Lakes and ponds are bodies of open standing water
Their physical conditions and life vary with distance from the shore.
Littoral zone: Shallow water at the pond edge. Plants anchor in the mud, leaves reach water surface. Nutrients and plant growth make this zone rich in invertebrates (insect larvae, snails, crayfish)
Benthic Zone: extends along the bottom of the entire pond. Invertebrates live in the mud feeding on detritus (or each other)
Zones of life in the Pond
Limnetic Zone: Open portion away from the shore where sunlight penetrates. Photosynthetic phytoplankton support zooplankton which support fish.
Turbidity affects the depth of sunlight penetration
Profundal Zone: Open water that sunlight does not reach. Low in dissolved oxygen – support few animals
Streams and runoff naturally bring nutrients and sediment to a pond over time.
Eventually ponds may fill in completely through aquatic succession
Man can accelerate the process of change through the addition of excess nutrients (phosphorus and nitrogen)
Eutrophication
1. Excess phosphorus enters water2. Fertilizes algae and aquatic plants making
them grow faster3. Algae can grow quickly and cover the pond
surface4. As algae die bacteria decompose them5. Increased bacterial activity depletes the
dissolved oxygen6. Dissolved oxygen can become too low to
support fish
Artificial Eutrophication