Researchers Look at Ways for Coral to Survive Bleaching, Climate Change – Dec 8, 2015 The Maui News
The Maui News,
“One of the most important local factors for recovery is going to be a healthy population of herbivores,” said researcher Benjamin Neal, who led an XL Catlin Seaview Survey team on a weeklong dive of reefs around Maui, Molokai, Lanai and Molokini last month.
Started in 2012, the survey aims to document the composition and health of coral reefs worldwide.
[Above photo] Brown water runs from Mahana Ridge into the stream and out into the ocean in West Maui. The runoff carries sediment into the ocean that could suffocate reefs, making their recovery even more challenging. DANA REED photo
[Above] A side-by-side comparison of a coral colony just outside of Kahului Harbor shows signs of bleaching. This photo was taken in August. XL Catlin Seaview Survey photo
[Above] This photo was taken Nov. 7. XL Catlin Seaview Survey photo
The team spent eight days in November surveying 20 sites, including Molokini, off of Central, West and South Maui, around Lanai and along the southeastern shore of Molokai. Bleaching, though at varying levels, was observed at every site, Neal said.
Researchers also noted how few parrotfish were spotted around Maui County waters, especially compared to how many had been seen during an expedition a decade ago.
“Parrotfish are particularly important for chewing up the algae,” Neal said.
Experts have warned that Hawaii stands to face its worst bleaching event ever this fall. Corals turn bone-white, or bleach, when ocean temperatures become warmer than the corals are used to. Though bleaching does not necessarily mean the corals will die, bleached corals become more susceptible to disease and other harmful conditions.
Neal said he expects that some of the sites that have experienced severe bleaching, such as Cathedrals off Lanai, are likely to be changed forever. McGregor Point near Maalaea, Molokini crater and Kahului Point also saw severe bleaching, though “it is not yet apparent why these sites were the worst,” Neal said.
World leaders are currently convening at a conference in Paris to discuss policies that could mitigate climate change. In the meantime, there are efforts local communities can undertake to better the reefs’ chances for recovery.
“One of the factors that will significantly influence recovery and how those corals come back is maintaining good water quality,” Neal said.
The Maui Nui Marine Resource Council released a report in October that found the state of Maui’s reefs is “poor.”
The report was recently presented to the Maui County Council Infrastructure and Environmental Management Committee, and it claims that nearly a quarter of Maui’s corals have been lost since 1993. The report identifies three primary drivers behind the decline of reef health: land-based pollutants and sediment that run off into the ocean; overfishing from the lack of regulation enforcement; and insufficient “resting” of certain sites to allow marine species to recover and replenish stocks.
“It’s like when someone is already very sick and then a flu epidemic comes along,” explained Robin Newbold, chairwoman of the Maui Nui Marine Resource Council. “They’re much more likely to die because their immune system is already compromised.”
Similarly, if corals are already stressed from being suffocated by sediment or overgrown algae, they’re less likely to survive a global event like ocean warming.
Higher ocean temperatures this summer “hit the reef when it was already at the tipping point,” Newbold said.
“We really need to do what we can to malama (take care of) the reef and get it back to health,” she said.
Limiting the impact of development in sensitive areas, like the proposed 1,500-home Olowalu Town project above Olowalu reef, is part of the challenge. Newbold and other environmentalists have been working with elected officials to negotiate initiatives that can be put in place to protect reefs.
One of the most immediate actions the community can take is to restrict fishing of herbivores, which feed on algae and keep it from suffocating the reef. Herbivores include parrotfish, rudderfish, surgeonfish and urchins.
The state adopted stricter bag and size limits last year for parrotfish and goatfish caught around Maui island, but Newbold said enforcement has been lax. She has seen photos of a group of fishermen who launch from Mala Wharf at night and dive with tanks, catching more than 50 fish at a time.
Under current law, no more than two parrotfish may be taken at a time, and no blue male parrotfish may be taken at all.
“None of these regulations are going to help without ample enforcement,” Newbold said. “We really think community management is an important step to take.”
Researchers predict that coral in the Kahekili Hervivore Fisheries Management Area and the Manele-Hulopoe Marine Life Conservation District on Lanai will make a faster and fuller recovery than other sites where herbivores aren’t protected, though they have yet to confirm that hypothesis. The Catlin Survey group hopes to return to Maui next year to document how corals have changed or recovered from the bleaching event.
* Eileen Chao can be reached at [email protected].