Randi D. Rotjan, Ph.D., is a coral reef scientist and researcher with New England Aquarium who has traveled the world studying reefs and marine ecosystems from the Caribbean to the Red Sea. She knows well the uncertain fate of our planet’s reefs in a changing climate.
E Magazine: How do you determine whether a reef is in recovery or in decline?
Randi D. Rotjan: You really need to visit a system over time, to get a sense for where it’s going, and that is something that scientists really struggle with because we’ve only been studying reefs for a relatively short period. What we tend to do is integrate information from a variety of sources. We look at Paleo data [data from natural sources, like tree rings and coral growth], and we use a huge series of indicators to assess the health or state of a reef to figure out whether the trajectory is trending up or down.
E: Why is it that some reefs are on the upswing while others fail?
R.D.R.: For reefs, it’s death by a thousand cuts. There are so many problems affecting reefs right now that the minute one stressor is relieved, another stressor takes over. There’s over-fishing, climate change, too many nutrients in the water, coral disease, destruction, over-sedimentation, habitat loss, coastal development—all of these things impact reefs in various ways.
E: How have marine species and ecosystems responded to global changes like warmer waters and rising sea levels?
R.D.R.: Warmer waters are particularly problematic for coral reefs because corals are animals that rely on a symbiosis with plantlike cellular organisms, which photosynthesize the same way plants do. These algal symbionts rely on sunlight and live within an extremely narrow temperature range, and many of them are intolerant of very wild temperature fluctuations. So when you have these temperature changes, the symbiosis generally breaks down
and the coral really can’t survive. If you don’t have coral able to grow, the whole system eventually breaks down.
E: As more and more reefs begin to decline and disappear what are we at risk of losing?
R.D.R.: I think we’re at risk of losing one of the most aesthetically pleasing and beautiful places on the planet, but we’re also at risk of losing one of the most important economic habitats in the world. [Coral reefs] have incredible economic value in terms of shoreline protection, nutrient acquisition and trade for countries, and they host a really remarkable amount of the ocean’s biodiversity.
E: What does it mean when an ecosystem becomes a legally protected area, and are such restrictions enough to prevent collapse?
R.D.R.: Protection can mean everything from truly hands off—no boats, no fishing, nobody’s allowed in—to something that says “We recognize that this is an area to be protected so we”ll monitor it, but we won’t prevent any fishing or any traffic”—and everything in between. Protection is a loaded word.