The XL Catlin Seaview Survey revisits Hawaii


Image: Site selection for the Hawaii expedition

 

The XL Catlin Seaview team is returning this week to the central islands of Hawaii, where we performed a photographic survey in August. Since that time these islands have been hit with coral bleaching, and our goal now is to re-survey the same areas we visited in August to see how many of the corals have been affected by this bleaching, and to eventually understand how many may be dying or damaged as a result of this stress.

 

 

Corals in stress

 

Coral bleaching is aptly named, as the colonies turn stark white. This color change is due to the corals expelling their symbiotic algae, which live inside their tissues. These microscopic algae contain photosynthetic pigments (just like leaves), and produce much of the nutrients that sustain corals. However, this happy symbiosis breaks down when corals suffer from heat stress, as the algae cells are expelled. While the coral hosts are not killed directly by bleaching, and can recover their symbionts and return to normal physiology when temperatures reduce, it is always a very stressful time for them, and can lead to substantial mortality.

 

 

Warming waters

 

This bleaching is happening in response to the record warm ocean temperatures this year. A large body of warm water has moved eastward across the Pacific, and the waters around and south of the Hawaiian chain have never been this warm for this long. The iconic Hawaiian reefs, which ring the islands like jewels, protecting shorelines, sustaining substantial reef fisheries, and even forming the very physical basis for most of the cherished surf breaks, have been surrounded by this water for weeks, and they are suffering. As corals die, their calcium carbonate skeletons are left standing for only a few years before they dissolve back into the sea. The complex structure they created, like trees in the forest, is then gone, and the fish and other animals that sheltered in these cities under the sea are left without homes.

 

 

Building understanding

 

Our goal is to determine how extensive this bleaching is within the coral community, and to determine which species are most affected. With this information we can increase our ability to understand how future coral reefs in a warmer world might respond to more frequent stress events like this, and determine the best ways to manage the stresses affecting these vital ecosystems. Our unique self-powered, semi-automated panoramic camera system can gather almost a thousand images in an hour, which facilitates a fast response on our part to these transient events. We hope to gather over 15 thousand high-definition images in the week we are here, providing a valuable snapshot of this bleaching event, and a baseline against which we can compare future observations.

 

 

A global problem

 

Hawaii is the most isolated occupied landmass in the world, and as such might be considered secure from the influences of the mainland. However, this event shows that global climate change is affecting even the farthest corners of the world, and corals are some of the first to suffer. The carbon emissions from distant tailpipes in China, Brisbane, Los Angeles, Jakarta and elsewhere are making their impacts felt here – nearly as far out at sea as one can be on the planet. In this age of global environmental change, no place and no man remains an island any more, and we hope our coral bleaching research in Hawaii will hopefully help us collectively understand and protect the great natural resources we all share.

 

 

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