A disappearing underwater world

From the NYT Scientists at Work feature, by Dr. Mark Hay of Georgia Tech:

Despite my growing up in Kentucky, not having a passport until my early 20s and not seeing a tropical coral reef until I was in graduate school, whenever I step off a plane in the tropics, I feel like I’ve come home. The organic, fungal smell of heavy tropical humidity is somehow comforting and “right” for me; I also associate it with coral reefs, and a wonderful, but disappearing, underwater world that has become a major focus of my life’s work.

After 28 hours of flying, layovers, slow immigration and customs lines and a long in-country bus ride, I finally arrive in Votua Village on the coral coast of Viti Levu, Fiji, where my group has established a small lab to work on the ecology of coral reefs. We chose Votua Village because the villagers here have been especially proactive in establishing and protecting an area of their reef (a Marine Protected Area). They welcomed us, wanting to know more about how to best conserve their reef and associated resources.

Reef preservation, much less recovery, is a daunting challenge. In the 30 years I’ve worked on reefs in the Caribbean, Indian Ocean and tropical Pacific, we have learned more about reef function and the processes that keep them healthy, but these processes are degrading rapidly and reefs worldwide seem to be in a biotic death spiral. I have two sons in their 20s and cannot show them an average Caribbean reef like the ones I worked on when they were born, much less a “good” one. Healthy Caribbean reefs have disappeared in that short time.

When my sons were born, an average Caribbean reef was covered by 50 to 60 percent live coral; today it is 5 to 10 percent. This is the equivalent of losing pine forests from Georgia or aspens from the Rocky Mountains in less than 30 years. During this same period, the Great Barrier Reef in Australia lost about 50 percent of its coral cover. Worldwide, coral reefs are being converted to seaweed-covered meadows that do not support the biodiverse assemblage of species that allow a reef to function.

With reef loss, the villagers of Fiji lose food security (fish from the sea), the protection from storm surge that the reef provides, income from tourists who come to Fiji for its beautiful reefs, and many other critical ecosystem services that are the lifeblood of tropical island nations and peoples.

Reef loss results from a host of synergistic and growing environmental insults: overfishing, global change, ocean acidification, pollution, coral disease. What can local villagers do to preserve reefs when so many of the stresses are global? Will local efforts to manage fishing and pollution be enough, or will global-scale ocean warming and acidification kill the reefs anyway? The long-term answer is unclear, but the short-term results are promising. When fishing is prohibited, the intact food web on a reef helps it recover from even large-scale climate stresses, disease outbreaks, etc.

Our present work in Fiji focuses on determining how seaweeds affect corals (some seaweeds poison corals when they come into contact); which fishes best control the most damaging seaweeds (by eating them despite the bioactive chemicals they produce); and how villagers might limit or focus fishing practices to leave critical components of the food web intact, allowing corals, fishes, seaweeds, and villagers to sustainably coexist in a way that preserves reef presence and function. Much of this work is focused on understanding chemical signals in the sea and how transmission of these chemicals among organisms constitutes the language of life on a reef, altering organism behaviors in ways that can facilitate reef health and recovery or, if interfered with, cause reef decline and initiate the biotic death spiral that modern reefs seem to be experiencing.