September 7, 2013 3:21:51 PM
I don't remember decades ago hearing about blooms of jellyfish, jellyfish so clogging beaches that people could not go into the water. Such things did use to happen, but nowadays there are plenty of such reports; just use Google to see if there is any news about jellyfish, and you will easily find such blooms, and also reports of people being hospitalized due to the ensuing stings. I had thought that this was the big disadvantage of a jellyfish imbalance, the stings they dealt people. I have learned that this is actually only a small part of the problem. Despite its title, relatively few of the pages of Stung!: On Jellyfish Blooms and the Future of the Ocean (University of Chicago Press) by marine biologist Lisa-ann Gershwin have to do with the pain jellyfish tentacles inflict on human bodies. Instead, Gershwin explains that jellyfish are doing wonderfully well at the cost of the diversity of other marine species, and our oceans are going through something they have not had in millions of years, a "rise of slime." This is truly a book that is distressing without being alarmist. Jellyfish, Gershwin says, might be analogous to canaries in a coal mine; when the canary falls off its perch because it cannot breathe, it is time for the miners to get out fast. Jellyfish, however, thrive (instead of dying) when the environment is in degradation, and not only do we have nowhere to escape (the oceans and we are on this planet for good), it increasingly looks like there is nothing we can do.
Let's think about the simple stings first. Plenty of us who have been to the beach have been stung by jellyfish. It hurts, enough to bring tears, but that isn't all. A jellyfish called Chironex fleckeri is doing quite well now, and if you get stung by a few feet of its tentacle, you might die in a couple of minutes. It somehow makes the heart seize up. Then there is a group of jellyfish called the Irukandji, which are about the size of your thumb. A brush of its little tentacle might not even sting, but then hammering backache, nausea, relentless vomiting, trouble breathing, and worse come on. The jellyfish are small, and nearly invisible in the water; the symptoms of their stings are diverse; they leave no mark and no venom which can be found within the body; and so they kill far more people than they get credit for, because victims seem to have drowned or suffered heart attacks or strokes.
Stinging is among the least of our problems with these strange creatures. There are other direct problems that they cause us. Their masses have clogged up the intakes of the nuclear-powered supercarrier USS Ronald Reagan and disabled the ship. They can get sucked up into shoal-based fuel-burning power stations causing blackouts, and they stall desalinization plants in the same way. They have caused unscheduled outages in nuclear power plants. They suffocate salmon in salmon farms and transfer bacteria to them. Like jellyfish stings, these types of nuisance might have good solutions: stay out of the water if jellyfish are in it, and develop better nets and filters to keep them from interfering with power production or commerce. (No one has actually been able to do this; chemical repellants, electroshock, poisons, and bubble curtains have failed to have much effect.) The real problem posed by jellyfish, however, is not that they sting, or clog up our machines. They are changing the oceans, perhaps forever, and we are continuing to welcome them to do so.
Gershwin invites us to think of jellyfish as weeds; of course they are not plants, but they have weedy behaviors that make them continue when other species have given up: "They are highly tolerant of a broad range of environmental conditions; they grow fast, breed early and often, and have a large number of young; and they will eat just about anything that they can get their lips around." They had been in the ocean for millions of years before any other creatures evolved shells or bones, and they didn't get wiped out by any of the five mass die-offs that took away all those other creatures we know only from fossils. "They survived conditions that drove others extinct and stimulated evolution of entirely new forms. And now, in our rapidly changing oceans and climate, jellyfish are again experiencing a renaissance."
The renaissance is happening because we are making it easy for jellyfish to thrive. We are changing the oceans in ways that are for jellyfish "a dream come true" (a phrase Gershwin uses more than once). People may debate whether humans are causing, say, global warming, but there is certainty that we are causing the boom in jellyfish. Many of Gershwin's chapters detail (often at length and inarguably) the multiple ways that we are doing this, ways that are summing up for an ocean disaster. Overfishing means that there is less predation on jellyfish, and less competition for food resources they enjoy. Pollution affects plenty of creatures in the sea, but barely bothers jellyfish unless it kills off their prey. Coastal construction gives them firm foundations for their polyps to colonize. Eutrophication, the flow of excess nutrients or fertilizer into the ocean, causes an overgrowth of algae which leads to dead zones on the sea floors, and the jellyfish eat the creatures that are supposed to eat the algae. This means there are more jellyfish, fewer fish, and more dead zones. Climate change means low dissolved oxygen, which jellyfish can tolerate better than other creatures, and they aren't as bothered by ocean acidification, either. Jellyfish in many areas have been "the last man standing," and are doing just fine in the remaining areas, too. And if they aren't bothering an area yet, just wait - they happily hitch free rides in the ballast water our ships carry from place to place.
Jellyfish have formed their blooms as a natural part of their life cycle for millions of years, but the changes we have wrought are enabling them to do it bigger, more often, and in more places than ever before. Generally jellyfish are not able to take over a healthy ecosystem. Fish, for instance, are mobile, bigger, and smarter than jellyfish (which, after all, have no brains), and can never lose to them on a level playing field. But if the fish are burdened with overfishing or pollution, the opportunistic jellyfish move in. Gershwin writes of the "double whammy" they inflict of predation (on the eggs and larvae of species higher on the food chain) and competition (for the plankton lower on the food chain which those species would otherwise eat). We ourselves would like to be eating some of those fish species, and jellyfish are starting to outcompete us.
It is all bad news, perhaps with the tiny exception that the jellyfish that people eat will be there in abundance ("only 36 calories per 3-ounce portion"). Gershwin's book is a serious look at a real problem, but she is a funny and chatty writer who can't let doom get in the way of a jaunty sentence. "It is now clear," she writes, "that our marine ecosystems are in freefall due to multiple stressors, and there is no easy fix. Hell, there isn't even a hard fix. The startling truth is we screwed up." She says you can wear protective clothing when you go swimming in the sea, and you can get a jellyfish forecast on your Smartphone. But neither she nor anyone else has solutions to the jellyfish problem or even realistic suggestions, except for exactly one word that ends the book, and which I will not tell you here. Read it and weep.
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