A rapid survey team assessing the reefs on Tonga reports observations
of the first stages of mass coral bleaching.
The SPREP (South Pacific Regional Environmental Programme) BioRAP (Biodiversity
Rapid Assessment Programme) working in the northern Tonga group of islands
called “Vava’u” reports about 1-3% of corals are bleached. Some corals are white; others partly white,
and others are neon colors like light blue or yellow.
Due to increasing water temperatures, the NOAA Coral Watch
program previously announced a bleaching watch for Tonga (February 2014). The team, recorded seawater temperatures
rising in the last week to about 30.5o C, as well as the appearance
of bleached corals. Most of the bleaching
observed was between 10 meters and the surface, however individually bleached
coral colonies were observed up to depths of 30 meters in some places. A range
of coral species was recorded as bleaching.
Corals bleach when increased seawater temperatures occur
over a period of time; the corals, which are made up of skeletons, animals and
single-cell plants, are placed under stress. When the algae (zooxanthellae or
plant living within the animal), which give corals not only its color but also
the ability to photosynthesize and feed, are released by the coral colony, the
coral becomes bright white. As the coral has lost the plant component it loses
them as a food source and is under extreme stress to survive. Corals may recover from bleaching events if seawater
temperatures decrease to within the limits of coral development. Bleaching
events effect many different areas of the marine ecosystem including the reef
fish as well as weakened coral reefs provide little protection for shorelines.
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| Area of bleaching coral within the Vava'u archipelago. |
Most days have been sunny, with very light winds and small
waves, but February 28th was cloudy and rainy when the team departed Vava’u. The SPREP BioRAP team was surveying reefs and
terrestrial ecosystems in the Vava’u group in support of conservation planning
in Tonga. The Kingdom of Tonga is
located north and slightly east of New Zealand, and east of Fiji in the
Pacific, and the Vava’u group of islands is at about 18.6500o S.
The coral reef areas identified as bleaching sites will
continue to be monitored and recorded for further analysis.
The marine team was based on the Waitt Institute Scientific
Platform to conduct the marine surveys of Vava’u as part of the BioRAP
programme with SPREP, Ministry of Lands, Environment, Climate Change, and Natural Resources, Waitt Foundation and
VEPA.
