Water Quality and Pollution

Bio-accumulation means the accumulation or enrichment of the contaminants or chemical substances into an organism that occurs by the process of absorption which occurs at a faster rate than that of excretion.

Algal bloom is a rapid increase or accumulation in the population of algae in an acquatic system. The nutrients like potassium and nitrogen are key nutrients for the growth of algae. The presence of these materials and availability of sunlight are key factors for the growth of algae.

Non- biodegradable compounds such as DDT and mercury accumulate in the tissues of organisms that consume them since they do not break down easily. As a result, when they, in turn, are consumed by secondary organisms their amount magnifies. This is known as biomagnification. Hence, such non-biodegradable compounds affect the organisms of higher trophic level more. So, the correct option is 'heavy metal salts and non-biodegradable phenolic compounds'.

Environmental pollution is defined as the introduction of harmful materials or unfavorable alterations into the environment that cause adverse effects on living organisms.

Eutrophication can have serious effects, like algal blooms that block light from getting into the water and harm the plants and animals that need it. If there's enough overgrowth of algae, it can prevent oxygen from getting into the water, making it hypoxic and creating a dead zone where no organisms can survive.

• Algal bloom: It is the rapid growth of algae in water due to which coloured scums are formed on the surface.
• Biomagnification: When a toxic substance gets incorporated in the food chain, its concentration gets increased at each successive trophic level. This is called biomagnification.
  
• Eutrophication: It is the phenomenon of nutrient enrichment of nitrogen and phosphorus in a water body that supports a dense growth of plants and animal life. Due to nutrient enrichment, excess growth of algae occurs which is called algal bloom. When these algae die, their organic matter gets decomposed and this results in the depletion of oxygen leading to death of aquatic animals. This process is called eutrophication. 

If a lake is polluted with pesticides, large fish will contain the maximum amount of pesticide. The process due to which large fish will contain the maximum amount of pesticide is called biological magnification. It is also called as biomagnification. Phytoplanktons and zooplanktons absorb pesticide from the polluted water. Small fishes eats phytoplankton and zooplanktons. There will be increased accumulation of pesticide in their bodies. These small fishes are eaten by big fish. Hence, the big fish will have the maximum amount of pesticide.

• Biochemical oxygen demand (BOD) is a measure of how much organic pollution is in water. The BOD test measures the amount of dissolved oxygen in water that is used up due to the breakdown of organic pollutants, such as sewage, in a certain number of days. 
  
• Increased BOD means that a lot of oxygen is being used up, typically by bacteria breaking down organic material. 
  

Biomagnification is defined as the process by which a compound (such as a pollutant or pesticide) increases its concentration in the tissues of organisms as it moves up the trophic levels

The different trophic level of an ecosystem interacts with each other and they are interdependent on each other. Biological magnification is a process where pollutants such as pesticides or heavy metals move up the food chain, passes into rivers or lakes and consumed by aquatic organisms such as fish, which in turn are eaten by large birds, animals or humans. It occurs when the concentration of a substance, such as DDT or mercury, in an organism, exceeds the background concentration of the substance in its diet. 

A few toxic substances, often present in industrial wastewaters, can undergo biological magnification (biomagnification) in the aquatic food chain. Biomagnification refers to an increase in the concentration of the toxicant at successive trophic levels. This happens because a toxic substance accumulated by an organism cannot be metabolised or excreted, and is thus passed on to the next higher trophic level in a food chain.

Biomagnification, also known as bio-amplification or biological magnification, is the increasing concentration of a substance, such as a toxic chemical, in the tissues of tolerant organisms at successively higher levels in a food chain. The substances become increasingly concentrated in tissues or internal organs as they move up the chain. Bioaccumulants are substances that increase in concentration in living organisms as they take in contaminated air, water, or food because the substances are very slowly metabolized or excreted.

 It is seen that the level of toxicant increases as the food chain progresses. It means, the primary consumers will have more toxicant concentration than the producers, the secondary consumers will have more than primary consumers and so on. The highest concentrations will be seen in the top carnivore. This is because the consumers at the successive trophic level consume more than the previous level to fulfil the energy requirements. Due to this, toxicant keeps on accumulating in the successive trophic levels in higher concentrations. This process is called the biomagnification. So, planktons will have least and birds will have the most toxicant presence.

Biomagnification, also known as bioamplification or biological magnification, is the increasing concentration of a substance, such as a toxic chemical, in the tissues of tolerant organisms at successively higher levels in a food chain. Biomagnification process occurs when certain toxic chemicals and pollutants such as heavy metals, pesticides or polychlorinated biphenyls (PCBs) compounds go up the food chain by working their way through the environment and into the soil or the water systems after which they are eaten by aquatic animals or plants. Biomagnification occurs in the higher trophic levels of the food chain/web , where exposure to chemicals takes place mostly through food consumption rather than water uptake. Spraying a marsh to control mosquitoes will cause trace amounts of DDT to accumulate in the cells of microscopic aquatic organisms causing accumulation which cannot be metabolized.

Several outbreaks worldwide caused by the presence of E. histolytica have been reported associated with sewage contamination.