| Ecosystem metabolism is an integrative indicator of organic matter cycling in stream ecosystems. Metabolism is expected to vary predictably based on habitat characteristics that control the flow of nutrients and organic matter through stream ecosystems. Further, habitat characteristics affecting metabolic regimes may operate over multiple spatial scales. We estimated whole-stream ecosystem metabolism at seven reaches along an agriculturally-impacted stream over a year to investigate variation within and among reaches. Segment-scale regressions and multilevel models suggested nitrogen limitation and phosphorous suppression of gross primary production. Multilevel models demonstrated that reach-level average turbidity and nutrient concentrations were controls on within-reach drivers of metabolism. The present study suggests that turbidity and nutrients control segment-scale metabolism, not due to direct correlations with gross primary production and ecosystem respiration, but rather by determining the strength of relationships between reach-scale controls and metabolism.
Keywords: ecosystem metabolism; cross-scale interactions; reach-scale; turbidity; stream |