DISTRIBUTION AND POPULATION-DYNAMICS OF BENTHIC FORAMINIFERA FROM THE SOUTHERN NORTH-SEA

The living foraminiferal assemblages of the inner shelf of the southern North Sea are dominated either by Elphidium excavatum or by Fursenkoina fusiformis. The dead assemblages are more diverse and show some notable taxonomic differences from the living (stained) assemblages. In particular, dead E. excavatum is much more widely distributed and F. fusiformis more restricted in distribution than their living counterparts. Dead individuals of Eggerelloides scabrum are more abundant and widespread than living individuals. Syn-depositional dissolution of calcareous tests is taking place in the muddy sands off eastern England. Elphidium excavatum reproduces throughout the year and has a generation time of 2-4 months. The annual production of tests is estimated at 15-253 per 10 cm2 of sea floor and biomass at 0.10-1.77 mm3 per 10 cm2 sea floor. For Fursenkoina fusiformis the values are 159-270 tests per 10 cm2 sea floor and biomass 0.13-0.30 mm3 per 10 cm2 per year. Elphidium excavatum is infaunal down to at least 10 cm below the sediment/water interface and only about 25% of its standing crop is present in the top 1 cm of sediment. Four of the six sites sampled seasonally were numerically dominated throughout the year by either Elphidium excavatum or Fursenkoina fusiformis. One site showed a succession of dominant genera and the other site yielded few living individuals. Comparison of these results with those previously obtained suggests that a faunal change has taken place during the past 30 years. This change is marked by a southward retreat of assemblages dominated by Ammonia beccarii.