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The sedimentation of particulate organic material was investigated in Disko Bay, West Greenland, during June 2001. Post spring-bloom conditions were encountered, with seasonally decreasing phytoplankton biomass associated with the pycnocline. Calanus finmarchicus, C. glacialis, and C. hyperboreus dominated the zooplankton community, comprising up to 88% of the copepod biomass. Faecal pellet production by C. finmarchicus and C. glacialis was positively correlated to the available food (chlorophyll a >10 µm). Results from short-term sediment trap deployments (6 h) showed that particulate organic carbon (POC) sedimentation from the euphotic zone was, on average, 628 mg C m -2 d -1, with copepod faecal pellets contributing, on average, 29% of this amount. The faecal pellet contribution to the vertical sinking export of POC was equivalent to that of phytoplankton and amorphous detritus. Yet, on average, 35% of the copepod faecal pellet production was retained within the euphotic zone. The POC : PON (particulate organic nitrogen) ratio of the suspended material in the euphotic zone (8.1 ± 0.4) was comparable to that of the material collected in the sediment traps just below the euphotic zone (8.0 ± 0.9). In addition, the daily loss rates of POC and PON within each sampling depth were similar, and the carbon to nitrogen ratio in the sediment traps did not change with depth. These results indicate that the pelagic system had a low retention efficiency of nitrogen just after the spring bloom.KEY WORDS: Arctic marine ecology · Sedimentation · Faecal pellet production · Calanus spp. · Carbon flux 314: 239-255, 2006 able to exploit the developing bloom (Hirche 1996, Madsen et al. 2001, Pasternak et al. 2001. Moreover, the large Calanus species also contribute to the vertical export of carbon from the euphotic zone by packaging organic material into large fast-sinking faecal pellets. Resale or republication not permitted without written consent of the publisher OPEN PEN ACCESS CCESSMar Ecol Prog SerSedimentation of phytoplankton from the euphotic zone is the principal mechanism in transporting organic material to the benthic communities in marine systems, either directly as intact cells or in the form of faecal pellets and amorphous detritus. During its transit to depth, the organic material produced in the euphotic zone is transformed by a range of processes that influence the quality and quantity of the sedimenting material that reaches the benthos (González & Smetacek 1994, Olesen & Lundsgaard 1995, Acuña et al. 1996, Kiørboe et al. 1996, Wassmann 1998.The pelagic food web has been extensively studied in Disko Bay, West Greenland, during the last decade (Nielsen & Hansen 1995, Levinsen et al. 2000a,b, Madsen et al. 2001, Levinsen & Nielsen 2002. Previous studies primarily focused on the interactions between the different trophic levels in the pelagic food web. However, little is known about the vertical export of particulate organic material in this region. The Disko Bay area is an important fishing ground,...

The Kattegat in the inner Danish waters has been trawled for at least 80 yr, but so far only few attempts have been made to quantify the trawl effort, its spatial distribution and its potential ecological impact on the benthic fauna. GIS-analyses of VMS-data from trawling in the Kattegat by both Danish (2005−2009) and Swedish (2007−2009) vessels show that 95% of all trawling occurs below 22 m depth. Most activity takes place on homogeneous benthic habitats with muddy sediment at depths below the halocline and with almost the same salinity across the entire area. Furthermore, the estimate of trawled area demonstrated that the habitats are nearly 100% impacted, and frequencies of trawling beneath 100 m depth can reach 20 events per year. Multivariate analysis of community composition could not discriminate between lightly trawled and heavily trawled areas. However, a strong habitat selectivity of the trawl activity and inter-correlation between trawl activity and depth-related community structures complicated interpretation of the results. Species with biological traits previously categorized as sensitive to physical disturbance showed higher abundance in areas with low trawl activity compared to areas with higher activity. Thus, the Kattegat has been impacted to an extent where areas with reference conditions for certain habitats below 22 m no longer exist. Consequently, it is unknown how the benthic communities would have appeared without trawl disturbance and, thus, difficult to determine the impact of continued disturbance.

Total sedimentation and the fraction due to copepod fecal pellets were measured during the growth season (March–October 1989) in the southern Kattegat, Denmark. In this period the sedimentation of detritus made up 52 g C m−2, equal to 82% of the sedimenting matter from the euphotic zone, but fecal pellets (11 g C m−2) constituted only a minor fraction. The remaining detrital matter was produced by other heterotrophs than copepods. Published data on heterotrophic biomass and grazing obtained during the investigation in the Kattegat are reviewed in order to relate the sedimentation to processes in the pelagic system. Copepod defecation nearly equaled the sedimentation of fecal pellets, indicating that retention of this matter in the pelagic system was insignificant. A considerable fraction (10–24%) of the carbon flow processed by heterotrophic pico‐, nano‐, and microplankton was converted to detritus that was lost from the mixed system by sedimentation. The microbial food web is thus not an exclusively regenerating system.