Exogenously produced CO<sub>2</sub>doubles the CO<sub>2</sub>efflux from three north temperate lakes

Wilkinson, Grace M.; Buelo, Cal D.; Cole, Jonathan J.; Pace, Michael L.

doi:10.1002/2016gl067732

Cited by 52 publications

(58 citation statements)

References 44 publications

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“…1). We have previously observed the reference lake to have an early season period of DO %sat near or above 100%, followed by a persistent decline to undersaturation for the remainder of the season (30).…”

Section: Resultsmentioning

confidence: 96%

Reversal of a cyanobacterial bloom in response to early warnings

Pace

Batt

Buelo

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Directional change in environmental drivers sometimes triggers regime shifts in ecosystems. Theory and experiments suggest that regime shifts can be detected in advance, and perhaps averted, by monitoring resilience indicators such as variance and autocorrelation of key ecosystem variables. However, it is uncertain whether management action prompted by a change in resilience indicators can prevent an impending regime shift. We caused a cyanobacterial bloom by gradually enriching an experimental lake while monitoring an unenriched reference lake and a continuously enriched reference lake. When resilience indicators exceeded preset boundaries, nutrient enrichment was stopped in the experimental lake. Concentrations of algal pigments, dissolved oxygen saturation, and pH rapidly declined following cessation of nutrient enrichment and became similar to the unenriched lake, whereas a large bloom occurred in the continuously enriched lake. This outcome suggests that resilience indicators may be useful in management to prevent unwanted regime shifts, at least in some situations. Nonetheless, a safer approach to ecosystem management would build and maintain the resilience of desirable ecosystem conditions, for example, by preventing excessive nutrient input to lakes and reservoirs.

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Section: Resultsmentioning

confidence: 96%

Reversal of a cyanobacterial bloom in response to early warnings

Pace

Batt

Buelo

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…Our experimental results contrast with the significant CO 2 declines observed in five of eight previous whole‐lake nutrient enrichment experiments (Supporting Information Table S4). Stronger CO 2 declines may be due to the larger importance of C uptake by primary producers for the whole‐lake C budget, given that these experiments were carried out in more productive lakes than our systems (Carpenter et al ; Wilkinson et al ) or in seepage lakes with low terrestrial C inputs (Kling et al ; Findlay et al ). A further reason for stronger responses could be that N supply was similar or higher in these previous experiments (> 1.2 mg N m −2 d −1 ) and combined with P addition.…”

Section: Discussionmentioning

confidence: 99%

Weak response of greenhouse gas emissions to whole lake N enrichment

Klaus

Bergström

Jönsson

et al. 2017

Limnology & Oceanography

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Global warming and land use scenarios suggest increased 21st century nitrogen (N) inputs to aquatic systems. Nitrogen affects in‐lake processing and, potentially, atmospheric exchange of greenhouse gases, probably being most relevant in unproductive systems. Here, we test for the first time the effect of a whole‐lake experimental increase (threefold) in external nitrate loads on the atmospheric exchange of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from N‐limited unproductive boreal lakes. Nitrate enrichment effects were assessed within a paired Before/After‐Control/Impact framework based on 2‐hourly to biweekly surface‐water sampling of dissolved gas concentrations, and monthly whole‐lake inventory surveys, carried out over 4 yrs in six lakes. Nitrate enrichment did not affect gas exchange during summer stratification and whole‐lake gas inventories during summer and winter stratification. This finding specifically emphasizes the modest role of internal carbon fixation for the CO2 dynamics of unproductive boreal lakes. A global synthesis of 52 published studies revealed a wide range of nutrient fertilization effects, both in systems similar to our experimental lakes, and other more productive systems. Effects depended mainly on the spatiotemporal scale of the study and became more pronounced when N enrichment was combined with phosphorous. Conclusively, although short‐term and habitat‐specific effects can occur, changes in N supply have only weak whole‐ecosystem effects on greenhouse gas emissions from unproductive boreal lakes.

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“…Even if the DIC budget is complicated by the addition of lime to the lake (see supporting information), our data suggest that the majority of the CO 2 emission was driven by mineralization of OC in the water column and in the sediments (Figure ) [ Chmiel et al ., ]. While this finding is in line with some previous studies [ Jonsson et al ., ; Hanson et al ., ; Kortelainen et al ., ; Sobek et al ., ], it contrasts with other studies that suggested a strong terrestrial DIC supply of lake CO 2 emission [ McDonald et al ., ; Weyhenmeyer et al ., ; Wilkinson et al ., ]. These different observations may be related to regional‐scale differences in, e.g., geology [ Marce et al ., ], climate [ Kosten et al ., ], topography, and land cover [ Sobek et al ., ] affecting both catchment DOC and DIC load and in‐lake processes.…”

Section: Discussionmentioning

confidence: 99%

High terrestrial carbon load via groundwater to a boreal lake dominated by surface water inflow

2017

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The input of dissolved organic and inorganic carbon (DOC and DIC) via direct groundwater seepage to boreal lakes is often assumed to be small in noncarbonaceous areas. However, measurements are rare. We estimated the terrestrial load of DOC, DIC, and methane (CH4) to a small boreal lake for the open water period, on the basis of measured concentrations of carbon species in near‐shore groundwater wells and inlet streams, and measured area‐specific discharge. The subcatchment directly draining into the lake via groundwater seepage contributed 18% to the total water input during the open water season. Compared to stream and lake water, near‐shore groundwater concentrations of DOC were slightly elevated, and groundwater DIC and CH4 concentrations were highly elevated. Consequently, direct groundwater seepage contributed 27% to the total DOC load, 64% to the total DIC load, and 96% to the total CH4 load from the catchment to the lake. Groundwater DIC import corresponded only to 5–8% of lake carbon dioxide (CO2) emission. In incubation experiments, we observed higher photochemical DOC loss rates in stream and groundwater samples (18–55% DOC loss upon 72 h UV‐A exposure) than in lake water (15% DOC loss) and detected significant DOC flocculation in groundwater samples in both light and dark incubations (2–24% DOC loss). We conclude that even in regions where lake hydrology is dominated by surface water inflow via inlet streams, direct groundwater seepage can represent an important carbon source to boreal lakes, and groundwater DOC may be susceptible to in‐lake removal via degradation and flocculation.

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Exogenously produced CO₂doubles the CO₂efflux from three north temperate lakes

Cited by 52 publications

References 44 publications

Reversal of a cyanobacterial bloom in response to early warnings

Reversal of a cyanobacterial bloom in response to early warnings

Weak response of greenhouse gas emissions to whole lake N enrichment

High terrestrial carbon load via groundwater to a boreal lake dominated by surface water inflow

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Exogenously produced CO2doubles the CO2efflux from three north temperate lakes

Cited by 52 publications

References 44 publications

Reversal of a cyanobacterial bloom in response to early warnings

Reversal of a cyanobacterial bloom in response to early warnings

Weak response of greenhouse gas emissions to whole lake N enrichment

High terrestrial carbon load via groundwater to a boreal lake dominated by surface water inflow

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Exogenously produced CO₂doubles the CO₂efflux from three north temperate lakes