The foraminiferal fauna of the Bony estuary: A baseline study.

Abstract

The effect of oil exploration, production and other oil related industrial activities on the estuarine environment of the Niger Delta has resulted in increasing need of baseline information to be used as background levels against which pollution effects could be detected and monitored. A one-year (December, 1986 - December, 1987) baseline survey of the benthic foraminiferal fauna of the Bonny estuary showed that arenaceous forminifera strongly dominated the total and living assemblages. The subordinate calcareous groups were mostly found in the lower reaches of the estuary. The foraminiferal fauna was represented by thirty-three species, twenty-three of which were arenaceous, nine calcareous and one porcellaneous. Twenty nine of the thirty-three species identified were found living. Population densities in the estuary varied from 6-1,604 specimen per 20cc wet sediment for total population and 2-392 specimens for living populations. Two indices of species diversity, the species number [S] and fisher  index were employed in estimating diversity trends in the benthic foraminiferal fauna. Species number [S] per 20cc wet sediment varied between 2-18, while fisher  index ranged from 0.9-4. Some environmental indicators species identified in the area of study include, Arenoparella mexicana, Ammobaculites spp, Miliammina fusca, Trochammina inflata, Haplophragmoides subinvolutum, Ammotium cassis, A. aff. Okrikum, Elphidium excavatum and Ammonia beccarii variants