Marine pollution occurs when harmful, or potentially harmful, effects result from the entry into the ocean of chemicals, particles, industrial, agricultural and residential waste, noise, or the spread of invasive organisms. Most sources of marine pollution are land based. The pollution often comes from nonpoint sources such as agricultural runoff and wind blown debris and dust. Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters, in which excess nutrients, usually nitrogen or phosphorus, stimulate algal growth.
Many potentially toxic chemicals adhere to tiny particles which are then taken up by plankton and benthos animals, most of which are either deposit or filter feeders. In this way, the toxins are concentrated upward within ocean food chains. Many particles combine chemically in a manner highly depletive of oxygen, causing estuaries to become anoxic.
When pesticides are incorporated into the marine ecosystem, they quickly become absorbed into marine food webs.
Once in the food webs, these pesticides can cause mutations, as well as
diseases, which can be harmful to humans as well as the entire food
web.
Toxic metals
can also be introduced into marine food webs. These can cause a change
to tissue matter, biochemistry, behaviour, reproduction, and suppress
growth in marine life. Also, many animal feeds have a high fish meal or fish hydrolysate content. In this way, marine toxins can be transferred to land animals, and appear later in meat and dairy products.
Agricultural runoff = can carry sediments such as pesticides to open water source
Algal growth may cause the underwater living things to function abnormally due to lack of sunlight
Waste products disposed into the sea causing harms to living creatures
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