The causes and effects Marine Pollution

Pesticides
1. A pesticide is a chemical used to kill pests they include insecticides: used to kill insect pests that damage a crop and Pesticides: used to kill plants that compete with a crop (e.g. weed)
  1. Insecticides
    1. Plants provide food for a wide range of animals and insects that will eat crops if not protected. These animals (pests) damage plants- reducing their ability to make food and produce new tissues, resulting in smaller crop yields.
      1. Insecticides are useful: they are sprayed onto plants and eaten by pests, killing/harming them. This helps to increase crop and growth yield.
    2. Problems:
      1. Killing lots of different types of insect in an area will reduce the amount of food available for any animals that specialise in eating insects (e.g. insectivorous birds). This will affect other organisms in the food web, because they depend on each other/
      2. If the other species that are killed are predators of the pest then, once the insecticide has been washed away by rain, it is possible for pest species to return and increase in number even more rapidly, causing even more damage to crop.
      3. Pest species evolving resistance to chemicals: individuals that survive use of insecticide more resistant than those killed. The individuals that reproduce have offspring that carry genes for resistance. Farmers responded by using greater amounts of insecticide- increasing damaging effects on environment.
  2. Herbicides
    1. Usually sprayed on field where they selectively kill weeds, leaving crop plants unaffected. Clears any plants that might compete with crop for nutrients, water and light. So crop can grow more rapidly and produce greater yield.
      1. Problems:
        Many weeds important food plants for wide range of insect species. Removing all weeds reduces food and shelter available for them. Some insects may be pests of crop, however some insect species may be predators of insect pest species. Clearing weeds may make it easier for insect pest species to increase in number more quickly.
        Some herbicides quickly break down in soil to simple substances that are no danger to environment. Some include highly dangerous substances that can poison soil organisms and anything that eats them.
Nuclear fall-out
1. Contains radioactive particles that get into environment from accidental leakage of radioactive materials from a nuclear power station or processing plant, or as result of an explosion involving nuclear material.
  1. If particles thrown high into atmosphere by explosion, they may be transported by winds over long distances before they fall to the ground. Larger particles fall out more quickly- nearer to explosion site than smaller particles (may travel hundreds of miles)
    1. Problems:
      1. Some radioactive particles stay radioactive for long time and may cause damage if touch living material (e.g. burning tissue, cause cancer)
      2. Radioactive particles of elements that are normally stored in tissue (e.g. iodine) can cause great problems as can be passed along food chain in animal tissue. Results in increasing amounts of radioactivity in each trophic level of food chain, leading to greater risks of damage in animals higher up chain.
Discarded plastics
1. Many plastics non-biodegradable: cannot be decayed by action of decomposers. If left in environment, remain unchanged for many years.
  1. Problems:
    1. Landfills: once covered with plastic refuse, land cannot be used for growing crops or grass for herd animals, due to risk of leakage of poisonous chemicals. Only used for building decades after burial, when ground settles/no decay gases produced.
    2. Plastics that get into water systems may end up at sea, where it collects in huge areas: "garbage patches", where the oceans circulate
      1. Plastic bags may be swallowed by animals: turtles that mistake them for prey, jellyfish.
      2. Plastic nets/ropes entangle organisms: die of starvation
      3. Plastic broken down to release toxins that affect organisms in area.
      4. Plastic may break down into smaller particles "nurdles" that are swallowed by animals that mistake them for food.
Sewage
1. Human waste, faeces and urine. Contain high concentrations of nitrogen-containing substances, and so are good sources of nutrients for plants and microorganisms.
  1. Problems:
    1. When untreated sewage added to water, nutrients dissolve. This leads to eutrophication, increasing plant and algal growth, resulting in increase in bacterial growth, a fall in oxygen concentration in water and death of aquatic organisms.
    2. Human waste contains many bacteria: can cause infection, leading to vomiting, diarrhoea, fever and death.
    3. Sewage may contain concentrations of substances that can cause harm to organisms. Female sex hormones used in contraceptive pills excreted in urine: tiny amounts not broken down by sewage treatment left in water and is returned to natural water systems e.g. rivers. Male fishes may have reduced sperm count and produce eggs instead of sperm (feminization of males). Drinking water from these rivers with sufficient concentrations of hormones may affect men and reduce sperm count.
Liquid waste from industries:
1. Problems:
  1. Some substances, like sewage can lead to eutrophication.
  2. Metals copper, mercury and lead and some organic chemicals are toxic. These must be cleaned completely from waste water that drains into water systems. Prevents toxins from being absorbed by plants and animals and passing into food chains where they can cause damage.
Fertilisers and eutrophication
1. Fertilisers are chemicals that farmers use on fields to add nutrients (nitrates) to help crops grow better and produce greater yields.
  1. Problems:
    1. If too much fertiliser added to field than crops can absorb, remaining nutrients soak away in ground water to nearby streams and rivers. Also, If there is heavy rainfall soon after fertiliser spread, nutrients will dissolve in rain water and run off the surface of the field into streams and rivers.
      1. Eutrophication: adding nutrients to water.
        Eutrophication increases rate of growth of photosynthesising organisms (producers) e.g. algae on surface of water. Producers grow so much that they block light to plants growing deeper in water, which die as they cannot photosynthesise. This provides more food for decomposers, which increase in numbers rapidly. Decomposers respire more rapidly to make new materials for growth and reproduction. Respiration reduces oxygen concentration in water. Other aquatic animals find it difficult to get oxygen for respiration- many organisms e.g. fish die. Decay of dead organisms provides more nutrients, so more bacteria grow, respire and take more oxygen from water. Eventually, most large aquatic plants and animals in water die.

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	Created by 122559 over 8 years ago