Heterogeneity and scaling of photosynthesis, respiration, and nitrogen uptake in three Atlantic Rainforest streams

Abstract

Leaves, epilithon, macrophytes, and fine benthic organic material are central ecosystem compartments to food webs and mediate nutrient fluxes in streams. Most estimates of gross primary production (GPP) and ecosystem respiration (ER) are made at a reach scale, averaging across compartments. Thus, there is little information on how individual compartments contribute to and scale up to whole‐stream estimates across watersheds. We compared estimates of GPP, ER, and nitrogen (N) uptake of individual ecosystem compartments (dm) and stream reaches (~100 m) in three sizes of streams in a preserved Atlantic Rainforest watershed. The smallest stream had dense forest canopy cover, whereas the largest was more open. We measured substratum‐specific rates of GPP and ER, as well as ammonium and nitrate 15N uptake in recirculating chambers. We compared these decimeter‐scale measurements to whole‐stream estimates, using single‐station dissolved oxygen (GPP and ER) and pulsed N uptake methods. Epilithon and macrophytes (when present) were the dominant GPP and N uptake compartments in open‐canopy sites, and leaves contributed strongly to ER at all sites, even though they covered <3 percent of the stream bottom. Ammonium and nitrate uptake per unit N content varied significantly among substrata and streams. Upscaled inorganic N uptake per unit area was greater when macrophytes were present. Chamber measurements overestimated metabolic rates in the larger streams, but not in the smallest one. The smallest transient storage zone streams were more active than the biggest one, and this influenced the mismatch between whole‐stream and chamber nutrient uptake estimates. We conclude that scaling to the whole watershed requires information on location in the watershed (e.g., where canopy cover is dense), rates of individual compartments, and reach‐specific hydrodynamic information as influenced by large‐scale geomorphic details (i.e., the size and activity of the transient storage zones).

Agriculture influences ammonium and soluble reactive phosphorus retention in South American headwater streams

“…Similarly, Sheibley, Duff, and Tesoriero () reported small amounts of transient storage in seven agriculturally influenced streams in the United States and found A S / A values between 0.020 and 0.111, which are even lower than our values (Table ). Values of A S / A reported by Gücker et al () and Tromboni et al () for agricultural Brazilian Cerrado and pristine Atlantic rainforest streams were in the range of the values found in the present study (from 0.12 to 0.31, and from 0.04 to 0.61, respectively).…”

“…Geomorphic, hydrologic, and hydraulic factors such as discharge, channel size, and transient storage are also relevant for nutrient uptake because they influence water residence time and therefore the contact time between dissolved nutrients and reactive substrates (Cunha et al, ; Ensign & Doyle, ; Gücker & Boëchat, ; Thomas, Royer, Snyder, & Davis, ; Tromboni, Dodds, Neres‐Lima, Zandonà, & Moulton, ; Valett, Morrice, Dahm, & Campana, ). Increasing hydrologic connectivity between the channel and the hyporheic zone and promoting hydrological exchange between the stream and its floodplain increase nutrient retention through biological assimilation, denitrification, and/or adsorption to clay particles.…”

Nutrient uptake in a simplified stream channel: Experimental manipulation of hydraulic residence time and transient storage

“…Ambient uptake rates for NH 4 + in our study reached a maximum of approximately 295 versus 96 μg m −2 min −1 as the greatest reported value for the other studies. Our NH 4 + uptake rates are higher than those reported by Tromboni et al () for pristine Atlantic Rainforest streams. Some studies have highlighted the significant retention capacity of tropical streams.…”

“…In streams and rivers, these both nutrients can be removed from the water column through sedimentation (Bouwman et al, ; Gabriele, Welti, & Hein, ), adsorption to organic and inorganic particles (Peterson et al, ), complexation (Reddy, Kadlec, Flaig, & Gale, ), and other chemical reactions in both aerobic and anaerobic conditions (González‐Sanchis, Comín, Murillo, & García‐Navarro, ; Small et al, ). N and P can also be stored in organic matter through biotic uptake by bacteria or algae (Mulholland et al, ; Tromboni, Dodds, Neres‐Lima, Zandonà, & Moulton, ). Permanent removal of N through denitrification (releasing N 2 to atmosphere) is an important pathway accounting for 20–35% decrease in organic N concentrations in tropical streams (Potter, McDowell, Merriam, Peterson, & Thomas, ).…”

Variabilidade espacial e temporal da reaeração superficial em riachos: estimativa por meio dos métodos do traçador gasoso e da sonda solúvel flutuante

“…Para a obtenção do coeficiente de dessorção do gás traçador SF 6 (K SF6 ) foi utilizado, por meio do ajuste linear entre o logaritmo da área do cromatograma e a distância total dos trechos dos riachos, o coeficiente angular fornecido pela Equação 12 (BENSON et al, 2014;TROMBONI et al, 2017). Para a obtenção do K 2 de cada trecho, foi utilizada a relação existente entre K SF6 e K 2 (Tabela 4 e Equação 6).…”