Aquatic Ecosystems

Fresh Water, Brackish Water, and Salt Water

Fresh Water

  • defined as having low salt concentration
  • types of freshwater regions: ponds, lakes, streams, rivers, and wetlands
  • zones (3) 1) limnetic zone: near-surface open water surrounded by the littoral zone (dominated by plankton, phytoplankton, & zooplankton) 2) profoundal zone: much colder and denser than other zones, deep-water part of lake/pond 3) littoral zone: topmost zone near shore, includes species of algae, grazing snails, clams, insects
  • more than half of drinking water for humans/animals comes from this resource
  • plants: blue flag iris, water lilies
  • animals: otters, goldfish, hippo
  • locations: Lake Victoria, Great Lakes, Nile River
  • career: Quantitative Environmental Scientist- will manage, analyze, and interpret various physical & biological data under the supervision of a senior scientist or program manager

Brackish Water


  • has more salinity than fresh water, but not as much as seawater
  • mostly occurs when fresh water meets sea water
  • primary waste product of the salinity gradient power progress
  • plants: red tiger lotus, red mangrove, anachris
  • animals: caspian seal, bull shark
  • locations: Baltic Sea, Black Sea, Caspian Sea
  • job: Ecologist- study and explain how human actions affect other living things and their environment

Salt Water

  • large salt composition compared to fresh water
  • covers more than 2/3 of the Earth's surface
  • one of the most bio diverse environments in the world
  • plants: coral reef, seaweed
  • animals: octopus, killer whale, shortfin mako shark
  • 4 types of salt water ecosystems: 1) wetlands 2) estuaries 3) coral reefs 4) The Open Ocean
  • 4 zones: 1) Intertidal 2) Pelagic 3) Benthic 4) Abyssal
  • Intertidal: area that is above water at low tide & under water at high tide (in short, area between tide marks)
  • Pelagic: everything except areas near the coast and the sea floor
  • Benthic: lowest level of a system & includes the sediment surface, the water just above it, and some sub-surface layers
  • Abyssal: layer that contains the very deep communities near the bottom of oceans
  • locations: Atlantic Ocean, Pacific Ocean, Arctic Ocean
  • career: Marine Biologist- studies all types of sea creatures