Do climatic oscillations influence cyclical patterns of soft bottom macrobenthic communities on the Swedish west coast?

Soft sediment macrofauna has been monitored at 10 stations (10 to 300 m) off the west coast of Sweden for periods of 12 to 20 yr. Macrobenthic abundance and biomass in this region show a distinct cyclical pattern of approximately 7 to 8 yr. Macrobenthic oscillation patterns down to 100 m depth are generally in phase, suggesting a causative mechanism operating at a regional scale. At the 300 m deep station, the cycles did not appear to be in phase with the stations in shallower water. Spectral analysis of the 130 yr record of the North Atlantic Oscillation (NAO) index indicated that the dominant component of the index occurred at a period of 7.9 yr. The NAO index over the period 1970 to 1990 was significantly positively correlated with Skagerrak deep water (600 m) temperature and significantly negatively correlated with stream flow from western Sweden. Stream flow was significantly positively correlated with benthic abundance and biomass at stations down to 100 m depth, but negatively correlated with bottom water oxygen content. We therefore propose that climatological linkages affecting primarily surface primary production result in bottom-up control of benthic population changes. We suggest that climatic variability in the region may be a more basic causative factor for benthic disturbance than eutrophication and other possible factors which have previously been proposed.