Sediments and Macrofauna in the Baltic Sea — Characteristics, Nutrient Contents and Distribution

The nutrient load to the Baltic Sea has increased markedly in the last century (Larsson et al. 1985; Elmgren 1989; Wulff et al. 1990; Sanden et al. 1991; Jonsson and Carman 1994). This increase has resulted in greatly extended bottom areas with hypoxia or anoxia, and large-scale elimination of the macrofauna in the Baltic proper (Cederwall and Elmgren 1990). One consequence is that bioturbation has disappeared, and an expansion of laminated sediments has followed (Jonsson and Jonsson 1988; Jonsson et al. 1990). Fluxes of dissolved nutrients across the sediment-water interface and burial of different chemical substances fluctuate on a seasonal or annual basis, in response to variable inputs of minerogenic material and organic detritus. By a combination of diagenetic processes the nutrients are either retained in the sediments or released to the overlying water. The interplay between burial and release is determined by complex interactions between different biogeochemical processes (see Chap. 9).