Opportunistic features of the foraminifer Stainforthia fusiformis (Williamson): evidence from Frierfjord, Norway

Abstract. Frierfjord is the innermost part of a fjord system which connects with the open sea via Grenlandsfjord. Sills between fjords restrict bottom water circulation and in Frierfjord (sill depth: 23 m, max. water depth: 100 m) efficient deep water renewals at depths greater than about 50 m occur once every one to three years (Rygg et al., 1987). For several centuries waste products (primarily bark and wood fibres), initially from saw mills and later from pulp and paper industries, have been deposited in Frierfjord. Additionally, the fjord has received substantial amounts of organic material and nutrients from domestic sewage. In summary, this led to more or less permanent anoxic deep bottom water conditions. However, slight improvements have occurred over the last decade in response to reduced pollution input (Alve, in prep.). Investigations of short sediment cores (<50 cm) from the deeper areas of Frierfjord (>50 m) show that Stainforthia fusiformis exhibits typical opportunistic features. The oxygen concentration of the bottom water immediately above the sediment–water interface was > 1 ml I¹at all stations at the time of collection, but the surface sediments reflected recent anoxic conditions. This was especially evident at >70 m where the sediments had a soupy appearance and black colour, with brownish faecal pellets and sometimes light grey, fluffy sediment aggregates in the topmost veneer. The total organic carbon content of the surface sediments is typically between 4 and 6%.

DISCUSSION

The following features characterize Stainforthia fusiformis as an opportunistic r-strategist:

Distribution. Stainforthia fusiformis is a . . .