To the list of climate change's victims, you can now add the suffering Gorgonia. Scientists at Spain's Higher Council of Scientific Investigation (CSIC) have discovered that lengthening summers in the Mediterranean are having dire effects on the familiar fan-shaped coral, as well as on many other kinds of marine invertebrates. In a study published April 14 in the journal Proceedings of the National Academy of Sciences, they argue that for the Gorgonia and its kin, longer summers equal nothing short of mass death.
The climatological finding isn't new. For years now, scientists around the world have recognized that global warming affects the seasons, triggering springtime events like the flowering of plants as much as six weeks earlier than normal, and pushing the arrival of fall ever further back in the calendar. Lengthening summers have translated not just to more days of warm temperatures but more drought and wildfires as well. (See pictures of coral reefs in peril.)
What's new is that the CSIC study, co-authored by Marta Ribes and Rafel Coma, suggests the phenomenon doesn't just occur on land. By focusing on the Gorgonia, one of the most emblematic and significant corals in the Mediterranean, Ribes and Coma have found that seas have their seasons, too and with equally dire effects. Between 1974 and 2006, summer conditions in the Mediterranean expanded by 40%, meaning the season has grown on average one day longer each year. For the Gorgonia and other sensitive suspension invertebrates the term refers to the organisms' habit of feeding on particles suspended in the water the added length has made an already tough season even tougher.
"Summer is already an unfavorable period for these invertebrates," says Ribes. "But now we're seeing mortality in as much as 50% of the population, depending on the area."
For the Gorgonia, which can grow up to 1 m (3 ft) tall, the problem stems from its own seasonally affected energy resources. Suspension invertebrates, which include sponges as well as corals, require more energy to breath in warmer temperatures. And that, in turn, means they need more food. But grim irony warmer temperatures also stratify the water, making it harder for edible organisms like plankton, which prefers cold water, to get to the animals who eat them. For suspension invertebrates, the result is a food shortage that occurs precisely at the moment when they need more food. (See pictures of the effects of climate change on Europe.)
The resulting physiological stress, says Ribes, explains why there have been so many instances of massive mortality among suspension invertebrates in the past few decades. "Even though they're normally vulnerable during summer, these organisms can survive the average season. But when the season becomes abnormal, when you have these atypically high temperatures for longer periods of time, they don't have the energy resources for it."
Mass death, needless to say, is bad enough for the corals themselves. But it also bodes ill for other species, such as bivalves and sponges. Corals help diminish turbulence in the water, making it easier for other species to snatch their own food and for the larvae of those species to stay closer to the mother colonies that feed them. "We call [corals] the engineers of the ecosystem," says Ribes. "Without them, other invertebrates won't be able eat either. It's a chain reaction."
A chain reaction that is one more piece of evidence of global warming's devastating impact. Coupled with other climate change phenomena, like the boom in jellyfish off the coast of Spain and the appearance of a new, ecosystem-upsetting species of shrimp near Tunisia, Gorgonia mortality looks to be remaking the sea into a very different place.