Species of zooplankton decrease with increasing acidity and again some species may increase in abundance either through reduced competition or grazing by higher organisms. Stoneflies and caddis on the other hand are usually carnivorous or omnivorous, either eating their prey direct or shredding organic debris, and may benefit from decreased rates of organic breakdown in acid waters or reduced predation by the fish that feed on them. In forest streams there is reduced detritus as little leaf litter reaches the streams another factor affecting species abundance. Increased stream drift also may reduces density. Species affected may depend upon whether they overwinter as an egg, or an nymph, as most acid flushes happen in late autumn or early spring.
Mayflies also tend to have more fine gills than caddis or stoneflies so are more sensitive.
Those that are only around as nymphs in the summer may benefit enormously from the reduced competition. Fish Effects include toxicity and corrosion. Effects osmoregulation, the ionic balance of the fish the nervous system and will affect growth and cause skeletal deformities due to upsets of calcium metabolism. In addition Al also upsets gill permeability and respiration as the gills clog up with mucus. Older fish are more sensitive than eggs or fry, although acidity alone affects eggs and fry more than adults.