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Biodiversity and energy transfer to top trophic levels in two contrasting Arctic fjords

100%

Weslawski J. M., Kwasniewski S., Stempniewicz L., Blachowiak-Samolyk K.

Polish Polar Research

2006

tom 27

nr 3

259-278

The food and foraging strategy of fifteen species of seabirds and sea mammals from two high Arctic fjords were analysed. One of the fjords, Kongsfjord, is strongly influenced by warm waters from the Atlantic, while Hornsund is of a more Arctic character. Prey species in the Atlantic waters were more diverse (82 species and 16 functional groups) compared to those of Arctic waters (67 prey species and 14 functional groups). The consumption of top predators from Hornsund in the peak season of July was estimated at 2.86*106 MJ, while that in Kongsfjord was 1.35*106 MJ. For the analysed function of the ecosystem (the transfer of energy to the top trophic levels) the specific character of prey species is of key importance and not the diversity, abundance or biomass per se. Lower species diversity and biomass in Arctic waters is compensated for by the occurrence of larger individuals of these species, which permits top predators to prey directly on lower trophic levels.

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Greenland whales and walruses in the Svalbard food web before and after exploitation

100%

Weslawski J. M., Hacquebord L., Stempniewicz L., Malinga M.

Oceanologia

2000

tom 42

nr 1

Between 1600 and 1900 two numerous and ecologically important large marine mammals were extirpated in the Svalbard archipelago. These were the pelagic-feeding Greenland whale (Balaena mysticetus) and the benthic-feeding walrus (Odobaenus rosmarus rosmarus), the initial stocks of which prior to exploitation are estimated to have numbered approximately 46 000 and 25 000 animals respectively. Their annual food consumption at that time is estimated to have been some 4 million tons of plankton and 0.4 million tons of benthic organisms. Assuming that the primary and secondary production of the shelf/coastal ecosystem in the 16th century (before the peak of the Little Ice Age) was similar to that of the present day, the authors have concluded that a major shift in the food web must have occurred after the Greenland whales and walruses were eliminated. Planktonivorous seabirds and polar cod (Boreogadus saida) very probably took advantage of the extirpation of the Greenland whales, while eiders (Somateria mollissima) and bearded seals (Erignathus barbatus) benefited from the walrus's extinction. In turn, the increased amount of pelagic fish provided food for piscivorous alcids and gulls, and may have given rise to the huge present-day seabird colonies on Svalbard.

Ograniczanie wyników

1 Oceanologia

1 Polish Polar Research

2 Stempniewicz L.

2 Weslawski J. M.

1 Blachowiak-Samolyk K.

1 Hacquebord L.

1 Kwasniewski S.

1 Malinga M.

1 2006

1 2000

Wyniki wyszukiwania

Biodiversity and energy transfer to top trophic levels in two contrasting Arctic fjords

Greenland whales and walruses in the Svalbard food web before and after exploitation