger size modes in the distribut ion were more evident, in the upper mixed layer of stratified water th an in areas where the water column was fully mixed. The detrital conte nt was estimated at 52% of total particulate matter above the thermocl ine in stratified regions and at around 97% at mixed water sites. In s tratified regions the predominance of larger sized phytoplankton and l ower levels of detritus is argued to support a more direct and efficie nt transfer of energy to fish larvae via larger sizes of copepods. Con versely, in mixed areas of high detrital loading the smaller size spec trum of particulates incorporates a less efficient transfer of energy through bacterial cycling and smaller copepods.