Research

  • Northwestern Hawaiian Islands Connectivity
  • Ecosystem Monitoring Studies
  • Coral Health Assessment Program
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    Introduced species and coral disease

    The Research Problem

    Impacts from global climate change predict that the world’s coral reefs will experience increased frequency and duration of bleaching events and higher levels of disease. The reefs found in the Papahānaumokuākea Marine National Monument are no exception and have already experienced two major bleaching events (2002 and 2004) and an outbreak of the coral disease, Acropora white syndrome. Our objective is to investigate diseases in the Papahānaumokuākea Marine National Monument to provide managers with the information required to make management decisions on how to maintain coral reefs in the face of changing climatic conditions.

    Methods

    In order to manage disease in wildlife populations, you must first understand the distribution, prevalence, incidence and pathogenesis of the diseases. As such, we established permanent sites at various islands/atolls within the Northwestern Hawaiian Islands in 2005 to monitor any changes in disease levels through time and to determine the incidence and virulence of diseases of concern.

    Findings

    We have determined that while most reefs within the Northwestern Hawaiian Islands are maintaining their health, the acroporid (table coral) populations at French Frigate Shoals are under threat by Acropora white syndrome (AWS), which results in massive colony death and Acropora growth anomalies that reduce reproduction and produce partial colony mortality. At one of our permanent monitoring sites at French Frigate Shoals, mortality from these diseases has resulted in the average coral cover dropping from 60% to 26%.

    Importance

    Clearly, without any management interventions AWS can devastate reefs. Further research is needed to determine what causes AWS and how it is getting transmitted between colonies and reefs. Once this information is known, then we can start to predict how AWS may respond to global climate change and investigate methods to slow down or stop the spread of AWS on the reefs.

    Other research

    We are also investigating a parasitic fish disease that has been brought into the Hawaiian ecosystem with the introduction of the blue-line snapper, Lutjanus kasmira (ta‘ape). Ta‘ape were intentionally introduced into the Main Hawaiian Islands in the 1950s and have since spread up into the Northwestern Hawaiian Islands. The parasitic nematode, Spirocamallanus istiblenni, lives in the guts of ta‘ape and we found that it has spread to native goatfish species. An examination of the parasites distribution in ta‘ape populations within Papahānaumokuākea Marine National Monument shows that the disease extends to Pearl and Hermes but has not yet made it into fish populations at Midway Atoll. Our research showed that this parasite has a multi-host life cycle and can use planktonic copepods as an intermediate host, providing a mechanism of dispersal for this disease up the Hawaiian chain. In collaboration with Dr. Bowen’s lab, a comparison of the genetic structure of the parasite in Hawaiian fish with parasites is underway to verify the status of the infection in both introduced and native species.

    We have also discovered that the endemic surgeonfish, Ctenochaetus strigosus, found in the Northwestern Hawaiian Islands is subject to a skin discoloration that was discovered to be cancer. We are currently conducting surveys to determine how widespread this disease is in fish populations throughout the Hawaiian Archipelago. Future work is planned to determine what may causing this disease (etiology) in fish populations.

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