Nutrients and temperature additively increase stream microbial respiration. (12th October 2017)

• Record Type: Journal Article
• Authors: Manning, David W. P.; Rosemond, Amy D.; Gulis, Vladislav; Benstead, Jonathan P.; Kominoski, John S.
• Is Part Of: Global change biology. Volume 24:Number 1(2018)
• Page Start: e233
• Page End: e247
• Publication Date: 2017-10-12
• Subjects: benthic organic matter -- metabolic theory of ecology -- microbial activity -- nitrogen -- phosphorus -- rivers -- temperature dependence; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.13906
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Rising temperatures and nutrient enrichment are co‐occurring global‐change drivers that stimulate microbial respiration of detrital carbon, but nutrient effects on the temperature dependence of respiration in aquatic ecosystems remain uncertain. We measured respiration rates associated with leaf litter, wood, and fine benthic organic matter (FBOM) across seasonal temperature gradients before (PRE) and after (ENR1, ENR2) experimental nutrient (nitrogen [N] and phosphorus [P]) additions to five forest streams. Nitrogen and phosphorus were added at different N:P ratios using increasing concentrations of N (~80–650 μg/L) and corresponding decreasing concentrations of P (~90–11 μg/L). We assessed the temperature dependence, and microbial (i.e., fungal) drivers of detrital mass‐specific respiration rates using the metabolic theory of ecology, before vs. after nutrient enrichment, and across N and P concentrations. Detrital mass‐specific respiration rates increased with temperature, exhibiting comparable activation energies ( E, electronvolts [eV]) for all substrates (FBOM E = 0.43 [95% CI = 0.18–0.69] eV, leaf litter E = 0.30 [95% CI = 0.072–0.54] eV, wood E = 0.41 [95% CI = 0.18–0.64] eV) close to predicted MTE values. There was evidence that temperature‐driven increased respiration occurred via increased fungal biomass (wood) or increased fungal biomass‐specific respiration (leaf litter). Respiration rates increased under nutrient‐enriched conditions on leaves (1.32×) and wood (1.38×), but not FBOM. Respiration rates responded weakly to gradients in N or P concentrations, except for positive effects of P on wood respiration. The temperature dependence of respiration was comparable among years and across N or P concentration for all substrates. Responses of leaf litter and wood respiration to temperature and the combined effects of N and P were similar in magnitude. Our data suggest that the temperature dependence of stream microbial respiration is unchanged by nutrient enrichment, and that increased temperature and N + P availability have additive and comparable effects on microbial respiration rates. Abstract : Rising temperatures and nutrient enrichment are co‐occurring global‐change drivers that stimulate respiration of detrital carbon in streams; however, these two drivers have the potential to interact and affect stream microbial respiration rates in unknown ways. We tested the combined effects of temperature and nutrients on stream microbial respiration using seasonal temperatures and experimental nutrient additions and found that nutrients and temperature stimulated respiration rates on detritus, but did not interact. Our results imply that nutrients and temperature additively increase microbial respiration rates, with comparable increases in stream microbial respiration in response to both drivers.