Pond Ecosystems

Biotic Zones of a Pond A pond is broken up into 4 zones Littoral Zone Limnetic Zone Profundal Zone Benthic Zone

Littoral Zone: Emergent Emergent plants are those producing biomass above and below water level

Littoral Zone: Floating Floating plants are those producing biomass at and below water level

Littoral Zone: Submergent Submergent plants are those producing biomass solely below the water level

Limnetic Zone The limnetic zone is an open water area where light penetrates and floating algae and plankton dominant

Profundal Zone Area of open water where light can’t penetrate The profundal zone lacks producers but contains mobile higher level consumers that are dependent on the littoral and limnetic zones

Benthic Zone Area on the bottom of the pond where light can’t penetrate The benthic zone lacks both producers and consumers. This zone is dominated by decomposing organisms, from microscopic bacteria to macroinvertebrates like the crayfish.

Abiotic Factors: Temperature Seasonal changes in water temperature in a mid-latitude ponds is critical to the ecology of the pond The changes in temperature are associated with important physical properties of water

Summer Stratification As summer peaks, the difference between the water temperature at the surface and the bottom of the pond increases. The warm water at the surface is less dense and sits above the colder denser water at the bottom. The stratified water reduces mixing between layers, epilimnion and hypolimnion. The epilimnion develops relatively high levels of oxygen through photosynthesis while the hypolimnion develops high levels of nutrients from decomposition.

Fall Overturn As summer is replaced by fall, the surface waters cool and the stratified layers start to disappear. At some point the water temperature reaches a common value. Now, when the wind blows, water circulates within the entire pond, allowing surface and bottom water to mix. Oxygen replenishes the hypolimnion while nutrients replenish the epilimnion.

Winter Stratification As winter peaks, the difference between the water temperature at the surface and bottom of the pond increases. In contrast to summer stratification, the surface temperature becomes colder than the bottom temperature. As water freezes, it becomes less dense, floats, and insulates the water below, protecting the aquatic life from freezing.

Spring Overturn As winter is replaced by spring, the surface waters warm. At some part the water temperature reaches a common value. As the wind blows, the water circulates within the entire pond again allowing surface and bottom water to mix oxygen and nutrients.