Trace Metal Contamination in Sediments from U.K. Estuaries: An Empirical Evaluation of the Role of Hydrous Iron and Manganese Oxides Variation of the Marine Soft Bottom Macrofauna in Western Sweden

A seven to 13 year data series of yearly macrobenthic (infaunal) mean abundance data from eight stations in, or adjacent to Gullmarsfjorden, on the Swedish west coast were compared to the freshwater runoff to the fjord, temperature at 600 m depth in the Skagerrak (temp 600) and to the North Atlantic Oscillation (NAO) index. The NAO index was positively correlated with temperature at 600 m depth in the Skagerrak and negatively correlated to the runoff. Macrobenthic abundances at the three stations outside the fjord (depth range 40-100 m) and two stations inside the fjord (118 m and 44 m), correlated negatively to temperature at 600 m depth in the Skagerrak. This study indicates that the correlation may be caused by a NAO influenced, periodically increased upwelling of deep water, rich in dissolved inorganic nutrients, resulting in a corresponding primary production and food input increase to the benthos. There was a positive correlation of macrobenthic abundances at these stations to runoff, probably caused by the input of depositing organic detritus. Macrobenthic abundances at the three stations in the inner part of the fjord (depth range 25-65 m) correlated positively to the NAO index. This is proposed to be an effect of strong stratification when the NAO index is low, which causes low primary production.