Patterns in Dissolved Organic Matter Lability and Consumption across Aquatic Ecosystems

Giorgio, Paul A. del; Davis, Jeanette

doi:10.1016/b978-012256371-3/50018-4

Cited by 131 publications

(125 citation statements)

References 69 publications

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“…BGE can also be measured in so-called DOC-degradation experiments (del Giorgio & Davis 2003), where the decrease in DOC is compared to the increase in POC (or bacterial biomass). These are often called 'long-term' BGE determination experiments, compared to the 'short-term' (i.e.…”

Section: How Accurately Are We Measuring Bacterial Activities?mentioning

confidence: 99%

Towards a better understanding of microbial carbon flux in the sea*

Gasol¹,

Pinhassi²,

Alonso‐Sáez³

et al. 2008

Aquat. Microb. Ecol.

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We now have a relatively good idea of how bulk microbial processes shape the cycling of organic matter and nutrients in the sea. The advent of the molecular biology era in microbial ecology has resulted in advanced knowledge about the diversity of marine microorganisms, suggesting that we might have reached a high level of understanding of carbon fluxes in the oceans. However, it is becoming increasingly clear that there are large gaps in the understanding of the role of bacteria in regulating carbon fluxes. These gaps may result from methodological as well as conceptual limitations. For example, should bacterial production be measured in the light? Can bacterial production conversion factors be predicted, and how are they affected by loss of tracers through respiration? Is it true that respiration is relatively constant compared to production? How can accurate measures of bacterial growth efficiency be obtained? In this paper, we discuss whether such questions could (or should) be addressed. Ongoing genome analyses are rapidly widening our understanding of possible metabolic pathways and cellular adaptations used by marine bacteria in their quest for resources and struggle for survival (e.g. utilization of light, acquisition of nutrients, predator avoidance, etc.). Further, analyses of the identity of bacteria using molecular markers (e.g. subgroups of Bacteria and Archaea) combined with activity tracers might bring knowledge to a higher level. Since bacterial growth (and thereby consumption of DOC and inorganic nutrients) is likely regulated differently in different bacteria, it will be critical to learn about the life strategies of the key bacterial species to achieve a comprehensive understanding of bacterial regulation of C fluxes. Finally, some processes known to occur in the microbial food web are hardly ever characterized and are not represented in current food web models. We discuss these issues and offer specific comments and advice for future research agendas.

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Section: How Accurately Are We Measuring Bacterial Activities?mentioning

confidence: 99%

Towards a better understanding of microbial carbon flux in the sea*

Gasol¹,

Pinhassi²,

Alonso‐Sáez³

et al. 2008

Aquat. Microb. Ecol.

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show abstract

“…Bioavailability has traditionally been linked to the chemical composition and structure of DOC, but more recently it has been shown to also vary depending on a range of other external factors (Raymond and Spencer, 2015). These factors include nutrient status, redox state, mineral-particle associations, terrestrial inputs, sunlight, biological production of recalcitrant compounds, changing microbial community composition, and the effect of priming or the extreme dilution of individual molecules (e.g., Amon and Benner, 1996;Thingstad et al, 1999;Del-Giorgio and Davies, 2003;Bianchi, 2011;Keil and Mayer, 2014;Arrieta et al, 2015;. About 4% of the ocean's net primary production escapes degradation in the surface layer to be exported as DOC to the ocean interior at a rate of about 2 Pg C year −1 (Hansell et al, 2012), roughly equalling the annual net ocean uptake of CO 2 (Sarmiento and Gruber, 2006).…”

Section: Introductionmentioning

confidence: 99%

Large Stimulation of Recalcitrant Dissolved Organic Carbon Degradation by Increasing Ocean Temperatures

et al. 2018

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More than 96% of organic carbon in the ocean is in the dissolved form, most of it with lifetimes of decades to millennia. Yet, we know very little about the temperature sensitivity of dissolved organic carbon (DOC) degradation in a warming ocean. Combining independent estimates from laboratory experiments, oceanographic cruises and a global ocean DOC cycling model, we assess the relationship between DOC decay constants and seawater temperatures. Our results show that the apparent activation energy of DOC decay (E a ) increases by three-fold from the labile (lifetime of days) and semi-labile (lifetime of months) to the semi-refractory (lifetime of decades) DOC pools, with only minor differences between the world's largest ocean basins. This translates into increasing temperature coefficients (Q 10 ) from 1.7-1.8 to 4-8, showing that the generalized assumption of a constant Q 10 of ∼2 for biological rates is not universally applicable for the microbial degradation of DOC in the ocean. Therefore, rising ocean temperatures will preferentially impact the microbial degradation of the more recalcitrant and larger of the three studied pools. Assuming a uniform 1 • C warming scenario throughout the ocean, our model predicts a global decrease of the DOC reservoir by 7 ± 1 Pg C. This represents a 15% reduction of the semi-labile + semi-refractory DOC pools.

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“…Terrestrial mobilization and riverine processing of DOC have been studied over a wide range of climate zones (del Giorgio and Davis, 2003), but less is known about the fate of POC associated with suspended and deposited sediments in inland waters and floodplains. The long-held assumption that POC is a minor component of aquatic organic C is based on observations of large rivers, as exemplified by the high ratios of DOC to total organic carbon (TOC) between 0.6 and 0.8 found in lowland rivers (Meybeck, 1982).…”

Section: Introductionmentioning

confidence: 99%

Export, biodegradation, and disinfection byproduct formation of dissolved and particulate organic carbon in a forested headwater stream during extreme rainfall events

et al. 2014

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Abstract.Despite an increasing recognition of the importance of extreme rainfall events for organic carbon export to inland waters, little attention has been paid to the export and reactivity of particulate organic carbon (POC) and dissolved organic C (DOC) in mountainous headwater watersheds under monsoon climates. To investigate environmental implications of storm-enhanced export of POC and DOC in mountainous headwater streams, we examined the relationships between storm magnitude and C export from a forested watershed in the Haean Basin, South Korea, during 13 storm events over 4 years and compared potentials of DOC and POC for biodegradation and disinfection byproduct (DBP) formation during an extreme rainfall event with a total rainfall of 209 mm. Event mean concentrations and export of POC increased nonlinearly above thresholds of precipitation and discharge, far exceeding the relatively small increases of DOC. The export of POC during a few storm events with a total rainfall above 200 mm per event exceeded the annual organic C export during dry years. During the 209 mm storm event, concentrations of total trihalomethanes formed by POC-derived dissolved components changed synchronously with POC concentrations, exhibiting lower levels than those formed by DOC. During a 30-day incubation at 25 • C, DOC exported during peak flow exhibited rapid biodegradation of labile components within 7 days. In contrast, the concentrations of DOC leached from POC gradually increased following the initial decline. Gradual transformation of POCderived dissolved materials resulted in greater increases in the intensity of fulvic-and humic-like fluorescent components compared to the DOC treatment. The results highlight the significance of extreme rainfall events as "hot moments" for POC export from mountainous watersheds and also suggest that storm pulses of POC can provide potential sources of reactive organic components that can rapidly biodegrade and form DBPs after being released into headwater streams.

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Patterns in Dissolved Organic Matter Lability and Consumption across Aquatic Ecosystems

Cited by 131 publications

References 69 publications

Towards a better understanding of microbial carbon flux in the sea*

Towards a better understanding of microbial carbon flux in the sea*

Large Stimulation of Recalcitrant Dissolved Organic Carbon Degradation by Increasing Ocean Temperatures

Export, biodegradation, and disinfection byproduct formation of dissolved and particulate organic carbon in a forested headwater stream during extreme rainfall events

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