A before and after image of the bleaching in American Samoa. The main groups involved are XL Catlin Seaview Survey, the University of Queensland, and Reef Check.
Advertisement
From Hawaii to Papua New Guinea to the Maldives, coral reefs are bleaching – in so many regions that the US National Oceanographic and Atmospheric Administration (NOAA) officially declared a global bleaching event on 8 October.
The current bleaching event, which began in the north Pacific in summer 2014 and expanded to the south Pacific and Indian oceans in 2015, is hitting USA coral reefs disproportionately hard.
So far the 1998 bleaching was worse, but that was the second year of an El Nino and we’re in the first of two years now, Eakin said.
The total loss could amount to 5 percent of the world’s corals in 2015, according to Eakin. The event, the third in recorded history, is expected to grow worse in coming months.
The rise in the ocean temperatures is being caused by the background warming from climate change made worse by this year’s super El Nino weather event, and a Pacific warm water mass known as “the Blob”, the researchers say. “Locally produced threats to coral, such as pollution from the land and unsustainable fishing practices, stress the health of corals and decrease the likelihood that corals can either resist bleaching, or recover from it”, said Jennifer Koss, NOAA Coral Reef Conservation Program acting program manager.
Coral bleaching occurs when warm ocean waters – considerably warmer than corals evolved to live with for an extended period of time – leave the organisms stressed and cause them to banish the symbiotic algae that provide corals with both their color and also nutrients. Excessive heat stresses the coral, which turns white and becomes vulnerable to disease. “It’s still a bit of a mystery”, Eakin said.
“We may be looking at losing somewhere in the range of 10 to 20 percent of the coral reefs this year, ” NOAA coral reef watch coordinator Mark Eakin said.
Alice Lawrence, a marine biologist, assesses the bleaching at Airport Reef in American Samoa.
The first mass coral bleaching occurred in 1998, when about 16 per cent of the world’s reefs were affected.
These images are then used to help monitor and document the progression of bleaching events. At the same time, though, the event “really proved that the ability to measure temperature from space could predict where and when bleaching was going to occur, and as we found out later on, how intense it was going to be”. In a bay off the island of Oahu in Hawaii, a few corals that experienced bleaching in 2014 surprisingly managed to reproduce this year, even with back-to-back bleachings.
While corals can recover from mild bleaching, severe or long term bleaching is often lethal. The Global Coral Reef Monitoring Network, an worldwide government-based initiative, was reorganized in 2008 and shifted from gathering data on reefs to preparing reports on the basis of data from others. The NOAA says the livelihoods of 500 million people and income worth over $30bn (£19,6bn) are at stake.
The middle Florida Keys aren’t too bad, but in southeast Florida, bleaching has combined with disease to kill corals, Eakin said.
A long-nose file fish struggling to find coral polys to eat. “Almost one and a half square miles of reef bleached a year ago and are now completely dead”.
Advertisement
And once corals die, the consequences are not easily reversible.
