One of the largest and longest experiments ever done to test the impact of excess nutrient on coral reefs confirmed what scientists have long suspected: that this type of pollution from sewage, agricultural practices or other sources can lead to coral disease and bleaching.

A three-year, controlled exposure of corals to elevated levels of nitrogen and phosphorus at a study site in the Florida Keys, done from 2009 to 12, showed that the prevalence of disease doubled and the amount of coral bleaching, an early sign of stress, more than tripled.

However, the study also found that once the injection of pollutants was stopped, the corals were able to recover in a surprisingly short time.

“We were shocked to see the rapid increase in disease and bleaching from a level of pollution that’s fairly common in areas affected by sewage discharge, or fertilizers from agricultural or urban use,” said Rebecca Vega-Thurber, an assistant professor in the College of Science at Oregon State University.

“But what was even more surprising is that corals were able to make a strong recovery within 10 months after the nutrient enrichment was stopped,” Ms. Vega-Thurber said. “The problems disappeared. This provides real evidence that not only can nutrient overload cause coral problems, but programs to reduce or eliminate this pollution should help restore coral health. This is actually very good news.”

The findings were published in Global Change Biology, and offer a glimmer of hope for addressing at least some of the problems that have crippled coral reefs around the world. In the Caribbean Sea, more than 80 percent of the corals have disappeared in recent decades. These reefs, which host thousands of species of fish and other marine life, are a major component of biodiversity in the tropics.

Researchers have observed for years the decline in coral reef health where sewage outflows or use of fertilizers, in either urban or agricultural areas, have caused an increase in nutrients such as nitrogen and phosphorus. But until now almost no large, long-term experiments have actually been done to pin down the impact of nutrient overloads and separate them from other possible causes of coral reef decline.

This research examined the effect of nutrient pollution on more than 1,200 corals in study plots near Key Largo, Florida, for signs of coral disease and bleaching, and removed other factors such as water depth, salinity or temperature that have complicated some previous surveys. Following regular injections of nutrients at the study sites, levels of coral disease and bleaching surged.

One disease that was particularly common was dark spot syndrome, found on about 50 percent of diseased individual corals. But researchers also noted that within one year after nutrient injections were stopped at the study site, the level of dark spot syndrome had receded to the same level as control study plots in which no nutrients had been injected.

The exact mechanism by which nutrient overload can affect corals is still unproven, researchers say, although there are theories. The nutrients may add pathogens, may provide the nutrients needed for existing pathogens to grow, may be directly toxic to corals and make them more vulnerable to pathogens or some combination of these factors.

“A combination of increased stress and a higher level of pathogens is probably the mechanism that affects coral health,” Ms. Vega-Thurber said. “What’s exciting about this research is the clear experimental evidence that stopping the pollution can lead to coral recovery. A lot of people have been hoping for some news like this.

“Some of the corals left in the world are actually among the species that are most hardy,” she said. “The others are already dead. We’re desperately trying to save what’s left, and cleaning up the water may be one mechanism that has the most promise.”

Nutrient overloads can increase disease prevalence or severity on many organisms, including plants, amphibians and fish. They’ve also long been suspected in coral reef problems, along with other factors such as temperature stress, reduced fish abundance, increasing human population, and other concerns.

However, unlike factors such as global warming or human population growth, nutrient loading is something that might be more easily addressed on at least a local basis, Ms. Vega-Thurber said. Improved sewage treatment or best-management practices to minimize fertilizer runoff from agricultural or urban use might offer practical approaches to mitigate some coral reef declines, she said.

Collaborators on this research included Florida International University and the University of Florida.


Two hearings on electricity
cause confusion of the date


A key public hearing about private power generation already has taken place.

The hearing was Wednesday and not Thursday, as A.M. Costa Rica had incorrectly reported.

This was the hearing by the Authoridad Reguladora de Servicios Públicos that sought reaction to a draft measure that would allow all electrical consumers to generate their own power and perhaps sell the excess to their local electric company. The proposal is contained in a lengthy document released by the agency. The highly technical document specifies the requirements for hooking up to the national electrical grid.

Jim Ryan of ASI Power & Telemetry, S.A. in Liberia said he, too, was confused by the agency because it sent out two notices for hearings. One was for Wednesday and one is for today. Both are on electrical matters.

He said that those who favor private generation of power can still file comments with the agency via fax 2215-6002 or email  consejero@aresep.go.cr.


Man in Limón sustained
11 bullet wounds and died


Someone wanted a man in Limón very dead. Judicial agents said that police found the body of a man still unidentified in a parked car. The body had sustained 11 bullet wounds.

The Judicial Investigating Organization said that the man was between 30 and 35 years of age.

Airport police nearby in Limón were attracted to the car because a door was open and the lights were on about 11 p.m. Tuesday night. The officers found the body when they left the airport grounds to investigate.


Another geothermal loan
for project near volcano


The Instituto Costarricense de Electricidad is getting a $70 million loan from the European Investment Bank for the Las Pailas II geothermal generating plant.  The loan is for 25 years with a variable interest rate starting at 4.03 percent, said the firm known as ICE.

The central government is guaranteeing the loan so legislative approval is needed.

This is the second loan for the project.  Last week the Japanese Agency for International Cooperation agreed to loan $560 million for La Pailas II and two other projects.  All are near the Rincón de la Vieja volcano in northern Costa Rica.