The lake as an ecosystem

Lake ecology is a well established field of study that has been used in lake management around the world over a number of decades.

The health of a freshwater lake depends on its ability to maintain water quality across variations in seasonal conditions. Micro-organisms, algae, plants and animals can all play a role in helping to maintain water quality. They often interact in complex relationships to cycle nutrients through the food chain. Lake ecology is the study of the relationships between the different species that live in the water. It also includes the flow of nutrients and energy through the system.

A healthy food chain has the capacity to adjust to drought, floods or variations in nutrient inputs into the lake. This gives the lake a robustness to cope with environmental shocks without either food chain collapsing or for the water quality to vary erratically.

A more detailed overview of lake ecology (limnology) can be found at the site Lake Ecology Primer.

A food pyramid

Nutrients and energy move up through the food chain. At the bottom are the primary producers, which use energy from sunlight to convert nutrients into organic compounds. The food supply that predators and herbivores need comes from the animals and plants beneath them in the pyramid.

A young copepod that eats algae

Look closely to see many micro-organisms moving about

An adult copepod

A ciliate herbivore that has engulfed blue-green algae to digest

Lake ecology as a management tool for Lake Bolac

The preservation of good water quality in a lake depends on a number of ecosystem components and processes. These include having a diversity of phytoplankton and predatory zooplankton and also on having a diversity of fish and birds. These conditions are promoted when there are beds of aquatic plants growing within the lake. Plants take nutrients out of the water, and they are especially effective when there is natural filtration of the water through adjacent wetlands in the catchment and around the lake inlet.

The mixing of water in the lake also prevents dominance of blue-green algae, as they are favoured by warm, still water characterised by a more permanent thermocline.