|
|
| A Pachycerus coral in a reef at Palau displays three stages of health and disease: The dark band is the result of a cyanobacterial infection, the white area is dead coral skeleton and the other areas of this specimen show no signs of disease. Photo courtesy of C. Drew Harvell |
By Roger Segelken
Now that marine scientists know how fast disease epidemics can spread in the oceans -- up to 10,000 kilometers a year among fish, compared with 1,000 km. per year in diseases carried by flying birds -- they are focusing the largest-ever international assessment of ocean disease on dying organisms that can't move: the world's corals.
The assessment is called the Coral Reef Targeted Research and Capacity Building project. Supported by the Global Environment Fund and the World Bank at about $28.8 million for the first five years of an anticipated 15-year project life, the assessment aims "to fill critically important information gaps in the fundamental understanding of coral reef ecosystems so that management and policy interventions can be strengthened globally," according to C. Drew Harvell.
A Cornell professor of ecology and one leader of the coral reef assessment, Harvell said the World Bank and Global Environmental Fund are focusing on coral reefs because of their highly threatened condition worldwide and because of their importance to the economy of developing countries. "We hope the new information will guide management policy on marine organisms of all kinds. But first we have to learn what's killing the corals," she said.
Two recently published papers in the journals Frontiers in Ecology and the Environment and Trends in Ecology and Evolution sum up marine science's current understanding of ocean-based diseases. Both papers result from a working group on marine disease chaired by Harvell and funded by the National Center for Ecological Analysis and Synthesis.
In the Frontiers paper ("The Rising Tide of Ocean Diseases," Vol. 2, No. 7, by Harvell and 16 other researchers at Cornell and affiliated institutions), the researchers say fast-moving water-borne epidemics can leave the terrestrial kind in the dust. A 1999-2000 herpes epidemic in sardines spread along the Australian coast at approximately 10,000 km. a year, while a mid-1980s bacterial infection to long-spined urchins ripped through the Caribbean at 3,000 to 4,800 km. a year.
By comparison, birds in North America spread West Nile virus across the continent at about 1,000 km. a year. The findings, the Frontiers authors wrote, "suggest that pathogens may pose a particularly severe problem in the ocean."
The Trends paper ("Does Terrestrial Epidemiology Apply to Marine Systems?" by Hamish McCallum of Australia's University of Queensland, Harvell and four colleagues) explains the difficulties in controlling ocean disease with land-bound methods: Essentially, fish won't line up for flu shots and corals can't.
Even where limited vaccination is possible -- by including antibiotics in food for aquaculture fish, for example -- the treatment is problematic. "Spillover of antibiotics from fish pens can lead to low doses of antibiotic being delivered to the wider marine ecosystem, with resulting selection for antibiotic resistance" among disease pathogens, the researchers wrote.
Rather, the marine scientists suggest in the Frontiers article, prevention might be the best medicine: "The most practical immediate remediation for many marine communities is to reduce pathogen inputs (especially from land) and synergistic stressors, such as warm temperatures and eutrophic waters," they wrote before adding: "Reducing such inputs requires knowing the source of new marine pathogens -- research should focus on identifying sources and reducing inputs while at the same time developing control measures."
That is precisely the prescription marine scientists have written for the their global assessment of coral disease. Preliminary surveys are already under way, with full cooperation of local marine scientists, at the four sites they will target as Centers of Excellence: Australia, the Philippines, Mexico and the western Pacific island nation of Palau. In addition to research, the project also aims at scientific training and capacity-building at Centers of Excellence.
The ambitious project has a lot of questions to answer. Among them:
Project leaders say intensive research during the past decade has produced insights into the role of coral community structure and diversity in maintaining productive fish and invertebrate populations. They have begun to learn how disease affects coral community structure and diversity.
"Ultimately, this concerns the human community," said Susan M. Merkel, a Cornell microbiologist and coordinator of the project. "If we find that improvements in waste-water treatment, solid waste disposal and land-use practices can slow -- or even reverse -- the destruction of coral reefs and protect the fisheries that depend on the reefs, then local communities and governments need to know."
| Cornell Chronicle Front Page | | Table of Contents | | Cornell News Service Home Page |