2 research outputs found

    Change in the Abundance of Coral Across the Hawaiian Archipelago During 2000–2017 in Relation to Thermal Stress

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    Coral reefs are declining at unprecedented rates across the world, threatening ecosystem goods, services, and functionality. Previous research suggests thermal stress is a major driving factor of coral decline, however, these studies primarily draw conclusions from small-scale, in situ data collection. This study represents the first effort to quantify large-scale change in coral cover across the Hawaiian Islands over an extended time period using remote sensing. Hyperspectral imagery from the Airborne Visible-Infrared Imaging Spectrometer (AVIRIS) was used to quantify benthic cover of reef ecosystems across the Main and Northwestern Hawaiian Islands in 2000 and 2017. A total of 320.28 km2 of benthic area was mapped and analyzed across Kauaʻi, Oʻahu, Lanaʻi, Maui, and French Frigate Shoals. Average coral cover dropped from approximately 23% to 8% over the 17-year time period, representing a relative decline of more than 65%. Various thermal stress metrics were obtained through NOAA’s Coral Reef Watch bleaching area alert data and compared to the coral cover data. Adjusted R2 values ranged between 0.02 and 0.043, indicating weak correlations between bleaching area alert metrics and absolute change in coral cover. This study offers preliminary evidence that Hawaiian coral reefs are declining not only on a small-scale, but across entire reef ecosystems. However, thermal data alone cannot explain the decline in coral cover observed. Although the question of what causes this decrease in cover remains, hyperspectral remote sensing may be the missing link. Only once we understand coral change at the reef scale can we hope to conserve these ecosystems

    Change in Percent Coral Cover Across Main Hawaiian Islands Between 2000 - 2017 using the Airborne Visible Infrared Imaging Spectrometer (AVIRIS)

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    The current methods being used to study coral fails to account for coral health at a scale that encompasses the entire reef ecosystem. Hyper-spectral remote sensing through an airborne visible infrared imaging spectrometer (AVIRIS) sensor was used to quantify benthic cover of reef ecosystems. The images were processed pixel by pixel to retrieve benthic cover of coral, algae, and sand. The difference between the two data sets were calculated and used to quantify percent coral cover change. Studying benthic cover on a reef-wide scale through remote sensing can allow us to better understand spatial and temporal trends of coral health
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