The Effects of SCUBA Diving on Coral Reefs
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The Effects of SCUBA Diving on Coral Reefs Raychelle Marsman, Undergraduate Student, Dalhousie University Abstract Coral reef habitats are in danger of destruction due to the carelessness of divers. Stony coral, the foundation from which coral reefs are built, have proven to be the most easily damaged by SCUBA divers in the Caribbean and Red seas. Through observation of the behaviour of divers around coral habitats over ten minute intervals, researchers were also able to determine that the dive frequency of an area and the level of experience of the SCUBA divers are extremely important factors influencing how much damage is being done to corals. Overall, it is the areas of high dive intensity and the diving groups with the least experience that cause the most damage to all coral types. Aside from improving education of divers, it is important to monitor them and lessen the frequency at which certain sites are being dived in order to preserve the fragile balance of diversity within these habitats. 1. Introduction Coral reefs, renowned internationally for their beauty and colour, are being threatened by our desire to observe them. Americans spend 1.2 billion dollars annually on tourism, much of which goes towards Caribbean isle vacations (Camp & Fraser 2012). Here, they have the chance to dive in one of the most spectacularly diverse ecosystems in the ocean. Coral communities are not solely for recreation, however, as they provide shelter, food and breeding grounds for many coral- dependant and independent species (Hawkins et al 1999; Glynn 2004). Millions of humans are also dependant on coral reefs. Coral reefs buffer thousands of miles of inhabited coastline from the full brunt of ocean waves as well as bring in billions of dollars annually through tourism and fisheries (Hoegh-Guldberg et al 2007). The loss of these corals would not only upset the fragile coral community food chain (Glynn 2004) but could also cause an economic breakdown in countries whose income is dependent on reefs. Reefs also offer a unique opportunity to study a diversity of species in a relatively concentrated area (Glynn 2004; Hoegh-Guldberg et al 2007). SCUBA (Self-Contained Underwater Breathing Apparatus) became a means for scientists to study coral and their importance to the ecosystem more closely. With advancements in technology, SCUBA also became a leisurely venture by which tourists could see firsthand the majesty of coral reef communities. In order to dive with SCUBA, however, training is required (Camp & Fraser 2012). According to the Professional Association of Diving Instructors (PADI), almost one million people are certified every year for recreational diving. With interest in coral reefs growing and almost 250,000 dives per year within only 12 km of Red Sea coast alone (Zakai & Chadwick-Furman R. Marsman \ Oceans First, Issue 2, 2015, pgs. 33-41. 33 Disclaimer: This is exemplary work from a first-year science writing class. The views expressed herein are not necessarily endorsed by Dalhousie University. 2002), the damage being done to coral reefs is becoming extensive. All of the reviewed studies, focusing on SCUBA and corals, observed the physical activity of unsuspecting divers during 10 minute intervals, taking note of the extent of damage being done to corals through contact. They found that damage to coral reefs varies based on the intensity at which a certain site is being dived (Hawkins et al 1999), the type of coral (Rouphael & Inglis 1997) and the experience of divers (Zakai & Chadwick-Furman 2002). Although some may argue that the extent of damage to corals by individual divers is not enough to affect the overall health of local coral reefs (Rouphael & Inglis 1997), the data collected by Hawkins et al (1999) and Zakai & Chadwick-Furman (2002) suggest that the impact of coral diving on a large scale is far too great to be ignored. It is important to note the difficulty in determining a coral environment’s carrying capacity, which is an ecosystem’s specific ability to support itself without environmental degradation, with respect to diving activity. This is mainly due to the scientists’ inability to differentiate influences from factors such as climate change, ocean acidification and over-fishing, which all compromise the strength of coral reefs, from diving. Regardless, it is known that diving can weaken coral communities, lowering the carrying capacity and destroying entire areas in as few as 4000 dives per year (Hawkins et al 1999). In order to protect coral reefs while still being able to profit from tourism, many researchers have proposed strategies to limit human contact with corals. The effects of diving on coral reefs is a well researched and reviewed topic but there is still conflict regarding whether diving is harmful enough to affect whole coral populations. Therefore, through the compilation of various research studies, this paper will investigate the impacts of SCUBA diving on coral reef communities of the Caribbean and Red seas and offer a definitive answer as to whether diving is a threat to coral habitats. 2. Investigating the Impacts of SCUBA diving on Corals 2.1 What are Corals? Corals are classified under the class Anthozoan containing over 6000 species of invertebrate marine animals. According to Cole et al (2008), coral communities are highly self-sustaining and diversity dependent. They live symbiotically with many organisms but are also consumed for food. The species directly dependent on corals for food have their populations controlled by larger carnivorous organisms who are in turn controlled by top predators. This diversity is what sustains a healthy balance of life within the habitat. The foundations of coral reefs are stony corals (Scleratinians) whose thick CaCO3 shells provide shelter, protection and mating grounds for a diversity of marine life (Glynn 2004). These branching forms of coral have proven to be the most at risk of being damaged by SCUBA divers (Hawkins et al 1999). Damage to these corals, such as broken branches, does not always kill the organism but rather exposes their softer internal structure making them more susceptible to predators and disease (Hawkins et al 1999) (see Figure 1). R. Marsman \ Oceans First, Issue 2, 2015, pgs. 33-41. 34 Disclaimer: This is exemplary work from a first-year science writing class. The views expressed herein are not necessarily endorsed by Dalhousie University. Destruction of stony and other corals undermines the entire coral community through loss of essential diversity (Cole et al 2008). The threat to coral reefs is therefore apparent as without corals the entire ecosystem collapses. It is the fragility of these harmonious habitats that influence many researchers to investigate the exact cause of their widespread destruction. Figure 1: Elkhorn coral (Acropora palmata), a stony coral, suffering from white band disease. The disease is characterized by large white patches and eventual loss of living tissue, exposing the skeleton beneath. Diseases such as this are irreparable. [Image from http://celebrating200years.noaa.gov/visions/coral/image11_220.jpg]. 2.2 Methods used for observing divers and corals The papers reviewed here focused on corals from regions that are immensely popular with tourists: the Caribbean islands (Hawkins et al 1999; Rouphael & Inglis 1997; Tratalos & Austin 2001) and the Red Sea (Zakai & Chadwick-Furman 2002). In order to study how divers interact with corals and the potential damage being done, it was important that the study sites were secluded enough to not be impacted by urban development or pollution (Hawkins et al 1999). This is, of course, so that any results collected are only reflective of divers. Wave height, depth of water and reef structure were also crucial factors in determining the perfect location to study SCUBA. As a control, Hawkins et al (1999) used reserved coral communities that were similar in terms of topography (Figure 2). Determined to be the most effective time period through extensive testing by Rouphael & Inglis (1997), all studies used 10 minute interval observations of R. Marsman \ Oceans First, Issue 2, 2015, pgs. 33-41. 35 Disclaimer: This is exemplary work from a first-year science writing class. The views expressed herein are not necessarily endorsed by Dalhousie University. anywhere from 251 individual divers per site to over 9000 separate dives per site within a three month period (Zakai & Chadwick-Furman 2002; Figure 3). Figure 2: Stylistic representations of the general reef topography at the three types of dive sites used in the study. (From Rouphael & Inglis 1997) Figure 3: Estimated number of dives per 3 month period at 12 coral sites of the northern Red Sea in Eilat, Israel (January 1st-March 31st 1996). It is important to note that all bars in this bar graph are straight. (From Zakai & Chadwick-Furman 2002) Since divers ascend and descend from mooring buoys, studies by Hawkins et al (1999), Rouphael & Inglis (1997) and Tratalos & Austin (2001) analyzed their data based on the distance that damage was found from the mooring. The study by Zakai & Chadwick-Furman (2002) factored in diver experience when observing the R. Marsman \ Oceans First, Issue 2, 2015, pgs. 33-41. 36 Disclaimer: This is exemplary work from a first-year science writing class. The views expressed herein are not necessarily endorsed by Dalhousie University. susceptibility of different coral types. Damage done by guided dives, introductory course dives and open water dives (one star being the lowest level) were recorded separately (Figure 3). As seen in Figure 4, damage to corals was differentiated into being skeletal (pertaining to the outer shell of stony corals), tissue abrasive (pertaining to the softer, more life-sustaining parts of the coral) or loss of coverage (pertaining to the loss of entire sections of reefs) in order to determine the severity of damage being done by each group.