Last fall, a friend visited from England so we did the touristy stuff and stopped for lunch at Horseshoe Bay. Snapping photos, Tanya took a lovely image of a jellyfish just off the dock.
This past Saturday was World Oceans Day, a moment to appreciate everything oceans provide. But beneath the blue waves lie dark, troubled waters. And the jellyfish we had admired symbolizes greater problems ahead.
According to the Vancouver Aquarium, oceans provide at least 50 per cent of the air we breathe. Over 2.6 billion people depend on the oceans for their primary source of protein and over three billion people depend on marine and coastal biodiversity for their livelihoods. The oceans absorb 30 per cent of human-caused carbon dioxide, helping to buffer the effects of global warming.
Canadians should feel more than a little connected with the oceans. Surrounded by ocean on three sides, we have the longest shoreline in the world at 243,000 km. And along any coastline almost anywhere in the world is evidence of humanity’s dependence on the seas for food, recreation, and reflection.
But oceans are under stress. The evil twin of global warming is ocean acidification, a chemical condition that impacts marine food chains and slows down the ability of shellfish and corals to make shells. Marine organisms depend entirely on the oceans’ stable chemical balance that has allowed them to evolve in complex, ecological systems over millions of years.
Acidification is caused by increased levels of atmospheric CO2 absorbed by the oceans. Over the past 200 years, since the industrial revolution, oceans have become 30 per cent more acidic. According to Dr. Carol Turley, senior scientist at the U.K.’s Plymouth Marine Laboratory, when CO2 is added to sea water it forms a weak carbonic acid affecting the carbon ions that marine organisms like shellfish and corals depend on for shell-making.
Turley believes that it is the rate of change that is having such a devastating impact on marine life. Couple that with overfishing, pollution, release of raw sewage, and fertilizer runoff and it’s no wonder that marine ecosystems are under stress.
All this leads to jellyfish. Jellies are populating the seas at an explosive rate. UBC marine scientists have found that global warming has caused 2,000 species to bloom earlier and expand their numbers. According to studies at the Virginia Institute of Marine Science, the rise in ocean temperatures and the overfishing of marine predators has made conditions ideal for massive jellyfish blooms.
Baby jellies begin as polyps and, depending on their species, they can clone themselves into hundreds of jellyfish resulting in millions of jellies blooming at the same time. Jellyfish can turn a damaged ecosystem into one far worse. They have the unique ability to eat foods further up the food chain consuming everything – eggs, larvae, fish and plankton – that larger fish, seals, whales and seabirds depend on.
In sheer numbers, they can decimate ecosystems. In the 1980s jellyfish believed from the Gulf of Mexico were inadvertently introduced to the Black Sea in the ballast of one ship. They ate everything, collapsing a fishing economy. The sea’s biomass became 95 per cent jellyfish. In the Sea of Japan, the massive Nomura jellies are filling nets and crippling fisheries. Anchovy catches have decreased 20-fold. Off Namibia jellies have replaced sardine stocks. Jellyfish invade fish farms, get sucked into the cooling systems of power plants and ships and in Oman clog desalination plants. Venomous jellies are perilous to swimmers. And jellies thrive in low-oxygen dead zones.
A current fear is that the oceans could revert to the Precambrian world of 500 million years ago when jellyfish ruled.
It’s a sobering thought.
