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NAUI Master Scuba Diver 62 The Diving Environment Many pollutants are introduced into estuaries, which are the wetland areas where fresh and salt water mix. Estuaries are some of the most productive habitats on earth. Pollutants can be transferred through the complex food webs that exist here. They can also be exported outside of the estuaries to the open ocean by currents and by fish who use the estuary as a breeding ground. One major problem associated with marine pollution is called bioaccumulation. This occurs as marine organisms concentrate pollutants in their tissues through uptake, by filtering water, feeding, or passive absorption. In biomagnification, bioaccumulation is passed up through the food chain through various trophic levels, so that the concentration of the compound becomes increased. This is why the top organisms in the food chain, like fishes, tend to have the highest concentrations of pollutants. Some pollutants may take decades to accumulate and show their deleterious effects on the environment. These effects may also be difficult to quantify and somewhat subjective. Certain compounds can selectively target different groups of animals or plants, depending upon the habitat and natural history of the organism. Laboratory bioassays are experiments designed to expose organisms to various concentrations of pollutants under controlled conditions. They usually measure lethal effects on the organism or different life stage forms of an organism, such as the egg, larvae, or adult. These experiments are used to develop water quality standards for acceptable limits to be allowed in nature. Diver’s Effects on the Environment Divers in particular can have many direct effects on the environment. In diving, a good conservation ethic is “leave it better than you found it.” This might include picking up trash on the beach or underwater. Non-destructive diving minimizes a diver’s impact on the environment. It involves good buoyancy control, not allowing fins, gauges, bags, etc. to contact the bottom, not touching the bottom or organisms, and demonstrating care for the aquatic world. Do not touch coral polyps, as this can cause them to die. It is also not environmentally sound to hand-feed fish, FIGURE 2-33. SPEARFISHING IS REGULATED IN MOST WATERS. REVIEW THE RULES BEFOREHAND. as this can make them dependent upon humans for their food. It can tend to make them “tame,” which alters their natural behavior, and may put them at increased risk of being speared. There is also the risk of being bitten while hand feeding animals. Remember, these are wild animals which can (and should be!) unpredictable. It is best to resist shell collecting as well. Empty shells provide homes for some creatures that cannot build their own. If we take large amounts of any organism from the waters, those organisms are going to become more difficult for others to find in the future. The best policy is to look, not touch. When photographing underwater, do not move animals around to compose a “better” photograph. This might be harmful to them by exposing them to potential predators, by removing them from a cryptic habitat,


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