While mass coral bleaching has generally been predicted on the basis of excess thermal stress alone, it is actually the impacts of high temperatures on the function of photo-systems within the zooxanthellae that lead to bleaching. This product is the first to use both satellite-derived light and temperature data to predict coral stress that leads to bleaching.

The experimental Light Stress Damage (LSD) product provides a measure of the combined light and thermal stress on the coral photo-system. As currently designed, the LSD product will provide a relative measure of these effects via an index. This index has values that are usually in the range of 0 to 5, but can be greater than 5 if accumulated thermal stress is excessive. Generally speaking, a value of 0 indicates that there is no accumulation of damaging stress, a value of around 1 indicates that stress has accumulated to significant levels and bleaching is expected to begin, and values of 2 or more indicate escalating severity of stress and associated bleaching. Severe bleaching and significant mortality are expected at or beyond an LSD value of 5.

The LSD product is updated daily and currently has a resolution of 0.1 degrees. This will be increased to 0.05 degree resolution in the future.

This version of the LSD is tuned to massive corals of the Caribbean such as those of the genus Montastraea, and may need to be refined to be applicable to other corals. However, a test of the product over the Keppel Islands in the southern Great Barrier Reef, Australia, seemed to indicate that the LSD product may be more generally applicable than first thought.

The temperature data used in deriving the LSD are the daily NOAA/NESDIS 0.1 degree resolution geo-polar blended SST product.

Photosynthetically active radiation (PAR) is derived from the NESDIS/STAR GOES Surface and Insolation Product suite. Currently these products are produced at 0.1 degree resolution but will be transitioned to 0.05 degree resolution in the near future. Hourly PAR data from this product suite are summed to derive a daily total PAR. The daily PAR totals are then used to derive an anomaly product that measures the acclimation of the corals to changing light levels from day to day. It is important to note that there is a potential weakness of the LSD product since these satellite-derived daily PAR totals do not match well with in situ measurements of daily PAR totals. There is a high likelihood that this is due to the geometric mismatch between in situ ground-based measurements and satellite-based measurements. As a result, the mismatch does not mean that the satellite PAR products are inaccurate; it just means that it is a different measure of PAR when compared with in situ measurements. It will therefore be important to closely monitor the consistency of the satellite-derived PAR data during the early stages of product evaluation and testing (preliminary results are very promising).