Biomagnification is the magnification of a certain contaminant’s concentration through the members of an ecosystem. This is especially true for contaminants such as pesticides from agriculture which run off into lakes and bodies of water. These are then present in very small concentrations but they cause large algal blooms when coupled with the runoff of fertiliser (also from agriculture) which could be consumed by fish- and the concentration of the contaminant is then magnified from a small concentration to a larger one within the fish. When the fish are then eaten by water birds this concentration becomes even greater within the body of the birds and this is biomagnification. The contaminants are often harmful in very small concentrations but magnified in this way they cause harm to the larger organisms as the concentrations become higher and dangerous. can die off in this way thus affecting biodiversity. Algal blooms also have a direct effect on biodiversity because these are algae that will cover large sections of the surface of lakes and in this way obstruct sunlight from plants and species below. As the water becomes more acidic due to that thrive on the algae species in the lake themselves will be deprived of oxygen and many species will die further affecting food chains and biodiversity.