![]() The removal of a kelp forest or sea grass bed can have devastating effects not only on native plants and animals, but also on commercial fisheries. ![]() "If you dive in a kelp forest, you find a very different fish community than if you dive in a coral-dominated area." The loss of vegetation can completely change the community of species that live there, Vergés said. The shrimp, crab, and other species that often spend the first year of their lives hiding from predators in the protection of the grasses disappear when their cover is gone, leaving a void for the creatures that depend on them. But the warming of the Mediterranean has allowed their numbers to explode in recent decades, and the fish have deforested hundreds of miles of kelp there, Vergés said. Tropical rabbitfish have been swimming in the Mediterranean Sea since 1869 when they slipped in through the newly opened Suez Canal from the Red Sea. For instance, "parrotfish are capable of eating a lot of sea grass per individual," said marine scientist Joel Fodrie of the University of North Carolina at Chapel Hill. Once a tropical fish species arrives in a new area, it can quickly mow down vegetation and algae and destroy the lush habitat that protects other species. But when the herbivorous fish move toward more temperate waters, they often find a bountiful harvest of kelp or sea grass to feed their voracious appetites. Many tropical fish species are "browsers" or "scrapers" that clean coral of algae and plants that could otherwise choke the reefs. Their study appeared July 9 in the Proceedings of the Royal Society B. Vergés and her colleagues recently documented how tropical fish, which are normally a beneficial companion to coral beds, can devastate a kelp forest. The kelp and sea grass, however, are being replaced with other warm-water species such as coral that follow the arrival of tropical fish, said Vergés. Sea grass beds and kelp forests are often known as the sea's nurseries because they have nooks and crannies filled with nutrients that feed and protect fish larvae and juveniles. But the consequences of that mixing are already trickling up the food chain. "The faunas are mixing, and nobody can see what the outcome will be," said Ken Heck, a marine scientist at the University of South Alabama in Mobile. Invading tropical species are stripping kelp forests in Japan, Australia, and the eastern Mediterranean and chowing down on sea grass in the northern Gulf of Mexico and Atlantic seaboard. They are finding that the repercussions of the migration of tropical fish, in particular, are often devastating. Climate change is propelling fish and other ocean life into what used to be cooler waters, and researchers are scrambling to understand what effect that is having on their new neighborhoods. ![]() The bay is hundreds of miles north of the tropics, but now "it feels like a tropical place," said Vergés, a lecturer at New South Wales University in Australia. Marine ecologist Adriana Vergés emerged from a scuba dive in Tosa Bay off the coast of southern Japan last week and was amazed at what she'd seen: A once lush kelp forest had been stripped bare and replaced by coral. ![]()
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