Remote sensing of sea surface temperatures during 2002 Barrier Reef coral bleaching (original) (raw)
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Improved Satellite Techniques for Monitoring Coral Reef Bleaching
Satellite-derived sea surface temperatures (SSTs) have been used to identify the areal extent of coral reef bleaching. A new, high_resolution satellite SST climatology has been developed to produce anomaly fields. These fields make it possible to quickly pinpoint regions of elevated surface temperatures throughout the Tropics. Whenever positive SST anomalies occur during the warmest months of the year, often a 1bC elevation above the monthly mean maximum accompanies bleaching. To take advantage of this finding, an experimental SST chart has been developed for the Tropics that compares presently observed SSTs to the warmest monthly mean SSTs at each location. These special anomalies, that show SSTs in excess of the highest monthly values, denote potential bleaching activity is most likely underway wherever a +1bC elevation above the monthly mean maximum exists. These new fields are shown for bleaching episodes of 1990, 1991, 1994, and 1995.
2011
Limited information is available on the bleaching susceptibility of coral species that dominate high latitude reefs along the eastern seaboard of Australia. The main aims of this study were to: (i) monitor coral health and spatial patterns of coral bleaching response at the Solitary Islands Marine Park (SIMP) and Lord Howe Island Marine Park (LHIMP), to determine variability of bleaching susceptibility among coral taxa; (ii) predict coral bleaching thresholds at 30 °S and 31.5 °S, extrapolated from published bleaching threshold data; and (iii) propose a subtropical northern New South Wales coral bleaching model from biological and physical data. Between 2005 and 2007 minor bleaching was observed in dominant coral families including Pocilloporidae, Poritidae and Dendrophylliidae in the SIMP and Pocilloporidae, Poritidae and Acroporidae (Isopora and Montipora spp.) in the LHIMP, with a clear difference in bleaching susceptibility found between sites, both within and between locations. Bleaching susceptibility was highest in Porites spp. at the most offshore island site within the SIMP during summer 2005. Patterns of subtropical family bleaching susceptibility within the SIMP and LHIMP differed to those previously reported for the central Great Barrier Reef (GBR). These differences may be due to a number of factors, including temperature history and/or the coral hosts association with different zooxanthellae clades, which may have lower thermal tolerances. An analysis of published estimates of coral bleaching thresholds from the Caribbean, South Africa, GBR and central and northern Pacific regions suggests that the bleaching threshold at 30-31.5 °S ranges between 26.5-26.8 °C. This predicted threshold was confirmed by an extensive coral
Coral Reef Watch (CRW), a program of the National Environmental Satellite Data and Information Service (NESDIS) of the U.S. National Oceanic and Atmospheric Administration (NOAA) and a part of the NOAA Coral Reef Conservation Program (CRCP), has been operating the world’s only global satellite coral bleaching thermal stress monitoring system for the U.S. and global coral reef communities since 1997. Through more than a decade of satellite monitoring, CRW has evolved from providing a limited number of SST-based tools for coral bleaching monitoring, to implementing a decision support system (DSS) employing multiple satellite and model-based parameters. CRW’s mission is to utilize remote sensing and in situ tools for near-real-time and long-term monitoring, modeling and reporting of physical environmental conditions of coral reef ecosystems. With these tools, CRW assists the global community in the management, study, and assessment of impacts to coral reef ecosystems brought about by e...
Diversity, 2011
Limited information is available on the bleaching susceptibility of coral species that dominate high latitude reefs along the eastern seaboard of Australia. The main aims of this study were to: (i) monitor coral health and spatial patterns of coral bleaching response at the Solitary Islands Marine Park (SIMP) and Lord Howe Island Marine Park (LHIMP), to determine variability of bleaching susceptibility among coral taxa; (ii) predict coral bleaching thresholds at 30 °S and 31.5 °S, extrapolated from published bleaching threshold data; and (iii) propose a subtropical northern New South Wales coral bleaching model from biological and physical data. Between 2005 and 2007 minor bleaching was observed in dominant coral families including Pocilloporidae, Poritidae and Dendrophylliidae in the SIMP and Pocilloporidae, Poritidae and Acroporidae (Isopora and Montipora spp.) in the LHIMP, with a clear difference in bleaching susceptibility found between sites, both within and between locations. Bleaching susceptibility was highest in Porites spp. at the most offshore island site within the SIMP during summer 2005. Patterns of subtropical family bleaching susceptibility within the SIMP and LHIMP differed to those previously reported for the central Great Barrier Reef (GBR). These differences may be due to a number of factors, including temperature history and/or the coral hosts association with different zooxanthellae clades, which may have lower thermal tolerances. An analysis of published estimates of coral bleaching thresholds from the Caribbean, South Africa, GBR and central and northern Pacific regions suggests that the bleaching threshold at 30-31.5 °S ranges between 26.5-26.8 °C. This predicted threshold was confirmed by an extensive coral
Journal of Operational Oceanography
Data from real-time sensor networks along the Great Barrier Reef (GBR) over the 2015-2016 austral summer showed that reef water temperatures exceeded empirical coral bleaching thresholds at a number of sites. Temperatures in the southern GBR were within historically normal limits with temperatures below the empirical bleaching threshold. The central GBR just reached the empirical bleaching threshold while, in the north, Lizard Island recorded four consecutive days above the bleaching threshold. Thursday Island in the far northern GBR experienced 10 days above the bleaching threshold. The in situ data predicted only slight bleaching in the southern GBR, moderate bleaching in the central GBR, widespread bleaching in the north and severe bleaching in the far north, which compares well with the initial survey data. Peak temperatures occurred later in the year in the north (mid-March 2016) than in the south (early February 2015) with temperatures remaining above the long-term mean well into the austral autumn. Comparison against satellite sea surface temperature data highlighted issues of cloud cover with data only being available for 30-40% of days over the summer. While the agreement with the in situ data was good, the satellite data missed fine-scale events and underestimated the event at Thursday Island.
Improved predictions of coral bleaching using seasonal baselines and higher spatial resolution
Limnology and Oceanography, 2008
Coral bleaching spread across the southern Great Barrier Reef in January 2006, after sea temperatures reached climatological summer maxima 2 months before normal. Current satellite-derived warning systems were unable to detect severe bleaching conditions in the region because of their use of a constant thermal threshold (summer maximum monthly mean) and low spatial resolution (50 km). Here it is shown that such problems can be ameliorated if the thermal threshold is adjusted for seasonal variation and a 4-km spatial resolution is used. We develop a seasonally and spatially improved thermal threshold for coral bleaching on the basis of a weekly climatology of sea surface temperatures extending from austral spring to late summer, and apply the method to two case-study sites. At both sites, and in particular at the nearshore site that was undetected by the 50-km satellite product, the seasonally adjusted thermal threshold produced a greatly improved consistency between accumulated heating and bleaching severity. The application of thermal stress algorithms that reflect the longterm mean pattern in seasonal variation allows coral bleaching to be forecast with higher precision.
Climate Variability and Change: Monitoring Data and Evidence for Increased Coral Bleaching Stress
Coral reefs live within a fairly narrow envelope of environmental conditions constrained by water temperatures, light, salinity, nutrients, bathymetry and the aragonite saturation state of seawater. While the natural environment can be highly variable and potentially stressful to corals, humans are now placing the world’s coral reefs in crisis as a result of direct local- to regional-scale insults combined with accelerating global changes. The global-scale insults result from increased concentrations of atmospheric greenhouse gases that are rapidly acidifying and warming ocean waters. This chapter focuses on the changing physical environment surrounding coral reef ecosystems and especially the rising SSTs that are responsible for most mass coral bleaching events. We make use of improved long-term records of surface ocean climate to document SST changes in the vicinity of coral reefs and how the risk of SST conditions conducive to coral bleaching varies with climate variability such as El Niño--Southern Oscillation events. We describe the application of satellite-based SSTs and related products that have been developed to detect and monitor environmental conditions leading to coral bleaching around the globe.