Recycling versus export of bioavailable dissolved organic matter in the coastal ocean and efficiency of the continental shelf pump

Lønborg, Christian; Álvarez‐Salgado, Xosé Antón

doi:10.1029/2012gb004353

Cited by 94 publications

(82 citation statements)

References 102 publications

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“…DOP was highest in the coastal ecosystems (Table 2), with seasonal differences in some regions (Supplementary Figure 14). The average C:N:P stoichiometry of the DOM pool was 367:49:1, which was higher than the Redfield ratio but comparable with ratios reported for coastal waters worldwide (Lønborg and Álvarez-Salgado, 2012). Table 1).…”

Section: Environmental Conditionssupporting

confidence: 82%

“…Differences in GPP:CR ratios can be caused by differences in (1) light and nutrient availability; (2) food web organization; (3) changes in phytoplankton community structure and cell sizes; and/or (4) bioavailability of the organic matter pool which varies over both seasonal and spatial scales (Mallin and Paerl, 1992;Lønborg and Álvarez-Salgado, 2012;Marañón, 2015). Due to our current limited understanding of plankton community composition and the supply mechanisms of nutrients and organic matter in these waters means it is difficult to account for the main driving force of the variable GPP: CR ratio.…”

Section: Discussionmentioning

confidence: 99%

“…These differences could be due to differences in methodology or to spatio-temporal variation in metabolic balance. Spatio-temporal variation has been attributed to factors such as (1) changes in environmental conditions (e.g., temperature: Regaudie-de-Gioux and Duarte, 2012); (2) differences in the input and composition of nutrients (Martínez-García et al, 2010); (3) changes in plankton abundance and productivity of primary producers (Gasol and Duarte, 2000); (4) variation in the phytoplankton size structure and growth rate (Marañón, 2015); and (5) the amount and reactivity of the locally produced (autochthonous) and imported (allochthonous) organic matter (e.g., Serret et al, 1999;Robinson et al, 2002;Lønborg and Álvarez-Salgado, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Plankton Respiration, Production, and Trophic State in Tropical Coastal and Shelf Waters Adjacent to Northern Australia

et al. 2017

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In a changing ocean, tropical waters can be instructive as to the potential effects of climate induced changes on marine ecosystem structure and function. We describe the relationships between planktonic community respiration (CR), net community production (NCP), gross primary production (GPP), and environmental variables in 14 regions and three ecosystem types (coastal, coral reef, and open sea) from Australia, Papua New Guinea, and Indonesia. The data are compiled from separate studies conducted between 2002 and 2014 with the goal of better parameterizing the metabolic balance in tropical marine waters. Overall, these regions were strongly autotrophic (average GPP:CR ratio: 2.14 ± 0.98), though our dataset of 783 paired measurements did include some oceanic stations where heterotrophy (GPP:CR < 1) was predominant, and some coastal stations that were intermittently heterotrophic. Our statistical analysis suggested that temperature was the most important determinant of CR in coral reef and ocean ecosystems but less so in coastal ecosystems, where chlorophyll concentration was more important. In contrast, chlorophyll and sampling depth were more important in regulating GPP than temperature. The relationships between temperatures and metabolic rates showed that these were ecosystem-dependent, with coastal ecosystems showing less response to temperature than coral reef and open sea sites. The threshold of GPP to achieve metabolic balance fell in a range between 0.715 mmol O 2 m −3 d −1 in the Coral Sea to 10.052 mmol O 2 m −3 d −1 in mangrove waterways of Hinchinbrook Channel. These data allow regions in and around northern Australia to be ranked in terms of trophic state, ranging from the oligotrophic Scott Reef (GPP:CR = 0.84 ± 0.08) to productive surface waters of the Kimberley coast (GPP:CR = 5.21 ± 0.62). The measurement of pelagic metabolism shows potential as a quantitative tool to monitor the trophic state of coastal waters.

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Section: Environmental Conditionssupporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Plankton Respiration, Production, and Trophic State in Tropical Coastal and Shelf Waters Adjacent to Northern Australia

et al. 2017

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“…The main processes responsible for the removal of DOC from the ocean water column are: (1) photochemistry, where DOC is degraded directly to CO 2 , carbon monoxide (CO) or low molecular weight organic compounds readily available for prokaryote uptake (Moran and Zepp, 1997;Mopper et al, 2015); (2) abiotic aggregation into microparticles (Kerner et al, 2003) or sorption to particles (Chin et al, 1998); (3) abiotic degradation via free radical reactions with oxygen (Rontani et al, 2014); and (4) degradation by marine heterotrophic prokaryotes (Lønborg and Álvarez-Salgado, 2012), with the latter representing the major DOC sink in the ocean .…”

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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“…These long-term assays have not been based on growth, but on changes in bulk nutrient concentrations in solution (Lonborg and Anton Alvarez-Salgado, 2012). However, during long incubation periods various factors can interfere with the uptake of bioavailable resources, such as the dynamics of viruses and the development of toxic conditions that may arise from repeated bacterial regeneration of resources (Cho et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

New insights on resource stoichiometry: assessing availability of carbon, nitrogen, and phosphorus to bacterioplankton

et al. 2017

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Abstract. Boreal lake and river ecosystems receive large quantities of organic nutrients and carbon (C) from their catchments. How bacterioplankton respond to these inputs is not well understood, in part because we base our understanding and predictions on "total pools", yet we know little about the stoichiometry of bioavailable elements within organic matter. We designed bioassays with the purpose of exhausting the pools of readily bioavailable dissolved organic carbon (BDOC), bioavailable dissolved nitrogen (BDN), and bioavailable dissolved phosphorus (BDP) as fast as possible. Applying the method in four boreal lakes at base-flow conditions yielded concentrations of bioavailable resources in the range 105-693 µg C L −1 for BDOC (2 % of initial total DOC), 24-288 µg N L −1 for BDN (31 % of initial total dissolved nitrogen), and 0.2-17 µg P L −1 for BDP (49 % of initial total dissolved phosphorus). Thus, relative bioavailability increased from carbon (C) to nitrogen (N) to phosphorus (P). We show that the main fraction of bioavailable nutrients is organic, representing 80 % of BDN and 61 % of BDP. In addition, we demonstrate that total C : N and C : P ratios are as much as 13-fold higher than C : N and C : P ratios for bioavailable resource fractions. Further, by applying additional bioavailability measurements to seven widely distributed rivers, we provide support for a general pattern of relatively high bioavailability of P and N in relation to C. Altogether, our findings underscore the poor availability of C for support of bacterial metabolism in boreal C-rich freshwaters, and suggest that these ecosystems are very sensitive to increased input of bioavailable DOC.

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Recycling versus export of bioavailable dissolved organic matter in the coastal ocean and efficiency of the continental shelf pump

Cited by 94 publications

References 102 publications

Plankton Respiration, Production, and Trophic State in Tropical Coastal and Shelf Waters Adjacent to Northern Australia

Plankton Respiration, Production, and Trophic State in Tropical Coastal and Shelf Waters Adjacent to Northern Australia

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

New insights on resource stoichiometry: assessing availability of carbon, nitrogen, and phosphorus to bacterioplankton

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