July 1, 2009

The Bloody Bay Wall

Assistant Professor of Biology and Environmental Science at CUNY, Baruch College and Reseach Associate, American Museum of Natural History

LITTLE CAYMAN, Cayman Islands | One of the most prominent underwater features of Little Cayman is the Bloody Bay Wall—a sheer cliff that begins just off the northern part of the island in 18 feet of water and plummets thousands of feet into the abyssal Cayman Trench. According to island legend, the wall is named for a battle between pirates and Britain’s Royal Navy sometime in the 1700s. Just as likely is that the name was inspired by the wall’s crimson-colored corals, sponges and fishes.

I’m working here with two Florida colleagues, Rick Riera-Gomez and Casey Coy, who bring some of the most advanced technical scuba diving expertise to the expedition. Over the next five days, we will be descending to depths of 300 feet along the Bloody Bay Wall to study part of an ecosystem that is rarely seen by human eyes –the deep reef. The goal of our expedition is to better understand the relationship and differences between the deep corals and shallow corals. Submarine records report photosynthetic corals as deep as 540 feet. But because of the difficulties and dangers of exploring the deep reef, most studies have been performed on reef in depths of less than 100 feet. That has left a potentially large part of this ecosystem unexplored. Are the same species found further down? Are the deep reefs healthier than shallow reefs? Are they a source of juvenile recruits to the shallow reef?

Corals are one of the few organisms on the planet that possess fluorescent proteins—along with some jellyfish, anemones and copepods. The function of these proteins has been hotly debated. Some believe it may be a type of sunscreen for the corals, others think it may provide suitable light for algae to perform photosynthesis. So another goal of our explorations is to determine whether deep corals produce the same quantity of fluorescent proteins as shallow ones.

Scientists tend to specialize, focusing on a particular area within their fields. I’m interested in a particular order of corals, known as scleractinia. These are stony, reef-building corals that first appeared about 240 million years ago. Yet their age belies their complexity. First, corals secrete a calcium carbonate skeleton that, over time, forms vast geologic reef structures. Only the very top layer of these structures is the living coral animal. Second, corals are engaged in a unique relationship with unicellular algae that allows them to thrive in such clear waters devoid of nutrients. The algae reside inside the coral’s tissue and share and secrete the energy they gain from photosynthesis. The relationship itself has perplexed scientists: Many questions remain about how this unlikely pair has teamed up. What is known is that when the relationship is broken and the algae are released or leave the coral –as in times of physiological stress –the coral will soon “bleach” and die.