Freshwater Food Web
Leeches and bullfrogs Leaches suck the blood out of bullfrogs. this is a parasitic relationship because the leech is on the bullfrog and sucking it's blood out, which will hurt the frog.
Mussels and Catfish The mussel larvae attach to the fins/gills of a catfish to grow, and the catfish uses mussels as food and their shells as a habitat. This is a mutualistic relationship because the mussel larvae get a ride as they grow up and the catfish gets food and shelter.
Red-backed Salamander and plants The Salamander digs through the ground to find food and get shelter, and salamander mixes up the nutrients. This is a commensalistic relationship because the salamander gets food and shelter, while the plants get nutrients.
How Humans Are Effecting The Environment
Freshwater ecosystems near towns and cities face threats from runoff and pollution. Industrial dumping, particulate pollution from combustion engines, and agricultural fertilizers and pesticides can all end up in rivers and streams, either falling there directly or carried to the waterways by rain. Particularly toxic pollutants may wipe out an ecosystem entirely, but even small amounts of less lethal compounds can have an effect on wildlife. Some of these toxic substances can even cause altering the life cycle of fish, amphibians and other wildlife and causing birth defects that can destroy a population over time.
Amazon River Dolphin
A large, mostly plant-eating mammal, the hippopotamus is found in rivers and lakes throughout Africa. The hippo is semiaquatic and thought to be more closely related to whales than to other hoofed animals. Adults can measure up to 11 feet long, stand 5 feet tall and weigh up to 1.5 tons. It has been known to live up to 45 years in the wild.