Macrofauna investigations along a transect from the inner German Bight towards the Dogger Bank

Abstract

During the Bremerhaven Workshop in March 1990 macrofauna san~ples were taken at 9 stations along a transect from the inner German Bight towards the offshore area of the Dogger Bank. Several statistical methods, univariate and multivariate, were applied to identify and describe changes in the communities along this profile. In general, 3 well-described communities were encountered: the Nucula-nitidosa-community in the inner German Bight, the Amphiura-filiforrnis-community from the former Pleistocene valley of the River Elbe and the Tellina-fabula-community from the Dogger Bank. These sediment dependent structures combined with changes due to increasing distance from the shore (including increasing water depth) are superimposed on possible additional changes due to pollution or eutrophication and veil them along the gradient investigated. Thus, indications of impact can only be suggested within the communities. However, even the most offshore Dogger Bank station appears to be disturbed.

Benthic macrofauna communities of the submersed Pleistocene Elbe valley in the southern North Sea

“…Within the valley, diversity and evenness decreased with increasing distance to the coast (towards the northern end of the valley). This is in contradiction to other investigations Kröncke and Rachor 1992), but shows a good correlation to the data from the intermediate part of the Pleistocene Elbe valley presented by Salzwedel et al (1985). For the southern part of the valley, no such trend was recorded (Büsselberg 1985;Salzwedel et al 1985).…”

“…In general, the benthic biomass in the southern North Sea decreases with increasing distance from the coast (Rachor 1982;Kröncke and Rachor 1992;Künitzer et al 1992). A negative correlation of biomass with latitude was found by Heip et al (1992), which holds true also for the macrozoobenthic community of the Pleistocene Elbe valley.…”

“…Rachor (1990) stated an increased biomass in 1975 due to eutrophication in comparison to the survey carried out by Hagmeier (1925) in 1923. It is supposed that the trend of increased eutrophication has continued until nowadays (Kröncke and Rachor 1992;Rachor and Nehmer 2003). Recent observations from long term community data oV Helgoland (Schröder 2003) support the suggestion that the ecosystem of the inner German bight showed a trend back towards the state of the 1970s (Radach 1998).…”

Cold winter effects on benthic macrofauna communities in near- and offshore regions of the North Sea

“…2 Deviations of mean monthly sea surface temperatures from the longterm average (1973-1993) (anomalies) These communities have already been described by Salzwedel et al (1985), Kro¨ncke and Rachor (1992), Kro¨ncke (1992), Rachor and Nehmer (2003), Wieking and Kro¨ncke (2003), Kro¨ncke et al (2004) and Reiss and Kro¨ncke (2005). They are dominated by the species given in Table 2.…”

“…Samples were taken with a 0.1 m 2 van Veen grab, except in 1995 when a small box corer (122 cm 2 ) was used. In March 1990, the samples were taken with two different grabs (Kro¨ncke and Rachor 1992). At stations GB2 and GB5 a 0.1 m 2 van Veen grab, at stations OG7 and DG9 a 0.2 m 2 van Veen grab was used.…”