Joiris C.,Laboratory for Polar Ecology PolE |
Gannier A.,British Petroleum |
Kenney R.D.,University of Rhode Island
Journal of Cetacean Research and Management | Year: 2010
The Ligurian Sea is one of the most attractive areas for cetaceans in the Mediterranean Sea, and is now included in a Marine Protected Area, the Pelagos Sanctuary. Despite a lower species diversity than in other parts of the world, because of their abundance, cetaceans are thought to represent significant consumers in this ecosystem. Surveys were conducted within the Pelagos Sanctuary from 2001 to 2004. Densities of five species: striped dolphin (Stenella coeruleoalba); fin whale (Balaenoptera physalus); sperm whale (Physeter macrocephalus); long-finned pilot whale (Globicephala melas); and Risso's dolphin (Grampus griseus), were estimated and converted to biomass. Total biomass density of cetaceans in the Ligurian Sea was estimated as 93kg km -2 (CV=28%) in winter (October to March) and 509kg km-2 (CV= 16%) in summer (April to September). Daily predation rates by cetaceans were estimated as 2.9kg km-2 d-1 in winter, increasing to 10.4kg km-2 d-1 in summer, corresponding to a total annual ingestion of 2.4t km-2 y-1. The annual primary production required for cetaceans was estimated to be 12.6gC m-2 y -1, corresponding to 6-15% of the net primary production known for this area. Estimated cetacean prédation on fish was similar to reported fisheries landings, nevertheless, management of artisanal fisheries and accurate quantification of the resources they exploit will be necessary for the responsible management of fisheries in this Mediterranean Marine Protected Area.
Joiris C.R.,Laboratory for Polar Ecology PolE |
Humphries G.R.W.,University of Otago |
De Broyer A.,Royal Belgian Institute Of Natural Sciences
Polar Biology | Year: 2013
The first aim of our long-term study on the at-sea distribution of the upper trophic levels-seabirds and marine mammals-in polar marine ecosystems is to identify the main factors affecting their distribution: water masses and pack ice, fronts and ice edge as defined on the basis of water temperature, salinity and ice overage. In this study, seabird at-sea distribution was determined in the south-eastern Atlantic Ocean in summer along four return transects between Cape Town, South Africa, and Queen Maud Land, Antarctica: two on board icebreaking MS Ivan Papanin and two on board icebreaking RV Polarstern between December 2007 and January 2012. During a total of 1,930 half-an-hour transect counts devoted to seabird recording, 69,000 individuals were encountered, belonging to 57 species (mean: 36 individuals per count, all species and expeditions pooled). In comparison, the adjacent Weddell Sea shows a lower seabird biodiversity (30 species and 150 individuals per count) than in the area covered by this study. European Arctic seas reflect an intermediate biodiversity, with 30 species and 60 individuals per count; the major difference is observed in closed pack ice, almost empty in the Arctic but showing a very high biomass in the Antarctic. On the other hand, following the same route in different years allowed to compare results: density and abundance were found to be homogenous and reproducible between years for some species, while very important patchiness was detected for others, causing large heterogeneities and differences between expeditions. © 2013 Springer-Verlag Berlin Heidelberg.
Bergmann M.,Alfred Wegener Institute for Polar and Marine Research |
Sandhop N.,Alfred Wegener Institute for Polar and Marine Research |
Schewe I.,Alfred Wegener Institute for Polar and Marine Research |
D'Hert D.,Laboratory for Polar Ecology PolE
Polar Biology | Year: 2015
Although recent reports indicate that anthropogenic waste has made it to the remotest parts of our oceans, there is still only limited information about its spread, especially in polar seas. Here, we present litter densities recorded during ship- and helicopter-based observer surveys in the Barents Sea and Fram Strait (Arctic). Thirty-one items were recorded in total, 23 from helicopter and eight from research vessel transects. Litter quantities ranged between 0 and 0.216 items km−1 with a mean of 0.001 (±SEM 0.005) items km−1. All of the floating objects observed were plastic items. Litter densities were slightly higher in the Fram Strait (0.006 items km−1) compared with the Barents Sea (0.004 items km−1). More litter was recorded during helicopter-based surveys than during ship-based surveys (0.006 and 0.004 items km−1, respectively). When comparing with the few available data with the same unit (items km−1 transect), the densities found herein are slightly higher than those from Antarctica but substantially lower than those from temperate waters. However, since anthropogenic activities in the Fram Strait are expanding because of sea ice shrinkage, and since currents from the North Atlantic carry a continuous supply of litter to the north, this problem is likely to worsen in years to come unless serious mitigating actions are taken to reduce the amounts of litter entering the oceans. © 2015 The Author(s)
Joiris C.R.,Laboratory for Polar Ecology PolE
Polar Biology | Year: 2011
In the frame of our long-term study of the distribution of seabirds and marine mammals in polar seas, observers from this team participated in the European Arctic expeditions of icebreaking RV Polarstern during summer 2008. The main aims were to obtain more information on the mechanisms underlying the at-sea distribution of the 'higher trophic levels' and to detect possible temporal and spatial changes in numbers, especially in function of climatic changes and decreasing ice coverage in the Arctic. In total, 1,175 half-an-hour transect counts were devoted to seabird and marine mammal distribution in the Greenland and Norwegian Seas, from 14 June to 15 August, 2008. A major feeding ground for cetaceans and seabirds was detected in the south-western Greenland Sea and the Denmark Strait in the Polar Front between Polar and Arctic Water masses. For the main cetacean and seabird species, almost all individuals recorded during the whole expedition were encountered in this limited zone of 33 counts: 135 humpback whales Megaptera novaeangliae and 1,940 common guillemots Uria aalge. Moreover, 4,400 fulmars Fulmarus glacialis light morph were observed in this zone, i. e. close to half of the total. All were actively feeding, making this zone the major feeding ground for the higher trophic levels in the European Arctic Seas and so confirming the great importance of fronts (upwellings) for the biological productivity of the oceans. Such data are essential for a successful conservation and management of the Denmark Strait and adjacent areas. © 2011 Springer-Verlag.
Joiris C.R.,Laboratory for Polar Ecology PolE |
Falck E.,Geophysical Institute and Bjerknes Center for Climate Research
Polar Biology | Year: 2011
Among the most numerous seabird and pinniped species of the Fram Strait and the Greenland Sea, little auks Alle alle and harp seals Pagophila (Phoca) groenlandica are very abundant in the mixed Polar/Arctic Waters at the front between the two water masses. This must reflect the presence of very high concentrations of their food, Arctic zooplankton and nekton, massively attracting their predators. Such a high biological production seems to be depending on new primary production based on upwelling and high nutrient concentration. This usually takes place at the ice edge (e. g. July 2005), but hydrological conditions such as eddies can modify its position, east of the front in open water as caused by a subsurface eddy (August 2005), or in ice-covered areas if westerly winds push the pack ice to the east, eventually covering an eddy and causing very high concentrations of little auks and harp seals (July 2008). On the other hand, a dramatic decrease of pack ice coverage can move this water mass farther north and west, making it inaccessible to little auks during their breeding season, and apparently causing breeding failure in Jan Mayen in July 2005. In future years, if a much stronger diminution in sea ice coverage will take place, similar to the retreat in 2005 and 2007, the failure might affect the whole Spitsbergen population, as well as other seabird species feeding mainly at the ice edge. © 2010 Springer-Verlag.