By Deborah Jones
VANCOUVER, February 2012
When dead sea mammals began washing ashore on Canada’s west coast, in ever-greater numbers, marine biologist Andrew Trites was distressed to find the causes of their deaths were domestic animal diseases.
Seals, otters and other species around the world are increasingly being infected by parasites and other diseases long common in goats, cows, cats and dogs, marine mammal experts told a major science conference.
And the diseases also increasingly threaten people who use the oceans for recreation, work or for seafood, scientists told a news conference at the annual meeting of the American Association for the Advancement of Science, in Vancouver.
The symposium “Swimming in Sick Seas” was just one of many sessions at the conference to draw a bleak picture of the state of the world’s oceans, which are increasingly acidic, warming in some areas, being inundated with melting ice, and experiencing other climate change effects.
“There are dramatic shifts in the ocean ecosystem,” said Jason Hall-Spencer of the UK University of Plymouth. His research in Italy, Baha California, and Papua New Guinea is “all showing the same thing. As you increase CO2 you get a 30 per cent drop in microbes, plants and animals” in the oceans.
Gretchen Hofmann of the University of California at Santa Barbara said increasing ocean acidity, caused by CO2 from fossil-fuel burning, is killing the young of shellfish – called spat –worldwide.
In the Pacific Northwest region of Canada and the United States, the failure of spat hatcheries threaten a commercial industry worth more than $200-million (US), said Hofmann.
Lisa Levin of the Scripps Institution of Oceanography in La Jolla,California, said warming of the water reduces how much oxygen it can hold, newly threatening deep-sea creatures that have survived for millennium under stable conditions.
“We’ve seen less than 5 per cent of (animals) on the deep sea floor, and if we’re wiping them out we’ll never see them,” Levin told the conference. “There are undoubtedly organisms down there that can be very beneficial to us, that we have yet to find.”
“I see the dead mammals coming ashore as canaries in a coal mine,”said Trites, director of the Marine Mammal Research Unit in at the Fisheries Centre at University of British Columbia.
Parasites, funguses, viruses and bacteria are increasingly passed from land to sea animals because human settlements on coastlines change water patterns through paving, in-filling of wetlands that are natural filters, and intensive agriculture run-off, said scientists.
Toxoplasma gondii (sometimes called kitty litter disease), round-worm, single-celled parasites that cause brain swelling, and diseases that cause cows to abort their fetuses, add to the challenges marine animals face from human pollution, Trites said.
Diseases from large agriculture operations can cause “abortion storms” in sea animals, said Michael Grigg, an American expert in parasites with the National Institutes of Health in Bethesda, Maryland.
Grigg said a virulent new Type X strain in California “is now spreading across the United States” and samples have found it in South America and Asia. Grigg noted strains of Toxoplasma gondii are already common in people, infecting as many as 25 per cent of North Americans and from 50 to 70 per cent of adult Europeans.
Changes and frequency of diseases in sea animals “could have unrecognized impacts on humans as well,” said Melissa Miller, a veterinarian in California. “We live in the same areas, and harvest and eat many of the same foods.”
Copyright Deborah Jones 2012
Originally published with Agence France-Presse (AFP)