Sunlight controls water column processing of carbon in arctic fresh waters

Cory, Rose M.; Ward, Collin P.; Crump, Byron C.; Kling, George W.

doi:10.1126/science.1253119

Cited by 471 publications

(719 citation statements)

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“…Our results supported our initial hypothesis that freshet DOM bioavailability would continually increase throughout the irradiation incubation, and were consistent with prior observations of photodegradation in a range of riverine (e.g., Opsahl and Benner 1998;Moran et al 1999;Spencer et al 2009) and other freshwater (e.g., Bertilsson and Tranvik 2000;Osburn et al 2001;Cory et al 2014) environments.…”

Section: Photoreactivity Of Mackenzie River Freshet Domsupporting

confidence: 80%

“…8b), where an initial sharp increase in SBP also suggested that the surviving bacteria were released from a relative shortage of growth substrate. Increased BP and growth have been observed in the presence of irradiated DOM in many freshwater systems (e.g., Anesio et al 2005;Paul et al 2012), including in the circumpolar Arctic (Cory et al 2013;Ward et al 2017), where photochemical oxidation of DOM accounts for the majority of C processing (Cory et al 2014). Prior work in the Mackenzie Delta has shown that lower molecular weight DOM derived from macrophytes supports higher rates of BGE in communities isolated from a variety of habitats (including TK and CON lakes;Tank 2009).…”

Section: Photoreactivity Of Mackenzie River Freshet Dommentioning

confidence: 99%

“…Heterotrophic grazers subsequently consume bacteria, which shunts otherwise unavailable carbon, organic matter, and energy back into the aquatic food web via the microbial loop (Azam et al 1983). This is a critical process that mobilizes otherwise unavailable DOM molecules in high-latitude aquatic environments (Cole 1999;Cory et al 2014) via bacteria, contributing to overall food web production in Mackenzie Delta lakes (Spears and Lesack 2006;Tank et al 2011), the Mackenzie River (Vallières et al 2008), and the nearshore Beaufort Sea (Garneau et al 2008;Bell et al 2016). Because DOM is an important component of carbon budgets in aquatic ecosystems, an understanding of how photodegradation alters DOM bioavailability is critical to understand carbon fluxes through the landscape.…”

Section: Introductionmentioning

confidence: 99%

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Photodegraded dissolved organic matter from peak freshet river discharge as a substrate for bacterial production in a lake-rich great Arctic delta

Gareis

Lesack

2018

Arctic Science

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Lake-rich Arctic river deltas are recharged with terrigenous dissolved organic matter (DOM) during the yearly peak water period corresponding with the solstice (24 h day −1 solar irradiance). Bacteria-free DOM collected during peak Mackenzie River discharge was exposed to sunlight for up to 14 days in June 2010. As solar exposure increased, carbon and lignin concentrations declined (10% and 42%, respectively, after 14 days), as did DOM absorptivity (62% after 14 days), aromaticity, and molecular weight. Photochemical changes were on par with those normally observed in Mackenzie Delta lakes over the entire open-water season. When irradiated freshet DOM was provided as a substrate, no significant differences were observed in community-level metabolism among five bacterial communities from representative delta habitats. However, bacterial abundance was significantly greater when nonirradiated (0 day) rather than irradiated DOM (7 or 14 days) was provided, while cell-specific metabolic measures revealed that per-cell bacterial production and growth efficiency were significantly greater when communities were provided irradiated substrate. This complex response to rapid DOM photodegradation may result from the production of inhibitory reactive oxygen species (ROS), along with shifts in bacterial community composition to species that are better able to tolerate ROS, or metabolize the labile photodegraded DOM.Key words: circumpolar river delta, photodegradation, dissolved organic matter, bacterial metabolism, Mackenzie River.Résumé : Les deltas arctiques riches en lacs sont rechargés en matière organique dissoute (MOD) terrigène pendant la période annuelle de crue maximale correspondant au solstice (irradiance solaire 24 h jour −1 ). De la MOD sans bactéries collectée durant la pointe de crue du fleuve Mackenzie a été exposée à la lumière du soleil pendant 14 jours en juin 2010. À mesure que l'exposition solaire se prolongeait, les concentrations de carbone et lignine diminuaient (10 % et 42 % respectivement, après 14 jours), tout comme le pouvoir d'absorption de la MOD (62 % après 14 jours), son aromaticité et son poids moléculaire. Les changements photochimiques correspondaient à ceux normalement observés dans les lacs du delta du Mackenzie sur l'ensemble de la saison des eaux libres. Lorsque de la MOD de crue irradiée fut utilisée comme substrat, aucune différence significative n'a été observée quant au métabolisme au niveau de la communauté en comparant cinq communautés bactériennes issues d'habitats représentatifs du delta. Néanmoins, l'abondance de bactéries était considérablement plus grande lorsque de la For personal use only.MOD non irradiée (0 jour) a été fournie au lieu de la MOD irradiée (7 ou 14 jours), tandis que les mesures de l'activité métabolique spécifique aux cellules ont révélé que la production bactérienne par cellule et le rendement de croissance étaient considér-ablement plus élevés lorsque les communautés avaient accès au substrat irradié. Cette réaction complexe à la photodégradation...

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Section: Photoreactivity Of Mackenzie River Freshet Domsupporting

confidence: 80%

Section: Photoreactivity Of Mackenzie River Freshet Dommentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photodegraded dissolved organic matter from peak freshet river discharge as a substrate for bacterial production in a lake-rich great Arctic delta

Gareis

Lesack

2018

Arctic Science

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“…Similar seasonal transformations of DOM NMR resonances have been observed in other lake environments and attributed to microbial degradation 53 . However, photo-oxidation can also be an important pathway of terrestrial DOM removal and modification in some lakes 54 , and in this context it is important to note that UAL in particular, and FLL are periodically ice covered, whereas LT is not, and thus the exposure time of DOM to ultraviolet also differs between these lakes.…”

Section: Discussionmentioning

confidence: 99%

Refractory dissolved organic nitrogen accumulation in high-elevation lakes

et al. 2015

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The role of dissolved organic matter (DOM) as either a sink for inorganic nutrients or an additional nutrient source is an often-neglected component of nutrient budgets in aquatic environments. Here, we examined the role of DOM in reactive nitrogen (N) storage in Sierra Nevada (California, USA) lakes where atmospheric deposition of N has shifted the lakes toward seasonal phosphorus (P)-limitation. Nuclear magnetic resonance (NMR) spectroscopy and isotope analyses performed on DOM isolated from Lake Tahoe reveal the accumulation of refractory proteinaceous material with a 100-200-year residence time. In contrast, smaller lakes in the same watershed contain DOM with typical terrestrial characteristics, indicating that proteins in Lake Tahoe are autochthonously produced. These data support the role of DOM as a possible sink for reactive N in these lake ecosystems and identify a potential role for DOM in affecting the inorganic nutrient stoichiometry of these environments.

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“…Once in the drainage network, it is susceptible to photochemical breakdown (e.g. Köhler et al, 2002;Cory et al, 2014) and may also be utilised as an energy and carbon source by heterotrophic organisms (e.g. Battin et al, 2008).…”

Section: 'On-site' and 'Off-site' Emissionsmentioning

confidence: 99%

The role of waterborne carbon in the greenhouse gas balance of drained and re-wetted peatlands

2015

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Article (refereed) -postprintEvans, Chris D.; Renou-Wilson, Flo; Strack, Maria. 2016. The role of waterborne carbon in the greenhouse gas balance of drained and rewetted peatlands [in special issue: Carbon cycling in aquatic ecosystems] Aquatic Sciences, 78 (3). 573-590. 10.1007/s00027-015-0447-y Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner.The role of waterborne carbon in the greenhouse gas balance of drained and re-wetted peatlands AbstractAccounting for greenhouse gas (GHG) emissions and removals in managed ecosystems has generally focused on direct land-atmosphere fluxes, but in peatlands a significant proportion of total carbon loss occurs via fluvial transport. This study considers the composition of this 'waterborne carbon' flux, its potential contribution to GHG emissions, and the extent to which it may change in response to land-management. The work describes, and builds on, a methodology to account for major components of these emissions developed for the 2013 Wetland Supplement of the Intergovernmental Panel on Climate Change. We identify two major components of GHG emissions from waterbodies draining organic soil: i) 'on site' emissions of methane (and to a lesser extent CO2) from drainage ditches located within the peatland; and ii) 'off site' emissions of CO2 resulting from downstream oxidation of dissolved and particulate organic carbon (DOC and POC) within the aquatic system. Methane emissions from ditches were found to be large in many cases (mean 60 g CH4 m -2 yr -1 based on all reported values), countering the view that methane emissions cease following wetland drainage. Emissions were greatest from ditches in intensive agricultural peatlands, but data were sparse and showed high variability. For DOC, the magnitude of the natural flux varied strongly with latitude, from 5 g C m -2 yr -1 in northern boreal peatlands to 60 g C m -2 yr -1 in tropical peatlands. Available data suggest that DOC fluxes increase by around 60% following drainage, and that this increase may be reversed in the longer-term through re-wetting, although variability between studies was high, especially in relation to re-wetting response. Evidence regarding the fate of DOC is complex and inconclusive, but overall suggests that the majority of DOC exported from peatlands is converted to CO2 through photo-and/or bio-degradation in rivers, standing waters and oceans. The contribution of POC export to GHG emissions is even more uncertain, but we estimate that over half of exported POC may eventually be converted to CO2. Although POC fluxes are normally small, they can become very large when bare peat surfaces are exposed to fluvial erosion. Overall, we estimate that waterborne carbon emissions may contribute about 1 to 4 t CO2-eq ha -1 yr -1 of additional GHG emissions from drained peatlands. For a number of worked examples this repres...

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Sunlight controls water column processing of carbon in arctic fresh waters

Cited by 471 publications

References 52 publications

Photodegraded dissolved organic matter from peak freshet river discharge as a substrate for bacterial production in a lake-rich great Arctic delta

Photodegraded dissolved organic matter from peak freshet river discharge as a substrate for bacterial production in a lake-rich great Arctic delta

Refractory dissolved organic nitrogen accumulation in high-elevation lakes

The role of waterborne carbon in the greenhouse gas balance of drained and re-wetted peatlands

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