Improving water quality can help save coral reefs

August 20, 2012 by admin  
Filed under Water Quality

Corals are made up of many polyps that jointly form a layer of living tissue covering the calcareous skeletons. They depend on single-celled algae called , which live within the coral polyps.

The coral animal and the associated zooxanthellae depend on each other for survival in a , where the coral supplies the algae with nutrients and a place to live. In turn, the algae offer the coral some products of their , providing them with an important energy source.

High can block photosynthetic reactions in the causing a build-up of toxic , which threaten the coral and can result in a loss of the zooxanthellae.

a nutrient-stressed staghorn coral

Light and temperature trigger the loss of symbiotic algae (bleaching) in a nutrient-stressed staghorn coral. Credit: University of Southampton

Without the algae, corals appear white, a state which is often referred to as ‘bleached’. Bleaching often leads to coral death and mass coral bleaching has had already devastating effects on coral reef ecosystems.

The study of University of Southampton, published in the latest issue of the journal Nature Climate Change, has found that of the water can increase the probability of corals to suffer from heat-induced bleaching.

Within the coral, the growth of zooxanthellae is restricted by the limited supply of nutrients. This allows the algae to transfer a substantial amount of their photosynthetically fixed carbon to the coral, which is crucial for the symbiotic relationship.

Algal growth becomes unbalanced when the availability of a specific nutrient decreases compared to the cellular demand, a condition called nutrient starvation.

Researchers from the University of Southampton based at the Coral Reef Laboratory in the National Oceanography Centre, Southampton, found that an increased supply of dissolved nitrogen compounds in combination with a restricted availability of phosphate results in phosphate starvation of the algae. This condition is associated with a reduction in photosynthetic efficiency and increases the susceptibility of corals to temperature and light-induced bleaching.

Dr Jörg Wiedenmann, Senior Lecturer of Biological Oceanography at the University of Southampton and Head of the Coral Reef Laboratory, who led the study, says: “Our findings suggest that the most severe impact on coral health might actually not arise from the over-enrichment with one group of nutrients, for example, nitrogen, but from the resulting relative depletion of other types such as phosphate that is caused by the increased demand of the growing zooxanthellae populations.”

Dr Wiedenmann adds: “Our results have strong implications for coastal management. The findings suggest that a balanced reduction of the nutrient input in coastal waters could help to mitigate the effects of increasing seawater temperatures on . However, such measures will be effective only for a short period of time, so it is important to stop the warming of the oceans, which will otherwise destroy most of the reefs in their present form in the near future.

“Finally, our results should help the design of functioning marine reserves.”

Journal reference:

Nature Climate Change
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Article source: http://phys.org/news/2012-08-quality-coral-reefs-video.html

Warmer oceans taking toll on world’s coral reefs

February 28, 2011 by admin  
Filed under Protecting Habitats


Global warming took a toll on coral reefs in 2010, endangering one of the world’s key ecosystems that benefit people in countless ways.

Coral reefs are habitat for almost 100,000 known marine species, including about 40 percent of all fish species. They feed millions of people, protect coasts by absorbing wave energy, and shelter creatures that could become sources of medicine for treating cancer, HIV/AIDS and other diseases.

National Oceanic and Atmospheric Administration satellite data show that 2010, the warmest on record, was hard on corals. Warmer than normal temperatures stressed tropical corals, causing them to bleach - expelling the algae that live in their tissue, giving them color and nourishment.

Some 75 percent of the world’s reefs are threatened by climate change, overfishing and pollution, according to a new assessment from the World Resources Institute and other conservation organizations. The number increased dramatically from the group’s last assessment in 1998.

“It will take a Herculean effort to reverse the current trajectory and leave healthy ocean ecosystems to our children and grandchildren,” said Jane Lubchenco, the marine scientist who heads NOAA. “How the world rises to this challenge is a reflection of our commitment to one another and to the natural world that gives us sustenance, wisdom and a reflection of our souls.”

Coral reefs cover less than a tenth of 1 percent of the oceans’ acreage, but that’s still about 100,000 square miles. Scientists who dive to study reefs can’t cover them all, so they’re turning increasingly for help from satellites.

NOAA’s satellite data on ocean heat showed that bleaching is occurring in all regions and becoming more frequent. Extreme bleaching kills corals because they can’t survive without the nourishment the algae provide. Less intense bleaching can weaken corals, reduce their growth and reproductive ability, and make them more vulnerable to disease.

Mark Eakin, a University of Miami-trained oceanographer who coordinates NOAA’s Coral Reef Watch satellite program, said that 2010 was only the second time on record that bleaching occurred globally.

The first global bleaching, from 1997 to 1999, came when an exceedingly strong El Nino - a periodic warming of ocean surface temperatures in the tropical Pacific - was followed by an especially strong version of its opposite counterpart, La Nina. About 15 percent of the world’s corals died then.

“Fast forward to 2010,” Eakin said. This time, El Nino and the La Nina that followed weren’t nearly as strong.

“The problem that we’re seeing is, as the oceans keep warming on a year-to-year basis, it doesn’t take as big or as unusual conditions to result in this sort of event.”

The bleaching from last year in many places was the worst since 1998. In the warmest months, bleaching hit the Pacific, the Indian Ocean, Southeast Asia and the southern Caribbean.

The Florida Keys and the northern part of the Caribbean, where unprecedented bleaching occurred in 2005, were spared last year because tropical storms cooled the waters.

Coral reefs are more diverse in life forms than even rain forests. The most abundant life is in the Coral Triangle, from the Philippines down to Indonesia and across to Papua New Guinea.

“I’ve been diving in some places there where I see more species on any given reef than we have in all of the Caribbean,” Eakin said.

Article source: http://www.miamiherald.com/2011/03/01/2091297/warmer-oceans-taking-toll-on-worlds.html

Endangered species’ top 10 list: Save these ecosystems

January 6, 2011 by admin  
Filed under Protecting Habitats

Oceana, an international ocean conservation group, yesterday released a new report that identifies vital habitats in need of protection, if key endangered species are to have a chance to survive climate change. According to the Intergovernmental Panel on Climate Change (IPCC), 20 to 30 percent of the world’s species will be at increased risk of extinction if global temperature increases exceed 1.5 to 2.5 C (3 to 5 F) above pre-industrial levels. The climate threats to species include increased disease, diminished reproduction, habitat loss, and declining food supply.

For species that are already struggling on the brink of extinction, global climate change threatens to push them over the edge, said Huta. We certainly need to reduce global warming pollution, but we also need to act now to prioritize and protect some of the most important ecosystems for imperiled wildlife. Endangered species don’t have the luxury of waiting for political leaders to act to slow the pace of climate change.

List of top 10 ecosystems to save for endangered species featured in the report:

1. Arctic sea ice, home to the polar bear, Pacific walrus and at least six species of seal

2. Shallow water coral reefs, home to the critically endangered elkhorn and staghorn corals

3. The Hawaiian Islands, home to more than a dozen imperiled birds, and 319 threatened and endangered plants

4. Southwest deserts, home to numerous imperiled plants, fish and mammals

5. The San Francisco Bay-Delta, home to the imperiled Pacific salmon, Swainsons hawk, tiger salamander and Delta smelt

6. California Sierra Mountains, home to 30 native amphibian species, including the Yellow-legged frog

7. The Snake River Basin, home to four imperiled runs of salmon and steelhead

8. Greater Yellowstone Ecosystem, home to the imperiled Whitebark pine, an important food source for the threatened Grizzly bear and other animals

9. The Gulf Coasts flatlands and wetlands, home to the Piping and Snowy plovers, Mississippi sandhill crane, and numerous species of sea turtles

10. The Greater Everglades, home to 67 threatened and endangered species, including the manatee and the red cockcaded woodpecker

Climate change is no longer a distant threat on the horizon, said Leda Huta, executive director of the Endangered Species Coalition. It has arrived and is threatening ecosystems that we all depend upon, and our endangered species are particularly vulnerable.

Seven additional ecosystems were nominated but did not make the Top 10. They nonetheless contain important habitat for imperiled species. These ecosystems include Glacier National Park, the Jemez Mountains, Sagebrush Steppe, U.S. West Coast, the Maine Woods, the Grasslands of the Great Plains and the Southern Rocky Mountains.

The new report, which includes information about each ecosystem, as well as recommended conservation measures, is available online at www.StopExtinction.org.

Scientists ranked Arctic sea ice and shallow water corals as two of the highest priority ecosystems threatened by climate change in an Endangered Species Coalition report demonstrating the urgency of saving habitat for endangered species. The report, entitled Its Getting Hot Out There: Top 10 Places to Save for Endangered Species in a Warming World was released January 5th, and examines how the changing climate is increasing extinction risk for imperiled fish, plants and wildlife.

Have your say: Is the reality of climate change still in question?

Article source: http://www.examiner.com/green-living-in-national/endangered-species-top-10-list-save-these-ecosystems