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Ecosystems of a Lake

An ecosystem is the interaction of the living and non-living elements of a particular environment such as lake, ocean, forest or meadow. A lake is an ecosystem all in itself. It contains zones based on light penetration, not based on the fish and zooplankton that inhabit the lake.

Littoral Zone
- The littoral zone occurs along the shoreline.
  
  The coastline area of a lake that is permanently under water comprises the littoral zone. In this zone, sunlight reaches the bottom of the lake. Photosynthetic plants such as lilies, green algae and plankton live there, and it is the most biodiverse area of the lake's ecosystem. The temperature in the littoral zone is greatly impacted by weather. At times it is warmer than the surrounding air, causing fog. Storm water run-off adds sediment and pollutants to this zone.
Limnetic Zone
- Sunlight does not reach the bottom in the limnetic zone.
  
  The limnetic zone is the surface area in the middle of the lake through which sunlight penetrates. Photosynthetic green algae and plankton live in this area. Generally, you won't find attached plants because roots can not attach to the bottom. The temperature of this zone is dependent on sunlight and surrounding air temperature.
Profundal Zone
- Ponds are smaller and shallower than lakes.
  
  The profundal zone is deep water that gets no sunlight penetration. This portion of the lake has no photosynthetic organisms. The temperature remains fairly constant throughout the year. It does not receive warming from the sun, nor is it impacted by air temperature. Animals in this zone get their nutrients by feeding on each other and by feeding on dead and decaying matter sinking from above.
Ponds Versus Lake Ecosystems
- Ponds are smaller and shallower than lakes.
  
  Pond ecosystems differ from lakes because they cover less area and have less depth. With a pond, the sunlight penetrates to the bottom throughout. Because of a pond's smaller size, local weather changes have a greater impact on ponds than lakes. Photosynthetic organisms live throughout a pond. In some ponds, plants can attach to the bottom everywhere, eventually filling it with decaying organic matter. When that happens the pond becomes a bog or a fen.

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