Coral Health

Corals play a critical role in maintaining the reef ecosystem by providing a framework for the ecological community. Coral reefs in the Papahānaumokuākea Marine National Monument are relatively isolated from human impacts but remain threatened by global disturbances. Addressing global threats to coral health is complicated; focusing on maintenance at the local level may be the best approach for conservation of coral communities.

Coral Disease
Ten disease states for corals have now been reported from the Northwestern Hawaiian Islands, including Acropora White Syndrome and Acropora Growth Anomalies. Permanent sites were established in 2005 at French Frigate Shoals to investigate these diseases with field and laboratory studies to determine the character, ecology and causes of the disease. Acropora Growth Anomalies are a widespread disease occurring at 4 of the 5 permanent sites (80%). Chronic energy drain from growth anomalies can ultimately result in the death of corals. More research is needed to understand the disease and thus allowing management decisions to be made based on the best available science. Research examining the role of biodiversity in influencing coral disease outbreaks and the outcomes is being conducted as well. This project is lead by Dr. Greta Aeby.

Coral reef health and Climate Change
The primary goals of this work is to synthesize mapping information for the Hawaiian Archipelago, investigate the impact of ocean acidification on coral reefs of the Northwestern Hawaiian Islands, and to develop predictive climate change models. A database of all available bathymetry data (ocean depth measurement) in the Hawaiian Archipelago has been compiled to provide comparisons between Papahānaumokuākea Marine National Monument and the Main Hawaiian Islands. During 2007 a total of 96 reef sites throughout the Monument were surveyed measuring fish diversity; determining coral, algae and invertebrate cover; as well as sediment characteristics. A spreadsheet-based model for projecting the effects of climate change on coral reefs at local-to-regional scales is currently being developed. Our Ecological Gradient Model has been developed calculate the impacts to coral reefs from changes in average sea-surface temperature and CO2 concentrations, as well as bleaching events. This project is lead by Dr. Paul Jokiel and Dr. Kuulei Rodgers.

Microbial Diversity
Identifying specific types of bacteria associated with corals may enable managers to monitor coral health and predict resilience. Methods to survey the diversity of bacteria associated with different species of Hawaiian corals has been developed using molecular biology techniques. The primary goals of this study are to characterize the biodiversity of microorganisms and microalgae of the Hawaiian Archipelago, and examine the effects of anthropogenic (human) stressors and global climate change on marine microbial communities. This work seeks to determine if microbes and corals form species-specific associations and whether these associations vary. It is important to identify the particular groups of bacteria that contribute to the differences we observe, as corals with different groups of bacteria may respond differently to environmental changes. This project is lead by Dr. Michael Rappé.

Micro-Spatial Coral Genetics
Researchers are trying to understand why coral colonies get sick, and why on a single reef, does one individual get sick when an identical individual, remains healthy? They examine how coral colonies within a reef are genetically related to each other and how this might influence their health. How genetically diverse a coral reef is can have a significant influence on its ability to withstand environmental stress such as disease. Scientists have mapped and sampled single patch reefs at French Frigate Shoals and Pearl and Hermes Atoll in the Papahānaumokuākea Marine National Monument to try and answer this question. It is important to understand the genetic variability on a reef and thus the adaptability of the reef to disturbances like climate change. This project looks at reefs from a micro-spatial scale to assess the genetic architecture of a reef in order to understand the underlying cause of individual differences in coral health and mortality. This project is lead by Dr. Stephen Karl.

Symbiodinium Diversity
An integral component of the coral reef ecosystem is the mutualistic symbiosis (where both partners benefit from the association) between coral and their symbiotic dinoflagellates, called Symbiodinium. They live inside the coral’s cells and provide nutrition to the coral that promotes growth of the coral skeleton to create habitat for thousands of marine invertebrates and fish. There are many types of Symbiodinium that are different from one another. Understanding how corals can change the type of Symbiodinium they have in response to the environment is paramount to understanding the resilience of coral communities to climate change. Corals respond to thermal stress by losing their coloration (coral bleaching), which reduces the densities of Symbiodinium. The goals of this research are to identify Symbiodinium types that render a coral more susceptible to disease and/or bleaching, to describe the diversity of Symbiodinium in the Monument, and to determine if and how the coral reefs in the Monument have been affected by environmental change. This project is lead by Dr. Ruth Gates.