Dear EarthTalk: What’s the prognosis for Hawaii’s coral reefs in the face of global warming, invasive algae and other environmental threats?—Bill Weston, San Francisco
Despite sweeping protections put in place near the end of George W. Bush’s presidency for large swaths of marine ecosystems around the Hawaiian Islands, things are not looking good for Hawaii’s coral reefs. Poisonous runoff, rising ocean levels, increasingly acidic waters and overfishing are taking their toll on the reefs and the marine life they support. Biologists are trying to remain optimistic that there is still time to turn things around, but new threats to Hawaii’s corals are only aggravating the situation.
To wit, a previously undocumented cyanobacterial fungus that grows through photosynthesis is spreading by as much as three inches per week on corals along the otherwise pristine North Shore of Kauai. “There is nowhere we know of in the entire world where an entire reef system for 60 miles has been compromised in one fell swoop,” biologist Terry Lilley told The Los Angeles Times. “This bacteria has been killing some of these 50- to 100-year-old corals in less than eight weeks.” He adds that the strange green fungus affects upwards of five percent of the corals in famed Hanalei Bay and up to 40 percent of the coral in nearby Anini Bay, with neighboring areas “just as bad, if not worse.” Lilly worries that the entire reef system surrounding Kauai may be losing its ability to fend off pathogens.
Meanwhile, some 60 miles to the east across the blue Pacific, an invasive algae introduced for aquaculture three decades ago in Oahu's Kāne‘ohe Bay is also spreading quickly. Biologists are concerned because it forms thick tangled mats that soak up oxygen in the water needed by other plants and animals, in turn converting coral reefs there into smothering wastelands.
“This and other invasive algal species...don’t belong in Hawai‘i,” says Eric Conklin, Hawaii director of marine services for The Nature Conservancy, which works to protect ecologically important lands and waters worldwide. He adds that there are not enough plant-eating fish to keep them under control.
Biologists are working hard to battle the algae in and around Kāne‘ohe Bay. Conklin and his colleagues from the Conservancy have joined forces with researchers from the state of Hawaii to develop an inexpensive new technology, dubbed the Super Sucker, which uses barge-based hoses and pumps to vacuum the invasive algae away without disturbing the underlying coral. Once divers clear a given reef of algae, they then stock it with native sea urchins raised in the state’s marine lab that can help keep new algal outbreaks in check. The system has been so successful at reducing invasive algae at Kāne‘ohe Bay that the state has begun producing tens of thousands of sea urchins for similar “outplanting” projects on other coral reefs around Oahu and beyond that are threatened by invasive algae.
Fast-growing algae and pathogens are only part of the problem. Decades of overfishing have reduced the biodiversity on and around coral reefs, reducing their ecological integrity and making them more vulnerable to climate change. Higher water temperatures and rising sea levels, two of the more dramatic symptoms of global warming, are hastening the bleaching of some particularly vulnerable reefs that have evolved over thousands of years.
CONTACT: The Nature Conservancy, www.nature.org.
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