Abiotic Characteristics of Lakes

Generally speaking, ecosystems are described by two main categories of variables, abiotic and biotic factors. Biotic factors describe the conditions and nature of living organisms in the ecosystem, while abiotic factors include the non-living characteristics of the site, including temperature, physical and chemical conditions. In the case of a lake ecosystem, like any standing water ecosystem, abiotic factors are particularly decisive in shaping local conditions for life in the ecosystem.

Temperature

• As with any ecosystem, temperature is a critical abiotic factor in a lake environment. The nature of a standing water ecosystem, containing large amounts of still water that tends to retain environmental temperatures and can even freeze at extreme lows, makes temperature even more significant in the context of a lake. Simply put, an ecosystem will hold only those life forms that can complete their life-cycle processes within local temperature conditions. In the case of pronounced seasonal variation, many species have adapted by changing their behavior in the warmest or coldest periods and developing compensating behaviors, like storing food in mild seasons. Any species that is not able to adapt to local temperature conditions will not be able to take root and reproduce in the area, making temperature a decisive abiotic factor in the ecosystem.

Physical Characteristics: Turbulence and Flow

• While, on the surface, a lake may seem like a stagnant ecosystem, most bodies of water are connected to a complex water cycle that involves evaporation and precipitation flows, in addition to connections with other superficial and subterranean bodies of water. Wind acting on the surface of the lake can also determine internal currents and the distribution of nutrients and debris in the lake. As a result, the physical situation created by conditions of turbulence and flow is another important abiotic consideration when studying organisms and life processes in the ecosystem. Certain organisms, for example, will not be able to reproduce in extremely turbulent lakes, while flows into the lake may create debris fields that serve as shelter for other organisms.

Physical Characteristics: Depth and Light

• Beyond the physical forces acting on a lake, the physical form of a lake in itself is an important abiotic factor. Dimensions of depth and diameter determine the volume of water present in the system and the amount of aquatic habitat available, just as habitat size or shape can also favor certain sizes of organisms over others, yet access to light is perhaps the most important abiotic factor related to physical conditions. Light is a critical energy source for both plant and animal life, and ecosystems are sometimes even divided into depth layers depending on levels of light precipitation. Of course, light availability can also vary in relation to other abiotic factors like altitude, local weather and turbidity.

Chemistry: Nutrients, Oxygen and pH

• Every organism on Earth relies on a series of chemical interactions -- from feeding to respiration or photosynthesis -- to stay alive. As a result, the chemical context of an ecosystem determines what organisms can inhabit it as a function of the chemical processes that can be completed in the area. In the case of a lake ecosystem, critical chemical abiotic factors include pH, the nature and amount of nutrients dissolved in the water and bottom sediments, and the amount of dissolved oxygen found in the water. Anaerobic bacteria, for instance, can only thrive in low-oxygen environments, while large fish require oxygen-rich environments and relatively neutral conditions.