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Chapter 18 Lecture Slides Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 18 The Impacts of Human on the Marine Environment Modification and Destruction of Habitats • Most habitat destruction occurs close to shore (due to the greater number of humans nearby) • Much of this destruction results from unplanned or poorly planned development • This destruction is more pronounced in developing countries, but it is not restricted to these areas Coral Reefs • Approximately one-fourth of all coral reefs have already been lost or are at risk • Pollution from sewage, sedimentation, and rising temperatures have caused some of this damage • Corals are also lost due to collection for the aquarium trade and for sale as souvenirs Coral Reefs • One-third of reef-building corals currently face extinction Problems Caused by Trawling • Trawl nets are a major threat to subtidal habitats • These nets, which drag along the bottom, cause resuspension of sediments which can kill suspension feeders • The trawls can also break off attached organisms Pollution • Pollution is described as the human introduction of a substance that reduces the quality of the environment • Some pollutants are liberated by human activities such as the release of heavy metals from mining • Most pollutants come from land-based substances Sources of Pollution 1. 2. 3. 4. Fertilizers Sewage Oil Persistent toxic substances Sources of Pollution • Fertilizers – Land-based fertilizers wash into streams and rivers and are carried into coastal waters – This influx of nutrients causes phytoplankton numbers to rise rapidly (called a “bloom”) resulting in eutrophification – These blooms can cause several problems including reducing the amount of light available to organisms attached to the bottom such as seagrasses and corals Sources of Pollution • Fertilizers – Other problems with these blooms occur after the phytoplankton die – As cells die and drop to the bottom, the influx of massive amounts of organic matter means decomposing bacteria begin to work – As a result of this breakdown, oxygen is consumed and anoxic conditions may occur Sources of Pollution Sources of Pollution • Sewage – Domestic sewage comes from homes and city buildings as well as stormwater runoff – Industrial sewage comes from factories, etc. and may contain a variety of substances – This sewage may contain disease-causing organisms – It may also contain heavy metals or other toxic substances even if treated Sources of Pollution Sources of Pollution • Oil – Organisms can accumulate components, many of which are toxic – These components can affect reproduction, growth, development and behavior – Organisms may also die of their feathers or fur is coated with oil (remember the Exxon Valdez and other accidents) – Estuarine organisms, seagrasses and corals are also at risk if coated with oil Sources of Pollution Sources of Pollution • Persistent Toxic Substances – Examples are chlorinated hydrocarbons and polychlorinated biphenyls (PCB’s) and heavy metals – In the case of chlorinated hydrocarbons, these substances are dissolved in the fats of organisms and are passed from prey to predator – As predators eat more prey, they continue to accumulate in their tissues (known as biological magnification) Sources of Pollution • Some fishes may not be safe to eat due to these levels • Fortunately, the levels of chlorinated hydrocarbons is not as high as it once was • The levels of PCBs and heavy metals in the ocean continues to be a problem as well Other Dangers to the Marine Environment • Solid wastes • Thermal pollution • Saline brines from desalination plants Threatened and Endangered Species • Organisms normally adapt to changing conditions through a process known as natural selection • If they cannot adapt, they go extinct • Human-induced extinctions can be called exterminations Threatened and Endangered Species • Threatened status – numbers of a species are low and a species is in danger of becoming endangered • Endangered status – species is in immediate danger of extinction Threatened and Endangered Species Threatened and Endangered Species • Example of an Extermination • Stellar’s sea cow • Extermination by overfishing • The species became known to science in 1741; the last known live individual was taken in 1768 Threatened and Endangered Species • Examples of other species imperiled today: – Whales – due to overfishing – Giant clams – for food and shells (collectors) – Cowries and cone shells – for shells (collectors) – Sharks – due to overfishing – Sea turtles – for food, jewelry, shells and other purposes Conservation Methods Used to Protect Marine Organisms and Habitats • Efforts to keep development at sustainable • • • • • levels These are on local, national and international efforts Fisheries management with EEZ’s Marine protected areas Habitat restoration Artificial reefs