Assessing’biogeochemical’cycling’of’surface’water’in’Eastern ...Ecology 90: 2556-2566....
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Assessing biogeochemical cycling of surface water in Eastern Siberian streams using shortterm solute addi9ons Seybold EC, Drake TW, Schade JD, Bulygina K, Bunn A, Chandra S, Davydov S, Frey KE, Holmes RM, Sobczak W, Spektor V, Zimov N, Zimov S INTRODUCTION Cole et al. (2007) developed a conceptual model that stressed the important contributions of inland aquatic ecosystems to the global carbon budget. This model considers aquatic ecosystems to be either “active processors” or “passive transporters”, with active processors significantly altering the amount of carbon that is transported to larger downstream ecosystems (Fig. 1). It does not, however, consider processing of other nutrients, nor the links between nutrient cycles that may influence the role of aquatic ecosystems as active processors of multiple elements. Headwater streams are positioned to be an important link between terrestrial ecosystems and large rivers and are in a prime position to act as carbon processing hotspots (Alexander et al. 2000). In addition, studies in Arctic watersheds suggest that under scenarios of increased permafrost thaw, input of labile carbon, nitrogen and phosphorus to headwater streams will significantly increase (Frey and Smith 2005, Bowden et al. 2008). The likely fate of these inputs is not well understood, nor do we know how effectively headwater streams will process them. The objectives of this study were to determine if Arctic headwater streams are active processers of nutrients and DOM and to assess variation across the landscape in the rate of processing of nitrogen (N) and phosphorus (P) inputs. This information is vital to our understanding of potential links between N and P enrichment and DOM processing in low order streams. METHODS We conducted a series of shortterm nutrient addiKon experiments to assess spiraling metrics in 6 streams in the Kolyma River catchment, 3 yedoma streams, and 2 floodplain streams. At each stream, a 50 meter experimental reach chosen; each reach had five crossstream transects placed approximately every 10m. At each transect, background water chemistry was taken, as well as YSI measurements of temperature, dissolved oxygen, pH, and conducKvity. Nutrient spiraling addiKons following protocols described by Payn et al. (2005) and Mulholland et al. (2002) were used to esKmate uptake length (Sw) and uptake rate (U) (Newbold et al. 1981). Biological oxygen demand assays were conducted. AddiKonally, sediments and N/P addiKons were made to determine if BOD increased under enrichment. DISCUSSION The substanKal differences in nutrient uptake between floodplain and yedoma streams indicate potenKal differences in nutrient limitaKon. Similar N and P uptake lengths in the yedoma streams suggest co limita9on, or limita9on by another nutrient, while significantly shorter P uptake lengths in the floodplain streams indicate P limita9on. AlternaKvely, high P uptake in all streams could be explained by high rates of physical sorp9on of phosphorous (Lodg and Stanley 2007). Differences in N uptake would indicate higher overall biological acKvity in yedoma streams (high N uptake) than in floodplain streams (low N uptake). We did not measure P sorpKon in this study, but plan to return to test these alternaKves. Nutrient limitaKon can be used as an indicator of the potenKal for biological processing in these streams. Differences in limitaKon suggest that these streams are biologically disKnct and will respond in different ways to climate change and subsequent nutrient loading. This could affect carbon processing in several ways: If permafrost inputs are mainly C and N dominated, then there will be no funcKonal differences between the streams, despite biological differences. If inputs from permafrost thaw are P rich, then floodplain streams will be more substanKal carbon processors than yedoma streams. If P uptake proves to be primarily physical, then yedoma streams will respond to N enrichment by permafrost thaw and affect instream carbon metabolism more than floodplain streams. Small arc9c headwater streams appear to be ac9ve P processors, but may be passively transpor9ng N to downstream riverine ecosystems. Differences in nutrient limita9on in streams at varying landscape posi9ons could lead to differences in how these streams process increased nutrients and organic maNer inputs from climate change. Acknowledgements First and foremost I would like to thank Professor John Schade and Travis Drake for their help with this research. Many thanks to the staff and participants of the Polaris Project for their assistance, and the Northeast Science Station for the use of their facilities. WORKS CITED Benstead JP, Rosemond AD, Cross WF, Wallace JB, Eggert SL, Suberkropp K, Gulis V, Greenwood JL, Tant CJ. Nutrient enrichment alters storage and fluxes of detritus in a headwater stream ecosystem. 2009. Ecology 90: 2556-2566. Bowden WB, Gooseff MN, Balser A, Green A, Peterson BJ, Bradford J. 2008. Sediment and nutrient delivery from thermokarst features in the foothills of the North Slope, Alaska: Potential impacts on headwater stream ecosystems. Journal of Geophysical Research 113: G02026,DOI:10Ð1029/2007JG000470. Cole et al. 2000. Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget. Ecosystems 10, 171-184. Frey KE, Smith LC. 2005. Amplified carbon release from vast West Siberian peatlands by 2100. Geophysical Research Letters 32: L09401,DOI: 10Ð1029/2004GL022025. Lottig NR, Stanley EH. Benthic sediment influence on dissolved phosphorous concentrations in a headwater stream. 2007. Biochemistry 84: 297-309. Mulholland PJ et al. 2002. Can uptake length in streams be determined by nutrient addition experiments? Results from an interbiome comparison study. Journal of the North American Benthological Society 21: 544-560. Newbold et al. 1981. Measuring nutrient spiraling in streams. Canadian Journal of Fisheries and Aquatic Sciences 38: 860-863. Payn RA, Webster JR, Mulholland PJ, Valett HM, Dodds WK. 2005. Estimation of stream nutrient uptake from nutrient addition experiments. Limnology and Oceanography-Methods 3: 174-182. Sobczak WV, Cloern JE, Jassby AD, Cole BE, Schraga TS, Arnsberg A. 2005. Detritus fuels ecosystem metabolism but not metazoan food webs in San Francisco estuary’s freshwater delta. Estuaries 28: 124-137. Webster JR, Meyer JL. 1997. Stream organic matter budgets. Journal of the North American Benthological Society 16: 3-4. Figure 1. A) Uptake lengths (Sw); B) uptake rates (U); C) S WN :S WP and D) U N :U P in yedoma and floodplain streams. Uptake lengths for N and P were significantly different in the floodplain streams, but not in yedoma streams (Figure 1A, p = 0.003 and 0.54 respectively), suggesting that yedoma streams may be co-limited by N and P, while floodplain streams may be limited by P. Uptake lengths of N and uptake ratios in yedoma streams were significantly different than floodplain streams (S WN , S WN :S WP , U N :U P p value = 0.003, 0.0005, 0.07 respectively) suggesting higher N processing in yedoma streams. Figure 3. Both biological oxygen demand and the amount of bioavailable carbon consumed increased significantly when phosphorous was added to BOD bohle assays, suggesKng P limitaKon (staKsKcs?). C Floodplain Stream #1
Transcript of Assessing’biogeochemical’cycling’of’surface’water’in’Eastern ...Ecology 90: 2556-2566....
Assessing biogeochemical cycling of surface water in Eastern Siberian streams using short-‐term solute addi9ons
Seybold EC, Drake TW, Schade JD, Bulygina K, Bunn A, Chandra S, Davydov S, Frey KE, Holmes RM, Sobczak W, Spektor V, Zimov N, Zimov S INTRODUCTION
Cole et al. (2007) developed a conceptual model that stressed the important contributions of inland aquatic ecosystems to the global carbon budget. This model considers aquatic ecosystems to be either “active processors” or “passive transporters”, with active processors significantly altering the amount of carbon that is transported to larger downstream ecosystems (Fig. 1). It does not, however, consider processing of other nutrients, nor the links between nutrient cycles that may influence the role of aquatic ecosystems as active processors of multiple elements.
Headwater streams are positioned to be an important link between terrestrial ecosystems and large rivers and are in a prime position to act as carbon processing hotspots (Alexander et al. 2000). In addition, studies in Arctic watersheds suggest that under scenarios of increased permafrost thaw, input of labile carbon, nitrogen and phosphorus to headwater streams will significantly increase (Frey and Smith 2005, Bowden et al. 2008). The likely fate of these inputs is not well understood, nor do we know how effectively headwater streams will process them.
The objectives of this study were to determine if Arctic headwater streams are active processers of nutrients and DOM and to assess variation across the landscape in the rate of processing of nitrogen (N) and phosphorus (P) inputs. This information is vital to our understanding of potential links between N and P enrichment and DOM processing in low order streams.
METHODS -‐ We conducted a series of short-‐term nutrient addiKon experiments to assess spiraling metrics in 6 streams in the Kolyma River catchment, 3 yedoma streams, and 2 floodplain streams. -‐ At each stream, a 50 meter experimental reach chosen; each reach had five cross-‐stream transects placed approximately every 10m. -‐ At each transect, background water chemistry was taken, as well as YSI measurements of temperature, dissolved oxygen, pH, and conducKvity. -‐ Nutrient spiraling addiKons following protocols described by Payn et al. (2005) and Mulholland et al. (2002) were used to esKmate uptake length (Sw) and uptake rate (U) (Newbold et al. 1981). -‐ Biological oxygen demand assays were conducted. AddiKonally, sediments and N/P addiKons were made to determine if BOD increased under enrichment.
DISCUSSION The substanKal differences in nutrient uptake between floodplain and yedoma streams indicate potenKal differences in nutrient limitaKon. Similar N and P uptake lengths in the yedoma streams suggest co-‐limita9on, or limita9on by another nutrient, while significantly shorter P uptake lengths in the floodplain streams indicate P limita9on.
AlternaKvely, high P uptake in all streams could be explained by high rates of physical sorp9on of phosphorous (Lodg and Stanley 2007). Differences in N uptake would indicate higher overall biological acKvity in yedoma streams (high N uptake) than in floodplain streams (low N uptake). We did not measure P sorpKon in this study, but plan to return to test these alternaKves.
Nutrient limitaKon can be used as an indicator of the potenKal for biological processing in these streams. Differences in limitaKon suggest that these streams are biologically disKnct and will respond in different ways to climate change and subsequent nutrient loading. This could affect carbon processing in several ways:
-‐ If permafrost inputs are mainly C and N dominated, then there will be no funcKonal differences between the streams, despite biological differences.
-‐ If inputs from permafrost thaw are P rich, then floodplain streams will be more substanKal carbon processors than yedoma streams.
-‐ If P uptake proves to be primarily physical, then yedoma streams will respond to N enrichment by permafrost thaw and affect in-‐stream carbon metabolism more than floodplain streams.
Small arc9c headwater streams appear to be ac9ve P processors, but may be passively transpor9ng N to downstream riverine ecosystems. Differences in nutrient limita9on in streams at varying landscape posi9ons could lead to differences in how these streams process increased nutrients and organic maNer inputs from climate change.
Acknowledgements First and foremost I would like to thank Professor John Schade and Travis Drake for their help with this research. Many thanks to the staff and participants of the Polaris Project for their assistance, and the Northeast Science Station for the use of their facilities.
WORKS CITED Benstead JP, Rosemond AD, Cross WF, Wallace JB, Eggert SL, Suberkropp K, Gulis V, Greenwood JL, Tant CJ. Nutrient enrichment alters storage and fluxes of detritus in a headwater stream ecosystem. 2009. Ecology 90: 2556-2566.
Bowden WB, Gooseff MN, Balser A, Green A, Peterson BJ, Bradford J. 2008. Sediment and nutrient delivery from thermokarst features in the foothills of the North Slope, Alaska: Potential impacts on headwater stream ecosystems. Journal of Geophysical Research 113: G02026,DOI:10Ð1029/2007JG000470.
Cole et al. 2000. Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget. Ecosystems 10, 171-184.
Frey KE, Smith LC. 2005. Amplified carbon release from vast West Siberian peatlands by 2100. Geophysical Research Letters 32: L09401,DOI:10Ð1029/2004GL022025.
Lottig NR, Stanley EH. Benthic sediment influence on dissolved phosphorous concentrations in a headwater stream. 2007. Biochemistry 84: 297-309.
Mulholland PJ et al. 2002. Can uptake length in streams be determined by nutrient addition experiments? Results from an interbiome comparison study. Journal of the North American Benthological Society 21: 544-560.
Newbold et al. 1981. Measuring nutrient spiraling in streams. Canadian Journal of Fisheries and Aquatic Sciences 38: 860-863.
Payn RA, Webster JR, Mulholland PJ, Valett HM, Dodds WK. 2005. Estimation of stream nutrient uptake from nutrient addition experiments. Limnology and Oceanography-Methods 3: 174-182.
Sobczak WV, Cloern JE, Jassby AD, Cole BE, Schraga TS, Arnsberg A. 2005. Detritus fuels ecosystem metabolism but not metazoan food webs in San Francisco estuary’s freshwater delta. Estuaries 28: 124-137.
Webster JR, Meyer JL. 1997. Stream organic matter budgets. Journal of the North American Benthological Society 16: 3-4.
Figure 1. A) Uptake lengths (Sw); B) uptake rates (U); C) SWN:SWP and D) UN:UP in yedoma and floodplain streams. Uptake lengths for N and P were significantly different in the floodplain streams, but not in yedoma streams (Figure 1A, p = 0.003 and 0.54 respectively), suggesting that yedoma streams may be co-limited by N and P, while floodplain streams may be limited by P. Uptake lengths of N and uptake ratios in yedoma streams were significantly different than floodplain streams (SWN, SWN:SWP, UN:UP p value = 0.003, 0.0005, 0.07 respectively) suggesting higher N processing in yedoma streams.
Figure 3. Both biological oxygen demand and the amount of bioavailable carbon consumed increased significantly when phosphorous was added to BOD bohle assays, suggesKng P limitaKon (staKsKcs?).
C
Floodplain Stream #1
