Supporting the management and sustainable use of marine biodiversity in Honduras Photos by George Stoyle    
 

   
 
Coral Bleaching
Coral bleaching is a phenomenon that occurs as a result of stressed coral organisms expelling the symbiotic algae which reside within their tissues. These algae, known as zooxanthellae, are not only responsible for giving corals their various colours, but also provide their hosts with the majority of their food. The process of photosynthesis results in carbon being converted into sugars and passed from zooxanthellae to coral organism. In return, waste products are passed back to the zooxanthellae. This mutually beneficial relationship is known as symbiosis.

Bleaching occurs when any one of a number of pressures cause the biochemical reactions associated with photosynthesis to produce toxic forms of oxygen. In order to protect itself the host coral organism literally drives out the zooxanthellae leaving part, or all of the coral colony white in appearance. Initially corals do not die, but because zooxanthellae provide between 50 - 95% of their metabolic functions mortality will eventually occur if environmental conditions do not return to favourable levels. If bleaching is not too severe and environmental conditions return, affected corals will regain their symbiotic algae within a few weeks.

Although the primary cause of coral bleaching is increased water temperature, other disturbances include:

  • Increased solar irradiance 
  • Subaerial exposure (e.g. tsunamis)
  • Sedimentation from development, deforestation, etc.
  • Freshwater dilution from runoff
  • Inorganic nutrients from untreated sewage
  • Xenobiotics from agricultural or industrial chemicals
  • Epizootics  (e.g. coral disease)
BleachWatch

BleachWatch is a community-based coral reef monitoring initiative developed during a mass-bleaching event in 2002 by the Great Barrier Reef Marine Park Authority (GBRMPA). In subsequent years, both the number of participants and its spatial coverage have expanded, now including countries on the Mesoamerican Barrier Reef such as Belize and Honduras.

The goals of BleachWatch are:
  • To inform the community about coral bleaching and to encourage individuals, tourism operators, organisations and fishers to participate in BleachWatch by reporting bleaching
  • To detect the early stages of coral bleaching events over a wide geographic range
  • To use coral bleaching as a means to communicate the broader impacts of climate change on the Mesoamerican Barrier Reef.

UCME, in cooperation with The Nature Conservancy is keen to enlist the assistance of all reef users to monitor and report coral bleaching in the region. In order to provide bleaching information, a simple report has been made available online for users to complete following their dives. Even if there is no bleaching, it is still important we are kept regularly informed about your sites. We appreciate your cooperation.

BleachWatch Report Online | BleachWatch Report Word Document
UCME are also involved in a 2-tier monitoring programme to assess the spatial extent and severity of coral bleaching and determine the direct ecological impacts (coral mortality) from bleaching. The first tier is a broad-scale random swim survey obtaining an overview of where bleaching is occurring at sites around Utila. Information recorded includes genus or species of bleached corals, level of bleaching on a 3-point scale of: paling, partly bleached and fully bleached, the depth, and approximate diameter of the colony.

The second tier of the monitoring program: is the fine-scale ecological impact assessment. This involves using the point intercept transect method (PIT), which records information on corals and other benthos. Percentage cover of coral is recorded along with categorising the level of bleaching of the coral colonies on the transect. The following 5-point scale provides an index for bleaching to be evaluated; 0 ­ No bleaching evident, 1 - Partially bleached (surface/tips) or pale but not white, 2 - White, 3 - Bleached and partly dead and 4 - Recently dead. This will provide a baseline data set for which mass bleaching events can be compared.
Current Status of Bleaching around Utila (updated every month)
  • Bleached colonies seen occasionally and conspicuous; vast majority of colonies not bleached
Links

Bleaching alert graph for Bay Islands, Honduras
NOAA Coral Reef Watch
NOAA Satellite Bleaching Alert E-mail List
Coral Bleaching HotSpots
Coral Bleaching Virtual Stations
 
 
Utila Centre for Marine Ecology, East Harbour, Utila, Honduras | | +5044253026