My editor chopped my lede about Maine’s record red tide, a toxic algal bloom that posed skin and respiratory risks to beachgoers and resulted in a summer-long suspension of shellfish harvesting in “Vacationland,” in favor of those familiar culprits jellyfish [yawn]. Otherwise, I’m very happy with the piece.
Warmer water is exacerbating problems in the oceans
THE fishermen of Kokongi, Japan, have seen record hauls this year. They are not, however, very happy. Their nets are trapping jellyfish: giant, gelatinous, wobbly and worthless. Jellyfish were once rare along these shores, but are now an almost annual occurrence.
It is the same story in many other parts of the world. Jellyfish are blamed for damaging fishing, shutting down power and desalination plants, and upsetting swimmers.
There is one man, though, who may be justified in saying “I told you so”. His name is Jeremy Jackson of the Scripps Institution of Oceanography, in San Diego, and for the past decade he has been touring the world giving a depressing presentation he calls the “Brave New Ocean”.
Dr Jackson is a commanding presence in any room, with his long, white ponytail and booming voice. The story he has been telling is quite simple, that the world’s oceans are undergoing a profound shift because of overfishing, habitat destruction and warming. The effects are seen in the rise of jellyfish, and also in algal blooms and “blobs”, something he describes as “the rise of slime”.
Indeed, a report recently identified increases in marine mucilage, a seasonal phenomenon consisting of a gelatinous mess of decomposing sea animals, plants, faeces and anything else that has become entrapped in the slime. Mucilage forms when decomposing material fails to sink rapidly to the bottom of the sea. In certain circumstances it can spread over hundreds of kilometres.
It isn’t new. Strands of the stuff were first reported off the coast of Italy in 1729, when it was dubbed mare sporco (dirty sea) by fishermen whose nets were clogged by the foul-smelling mucus, and it has popped up from time to time since then. But a study by Roberto Danovaro of the Polytechnic University of Marche, in Italy, and his colleagues shows that, like the jellyfish, it is more frequent these days—appearing more often in the past 20 years than in the previous 200.
Mucilages are also found in more places and are larger, what was once known only in the Adriatic Sea now pops up in the Aegean and the Tyrrhenian, too. Some strands have stretched up to 200 kilometres (120 miles)—and, because they are forming earlier in the summer they are persisting longer in the year.
The study, published in September in the Public Library of Science, suggests the cause is higher surface temperatures that are the result of global warming. Dr Danovaro says that recent studies have suggested similar globs could be forming in the North Sea and off the coast of Australia.
The rise of slime, though, is not attributable just to climate change. Overfishing is also to blame. Removing fish that would normally eat the young stages of organisms such as jellyfish has seen populations of these gelatinous giants balloon. Then there are regions of the coast where nutrient run-off is so bad that large portions of the oceans are dubbed “dead zones”: low oxygen regions where algal blooms are common. Dr Jackson argues that the oceans are becoming dominated by microbes, toxic algal blooms, jellyfish and disease.
Yet these are not insoluble problems. Strategies to reduce overfishing and marine-habitat destruction, or nutrient run-off into the ocean, are not beyond the wit of man. Dealing with the problem of ocean warming, which is linked to climate change, is harder but not impossible. There was a time when people believed that the ocean’s bounty was unlimited. Man’s hubris has caught up with him and now people must clean up the mess.
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Photo credit: owenstache (via Flickr)