Pond Ecosystems

Biotic Zones of a Pond

• A pond is broken up into 4 zones

1. Littoral Zone

2. Limnetic Zone

3. Profundal Zone

4. 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.