Wetland Abiotic Environment

Water movement is very important to the function and structure of a wetland. The water budget is a constant flux of the surface water, ground water, tides, and precipitation and evapotranspiration. The rate of input and output can change over time causing periods of stagnation or flooding. The movement of water is also an important mode of transport materials in and out of wetland ecosystems.

Because of the prolonged presence of water, dissolved oxygen tends to be used faster than it can be replenished. This is because diffusion from air to water is rather slow compared to the rate that organisms are respiring. This means that wetland soils tend to be anoxic. This forces the microbial community to use anaerobic respiration pathways. Microbes will oxidize other compounds or elements instead of oxygen which can turn the soil a certain color such as red or gray. Therefore, the soil color can be used as an indictor of anaerobic conditions.

Wetlands have a unique soil becuase of the presence of water. Their soils are hydric soils, meaning that the space between individual grains are filled with water. This is due to the prolonged pooling of water, causing higher rates of input than outputs. This complete saturation of the soil contributes to the anoxic conditions seen in wetland soils.

Internal nutrient cycling has an important role in wetland ecosystems. When plants and other organisms die, nutrients are returned to the water as decaying organic matter. However, decomposition is slowed in the anoxic water conditions. Therefore wetlands can have a large accumulation of organic matter and become a source of nutrients. Wetlands also receive nutrients from surface water, ground water, and sediments. Nitrogen and phosphorus are two major inorganic nutrients that wetlands recieve and cycle through uptake by plants.

Sediment is an important component of coastal wetlands for the formation sand bars and beaches. It's also used as a substrate for plants and animals. Sediment inputs come from upstream as well as transportation via wind. Ultimately, the sediment travels through the ecosystem, but it can spend time in storage in wetland areas before reaching the ocean. Incoming sediment is also ann external source for nutrients and minerals.

Wetlands have a broad range of water salinity, from fresh to saline or something in-between. This is dependent on the source(s) of water for a particular wetland. Tidal wetlands have to adjust to a salinity gradients as they are the interface between terrestrial and marine environments. Ocean inputs can mix with the terrestrial freshwater to create brackish conditions. Some habitats experience long periods of hypersalinity with most of the moisture coming from marine inputs. However, with seasonal rain, wetlands can quickly be dominated by freshwater. The ecosystem must be able to adapt to these changese in water salinity when necessary.