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Introduction | Identification | Impacts | Causes | Actions | More Info
|What are some of the biological and physical impacts to coral reefs?|
All animals survive best within a set of environmental conditions that suit their particular tolerance levels. Most tropical corals tolerate water temperatures between 18 °C and 30 °C and a few corals, like shallow reef-flat habitats, are adapted to lower or higher temperatures. Temperatures outside the coral's normal range can cause stress that threatens the important relationship between corals and their associated zooxanthellae (CRC Reef). Without zooxanthellae (bleached), corals lose an important source of nutrition from their symbiotic partner and are more likely to die as a result. Keep in mind that just because a coral is bleached does not necessarily mean that it is dead. However, bleaching does leave corals more susceptible to diseases. Under healthy conditions the coral has a good chance of recovery, but their reproductive ability might be stunted for several years to follow.
If the peak in water temperature is only brief, the zooxanthellae can increase rapidly to replenish the coral and return it to its original color and health. However, if the environmental stress levels remain high, entire reefscapes may die. Severely damaged coral reefs will take decades to recover. In some cases, it may take hundreds of years for coral reefs to fully recover from such massive bleaching events (CRC Reef). Other coral reef species that rely on corals for shelter and food will also be affected by these mass bleaching events.
Can coral reef damage also impact local communities and economies?
Dead corals result in unhealthy reef ecosystems that are unable to support the diversity of reef species that it once could. This lack of species abundance will affect local fisheries, subsistence needs, and tourism industries. During the 1997-98 mass bleaching event, losses in tourist revenue was estimated between US $350,000 to $15 million at four different diving locations in the Indo-Pacific (Schuttenberg et al. 2002). Coastal communities are more susceptible to storm damage if these dead coral structures break down. While tourism impacts have been well documented, fisheries impacts from a bleached event are less certain. A singular event may not demonstrate much change, a mass coral die off and/or repeated bleaching are likely to result in long term reductions in fisheries.
|Large colonies of bleached corals evident from the surface.
Location: Hikkaduwa, Sri Lanka
Photo by: A. Rajasuriya
(from ReefBase: http://www.reefbase.org)|