SOURCES (contd) A cargo ship pumps ballast water over the side Invasive species can take over once occupied areas, facilitate the spread of new diseases, introduce new genetic material, alter underwater seascapes and jeopardize the ability of native species to obtain food.
Marine debris is mainly discarded human rubbish which floats on, or is suspended in the ocean. Eighty percent of marine debris is plastic - a component that has been rapidly accumulating since the end of World War II. The mass of plastic in the oceans may be as high as one hundred million metric tons
SOURCES (contd) A mute swan builds a nest using plastic garbage. Discarded plastic bags , six pack rings and other forms of plastic waste which finish up in the ocean present dangers to wildlife and fisheries.Aquatic life can be threatened through entanglement, suffocation, and ingestion. Fishing nets usually made of plastic, can be left or lost in the ocean by fishermen. Known as ghost nets , these entangle fish , dolphins , sea turtles , sharks , dugongs , crocodiles , seabirds , crabs , and other creatures, restricting movement, causing starvation, laceration and infection, and, in those that need to return to the surface to breathe, suffocation.
Plastics accumulate because they don't biodegrade in the way many other substances do. They will photodegrade on exposure to the sun, but they do so properly only under dry conditions, and water inhibits this process.
Many of these long-lasting pieces end up in the stomachs of marine birds and animals,including sea turtles, and black-footed albatross.
Toxic additives used in the manufacture of plastic materials can leach out into their surroundings when exposed to water. Waterborne hydrophobic pollutants collect and magnify on the surface of plastic debris, thus making plastic far more deadly in the ocean than it would be on land
Apart from plastics, there are particular problems with other toxins that do not disintegrate rapidly in the marine environment. Examples of persistent toxins are PCBs, DDT, pesticides, furans, dioxins and phenols. Heavy metals are metallic chemical elements that have a relatively high density and are toxic or poisonous at low concentrations. Examples are mercury, lead, nickel, arsenic and cadmium.
Such toxins can accumulate in the tissues of many species of aquatic life in a process called bioaccumulation.
Eutrophication is an increase in chemical nutrients, typically compounds containing nitrogen or phosphorus, in an ecosystem. It can result in an increase in the ecosystem's primary productivity (excessive plant growth and decay), and further effects including lack of oxygen and severe reductions in water quality, fish, and other animal populations.
CORAL REEFS are aragonite structures produced by living organisms, found in marine waters containing few nutrients. In most reefs, the predominant organisms are stony corals , colonial cnidarians that secrete an exoskeleton of calcium carbonate . The accumulation of skeletal material, broken and piled up by wave action and bioeroders , produces a calcareous formation that supports the living corals and a great variety of other animal and plant life.
BENEFITS OF CORAL REEFS 1. Makes shore zones safe from waves by making them and breaking them up, and creates quiet water marine habitats for a variety of species. 2. High rates of CaCO 3 production play an important role in global carbon cycle 3. Biodiversity : One quarter of species in ocean live in and around reefs (also see 1 above). This makes them underwater tropical rainforests. Are they in the same state of decline? 4. Medicinal value of reef dwelling biota: some produce compounds active against asthma, heart disease, leukemia, tumors, HIV. Chemicals produced by sea slugs and sponges to repel fish are useful as insecticides. 5. Coral skeletons are being investigated as substrate for bone grafts. 6. Source of food : 10% of global fish catch 7. Economies of tropical countries built on tourism and fishing 8. Fossil reefs on land are a source of building stone, cement
ENDANGERMENT AND DECLINE OF CORAL REEFS 1. Extent of the problem: we are presiding over a major collapse a. Less than 10% of reefs in Indonesia, the Phillipines, Jamaica, among others, are healthy b. In 50 years, 75% of all reefs could be done in 2. Population growth, development of tropical coastline a. Three billion people live in coastal regions – this will double by 2050 b. Development, deforestation of inland areas 1. brings sediment-laden stream waters to coastal ocean 2. brings nutrient-rich waters to coastal ocean: algal blooms can suffocate reefs and lead to proliferation of starfish and urchins that can decimate reefs. 1 and 2 are cause of major declines in reefs in Jamaica, Barbados, Belize 3. Warming of tropical waters: El Nino, global warming Temperature, salinity balance upset led to coral "bleaching" events during 1980’s. Corals expel their zooxanthallae leading to their tissues being transparent instead of colored, leaving their white aragonite (CaCO 3 ) skeletons showing through. Corals can bounce back from these events, but not in the face of other environmental stresses such as poison and sediment and nutrient-rich runoff.
ENDANGERMENT AND DECLINE OF CORAL REEFS (CONTD...) 4. Overfishing of reefs a. Ecosystems thrown off balance: Fish that graze algae growing on reefs are wiped out, algae flourishes and suffocates reef b. Nefarious fishing methods: cyanide, bleach, crowbars, explosive charges. Fishing for food, and exotic aquarius sale more "normal" overfishing with nets, traps, and spearguns. 5. Carbon di oxide increae global warming, and sea level rise potential Note dependence of reefs on temperature, light, which are water depth dependent, and response of reefs to sea level. Note also dependence of reefs on CO 2 levels in the ocean. 6. Accumulated environmental stress Coral polyps deal with sediment, pollution stresses by secreting more mucous protein that coats their outer tissues, which depletes the organism’s metabolic reserves, increasing opportunity for infections.
Marine pollution is part of the problem of too much pollution by humans in general. There are only two ways to remedy this: either the human population is reduced, or the ecological footprint left behind by the average human is reduced. If we do not follow the second way, then the first way may be imposed upon us, as world ecosystems falter and cease to support us.