Kim Cobb, a marine scientist at the Georgia Institute of Technology, expected the coral to be damaged when she plunged into the deep blue waters off Kiritimati Island, a remote atoll near the center of the Pacific Ocean. Still, she was stunned by what she saw as she descended some 30 feet to the rim of a coral outcropping.
“The entire reef is covered with a red-brown fuzz,” Dr. Cobb said when she returned to the surface after her recent dive. “It is otherworldly. It is algae that has grown over dead coral. It was devastating.”
The damage off Kiritimati is part of a mass bleaching of coral reefs around the world, only the third on record and possibly the worst ever. Scientists believe that heat stress from multiple weather events including the latest severe El Niño, compounded by climate change, has threatened more than a third of Earth’s coral reefs. Many may not recover.
Coral reefs are the crucial incubators of the ocean’s ecosystem, providing food and shelter to a quarter of all marine species, and they support fish stocks that feed more than one billion people. They are made up of millions of tiny animals, called polyps, that form symbiotic relationships with algae, which in turn capture sunlight and carbon dioxide to make sugars that feed the polyps.
An estimated 30 million small-scale fishermen and women depend on reefs for their livelihoods, more than one million in the Philippines alone. In Indonesia, fish supported by the reefs provide the primary source of protein.
“This is a huge, looming planetary crisis, and we are sticking our heads in the sand about it,” said Justin Marshall, the director of CoralWatch at Australia’s University of Queensland.
Bleaching occurs when high heat and bright sunshine cause the metabolism of the algae — which give coral reefs their brilliant colors and energy — to speed out of control, and they start creating toxins. The polyps recoil. If temperatures drop, the corals can recover, but denuded ones remain vulnerable to disease. When heat stress continues, they starve to death.
Damaged or dying reefs have been found from Réunion, off the coast of Madagascar, to East Flores, Indonesia, and from Guam and Hawaii in the Pacific to the Florida Keys in the Atlantic.
The largest bleaching, at Australia’s Great Barrier Reef, was confirmed last month. In a survey of 520 individual reefs that make up the Great Barrier Reef’s northern section, scientists from Australia’s National Coral Bleaching Task Force found only four with no signs of bleaching. Some 620 miles of reef, much of it previously in pristine condition, had suffered significant bleaching.
In follow-up surveys, scientists diving on the reef said half the coral they had seen had died. Terry Hughes, the director of the Center of Excellence for Coral Reef Studies at James Cook University in Queensland, who took part in the survey, warned that even more would succumb if the water did not cool soon.
Toxins from harmful algae are present in Alaskan marine food webs in high enough concentrations to be detected in marine mammals such as whales, walruses, sea lions, seals, porpoises and sea otters, according to new research from NOAA and its federal, state, local and academic partners.
The findings, reported online today in the journal Harmful Algae, document a major northward expansion of the areas along the Pacific Coast where marine mammals are known to be exposed to algal toxins. Since 1998, algal toxin poisoning has been a common occurrence in California sea lions in Central California.
Certain drought-stressed wheat cultivars perform better when their roots are in symbiosis with beneficial fungi
Scientists at Aarhus University have discovered that fungi associated with plant roots may improve growth and yield of drought-stressed wheat.
Water scarcity has a negative impact on wheat production. As a consequence of exposure to drought, crops show poorer growth and lower yield. This is a serious problem as the predicted increase in frequency of extreme climate episodes will lead to multiple drought conditions during crop growth which in turn will reduce the yield of wheat, one of the world’s most important foods.
The UN Intergovernmental Panel on Climate Change predicts that drought stress in crops will become increasingly serious in the future. Globally, wheat yield is only 30-60 percent of its potential.
Fungi may help
A specific group of useful fungi – the so-called arbuscular mycorrhizal fungi (AM fungi) – may be able to help alleviate drought stress in wheat. These fungi live in a symbiotic relationship with plant roots. Recent research from Aarhus University demonstrates that the fungi can improve growth and yield in some wheat varieties under drought stress.