Marginal marine environments of the Skagerrak and Kattegat: a baseline study of living (stained) benthic foraminiferal ecology

This is the first detailed investigation of the distribution and ecology of living (stained) shallow water (0-6 m) foraminifera along the Skagerrak-Ka ttegat coast, eastern North Sea. A total of 25 species (13 agglutinated; 12 calcareous) are common in the 169 sediment surface samples which were coll ected from 27 geographic areas. The sediment grain size and total organic c arbon (TOC) content are strongly variable and the salinity and temperature ranges were 10-31 parts per thousand and 9-30 degrees C, respectively, at t he time of sampling (July to October) but temperatures down to freezing occ ur during the winter. The species are divided into six environmental catego ries of which the first five comprise euryhaline and the sixth essentially stenohaline taxa: (I) species associated only with marsh plants, (2) specie s basically, but not entirely, associated with marsh plants, (3) species ba sically, but not entirely, restricted to non-marsh areas, (4) species solel y recorded in non-marsh intertidal to subtidal environments, (5) species re stricted to subtidal areas, (6) species basically living in the most open m arine areas. in this region, marshes have a patchy distribution and they ar e small and compressed due to low tidal ranges (<40 cm). Balticammina pseud omacrescens (not reported here before) lives in the most elevated, landward , terrestrial parts of marshes and thus defines the uppermost limit of the influence of marine water. However, the marshes are generally dominated by Jadammina macrescens and Miliammina fusca at the landward and seaward sides , respectively. Judammina macrescens is observed living epiphytically on de caying Carex leaf debris. The most widely distributed euryhaline species ar e Elphidium williamsoni, Miliammina fusca, Ammonia beccarii, and Haynesina germanica. The former two are common only in sediments with a mud content l ess than about 60%, whereas the latter two are common even in sediments wit h >80% mud. Ammoscalaria runiana is common only in coarse-grained sediments (<20% mud) with low TOC (less than or equal to 0.7%). There are no marked biogeographic boundaries within the Skagerrak-Kattegat area but 10 of the 2 5 commonly occurring species have not been reported from the adjacent Balti c Sea, probably partly due to the brackish character of the water there. Th e southern limits of distribution of the northern species, Elphidium albium bilicatum, Ammotium cassis, and Ophthalmina kilianensis, an in the Kattegat -Baltic Sea. (C) 1999 Elsevier Science B.V. All rights reserved.