If the export of nutrients from the wetland is lower than the incoming nutrient load, the wetland is considered a net sink for nutrients. On the other hand, if the export of nutrients is greater than the nutrient inflow, the wetland will be a net source of nutrients. Net export of nutrients may occur as a result of high nutrient loading rate to a wetland followed by reduced loading rate. In many cases, some of the nutrients that accumulated under high loading rates continue to be exported from the wetland. Thus, a wetland that historically functioned as a nutrient sink may become a nutrient source as a result of chronic nutrient loading.
Wetlands can also function as net transformers of nutrients from inorganic to organic forms.
In contrast, nutrients exported from wetlands are predominantly in organic form, a consequence of the copious production of dissolved and particulate organic matter within a wetland. This net transformation of nutrients by wetlands is ecologically significant because organic forms of nutrients must undergo decomposition to inorganic forms prior to biological utilization. Because a large portion of the wetland nutrient export is not immediately bioavailable, nutrient-related impacts in downstream surface waters, such as excessive growth of algae, may be greatly reduced or eliminated. The nutrient transformation function of wetlands, coupled with their ability to buffer pulses of nutrients in the watershed by storing and slowly releasing nutrients to downstream waters, provides a significant measure of ecological stability to contiguous aquatic systems. Summary Wetland functions give rise to a number of societal benefits, or values.