LIHUE — The National Oceanic and Atmospheric Administration on Monday said abnormally warm waters that threaten the spread of major heat stress to Hawaiian reefs are likely to return.
Last autumn, Hawaii experienced widespread coral bleaching for the first time since 1996. If corals in Hawaii bleach again this year, it would be the first time it happened in consecutive years in the archipelago.
“Many healthy, resilient coral reefs can withstand bleaching as long as they have time to recover,” said Mark Eakin, NOAA Coral Reef Watch coordinator. “However, when you have repeated bleaching on a reef within a short period of time, it’s very hard for the corals to recover and survive. This is even worse where corals are suffering from other environmental threats, like pollution or overfishing.”
Beyond Hawaii, the equatorial Pacific, north Pacific and western Atlantic oceans are also predicted to experience rising ocean temperatures that threaten to kill coral and lessen the long-term supply of fish and shellfish.
Earlier this year, NOAA’s Coral Reef Watch four-month Coral Bleaching Outlook accurately predicted coral bleaching in the South Pacific, including the Solomon Islands, Papua New Guinea, Nauru, Fiji, and American Samoa. It also recently predicted the coral bleaching in the Indian Ocean, including the British Indian Ocean Territory and the Maldives.
“The bleaching that started in June 2014 has been really bad for corals in the western Pacific,” Eakin said. “We are worried that bleaching will spread to the western Atlantic and again into Hawaii.”
Coral bleaching occurs when coral is stressed by environmental changes, causing it to release the algae living in its tissue. Without its major food source, the coral turns pale or white, making it more susceptible to disease. Disease outbreaks can kill off large expanses of coral, thereby altering the habitat for fish and shellfish.
On Kauai, rising ocean temperatures may be causing problems beyond bleaching. Researchers say it may also be triggering the growth of a lethal, rapidly spreading coral disease found in nearshore waters called black band disease.
“The one thing that I was able to pull out by looking at environmental data is that there is a trend that when you have warmer water you see a higher prevalence of black band,” said Christine Runyon, a graduate research assistant at University of Hawaii’s Institute of Marine Biology. “So, in October, water temperatures were at their highest for the year and they were over 85 degrees. The warmth makes the coral susceptible to disease and it stresses it out.”
Runyon said nearshore Kauaian waters are predicted to be at least 2 to 3 degrees warmer this October than last October, when ocean temperatures reached their highest point.
The black band disease was first spotted at low levels on Kauai in 2004, then identified on the North Shore of Kauai in 2012 at 10 times background levels, according to the DLNR. It continues to plague the three Montipora (rice) corals found around the island.
The places most affected by the disease are the reefs surrounding Makua (Tunnels), Anini and Anahola beaches as well as Ahukini Landing, according to Runyon’s research.