Vegetation macrofauna and benthic meiofauna in the phytal zone of the archipelago of Luleå- Bothnian bay

Abstract

The archipelago of Luleå, in the northwestern part of the Bothnian Bay, is subjected to the lowest salinities and the most extreme weather conditions found in the Baltic Sea basin. A large scale systems ecology study of the Luleå archipelago was carried out during 1976 in order to reveal the general characteristics of the ecological communities excisting in this little known area. The quantitative studies of the phytal subsystem, presented here, revealed a very poor fauna and flora on the sandy shallow bottoms that dominate the area. The pelagic primary production is only about 10 per cent of that found in the northern Baltic proper. Together with the physical forces of ice and wave erosion and large, irregular water level fluctuations, this low production limits the distribution and production within the benthic communities. With a few exceptions, the macrofauna and macroscopic vegetation as well as meiofauna are composed by euryhaline fresh-water species able to tolerate the low salinities (0–3 ‰ S) of this region.

Biomasses, primary and secondary production estimates and sediment respiration rates have been used to construct a rough energy budget model for the phytal community. The model illustrates the extremely low overall productivity of the Bothnian Bay community, compared to those found further south in the Baltic proper, but also differences in the importance of different energy pathways within the system. The meiofauna has an equal importance to that of the macrofauna, and microphytes are probably more important than the macroscopic plants and algae in terms of energy flows. The lack of filter feeders and the high proportion of invertebrate carnivores within the system affect the level of secondary production and the amount of potential fish food produced in the system.