Explain how human activities can cause an imbalance in bioge

Explain how human activities can cause an imbalance

in biogeochemical cycling and lead to problems such as

cultural eutrophication and fish kills

Solution

Coastal waters like wetlands and estuaries, mangrove swamps and oceans are contaminated with the inputs of pollutants and wastes. About 40% of world’s population is living near the coast that predicted to be doubled by 2050. According to U.N environment problem about 80% of marine pollution initiated on land of which municipal sewage contributes major part from the coastal developing countries. The coastal developed countries dump municipal sewage into oceans without treatment. This causes overwhelming of coastal waters to biodegrade the wastes.

Sewage runoff and agricultural wastes into coastal waters accumulate heavy quantities of nitrates and phosphates, the plant nutrients that encourage explosive growth of harmful algae. These algal blooms are called red, brown or green toxic tides. These toxics algae release water born or air born toxins that cause damage to fisheries and even kill fish eating birds and sea food consuming individuals. About 60000 of American consuming shellfish contaminated by algal toxins are susceptible to food poisoning. The harmful algal blooms cause oxygen depletion zones in the water bodies thereby causing the death of several aquatic organisms.

Northern Gulf of Mexico occurring on the mouth of Mississippi River is the third largest oxygen depleted zone. This area includes the coastal waters of U.S states of Mississippi, Lousiana and Texas. The decreased oxygen levels cause suffocation to fish, crabs and shrimps that make them unable to move less polluted areas. The oxygen depleted zone spread to a large area such as U.S state of New Jersey. Due to its large size and agricultural importance, the waters near river basin are subjected to cultural eutrophication because of heavy fertilized zones of coastal areas.