Being a bookish person with an interest in all things environmental, I have read my fair share of doom-and-gloom exposés of how things are not going well for the world's ecosystems. It's a familiar theme these days that most people would likely prefer not to think about.
But we can't ignore reality.
One book that has alarmed me is Stung! On Jellyfish Blooms and the Future of the Ocean by Lisa-ann Gershwin. A biologist who specializes in jellyfish, Gershwin outlines why jellyfish are becoming the dominant organisms in many parts of the world's oceans and why we should be worried about this dramatic change.
Jellyfish are true survivors. They have been on the planet for millions of years. For a very primitive animal with no brain or heart, they are extremely adaptable and can survive conditions deleterious to many other species.
For example, they can live in waters with lower oxygen content than most other animals. With stinging tentacles that can ensnare large prey, they are efficient feeders that also catch a variety of plankton and small larvae. Many of the small larvae they catch would otherwise have the potential to grow into large fish - the kind humans like to catch and eat. They can grow rapidly to take advantage of periods when there is plenty of food,such as during plankton blooms, and can consume more than half their weight in food on a daily basis. If they do happen to run out of nourishment, they can simply shrink their body size and live on their own tissues for awhile.
Acidifying waters apparently pose few problems for jellyfish. In the ocean, marine turtles and sunfish are their main predators but both turtles and sunfish appear to be in decline. As for reproduction, they have a number of choices and can reproduce sexually as well as asexually. They live as two forms, the free-floating medusa stage with which people are most familiar and as a small attached polyp often found underwater on man-made structures and the nets around pens for farmed fish. These polyps can proliferate into large colonies and, then, when conditions are right, undergo a process known as strobilation and transform into many small medusas that then float away.
Roughly 1,500 species of jellyfish have been identified to date. The largest can be over 2 m in diameter with tentacles up to 50 m long and weigh 200 kg (most of which is water). As mankind over-harvests fish from the sea, pollutes estuaries and bays with sewage effluent, spews out more carbon dioxide into the atmosphere and thus acidifies the oceans, we are inadvertently creating conditions that favour more jellyfish.
For example, in the Antarctic, people are now fishing for krill to convert into fish meal, an extremely egregious example of fishing too far down the food chain. The krill are being replaced in the ecosystem by copepods, a much smaller type of zooplankton. Unlike krill, the copepods are too small for the penguins to feed on so the penguin population is declining. But copepods are the right size - any size is - for jellyfish, so jellyfish are ominously increasing in abundance as penguins decline.
Jellyfish blooms are an increasing problem in many parts of the world's oceans. The Black Sea, Caspian Sea, Baltic Sea and the Mediterranean are all experiencing increasing problems with massive numbers of jellyfish. Off the waters of China, Japan and Korea, jellyfish blooms are replacing the fish that once sustained the people of those nations.
In Florida, California, India, Israel and many other places, jellyfish blooms have clogged the water intakes of power plants.
Wherever we empty the seas of fish, we are creating advantageous conditions for jellyfish.
What's to be done? One of the most sensible actions that could be taken to re-balance the food chain in our oceans and protect ecosystems is to set aside areas where no fishing or other industrial activities are allowed. Just as we need terrestrial parks to serve as biological reservoirs of diversity on land that protect a full community of species, we also need marine protected areas where natural ecosystems can prevail.
Where such marine protected areas have been created, the results are usually impressive. Australia, with the largest barrier reef in the world, has wisely already protected 36% of its marine areas. In Canada, we have the longest coastline in the world but only 1% of it is protected. The Canadian Parks and Wilderness Society has identified and recommended a number of marine protected areas along the coast of B.C. Now, we await some action from the government.
Elaine Golds is a Port Moody environmentalist who is vice-president of Burke Mountain Naturalists, chair of the Colony Farm Park Association and past president of the PoMo Ecological Society.
