| Summary: | Since its introduction in 1956, the use of open-system, diel dissolved oxygen curves for estimating the components of ecosystem metabolism in the lotic setting have been important in
determining the current ecosystem theory of streams, both spatially among multiple systems and
longitudinally within the same system, as well as identifying potentially impaired systems,
especially when contrasted with streams considered unimpaired. Several factors have been
identified as controls on both components of ecosystem metabolism and include light, nutrients,
and stable substrates for gross primary production (GPP) and a source of organic matter (OM)
for ecosystem respiration (ER). Stream size is important at mediating these factors through the
presence or absence of a riparian canopy where small streams tend to have an intact canopy that
can severely limit light to primary producers but provide a good source of OM for respiration.
Alternatively, larger systems tend to lose canopy cover via widening of the stream and the
limitation of light is relaxed while input of OM decreases. Additionally, inputs from watershed
land use can affect GPP and ER in the stream via the inputs of nutrients to stimulate algal growth
or organic pollution that stimulates heterotrophic activity. In the following studies, the effect of
the presence or absence of a riparian canopy, watershed land use, and stochastic events such as
flooding on ecosystem metabolism in coastal plain streams of southeast Louisiana are described.
These systems behave similarly to previous studies and provide more evidence that the use of
ecosystem metabolism as a metric for stream health is beneficial. Recommendations for future
studies include the identification of more unimpaired systems while adding a temporal
component, modeling systems under different hydrologic or climate change regimes, and the
assessment of the impacts of stochastic events such as extreme weather events, exotic species invasions, or local extirpations of important species.
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