Wilhelmshaven, Germany
Wilhelmshaven, Germany

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Oehler T.,Alfred Wegener Institute for Polar and Marine Research | Martinez R.,Alfred Wegener Institute for Polar and Marine Research | Schuckel U.,Sudstrand | Winter C.,Marum Zentrum fur Marine Umweltwissenschaften | And 2 more authors.
Continental Shelf Research | Year: 2015

Benthic oxygen and nitrogen fluxes were quantified within the years 2012 to 2014 at different time series sites in the southern North Sea with the benthic lander NuSObs (Nutrient and Suspension Observatory). In situ incubations of sediments, in situ bromide tracer studies, sampling of macrofauna and pore water investigations revealed considerable seasonal and spatial variations of oxygen and nitrogen fluxes.Seasonal and spatial variations of oxygen fluxes were observed between two different time series sites, covering different sediment types and/or different benthic macrofaunal communities. On a sediment type with a high content of fine grained particles (<63μm) oxygen fluxes of -15.5 to -25.1mmolm-2d-1 (June 2012), -2.0 to -8.2mmolm-2d-1 (March 2013), -16.8 to -21.5mmolm-2d-1 (November 2013) and -6.1mmolm-2d-1 (March 2014) were measured. At the same site a highly diverse community of small species of benthic macrofauna was observed. On a sediment type with a low content of fine grained particles (<63μm) high oxygen fluxes (-33.2mmolm-2d-1 August 2012; -47.2 to -55.1mmolm-2d-1 November 2013; -16.6mmolm-2d-1 March 2014) were observed. On this sediment type a less diverse benthic macrofaunal community, which was dominated by the large bodied suspension feeder Ensis directus, was observed.Average annual rain rates of organic carbon and organic nitrogen to the seafloor of 7.44molCm-2y-1 and 1.34molNm-2y-1 were estimated. On average 79% of the organic bound carbon and 95% of the organic bound nitrogen reaching the seafloor are recycled at the sediment-water interface. © 2015 Elsevier Ltd.


Kroncke I.,Sudstrand | Reiss H.,Sudstrand | Eggleton J.D.,Center for Environment | Aldridge J.,Center for Environment | And 26 more authors.
Estuarine, Coastal and Shelf Science | Year: 2011

The North Sea Benthos Project 2000 was initiated as a follow-up to the 1986 ICES North Sea Benthos Survey with the major aim to identify changes in the macrofauna species distribution and community structure in the North Sea and their likely causes.The results showed that the large-scale spatial distribution of macrofauna communities in the North Sea hardly changed between 1986 and 2000, with the main divisions at the 50 m and 100 m depth contours. Water temperature and salinity as well as wave exposure, tidal stress and primary production were influential environmental factors on a large (North Sea-wide) spatial scale.The increase in abundance and regional changes in distribution of various species with a southern distribution in the North Sea in 2000 were largely associated with an increase in sea surface temperature, primary production and, thus, food supply. This can be most likely related to the North Sea hydro-climate change in the late 1980s influenced by the variability in the North Atlantic Oscillation (NAO). Only one cold-temperate species decreased in abundance in 2000 at most of the stations. Indications for newly established populations of offshore non-native species were not found.Differences in macrofauna community structure on localised spatial scales were predominantly found north of the 50 m depth contour off the British coast along the Flamborough Head Front towards the Dogger Bank, off the coast of Jutland and at the Frisian Front. These changes were most likely attributed to stronger frontal systems in 2000 caused by the increased inflow of Atlantic water masses in relation to the hydro-climate change in the late 1980s. © 2011 Elsevier Ltd.

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