Editor’s note: Alison Green, senior marine biologist at The Nature Conservancy, helped conduct an assessment of a proposed marine reserve in Mozambique. In this series of blog posts, she explains why the area is so special and what the Conservancy is doing to help preserve the marine resources here and the livelihoods that depend on them.
Climate change poses many threats to coral reefs. One of the most serious is rising sea temperatures, which causes coral bleaching.
Several episodes of mass coral bleaching have occurred over the past few decades, which resulted in significant losses of live coral around the world. The 1998 event was the worst on record, with the greatest coral mortalities recorded worldwide. One of the worst affected areas was the Indian Ocean, where reefs lost 90 percent of their live coral cover.
A few weeks ago, my fellow Conservancy marine scientist Rod Salm and I visited the coral reefs of the Segundas Archipelago in Mozambique. Prior to our visit, colleagues from CORDIO warned us that the West Indian Ocean was experiencing unusually high sea temperatures, with coral bleaching predicted in Mozambique.
Our observations confirmed that a major coral bleaching event was underway in the Segundas Archipelago. Like most bleaching events, it was extremely patchy within and among reefs with some areas experiencing extensive bleaching while others had very little bleaching.
There were also some really weird things happening…
As Rod observed, “This coral bleaching event was unlike any I’ve ever seen before. Corals species that are normally more resistant to coral bleaching were bleached, while those that are generally more susceptible were not.” He went on to say:
“Bleaching didn’t follow the classic patterns linked to heat stress. For example, as bleaching progresses, the tops of massive coral colonies usually bleach first followed by the sides (because light exacerbates the effects of the warm water temperatures). Here we saw the exact opposite on some corals! It seems that a combination of heat stress and sediment blasting from four-meter-waves generated by a recent cyclone may have combined to produce these patterns.”
The good news is that these reefs show excellent signs of being resilient to these disturbances:
- They had recovered well from previous bleaching events;
- Coral bleaching was patchy, indicating that some areas would survive to provide larvae to help other areas recover; and
- Coral recruitment was high, indicating good recovery potential.
What is needed now is a more detailed study of the susceptibility of the coral reefs in the archipelago, so that this can fed into the design and management of the proposed Primeiras and Segundas Reserve.
(Image 1: Unusual, uneven coral bleaching in the Segundas Archipelago. Source: Rod Salm/TNC. Image 2: Inverted pattern of coral bleaching with massive colony bleached on the sides and not on the top. Source: Rod Salm/TNC.)
Tags: Alison Green, archipelago, Climate Change, coral bleaching, CORDIO, Indian Ocean, mass coral bleaching, Mozambique, Mozambique expedition, reef resiliency, rising sea temperature, Rod Salm
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believe.. coral… be well taken care of.. when… always in see, protected mangrove
It has been predicted that China’s atmospheric pollution will be reaching California’s coast within a decade….. all of the coral reefs in the world are being affected by the atmospheric deposition of nitrogen (and other pollutants) emitted from industrialized countries including but not limited to Mexico, India, China and the USA . Excessive amounts of nitrogen have been documented in tissue samples of bleached corals. Global warming plays a role by warming the potpourri of pollution found in our oceans which causes algal blooms, coral diseases and eventually bleaching. We must reduce the nitrogen overload on our planet caused by fossil fuel emissions and the overuse of fertilizers and pesticides if we want to see coral survive into the next decade.