Stream metabolism

Stream metabolism, often referred to as aquatic ecosystem metabolism in both freshwater and marine ecosystems, includes gross primary productivity (GPP) and ecosystem respiration (ER) and can be expressed as net ecosystem production. Analogous to metabolism within an individual organism, stream metabolism represents how energy is created and used (respiration) within an aquatic ecosystem. In heterotrophic ecosystems, GPP:ER is <1 ; in autotrophic ecosystems it is >1. Most streams are heterotrophic. A heterotrophic ecosystem often means that allochthonous inputs of organic matter, such as leaves or debris fuel ecosystem respiration rates, resulting in respiration greater than production within the ecosystem. However, autochthonous pathways also remain important to metabolism in heterotrophic ecosystems. In an autotrophic ecosystem, conversely, primary production exceeds respiration, meaning that ecosystem is producing more organic carbon than it is respiring.

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