USGS scientist Thierry Work takes a sample from diseased coral at Tunnels Reef on the north shore of Kauai, Hawaii

A coral disease epidemic is killing unusually large numbers of coral on the north shore of the Hawaiian island, Kauai, and USGS scientists, in collaboration with researchers from the University of Hawaii Institute of Marine Biology, are investigating the cause.

Coral reefs cover less than 0.5 percent of the earth’s surface, but provide habitat for an estimated 25 percent of all marine species. Second only to tropical rainforests in size and complexity, more than one million species of plants and animals may be interlinked with coral reefs.

“Coral reefs are important to Hawaii’s underwater environments and the financial well-being of its tourism industry,” said USGS scientist Thierry Work. “Like it or not, ecosystem health is closely intertwined with human and animal health.”

What is Causing the Disease?

Scientists have collected coral samples from the diseased areas, which are referred to as lesions, and examined them in the laboratory. The lesions are closely associated with a mysterious cyanobacterial infection. Cyanobacteria, a type of blue-green algae, often cause visible blooms in freshwater lakes; however, many cyanobacteria are also present in the ocean. Some species of cyanobacteria produce toxins that can sicken wildlife, domestic animals, and humans. The effects of this current outbreak appear limited to corals.

This coral disease outbreak is the first instance where a cyanobacterial disease has been documented in Hawaii on such a large scale. Scientists are trying to figure out what is promoting the outbreak. An unusually large amount of sediment is present on two affected reefs, and this is known to adversely affect corals in other areas.  However, what role sediment or other land based pollution has in driving this disease remains unclear.

Cyanobacteria-affected coral taken at Makua, Kauai on August 5, 2012. The green dots indicate macroalgae; the red dots indicate cyanobacteria-associated tissue loss; and the blue dots indicate live coral.

Why Study this Outbreak? You Can’t Manage What You Don’t Measure and You Cannot Measure What You Don’t Know

Wildlife disease outbreaks are indicators that something is awry in the environment. Understanding causes of disease and what drives those causes is important because this information helps management agencies make informed decisions to prevent further spread of the disease or minimize impact of disease.  Like many other places, coral reefs in Hawaii are adversely impacted by global climate change, land-based pollution, overfishing, and disease. Understanding the role and causes of disease in corals and their prevention may contribute to prevention of additional outbreaks and aid in their recovery.

Coral Reefs are Important

Coral reefs are not only essential for other marine species, they are also economically important. Reefs shelter and provide nursery grounds for many commercially and culturally important species of fish and invertebrates, they protect the islands’ harbors, beaches, and shorelines from erosion and wave damage by storms, and they are vital to the Pacific’s marine tourism industry. Globally, these diverse ecosystems may provide valuable goods and services worth about $375 billion each year to communities around the world.

Coral reefs are sensitive indicators of the health of marine environments. Yet coral reefs are in decline in many parts of the world. It is estimated that 30 percent will be destroyed or seriously degraded in the next 10 years. Disease has played a major role in the decline of coral reef cover in certain parts of the globe such as the Caribbean. In many cases, the causes of mortalities of marine invertebrates are unknown. USGS is collaborating with state, territorial, and other federal agencies to develop tools to assess health of corals and other marine organisms and to determine causes of coral mortality to preserve this unique and valuable natural resource.

For more information on coral disease, see this publication:

Dr. Greta Aeby (left), a coral expert with the Hawai‘i Institute of Marine Biology at the University of Hawai‘i, and Dr. Thierry Work, wildlife disease specialist for the USGS National Wildlife Health Center exit the water at ‘Anini after more than six hours of documenting and photographing diseased rice corals.

Work, T.M., Russell, Robin, & Aeby, G.S. (2012). Tissue loss (white syndrome) in the coral
Montipora capitata is a dynamic disease with multiple host responses and potential causes. Proceedings of the Royal Society B-Biological Sciences, 279(1746), 4334-4341.

http://rspb.royalsocietypublishing.org/content/279/1746/4334.long

USGS biologists translocated critically endangered Laysan Teal, such as this adult with brood, from Laysan Island to Midway Island in the Northwest Hawaiian Islands to expand the species’ population and range and help guard against extinction.

Saving a critically endangered species takes time and patience. U.S. Geological Survey scientists learned this anew as they surveyed the toll on the critically endangered Laysan teal (Anas laysanensis) from last year’s Pacific Ocean Tōhuku Tsunami generated by an earthquake in Japan.

The population of Laysan teal, a small duck once found throughout the Hawaiʻian Islands, had grown rapidly from an estimated 450 birds on tiny Laysan Island to an estimated 830 birds by 2010 at two sites after successful reintroduction to Midway Atoll led by Michelle Reynolds, a research wildlife biologist with the USGS Pacific Island Ecosystems Research Center in Hawaiʻi Volcanoes National Park, Hawaii, in partnership with the U.S. Fish and Wildlife Service.

Rendered extinct on Hawaii’s main islands hundreds of years ago by the human introduction of rats, the teal had been found in recent times only in the remote Northwestern Hawaiian Islands, which are rat-free. In 2004 and 2005, Reynolds and her multi-agency team moved 42 of the surviving birds on Laysan Island within the Hawaiian Islands National Wildlife Refuge to Midway Atoll National Wildlife Refuge, a strategic World War II battlefield that is now part of the Papahānaumokuākea Marine National Monument – and that, like Laysan, is free of mammalian predators. The teal on Midway took to their new island home, managed by the U.S. Fish and Wildlife Service, and produced more ducklings than ever documented before.

Then came the March 2011 tsunami that washed over large areas of both Midway and Laysan islands. At Midway Atoll, the tallest wave was nearly 5 feet. As Reynolds and the U.S. Fish and Wildlife Service monitor the population to determine the impact of the tsunami on both refuge areas, they are reassured by the knowledge they gained from the successful reintroduction effort. Research on the conservation biology of endangered species will help not only the Laysan teal but many island species worldwide that are vulnerable to random disasters, and affected by climate change, habitat loss or predation by non-native species.

John Klavitter of the US Fish and Wildlife Service, left, and USGS biologist Michelle Reynolds attach transmitters to critically endangered Laysan teal that were translocated from Laysan to Midway Island to expand the species’ population and range.

“The species is still at risk,” Reynolds said. “The wild translocation to re-establish a second population was shown to be feasible and successful, but more populations are needed to reduce the high risks of living on low-lying tiny islands.”

In conservation biology, “translocation” is the managed relocation of members of a wildlife species – either captive-bred or from the wild – to someplace else in hope of expanding the species’ population and range. Fewer than half the translocations of threatened species are deemed successful by their investigators. Problems can arise with the population to be moved, such as lack of genetic diversity limiting its breeding success, or with the proposed new habitat, or because of an abundance of predators. Sometimes, the new home just doesn’t seem right to the translocated species and the animals will disperse across the landscape, and scientists have to find out why they don’t survive or breed. Many years ago, a previous effort to save the Laysan teal failed when the translocated birds simply turned up their bills at their new location – as sometimes happens – and tried to fly back to Laysan, never to be seen again.

Reynolds’ work with the Laysan teal emphasized not only keeping them close to the release site to acclimate them during the critical first few months after translocation, but also to learn everything possible about how the species uses and adapts to habitat. The birds’ flight feathers were trimmed when they were released at Midway, so they could not fly for the first year after translocation. This would not have been possible if rats, accidentally introduced during WWII, had not been removed from the atoll when the U.S. Fish and Wildlife Service took over Midway’s management in 1996. Extra food was set out near the release site that first season, so the teal might be less likely to scatter across the island rather than choose mates and breed.

Even so, Reynolds recalls, the birds “sometimes didn’t follow the plan.”

“We had one female bird that just went off by herself, just walked a couple of kilometers to the middle of the island, away from all potential mates, to nest without a drake. She produced multiple infertile nests there, until the population grew,” she said. Most ducks, however, found mates and produced successful nests in their first year on Midway. By 2010, there were more than 400 Laysan teal on Midway. The growth was leveling off, a sign that the species’ population density may have been reached. This is important to know for future translocations: A long-term goal is to return the Laysan teal – “Hawaiʻi’s own duck,” – Reynolds said – to a higher-elevation site in the main Hawaiʻian Islands. Reynolds’ and co-authors’ latest research is published in a recent issue of Animal Conservation.

USGS biologists translocated critically endangered Laysan Teal, such as this one, from Laysan Island to Midway Island in the Northwest Hawaiian Islands to expand the species’ population and range and help guard against extinction.

Because both Laysan and Midway are so remote, Reynolds has been able to visit the study sites with the Laysan teal only once or twice a year after the reintroduction. The refuge field camp at Laysan is a five- or six-day boat trip from Honolulu and an inter-island flight from Hawaiʻi Island, where Reynolds works at the USGS Kīlauea Field Station. Field biologists must stay for months and bring food, water and other supplies. Midway Atoll has an airstrip with thrice-monthly flights, but it is also remote, located approximately 350 miles northwest of Laysan.

Both Laysan and Midway are part of the Northwestern Hawaiian Islands (also called the Leeward Islands), small, low-lying islands and atolls running some 1200 miles northwest of Kauaʻi and Niʻihau in the Pacific Ocean. Jointly protected as the Papahānaumokuākea Marine National Monument, Hawaiian Islands National Wildlife Refuge, and Midway Atoll National Wildlife Refuge, the 140,000-square-mile region is designated by UNESCO as one of only 26 mixed (natural and cultural) World Heritage Sites on the planet. Remote and ecologically vulnerable, most of the Northwestern Hawaiian Island region is uninhabited and closed to the public. Midway has about 60 residents, as well as scientific installations including a USGS seismic monitoring station.

Coral reef affected by Montipora White Syndrome. Note the large swath of white skeleton tissue surrounded by normal (brown) corals.

Scientists have discovered an outbreak of coral disease called Montipora White Syndrome in Kāneʿohe Bay, Oʿahu. The affected coral are of the species Montipora capitata, also known as rice coral.

Rice corals provide valuable habitat, shelter, and foraging grounds for a variety of tropical marine fish and invertebrates and provide the fundamental structure of coral reefs. Rice corals are especially important to Hawai‘i’s marine ecosystems because they are one of the more abundant coral reef species in the region.

Thus, loss of corals can have negative effects on many other reef-associated organisms. In fact, losing a coral reef is similar to losing a rainforest, with many species reliant on that ecosystem for survival.

In addition, coral reefs in Hawai‘i are an important source of tourism and other economic income (fisheries).  For example, Kāneʿohe Bay, where this outbreak is concentrated, is a popular spot frequented by snorkelers, bathers, divers, boaters and fishermen.

While this particular disease outbreak seems limited to south Kāneʿohe Bay, coral diseases have the potential to be widespread, affecting large geographic regions. A prime example is the Western Atlantic and Caribbean where large tracts of coral reefs have either declined or disappeared due to diseases.

Science Helping Protect the Reefs

The investigation of this recent outbreak has been led by the University of Hawai‘i’s Hawai‘i Institute of Marine Biology in collaboration with University of Hawai‘i, West Oʿahu, and the USGS National Wildlife Health Center Honolulu Field Station.

Current efforts are focused on determining the extent of the outbreak and collecting samples for laboratory analysis. On a longer term scale, all three partner organizations are trying to devise better methods to detect coral disease and determine their cause.

For the most part, the causes of coral diseases are unknown. Since biologists do not know yet precisely what is killing corals, this has complicated management of coral reef diseases. Scientists are investigating many possible causes, including host immunity, host physiology, potential infectious agents like bacteria or parasites, and environmental variables such as increased seawater temperatures associated with climate change or land-based sources of pollution.

The USGS is one of the few organizations globally that has applied biomedical tools to investigate animal diseases to coral reefs (yes, corals are animals too). The USGS’s focus in this particular outbreak is to characterize the changes seen in sick corals by looking at the whole coral (what we see with the naked eye) as well as at the cellular level (under the microscope). The USGS is also developing other laboratory tools to help enhance our understanding of coral diseases with the eventual goal of pinpointing the causes of such important diseases.

What Is Montipora White Syndrome?

Corals are basically modified anemones, which are a group of predatory — and often strikingly pretty — marine organisms related to jellyfish. Corals secrete a calcium carbonate skeleton covered by a thin layer of tissues that form the foundation of coral reefs. Montipora White Syndrome affects the rice coral and involves loss of tissues from the coral until the underlying white skeleton is revealed/exposed, hence the name “white syndrome.”

History of Outbreak and Future Risks

Coral reef affected by Montipora White Syndrome. Note the large swath of white skeleton tissue surrounded by normal (brown) corals.

Based on surveys done since 2006 by the University of Hawai‘i and USGS, Montipora White Syndrome has historically been documented in coral reefs in Kāneʿohe Bay, albeit at low levels with scattered, isolated colonies affected. Large-scale outbreaks involving multiple coral colonies over a larger geographic area have only been documented since March 2011 and this recent event.

The reasons for this increase in outbreaks are presently unknown. Tissue loss diseases like white syndrome are particularly insidious in that they result in immediate loss of coral cover. Often, dead corals are then overgrown by algae, leading to permanent reduction in corals reefs and a change in the ecosystem from a coral-dominated to an algae-dominated reef.

Whether this will be the case here remains to be seen.

The USGS and partner scientists are actively involved in trying to better understand Montipora White Syndrome and other coral diseases. This will allow managers to also determine the environmental drivers of those causes, leading to better intervention and strategies to protect coral reefs.

For more information on this topic and other wildlife health related issues, visit the USGS Honolulu Field Station website.

Contact: Thierry Work, Jessica Robertson

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