to ostracods and young fish. These mixing zones tend to have many animals. The abundance is shown in Table3, which compares animals in of water. Comparison between clear and black waters Blackwater rivers resemble clearwater rivers in having a low conductivity and relatively low levels of dissolved solids, but clearwater rivers have water that often only is somewhat acidic (typical pH ~6.5) and very clear with a greenish color. The main Amazonian clearwater rivers have their source in the Brazilian Plateau (such as Tapajós, Tocantins, Xingu and some right tributaries of the Madeira), but some originate in the Guiana Shield (such as Nhamundá, Paru, and Araguari). Blackwater rivers of the world Amazonia Apaporis River: a tributary of the Japurá River Arapiuns River: a tributary of the Tapajós River Coari River Mazaruni River Mirití-Paraná River Piorini River Potaro River: a tributary of the Mazaruni River Rio Negro: The largest blackwater river in the world; one of the largest Amazonian tributaries. Tahuayo River Tefé River Uatumã River Urubu River Vaupés River Orinoco basin Morichal Largo River Atabapo River: from the Guiana highlands of Venezuela west into the Orinoco Caroní River: from the Guiana Highlands of Venezuela north into the Orinoco. Caura River: from the Guiana Highlands of Venezuela north into the Orinoco Inírida River: from Colombia northeast into the Guaviare River which flows into the Orinoco Ventuari River: from eastern Venezuela southwest into the Orinoco Vichada River: from Colombia east into the Orinoco Tomo River: from Colombia east into the Orinoco Tuparro River: from Colombia east into the Orinoco Southern United States Ashepoo River: along with the Edisto and the Combahee Rivers in South Carolina makes up the ACE Basin National Wildlife Refuge. Big Cypress, Black Cypress, and Little Cypress and the small rivers in the watershed of Caddo Lake in Texas and Louisiana Blackwater River: a tributary of the Chowan River in Virginia Blackwater River: a major river in the western Florida panhandle Blackwater River, West Virginia: Located in the Blackwater Canyon in Tucker County. Blackwater Falls, a five-story waterfall, is located along this river with rapids ranging from ClassIII-V+. Black River: a tributary of the Pee Dee River in North and South Carolina Cape Fear River, North Carolina: flows into the Atlantic Ocean. Cashie River, North Carolina: flows into Albemarle Sound. Caloosahatchee River, Florida: flows west from Lake Okeechobee to the Gulf of Mexico. Chowan River, North Carolina: flows into