Creatures that Live in the Water Environmental Science 4.2

Water Quality? Macroinvertebrate surveys are an important part of monitoring water quality Benthic macroinvertegrates – aquatic insects/organisms that have no backbone and are large enough to be seen w/o a microscope Benthic – their habitat is bottom of aquatic ecosystem Can not escape pollution Indicate water quality over a long period of time Index species – presence can tell us whether water is clean or polluted

Feeding Groups Collectors feed on decomposing organic matter, including feces and dead plants and animals Gathering collectors feed on the bottom where organic matter accumulates Filtering collectors (filter feeders) use structures to trap and strain small particles out of the water Scrapers graze on algae that is attached to surfaces of submerged rocks and other objects Shredders break large pieces of dead plant material into smaller pieces; get nutrition from algae, bacteria, and fungi on plants

Predators have adaptations for capturing other organisms Parasites have structures for attaching to and drawing fluids from other organisms Tubifex worms (sludge worms) are index species Presence indicates sewage or decaying vegetation Can tolerate low dissolved oxygen (DO) Leeches like quiet water and are parasites Fish bait Tolerant to organic pollution

Planaria cling to plants and stones in shallow water Insects and crustaceans eat them Sensitive to pollution Crawfish are active at night Food for fish, frogs, turtles, raccoons, etc. Somewhat sensitive to pollution Scuds (sideswimmers) live close to the bottom and are shredders Food for small fish

Aquatic sowbugs are shredders Food for small fish Somewhat sensitive to pollution Water fleas are filter feeders Largest part of small fish diet Abundant everywhere except rapid streams and polluted waters Spiders remain below the surface for long periods Predators feeding mainly on insects

Water mites are predators of insects and small fish; some are parasites Control for mosquitoes b/c a mosquito that is host to several mites will not feed Mosquito larvae are filter feeders; adult females need protein for development of eggs, so they seek blood Food for small fish Carry West Nile virus, yellow fever, malaria, encephalitis; cause heartworms in dogs

Midge flies are most important source of food for young fish Pollution tolerant Tolerate low DO Crane flies are shredders or predators Larger aquatic animals eat them Somewhat sensitive to pollution Black fly larvae form a black carpet on rocks Larvae are filter feeders; adults feed on blood of warm-blooded animals Pollution-tolerant

Backswimmers are predators and have a painful bite Eaten by other insect predators Water boatmen are omnivores Often shredders but sometimes pierce algae walls Feed on mosquito larvae Fish eat them Water scorpions are predators with a painful bite Water striders are predators that skim rapidly over the surface

Giant water bugs are fierce predators that sometimes bite swimmers Pests in fish hatcheries Predaceous diving beetles are very active predators Food for reptiles, fish, birds, raccoons, etc. Whirligig beetles are predators Somewhat sensitive to pollution Dragonflies and damselflies are predators that feed on mosquitoes Food for adult fish

Mayflies are the food for most aquatic predators Most abundant macroinvertebrates found in clean waters Index species Very sensitive to pollution Stoneflies and caddisflies are the most important part of the diet of trout and other fish Sensitive to pollution Presence indicates clean water and high levels of DO

Dobsonflies are eaten by fish and considered best bass bait Sensitive to pollution Water pennies cling to underside of rocks and are scrapers Food for dragonfly larvae Riffle beetles crawl on rocks in fast-moving water

Snails are scrapers that move over surfaces of all objects beneath water Some are pollution tolerant; some aren’t Mussels/clams Larvae are parasites on fish; adults are filter feeders Eaten by fish, ducks, and raccoons Excellent indicators of water quality Tolerate only low levels of pollutants More species of mussels are in jeopardy than any other type of aquatic organism