Maui’s bleached reefs now ‘priority site’ for recovery plan
Hardest hit areas are first up to get attention of program
During Hawaii’s mass coral bleaching event in 2014 and 2015, the reefs of leeward Maui were among the hardest hit. Now, they’ve been marked as a “priority site” in a recovery plan put together by environmental agencies.
Released last week, the state’s first-ever coral bleaching recovery plan looks at the top management strategies for areas most impacted by bleaching. Along with Maui, west Hawaii, north Kauai and Oahu’s Kaneohe Bay have been identified as priorities.
“Recent bleaching events in Hawaii are a major cause for concern, as coral reefs provide the foundation for most of our nearshore marine life,” Bruce Anderson, administrator for the state Department of Land and Natural Resources’ Division of Aquatic Resources, said in a news release. “We can expect an increase in both the severity and frequency of bleaching events as sea water temperatures rise in the future.”
The plan was put together by a committee of representatives from the Aquatic Resources Division, the University of Hawaii, The Nature Conservancy and the National Oceanic and Atmospheric Association.
In August 2014, a combination of warm weather in the North Pacific Ocean — including an El Nino — caused bleaching throughout the Hawaiian archipelago. Reefs around Maui, Kauai and Oahu took the brunt of the damage, according to the recovery plan. In the summer of 2015, bleaching was even more severe, especially in Maui and west Hawaii.
The same conditions that produce extensive reefs in leeward Maui also make them vulnerable to bleaching, explained Rusty Brainard, chief of NOAA’s Coral Reef Ecosystem Program.
“Because leeward habitat areas are generally protected from wind and wave exposure, thermal stress conditions can be exacerbated,” Brainard said. That’s because cooler waters from below don’t get mixed with warmer shallow waters.
Following the 2015 event, coral mortality rate for Maui was estimated at 20 to 40 percent.
Maui’s leeward reefs are mainly a mix of the fingerlike Porites stony corals and the platelike Montipora stony corals, said Bernardo Vargas-Angel, coral ecologist with NOAA’s Coral Reef Ecosystem Program.
“Leeward Maui exhibits the greatest levels of urbanization islandwide, and as such, many of these reefs have been and continue to be chronically affected by land-based sources of pollution, including sediments and nutrients,” Vargas-Angel said.
However, some of the highest levels of live coral cover are located in the larger Kaanapali area near the Wahikuli and Honokowai stream drainages, he added. South of Lahaina, the Olowalu reef is the largest and best developed, and Kihei also has plenty of reef, though the south shore is also impacted by land pollution.
After the major bleaching event, representatives from the four different agencies got together. They analyzed hundreds of peer-reviewed articles, surveyed scientists from around the world and held a workshop with Hawaii-based experts to rank the top strategies.
Creating a network of permanent, no-take, marine-protected areas and herbivore fishery management areas emerged as the best actions.
“Limiting or prohibiting the take of fish that eat algae, such as parrotfish, is particularly important,” Anderson said. “These fish help to prevent the overgrowth of algae on corals, as the algae prevents coral polyps from settling on hard surfaces and growing after a bleaching event.”
Other effective strategies included reducing sediment and polluted runoff that stresses coral reefs, as well as planting sea urchins and corals resistant to bleaching. Prohibiting the collection of aquarium fish ranked relatively low because most aquarium fish are not herbivores and represent a very small proportion of daily take by commercial and noncommercial fishermen, the DLNR said.
Now that the best practices have been laid out, the next step is to put them into action.
“It is not a one-size-fits-all situation,” Anderson said. “Management strategies need to be tailored to the most important stressors in the specific area where bleaching is a problem. For example, an effective strategy for west Hawaii may be very different than for Kaneohe Bay.”
Brainard said there’s a bright side for the reefs of leeward Maui and west Hawaii.
“Those are amongst the most developed coral reefs in the main Hawaiian islands,” he said. “That means they’re amongst the most likely to be resilient and recover because there’s enough coral that survived that they can reproduce. They can recover if appropriate management actions occur.”
Brainard and Vargas-Angel said there’s no complete answer yet for Maui’s reefs, but that the best steps could involve mitigating the impacts of land-based pollution; reducing direct damage from physical contact with boats, anchors, divers; effective fisheries management; and cutting down on toxic chemicals in the water, such as those found in some sunscreens.
As for what beachgoers can do in the meantime, the NOAA scientists said people can stay educated on the health status and threats to reefs, as well as volunteer with groups that monitor reefs, such as the West Maui Ridge2Reef Initiative. Using sun protection that doesn’t include toxic chemicals like oxybenzone is another way to help.
“This is a worldwide crisis,” Anderson said. “From a practical standpoint, we can’t do much about global warming, or the sea water temperature rise that is undoubtedly linked to global warming. However, we need to do what we can to help reefs recover from bleaching events and to try to make our reefs more resilient.”
The full coral bleaching recovery plan can be downloaded from dlnr.hawaii.gov/dar under the “Notices” section.
* Colleen Uechi can be reached at firstname.lastname@example.org.