Short paragraph of how decayed material become helpful and dangerous at the same time

Why does the amount or dose entering the body matter? ... A point would be reached where beneficial effects would disappear and harmful effects would start to be noticed. ... harmful is directly related to the amount of it taken into the body at one time. ... Chemicals with high toxicity only need small doses to cause poisoning.

Explanation:

a, i am pretty sure.

poor water quality affects most estuarine organisms, including commercially important fish and shellfish. the pollutants that have the greatest impact on the health of estuaries include toxic substances like chemicals and heavy metals, nutrient pollution (or eutrophication), and pathogens such as bacteria or viruses.