The boundless carbon cycle
TL;DR: The terrestrial biosphere is assumed to take up most of the carbon on land, but it is becoming clear that inland waters process large amounts of organic carbon and must be considered in strategies to mitigate climate change as mentioned in this paper.
Abstract: The terrestrial biosphere is assumed to take up most of the carbon on land. However, it is becoming clear that inland waters process large amounts of organic carbon and must be considered in strategies to mitigate climate change.
Citations
More filters
Yale University1, Université libre de Bruxelles2, University of Hamburg3, Uppsala University4, Wisconsin Department of Natural Resources5, United States Geological Survey6, University of Washington7, Stockholm University8, Finnish Environment Institute9, University of Waterloo10, Pierre-and-Marie-Curie University11, United States Naval Academy12
TL;DR: In this article, the authors report regional variations in global inland water surface area, dissolved CO2 and gas transfer velocity, and obtain global CO2 evasion rates of 1.8(-0.25) and 0.52 Pg C yr(-1) from lakes and reservoirs, where the upper and lower limits are respectively the 5th and 95th confidence interval percentiles.
Abstract: Carbon dioxide (CO2) transfer from inland waters to the atmosphere, known as CO2 evasion, is a component of the global carbon cycle. Global estimates of CO2 evasion have been hampered, however, by the lack of a framework for estimating the inland water surface area and gas transfer velocity and by the absence of a global CO2 database. Here we report regional variations in global inland water surface area, dissolved CO2 and gas transfer velocity. We obtain global CO2 evasion rates of 1.8(-0.25)(+0.25) petagrams of carbon (Pg C) per year from streams and rivers and 0.32(-0.26)(+0.52) Pg C yr(-1) from lakes and reservoirs, where the upper and lower limits are respectively the 5th and 95th confidence interval percentiles. The resulting global evasion rate of 2.1 Pg C yr(-1) is higher than previous estimates owing to a larger stream and river evasion rate. Our analysis predicts global hotspots in stream and river evasion, with about 70 per cent of the flux occurring over just 20 per cent of the land surface. The source of inland water CO2 is still not known with certainty and new studies are needed to research the mechanisms controlling CO2 evasion globally.
1,696 citations
TL;DR: The continental GHG sink may be considerably overestimated, and freshwaters need to be recognized as important in the global carbon cycle.
Abstract: Inland waters (lakes, reservoirs, streams, and rivers) are often substantial methane (CH4) sources in the terrestrial landscape. They are, however, not yet well integrated in global greenhouse gas (GHG) budgets. Data from 474 freshwater ecosystems and the most recent global water area estimates indicate that freshwaters emit at least 103 teragrams of CH4 year−1, corresponding to 0.65 petagrams of C as carbon dioxide (CO2) equivalents year−1, offsetting 25% of the estimated land carbon sink. Thus, the continental GHG sink may be considerably overestimated, and freshwaters need to be recognized as important in the global carbon cycle.
1,208 citations
TL;DR: In this paper, the authors use fluorescence spectroscopy to provide a novel approach to understand the dynamics and biogeochemical role of dissolved organic matter (DOM) in aquatic ecosystems.
Abstract: The biochemical composition of dissolved organic matter (DOM) strongly influences its biogeochemical role in freshwater ecosystems, yet DOM composition measurements are not routinely incorporated into ecological studies. To date, the majority of studies of freshwater ecosystems have relied on bulk analyses of dissolved organic carbon and nitrogen to obtain information about DOM cycling. The problem with this approach is that the biogeochemical significance of DOM can only partially be elucidated using bulk analyses alone because bulk measures cannot detect most carbon and nitrogen transformations. Advances in fluorescence spectroscopy provide an alternative to traditional approaches for characterizing aquatic DOM, and allow for the rapid and precise characterization of DOM necessary to more comprehensively trace DOM dynamics. It is within this context that we discuss the use of fluorescence spectroscopy to provide a novel approach to tackling a longstanding problem: understanding the dynamics and biogeochemical role of DOM. We highlight the utility of fluorescence characterization of DOM and provide examples of the potential range of applications for incorporating DOM fluorescence into ecological studies in the hope that this rapidly evolving technique will further our understanding of the biogeochemical role of DOM in freshwater ecosystems.
1,029 citations
Cites background from "The boundless carbon cycle"
...Dissolved organic matter (DOM) is one of the largest sources of biologically available organic carbon in aquatic ecosystems and its dynamics have implications for carbon cycling on local to global scales (Battin et al. 2009)....
[...]
TL;DR: In this paper, it was shown that carbon dioxide discharged to the oceans is only a fraction of that entering rivers from terrestrial ecosystems via soil respiration, leaching, chemical weathering, and physical erosion.
Abstract: Streams, rivers, lakes, and other inland waters are important agents in the coupling of biogeochemical cycles between continents, atmosphere, and oceans. The depiction of these roles in global-scale assessments of carbon (C) and other bioactive elements remains limited, yet recent findings suggest that C discharged to the oceans is only a fraction of that entering rivers from terrestrial ecosystems via soil respiration, leaching, chemical weathering, and physical erosion. Most of this C influx is returned to the atmosphere from inland waters as carbon dioxide (CO2) or buried in sedimentary deposits within impoundments, lakes, floodplains, and other wetlands. Carbon and mineral cycles are coupled by both erosion–deposition processes and chemical weathering, with the latter producing dissolved inorganic C and carbonate buffering capacity that strongly modulate downstream pH, biological production of calcium-carbonate shells, and CO2 outgassing in rivers, estuaries, and coastal zones. Human activities substantially affect all of these processes.
978 citations
References
More filters
01 Jan 2007
TL;DR: The first volume of the IPCC's Fourth Assessment Report as mentioned in this paper was published in 2007 and covers several topics including the extensive range of observations now available for the atmosphere and surface, changes in sea level, assesses the paleoclimatic perspective, climate change causes both natural and anthropogenic, and climate models for projections of global climate.
Abstract: This report is the first volume of the IPCC's Fourth Assessment Report. It covers several topics including the extensive range of observations now available for the atmosphere and surface, changes in sea level, assesses the paleoclimatic perspective, climate change causes both natural and anthropogenic, and climate models for projections of global climate.
32,826 citations
TL;DR: In this paper, the role of inland water ecosystems in the global carbon cycle has been investigated and it is shown that roughly twice as much C enters inland aquatic systems from land as is exported from land to the sea, roughly equally as inorganic and organic carbon.
Abstract: Because freshwater covers such a small fraction of the Earth’s surface area, inland freshwater ecosystems (particularly lakes, rivers, and reservoirs) have rarely been considered as potentially important quantitative components of the carbon cycle at either global or regional scales. By taking published estimates of gas exchange, sediment accumulation, and carbon transport for a variety of aquatic systems, we have constructed a budget for the role of inland water ecosystems in the global carbon cycle. Our analysis conservatively estimates that inland waters annually receive, from a combination of background and anthropogenically altered sources, on the order of 1.9 Pg C y−1 from the terrestrial landscape, of which about 0.2 is buried in aquatic sediments, at least 0.8 (possibly much more) is returned to the atmosphere as gas exchange while the remaining 0.9 Pg y−1 is delivered to the oceans, roughly equally as inorganic and organic carbon. Thus, roughly twice as much C enters inland aquatic systems from land as is exported from land to the sea. Over prolonged time net carbon fluxes in aquatic systems tend to be greater per unit area than in much of the surrounding land. Although their area is small, these freshwater aquatic systems can affect regional C balances. Further, the inclusion of inland, freshwater ecosystems provides useful insight about the storage, oxidation and transport of terrestrial C, and may warrant a revision of how the modern net C sink on land is described.
3,179 citations
TL;DR: The growth rate of atmospheric carbon dioxide (CO2), the largest human contributor to human-induced climate change, is increasing rapidly and three processes contribute to this rapid increase: emissions, global economic activity, carbon intensity of the global economy, and the increase in airborne fraction of CO2 emissions.
Abstract: The growth rate of atmospheric carbon dioxide (CO2), the largest human contributor to human-induced climate change, is increasing rapidly. Three processes contribute to this rapid increase. Two of these processes concern emissions. Recent growth of the world economy combined with an increase in its carbon intensity have led to rapid growth in fossil fuel CO2 emissions since 2000: comparing the 1990s with 2000 –2006, the emissions growth rate increased from 1.3% to 3.3% y 1 . The third process is indicated by increasing evidence (P 0.89) for a long-term (50-year) increase in the airborne fraction (AF) of CO2 emissions, implying a decline in the efficiency of CO2 sinks on land and oceans in absorbing anthropogenic emissions. Since 2000, the contributions of these three factors to the increase in the atmospheric CO2 growth rate have been65 16% from increasing global economic activity, 17 6% from the increasing carbon intensity of the global economy, and 18 15% from the increase in AF. An increasing AF is consistent with results of climate– carbon cycle models, but the magnitude of the observed signal appears larger than that estimated by models. All of these changes characterize a carbon cycle that is generating stronger-than-expected and sooner-than-expected climate forcing. airborne fraction anthropogenic carbon emissions carbon‐climate feedback terrestrial and ocean carbon emissions vulnerabilities of the carbon cycle
2,054 citations
TL;DR: In this article, the authors combine geophysics, microbial ecology and organic geochemistry to show geophysical opportunity and microbial capacity to enhance the net heterotrophy in streams, rivers and estuaries.
Abstract: Rivers may be efficient environments for metabolizing terrestrial organic carbon that was previously thought to be recalcitrant, owing to pockets that provide geophysical opportunities by retaining material for longer, and to the adaptation of microbial communities, which has enabled them to exploit the energy that escapes upstream ecosystems. Metabolism of terrestrial organic carbon in freshwater ecosystems is responsible for a large amount of carbon dioxide outgassing to the atmosphere, in contradiction to the conventional wisdom that terrestrial organic carbon is recalcitrant and contributes little to the support of aquatic metabolism. Here, we combine recent findings from geophysics, microbial ecology and organic geochemistry to show geophysical opportunity and microbial capacity to enhance the net heterotrophy in streams, rivers and estuaries. We identify hydrological storage and retention zones that extend the residence time of organic carbon during downstream transport as geophysical opportunities for microorganisms to develop as attached biofilms or suspended aggregates, and to metabolize organic carbon for energy and growth. We consider fluvial networks as meta-ecosystems to include the acclimation of microbial communities in downstream ecosystems that enable them to exploit energy that escapes from upstream ecosystems, thereby increasing the overall energy utilization at the network level.
1,246 citations