Krill are the world's most abundant crustacean and form the staple diet of many animals including seals, whales, fish, squid, penguins and many seabirds.
The research team have used a deep-sea video camera to film swarms of krill 700 metres (about 776 yds) below the surface of the Southern Ocean off East Antarctica. On the Australian Antarctic Division
website Krill Biologist, Dr So Kawaguchi, says the footage has revealed some surprising aspects of the private lives of krill including that the shrimp-like creatures are able to mate deeper in the ocean than previously thought.
“This research challenges previous ideas on the life cycle of krill and will have considerable implications for understanding the Antarctic marine ecosystem and for the management of the krill fishery,” Dr Kawaguchi said.
“After trawling through hours of video we noticed in one segment, filmed at 507 metres depth [about 554 yds], a frenzied twirling of three krill, which turned out to be two males pursing one female. The whole mating ritual only lasted 12 seconds and had five distinct phases which we’ve labeled the ‘chase’, ‘probe’, ‘embrace’, ‘flex’ and ‘push’.”
The find is very important as krill are vital to the entire Antarctic food chain. Scientists estimate there are about 500 million tonnes of Antarctic krill in the Southern Ocean. The biomass of this one species may be the largest of any multi-cellular animal species on the planet.
According to a British Antarctic Survey
completed in 2005 the numbers of Antarctic krill could already have dropped by about 80% since the 1970's. The most likely explanation is a dramatic decline in winter sea-ice. Science Daily
Krill feed on the algae found under the surface of the sea-ice, which acts as a kind of 'nursery'. The Antarctic Peninsula, a key breeding ground for the krill, has warmed by 2.5°C in the last 50 years, with a striking decrease in sea-ice. It is not fully understood how the loss of sea-ice there is connected to the warming, but could be behind the decline in krill.
PhD student James P. Robinson, of the Institute for Marine and Antarctic Studies
and Australian Antarctic Division
has found that ocean acidification and climate change are likely to adversely affect the krill. As the amount of CO2 in sea water increases, the survival and successful development of larval krill is decreasing and could result in up to 54% increase in mortality
"As krill are a keystone species, this would have major implications for Southern Ocean and Antarctic ecosystems and for the sustainable management of the Antarctic krill fishery." Robinson said.
According to projections based on the Intergovernmental Panel on Climate Change
, CO2 concentrations where the krill live and breed could rise to between 1000 and 2000 ppm
within this century.
Another possible threat to krill numbers is the krill fishing industry. Commercial fishing of krill has been going on since the early 1970s. They have been harvested for human consumption, nutritional supplements and aquaculture feed. With improving technology and more and more pressure on our food resources the Australian Antarctic Division
say that the 100,000 tonne catch is likely to be doubled in the near future. Researchers and environmental groups are carefully monitoring all fishing activities in Antarctic waters and will be quick to take action if there are breaches of the 1982 Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR)
and its corresponding catch limits.
I asked Krill biologist with the Australian Antarctic Division, Rob King, if he thought Antarctic krill numbers were in decline. He said "The evidence for this was not proven" but also said "any change to krill will have ripple effects to the food web of the Southern Ocean ecosystem". He named the greatest threats as "ocean acidification, climate change and a growing fishery".
So, despite this newly discovered ability for deep sea mating, the future for Antarctic krill is far from certain and numbers may decrease in the future. The challenge for researchers with the Australian Antarctic Division now is to accurately monitor krill numbers and identify the precise ‘tipping point’ at which CO2 will negatively impact krill’s life-cycle and development.
Please visit the Australian Antarctic Division website
to view the ground-breaking footage of krill mating in the depths of the Southern Ocean and also a another very cool animation by former Antarctic Arts Fellow Lisa Roberts.