Observations on Neuston and Floating Weed Patches in the Irish Sea

Neuston samples were collected from the Irish Sea during the summer of 1989 and the winter of 1990. There was little sign of a permanent neustonic community, winter samples containing negligible quantities of material. The summer euneuston was dominated by meroneuston, particularly fish larvae (mainly the rockling Gairdropsarus mediterraneus). Medusae (very abundant in 1989) were facultatively neustonic, showing diurnal patterns of vertical migration; their movements correlated with the shallow scattering layer. Neustonic makeup was patchy geographically, and particularly influenced by the presence/absence of floating weed. Trophic relationships amongst neustonic animals revealed greater variation in diet than expected. Particular attention was paid to the feeding biology of lumpsuckers (Cyclopterus lumpus L.); these proved to be opportunistic weedpatch specialists, eating crustacean larvae, gammarid amphipods, young fish and even insects. Relatively little rubbish or dead material of terrestrial origin was found and insects were few. However, the available evidence suggests that insects land on weed patches rather than open water.