Rapid krill decline: 80% over 35 years

Antarctica does not escape the Holocene Mass Extinction. Krill numbers have dropped sharply since the mid-70s and as a consequence penguins too are in decline, says new study in Monday’s edition of PNAS, that blames the ecological disturbances on climate change.

Average winter temperatures around the Antarctic Peninsula have already risen 5-6 degrees, leading to a smaller sea ice cover. Krill eat algae that grow under the ice (and in the small polynyas within), penguins eat krill.

As the ice melts, the entire food chain is strained and many species decline. The researchers argue this should be viewed as a problem on the Antarctic ecosystem level and that it is irrelevant whether other species too cling onto the ice or if they prefer adjacent bare rock.

As evidence they find both the (ice-loving) Adélie penguin and the (ice-avoiding) chinstrap penguin are in decline. The research, that has NOAA scientists involved, showed that due to starvation sometimes only 10 percent of the penguins survive their winter migration.

It is difficult to assess the total damage of climate change and other environmental stresses to the Antarctic ecosystem, as the Antarctic seas lack an official biodiversity database, so for many species there is no baseline against which to measure a decline.

Less krill, less fish?

Declining krill populations may also have ramifications for the fishing industry, which is increasingly interested in the still largely untouched Antarctic seas. There are 120 species and subspecies of krill, some also in the Arctic margins of the Atlantic and Pacific, where they are an essential food source for economically valued fish species as salmon, herring, mackerel, pollock and cod. Krill harvesting is also being explored by several companies, for use in omega 3 supplements – and possibly even as a protein source [already as fish food in the salmon industry].

© Rolf Schuttenhelm | www.bitsofscience.org

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