| A | B |
| salinity | the amount of dissolved salts the water contains |
| freshwater ecosystems | lakes, rivers, and wetlands |
| littoral zone | area near the shore with lots of plant & animal diversity |
| benthic zone | the bottom of a lake, with decomposers, insect larvae etc. |
| eutrophication | when the increase in nutrients eliminates oxygen |
| zooplankton | drifting, microscopic animal organisms |
| phytoplankton | microscopic plants that use photosynthesis |
| nekton | free-swimming organisms like fish & turtles |
| benthos | organisms that live on the bottom of the ocean like starfish & oysters |