Inter‐biome comparison of factors controlling stream metabolism

Abstract

SUMMARY1. We studied whole-ecosystem metabolism in eight streams from several biomes in North America to identify controls on the rate of stream metabolism over a large geographic range. The streams studied had climates ranging from tropical to cool-temperate and from humid to arid and were all relatively uninfluenced by human disturbances. 2. Rates of gross primary production (GPP), ecosystem respiration (R) and net ecosystem production (NEP) were determined using the open-system, two-station diurnal oxygen change method. 3. Three general patterns in metabolism were evident among streams: (1) relatively high GPP with positive NEP (i.e. net oxygen production) in early afternoon, (2) moderate primary production with a distinct peak in GPP during daylight but negative NEP at all times and (3) little or no evidence of GPP during daylight and a relatively constant and negative NEP over the entire day.' , 4. Gross primary production was most strongly correlated with photosynthetically active radiation (PAR). A multiple regression model that included log PAR and stream water soluble reactive phosphorus (SRP) concentration explained 90% of the variation in log GPP. 5. Ecosystem respiration was significantly correlated with SRP concentration and size of the transient storage zone and, together, these factors,explained 73% of the variation in R. The rate of R was poorly correlated with the rate of GPP. 6. Net ecosystem production was significantly correlated only with PAR, with 53% of the variation in log NEP explained by log PAR. Only Sycamore Creek, a desert stream in Arizona, had positive NEP (GPP: R > I), supporting the idea that streams are generally net sinks rather than net sources of organic matter. 7. Our results suggest that light, phosphorus concentration and channel hydrauh'cs are important controls on the rate of ecosystem metabolism in streams over very extensive geographic areas.

Influence of watershed‐climate interactions on stream temperature, sediment yield, and metabolism along a land use intensity gradient in Indonesian Borneo

“…At our focal streams, estimated rates of GPP ranged from 0.00026 g O 2 m À2 d À1 to 13 g O 2 m À2 d À1 , exceeding the range of GPP recorded across six tropical studies (0.10-4.6 g O 2 m À2 d À1 ) [Gücker et al, 2009;Hunt et al, 2012;Mulholland et al, 2001;Oliver and Merrick, 2006;Ortiz-Zayas et al, 2005;Townsend et al, 2011]. Available light has been identified as a strong contributing factor to high GPP, especially in reference streams [Bernot et al, 2010;Mulholland et al, 2001;Young and Huryn, 1999].…”

“…High stream respiration rates were particularly surprising because they occurred in a nonforest catchment. Previous studies suggest that forested catchments produce the greatest respiration rates as a result of high organic matter inputs from riparian vegetation and a tendency for pristine streams to retain organic matter [Delong and Brusven, 1994 [Gücker et al, 2009;Hunt et al, 2012;Mulholland et al, 2001;Oliver and Merrick, 2006;Ortiz-Zayas et al, 2005;Townsend et al, 2011]. In the mature oil palm stand in August 2009, low flow rates resulted from little antecedent precipitation.…”

“…Available light has been identified as a strong contributing factor to high GPP, especially in reference streams [Bernot et al, 2010;Mulholland et al, 2001;Young and Huryn, 1999]. The lowest GPP was measured in agroforest and forest streams, with riparian buffers potentially reducing light input compared with the oil palm streams.…”

“…In the oil palm streams, high GPP may be explained by a combination of higher light and nutrient availability. In Queensland and Puerto Rico streams that were not light limited, nutrient availability has been shown to influence GPP [Mosisch et al, 2001;Mulholland et al, 2001]. Specifically, greater algal production maintained by high nutrient inputs (e.g., fertilizers) would lead to higher GPP.…”

Eutrophication and trophic state in rivers and streams

“…Second, all the sites studied but one were relatively pristine small streams, so the data can be used to determine trophic boundaries mostly in the absence of human effects. Third, the streams were located in a variety of biomes, including one desert, one prairie, one tropical, one arid montane, one mesic montane, and four temperate deciduous biomes (Mulholland et al 2001). Whole-stream autotrophic state varied over 150-fold in this data set (very high rates of GPP were associated with the lighted desert stream), with the central one third of the distribution falling between 0.4 and 1.8 g O 2 m Ϫ2 d Ϫ1 (Table 5).…”