3.3rq 1.Why is the globe of Earth mainly blue. 2.List three major freshwater ecosystems: 3.Define sediment: 4.What is an important characteristic of all life in rivers and streams? 5.What is the major source of food for fish in slow moving water? 6.Describe an oligotrophic: 7.Define littoral zone: 8.Define limnetic zone: 9.Define plankton: 10.Define profundal zone: 11.List two characteristics of a wetland: 12.Define estuary: 13.Define intertidal zone: 14.Define photic zone: 15.Define aphotic zone: 16.Define benthic zone: 17.Define abyssal zone: 18.Where is the world’s largest coral reef?