BENTHIC FORAMINIFERA IN SEDIMENT CORES REFLECTING HEAVY-METAL POLLUTION IN SORFJORD, WESTERN NORWAY

Analysis of benthic foraminifera in two short sediment cores (15 and 53 m water depth) from heavy metal-polluted Sorfjord indicates that a faunal shift has taken place, due to heavy metal enrichment. Both cores reveal an upward transition from a moderately polluted environment represented by a Verneuilina media assemblage to an extremely polluted environment represented by an Eggerelloides scabrus assemblage. This faunal change may result from an increased competitiveness of some shallow water species in deeper water areas exposed to environmental stress, at the expense of more normal marine forms which have stricter ecological requirements. The total abundance of foraminifera decreases upward in both cores, whereas species diversity shows only a minor decrease. The frequent occurrence of abnormal and pyritized specimens is attributed to the effects of pollution, and seven different modes of test deformation are described.