The Demise of the Rainforest of the Sea
Chestnut Hill, Massachusetts
2017, , Prose
The window seat was a good choice. The only thing to look at to my right was blue: the sharp blue of the ocean and the pure blue of the sky, blending and mixing, with no clear horizon. To my left: the back of someone’s head as they looked out the window in this two seat-wide plane. This plane, albeit small and shaky, was delivering me to Eleuthera, The Bahamas, for 100 days on the 100-mile long island. The Island School was calling my name.
Oceans cover 70% of earth’s surface (US Department of Commerce). The vastness of the oceans makes them a biological desert (Townsend 2012). In places of upwelling and warm water, one of the most productive, biologically-rich ecosystems on earth is formed: a coral reef (Sheppard et al. 2002).
Be it a massive, encrusting, branching, columnar, foliaceous, fire, or black coral, all reefs are built from the remains of the skeletons of coral polyps, a tiny, fleshy calcium-carbonate-secreting animal (Sheppard et al. 2002). Polyps are suspension feeders that consume organic matter that falls on their tentacles and predators that consume smaller animals with the stinging cells on their tentacles (Townsend 2012). Not only are polyps animals, but they have their own primary-producing endosymbionts or photosynthetic dinoflagellates, known as zooxanthellae, which can photosynthesize up to 10 times more than phytoplankton (Townsend 2012).
Polyps and zooxanthellae are in an essential symbiotic relationship. Zooxanthellae photosynthesize more organic carbon than they need to grow, and provide the glucose for the polyps. This endosymbiont also removes toxic waste products for the polyp. Simultaneously, polyp respiration and metabolism supplies the zooxanthellae with the needed carbon dioxide and nutrients for photosynthesis. Polyps also protect zooxanthellae from grazers, and hold the zooxanthellae near the surface so that they can receive the sunlight for photosynthesis. The polyp zooxanthellae relationship is entirely self-sufficient: the waste from one organism are the nutrients for the other (Townsend 2012).
Polyps build and live in a calcium carbonate skeleton. Corals grow upward and outward as polyps build on top of existing skeletons, and are commonly the habitat to hundreds of thousands of species. The base of a food web, coral reefs are often coined the “rainforest of the sea.”
My dive gear is inexplicably heavy. It is only my third day in The Bahamas, and my skin is sensitive to the scorching heat and intensity of the piercing sun’s rays. Sweat drips down my back as I hoist my tank and BCD to the edge of the water.
After dropping the weight into the sand, I take off my shirt and pull up my wetsuit. With the assistance of a friend, I put my tank on like a backpack. I am ready for the ocean.
I slowly trudge into the water, carrying my fins in one hand and snorkel and mask in the other. The weight of the tank throws me off balance and I trip, landing sideways in the water. I look around; no one seemed to notice.
The waves bounce me up and down, forcing me to take several attempts to put on my fins. I continue to wade into deeper water, adjusting my tightly-fitted mask and snorkel. Today is unusually choppy; I strain to keep my eyes on the Dive Master. He reviews the instructions and gives the signal. My heart is pounding.
I sink. The surface disappears as the world under water fills my vision. My breathing is heavy. My eyes close and I attempt to equalize.
I finally hit the bottom. I am kneeling on the ground 10 feet below the surface, breathing underwater in the ocean for the first time.
Coral reefs are the cornerstone of marine biodiversity, yet they are extremely sensitive to their environment. All corals have a specific temperature niche between 18 and 20˚C, and cannot live in waters greater than 28˚C without negative effects (Townsend 2012). The water is warm enough for corals between the northern Tropics of Cancer and southern Tropics of Capricorn (Sheppard et al. 2002). Coral growth rates depend on the water temperature (Sheppard et al. 2002). Reefs exist in relatively shallow waters so that they can access sunlight, and can live up to depths of 60 m (200 feet) (Sheppard et al. 2002).
There are many identified stressors of corals: elevated seawater temperature, increased solar radiation, reduced salinity, and bacterial infections. Global warming can exacerbate many of these stressors and is the cause of further coral ramifications. (Brown)
Our corals are in trouble. In the Caribbean Sea alone, more than 50% of the coral was alive in 1977, yet less than 10% was living in 2002 due to increased seawater temperatures from global warming and increased aquatic pollution (Friedland et al).
Kneeling on the ocean floor, I tried to prevent myself from floating up. The surface of the water was finally more than 10 feet above my head and the Dive Master was about to lead us on our first “deep” dive.
I still had to use my arms to get around. I paddled and kicked my way over to a wall of coral and was so entertained by the minute details of the coral that my eyes could observe. It was beautiful.
But everything seemed startling grey. Maybe it was because it was a cloudy day? Maybe it was because my eyes hadn’t adjusted to the underwater lighting?
Yet most of the dark clouds disappeared before lunch; I had been in the water for at least thirty minutes, so surely my eyes had adjusted.
Still… the greyness did not disappear. The coral seemed to lack color and lack a certain quality of livelihood.
I told myself it was just the particular reef I was looking at. At least I hoped it was.
Originally a “natural” phenomenon, bleaching events used to be rare and localized (Reaser et al. 2000). As the average temperature of the earth has increased about 0.8˚C over the past century as the result of global warming, bleaching has become more common and exacerbated (Townsend 2012). Coral bleaching now occurs on a regular basis in the Caribbean and Indian and Pacific Oceans (Brown).
When the seawater temperature exceeds the upper limit of the tolerance level of coral, the cellular structure of corals is damaged, so the zooxanthellae die and are expelled (Friedland et al. 2015). The coral loses its photosynthetic pigments in the ejected zooxanthellae and turns white, the color of the remaining calcium carbonate skeleton (Brown). Zooxanthellae protect their coral from harsh UV rays; without this safeguarding, the coral absorbs more irradiance energy and has greater photosynthetic cellular damage (Brown). Further, the zooxanthellae deficiency causes a decrease in photosynthetic efficiency and photosynthesis of the coral, which can no longer create enough energy to survive (Brown). Bleaching can be a temporary reality for corals, but after a time, the coral will die (Friedland et al. 2015).
The death of coral reduces habitat space in the ecosystem; species richness declines after bleaching events (Friedland et al. 2015). Once a coral is bleached, it is colonized by seaweeds, which can act as a habitat to some species (Reaser et al. 2000). If sufficient living conditions for the corals remains or returns, the coral could recolonize an empty space and continue to grow (Reaser et al. 2000).
In the early 1980s, coral bleaching began to happen on a larger scale (Reaser et al. 2000). Now, it is an annual event of increased severity and occurs in almost every major reef in the world (Reaser et al. 2000). The 1998 bleaching event was the most geographically extensive and acute: over 60 countries were affected and reefs experienced up to an 80% mortality rate (Reaser et al. 2000). Corals are particularly sensitive to global-warming-induced bleaching because their temperature niche is so narrow, so any small increase in seawater temperature will have an adverse affect (Friedland; Brown).
Bubbles filled my vision. Beginning my descent into the underwater world, I breathed out for as long as I can. The sound of my breath going through the regulator calmed me. Although I was no longer breathing free air, the anticipation of what was to come occupies my thought, not fear.
I sunk. I was experienced enough at this point to not need to hold onto the 80 foot rope that connects the boat to its anchor at the bottom of the ocean. Taking my time, equalizing, I was kneeling on the floor 50 feet below in a circle with my classmates before I knew it. My teacher handed out the pencils and we dispersed to our assigned reefs to observe and take notes for the rest of the class period.
“My” reef was coated in algae; although there were a variety of small fish poking around at the top, there were no larger grazers in sight. Despite this reef area being off the coast of rural Eleuthera, the area is still under the control of humans: coral and fish species face adversity from sedimentation from construction and pressure from overfishing.
Sediments challenge coral survival. Corals have an upper tolerance level for sedimentation. Dredging and construction accelerate runoff, leading to increased turbidity and sedimentation and reduced light availability for photosynthesis which impacts the metabolism of the reef. As a result, coral efficiency is decreased and reefs can even be buried. Downstream currents increase the area affected by dredging (Rogers 1990). Further, sedimentation lowers coral growth rates because of less photosynthesis and diversion of energy to the removal of particles. As the corals suffer, the number of species and size of populations decrease and fisheries consequently weaken. Overall, in reef zones with heavy sedimentation, one can expect lower species diversity, less live coral, lower growth rates, and greater abundance of coral species with resistance to reduced light levels. “heavy sedimentation is associated with fewer coral species, less live coral, lower coral growth rates, greater abundance of branching forms, reduced coral recruitment, decreased calcification, decreased net productivity of corals, and slower rates of reef accretion. Sedimentation is one of the biggest sources of reef degradation from human activities in the Caribbean and the Pacific (Rogers 1990).
The nurse shark was directly under me. I didn’t move … it didn’t move. I didn’t need to move; it was asleep, or possibly just resting, on the ocean floor next to a chair-sized reef. With ease, I dived down to get as close as I dared. Consumed with fascination, I swam circles above, around, and adjacent to the shark. I lost all sense of time as I absorbed every detail that I could about my experience: the temperature of the water, the color and texture of the shark’s skin, the almost-supernatural clarity of the water, the number of fish species floating around the shark, the shades of purple and red and blue of the coral next to the shark. My heart fluttered and I never wanted to leave. But soon, my curiosity and sense of adventure outweighed my contentment: I was off, ready to find what else the Exuma Cays Land and Sea Park had to offer. There was a tangible difference between the species richness and vibrancy of the corals there in the marine-protected area and that off the coast of Eleuthera, where the coral and fish are more vulnerable to all sorts of attacks: attack from humans, attack from our fossil-fuel dependent lives, from our reckless yet inevitable pollution, from our seemingly unstoppable destruction of the natural world.
Our corals are in trouble. Silt from runoff, development, and poor farming methods, industrial effluents, damaging fishing techniques, diseases, bleaching, and ocean acidification are common dangers to coral. Global warming only exacerbates these hazards by increasing storm intensity and rising seawater temperatures. (Friedland et al. 2015)
We know that the demise of coral is not natural. It is becoming more extreme over time, and they are not recovering fully (Friedland et al. 2015). There are few document examples of complete reef recovery after severe sedimentation or bleaching events (Rogers 1990). Dredging and other harmful activities will only continue. But we must keep in mind that coral reefs are not just far away places to visit on exotic holiday trips; they are crucial habitats that support one of the greatest biodiversities in the world, that support the fisheries that millions of people rely on at subsistence levels (Friedland et al. 2015). “While the abundance of coral has declined in recent decades, the implications for humanity are difficult to quantify because they depend on ecosystem function rather than the corals themselves” (Iglesias-Prieto et al. 2013).
Is there hope? In a race between new growth and further decay, the importance of research and emission policies only grows. Local, preventative action must be paired with a low-carbon economy to prevent future drastic reef degradation. Although it is possible that corals can continue adapting to the rising stress and pressure they are facing, the extent of this adaption is unknown: coral damage must be mitigated. Coral reefs are too valuable to let slip away: the provisions of coastal protection, commercial fishing, tourism, animal protein, and sand production, and the source of the highest biodiversity in the ocean are just a short enumeration of the benefits of reefs. (Iglesias-Prieto et al. 2013)
During my 100 days in Eleuthera, I arrived as a naive student, and departed the island as an activist. Join me. Help protect the Rainforest of the Sea.
Brown, B. E. “Coral Bleaching: Causes and Consequences.” Coral Reefs 16.0 (1997): n. Pag. Web. Brown 1997.
Doney, Scott C., Victoria J. Fabry, Richard A. Feely, and Joan A. Kleypas. “Ocean Acidification: The Other CO2 Problem.” Limnology and Oceanography E-Lectures (2011): n. Pag. Web.
Friedland, Andrew J., Rick Relyea, David Courard-Hauri. Environmental Science for AP*. New York: W.H. Freeman, 2015. Print.
Iglesias-Prieto, Roberto, Max Wisshak, Maoz Fine, Emma V. Kennedy, Chris T. Perry, Paul R. Halloran, Christine H.L. Schönberg, Armin U. Form, Juan P. Carricart-Ganivet, C. Mark Eakin, and Peter J. Mumby. “Avoiding Coral Reef Functional Collapse Requires Local and Global Action.” Current Biology 23.10 (2013): 912-18. Web.
Pastorok, Ra, and Gr Bilyard. “Effects of Sewage Pollution on Coral-reef Communities.” Marine Ecology Progress Series 21 (1985): 175-89. Web.
Reaser, Jamie K., Rafe Pomerance, and Peter O. Thomas. “Coral Bleaching and Global Climate Change: Scientific Findings and Policy Recommendations.” Conservation Biology 14.5 (2000): 1500-511. Web.
Rogers, Cs. “Responses of Coral Reefs and Reef Organisms to Sedimentation.” Marine Ecology Progress Series 62 (1990): 185-202. Web.
Sheppard, Charles. Coral Reefs: Ecology, Threats & Conservation . Stillwater, MN: Voyageur, 2002. Print.
Townsend, David W. Oceanography and Marine Biology: An Introduction to Marine Science. Sunderland, MA: Sinauer Associates, 2012. Print.
US Department of Commerce, National Oceanic and Atmospheric Administration. “How Much Water Is in the Ocean?” NOAA’s National Ocean Service . N.p., 01 June 2013. Web. 22 May 2017.
From the Island School’s rigorous semester abroad program, I have brought back with me a deep passion for living sustainably and helping educate others about the seemingly unknown, yet ever imperative, dangers to the environment. At the Island School, I went on weekly dives for Marine Ecology class, when I saw first-hand the beauty of the coral reef ecosystem. Back at home, I learned about the pressures coral are facing around the world and was able to rationalize this information with what I saw. I want to help share what I have learned with others.