Abstract
When the icebreaker Oden passed between 39°36'S, 57°46'W and 39°59'S, 58°11'W on 20 November 2007, an extraordinary observation was made. A feeding Pygmy Right Whale Caprea marginata, a species rarely seen, was attended by eight Grey Phalaropes Phalaropus fulicarius, two Slender-billed Prions Pachyptila belcheri, and four Wilson’s Storm Petrels Oceanites oceanicus. The birds returned to feed around the head of the whale every time it surfaced, presumably copepod plankton straining out between the baleen. The site is off Rio de la Plata estuary where nutrient rich freshwater meets cold water of the Malvinas (Falkland) Current, creating a hotspot with high levels of plankton food. The conditions were extraordinarily favourable for observation with a calm sea, no wind and only a very weak swell. Six multispecies feeding groups were seen with a total of 42 species of birds, eleven species of whales, dolphins and porpoises, and three species of seals. Dusky Dolphins Lagenorhynchus obscurus and Great Shearwaters Puffinus gravis were predominant in the groups.
Highlights
When the icebreaker Oden passed between 39°36’S, 57°46’W and 39°59’S, 58°11’W on 20 November 2007, an extraordinary observation was made
Via the Rio de la Plata estuary, nutrient rich freshwater from the second largest catchment in South America (Piola et al 2005) empties into the sea and in the south meets the cold water of the Malvinas (Falkland) Current from and in the north the warm water of the Brazil Current (Brandini et al 2000), creating a potential hotspot for marine wildlife belonging to both subtropical and temperate/subantarctic seas
The Swedish icebreaker Oden is used for research in the ice-covered areas of the Arctic and Antarctic
Summary
When the icebreaker Oden passed between 39°36’S, 57°46’W and 39°59’S, 58°11’W on 20 November 2007, an extraordinary observation was made. Ductivity of the area was manifest by the extremely high species diversity and numbers of individuals and presence of several multispecies feeding groups, and high levels of chlorophyll and zooplankton in water samples and by the large fleet of fishing vessels active in the area. Dominating these groups were Dusky Dolphins Lagenorhynchus obscurus and Great Shearwaters Puffinus gravis (Figure 1), with other species of birds and cetaceans and South American Fur Seals Arctocephalus australis sometimes joining the fray.
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