This hinders nutrient release from the sediments and the lake waters become progressively nutrient-deficient. The presence of ions of aluminium in acid rain is highly toxic to many organisms. Among birds, the process of eggshell formation is disturbed. In the 1970s, when defective eggshells were first noticed, it was assumed that the birds were absorbing too much aluminium. But scientists soon realised that the ratio of calcium and aluminium was an important factor.
Calcium deficiency is known to hinder successful hatching of a variety of bird species.
Fish-eating birds and humans acquire mercury by eating fish with high levels of the metal in them. The fish in turn ingest microorganisms which consume mercury released by acid rain in the water. Acid rain also releases aluminium and cadmium. Cadmium can cause kidney disorders, besides accumulating in the outer layer of the kidney, causing wounds. Aluminium on the other hand, causes problems for kidney patients.