Rates of dissolved organic carbon production and bacterial activity in the eastern North Atlantic Subtropical Gyre during summer

Teira, Eva; Pazó, M. J.; Quevedo, Mario; Fuentes, M. V.; Niell, F. Xavier; Fernández, Emilio

doi:10.3354/meps249053

Cited by 44 publications

(36 citation statements)

References 85 publications

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“…A gradient in phytoplankton productivity and community structure from the African upwelling region to the oligotrophic region offshore has been previously reported for the subtropical NE Atlantic (Teira et al, 2003;Pelegrí et al, 2005;Alonso-Laíta and Agustí, 2006), including an increase in phytoplankton mortality rates and the proportion of dead phytoplankton cells along this gradient (Agustí et al, 2001;Alonso-Laíta and Agustí, 2006). The results presented here confirm these findings, with phytoplankton cell viability decreasing from upwelling-influenced waters to oligotrophic waters, particularly for diatoms, which showed a two-fold reduction in the percentage of living cells from the upwelling to the oligotrophic waters.…”

Section: Discussionmentioning

confidence: 99%

“…Phytoplankton cell death results in cell lysis (Brussaard et al, 1995;Agustí et al, 1998;Agustí and Duarte, 2000) and would lead to the release of incorporated carbon compounds. Veldhuis et al (2001) reported that senescent or dying cells, meaning those with a reduced viability (increased membrane permeability), still photosynthesized, although photosynthetic activity dropped by as much as 60 % relative to that of the viable cells. Recent studies, exploring the release of DOC by phytoplankton Lasternas et al, 2013), provided evidence that increasing phytoplankton mortality in oligotrophic waters led to increasing DOCp among senescent or dying natural populations and thus accounts for a large fraction of the photosynthetic carbon channeled through bacteria characteristic of oligotrophic marine communities.…”

Section: Introductionmentioning

confidence: 99%

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The percentage of living bacterial cells related to organic carbon release from senescent oceanic phytoplankton

Lasternas

Agustı́

2014

Biogeosciences

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Abstract. Bacteria recycle vast amounts of organic carbon, playing key biogeochemical and ecological roles in the ocean. Bacterioplankton dynamics are expected to be dependent on phytoplankton primary production, but there is a high diversity of processes (e.g., sloppy feeding, cell exudation, viral lysis) involved in the transfer of primary production to dissolved organic carbon available to bacteria. Here, we show the percentage of living heterotrophic bacterioplankton in the subtropical NE Atlantic Ocean in relation to phytoplankton extracellular carbon release (PER). PER represents the fraction of primary production released as dissolved organic carbon. PER variability was explained by phytoplankton cell death, with communities experiencing higher phytoplankton cell mortality showing a larger proportion of phytoplankton extracellular carbon release. Both PER and the percentage of dead phytoplankton cells increased from eutrophic to oligotrophic waters, while abundance of heterotrophic bacteria was highest in the intermediate waters. The percentage of living heterotrophic bacterial cells (range: 60-95 %) increased with increasing phytoplankton extracellular carbon release from productive to oligotrophic waters in the subtropical NE Atlantic. The lower PERs, observed at the upwelling waters, have resulted in a decrease in the flux of phytoplankton dissolved organic carbon (DOC) per bacterial cell. The results highlight phytoplankton cell death as a process influencing the flow of dissolved photosynthetic carbon in this region of the subtropical NE Atlantic Ocean, and suggest a close coupling between the fraction of primary production released and heterotrophic bacterial cell survival.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The percentage of living bacterial cells related to organic carbon release from senescent oceanic phytoplankton

Lasternas

Agustı́

2014

Biogeosciences

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“…The median value of BGE in the coastal ocean is 0.16 (0.19 ± 0.16; mean ± SD) compared with 0.08 (0.14 ± 0.14) in the open ocean (Robinson, 2008). Therefore, although PER in oligotrophic waters is relatively high, the DOC released by phytoplankton is generally insufficient to support bacterial growth (Teira et al, 2003b;López-Sandoval, 2011). This is probably because the nutrient limitation that drives the photosynthetic overflow of organic carbon into the DOC pool also limits the ability of bacteria to utilize the DOC pool.…”

Section: Dom Release and Microbial Food Websmentioning

confidence: 96%

“…Baines & Pace (1991) concluded that the DOC released by phytoplankton supports less than 50% of bacterial carbon requirements, based on a review of data from freshwater, estuarine and coastal environments, and modelling. Recent work has challenged this general assumption: DOC released by phytoplankton is sufficient to support the observed bacterial growth in the Southern Ocean (Morán et al, , 2002bMorán & Estrada, 2002) and in an area of coastal upwelling off the Iberian Peninsula in the Atlantic (Teira et al, 2003b).…”

Section: Dom Release and Microbial Food Websmentioning

confidence: 99%

“…The release of DOM by phytoplankton is a significant driver of secondary production by heterotrophic prokaryotes. Generally, DOM release by phytoplankton is considered insufficient to support the observed heterotrophic bacterial growth (Baines & Pace, 1991;Nagata, 2000;Morán et al, 2002b;Teira et al, 2003b). In addition, processes such as viral lysis and sloppy feeding contribute a significant amount of the phytoplankton DOM that is utilized by bacteria.…”

Section: Dom Release and Microbial Food Websmentioning

confidence: 99%

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Dissolved organic matter (DOM) release by phytoplankton in the contemporary and future ocean

Thornton

2014

European Journal of Phycology

365

311

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The partitioning of organic matter (OM) between dissolved and particulate phases is an important factor in determining the fate of organic carbon in the ocean. Dissolved organic matter (DOM) release by phytoplankton is a ubiquitous process, resulting in 2-50% of the carbon fixed by photosynthesis leaving the cell. This loss can be divided into two components: passive leakage by diffusion across the cell membrane and the active exudation of DOM into the surrounding environment. At present there is no method to distinguish whether DOM is released via leakage or exudation. Most explanations for exudation remain hypothetical; as while DOM release has been measured extensively, there has been relatively little work to determine why DOM is released. Further research is needed to determine the composition of the DOM released by phytoplankton and to link composition to phytoplankton physiological status and environmental conditions. For example, the causes and physiology of phytoplankton cell death are poorly understood, though cell death increases membrane permeability and presumably DOM release. Recent work has shown that phytoplankton interactions with bacteria are important in determining both the amount and composition of the DOM released. In response to increasing CO 2 in the atmosphere, climate change is creating increasingly stressful conditions for phytoplankton in the surface ocean, including relatively warm water, low pH, low nutrient supply and high light. As ocean physics and chemistry change, it is hypothesized that a greater proportion of primary production will be released directly by phytoplankton into the water as DOM. Changes in the partitioning of primary production between the dissolved and particulate phases will have bottom-up effects on ecosystem structure and function. There is a need for research to determine how these changes affect the fate of organic matter in the ocean, particularly the efficiency of the biological carbon pump.

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Spatial and seasonal variability of dissolved organic matter in the Cariaco Basin

et al. 2013

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[1] Dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) were measured monthly at the CARIACO Time Series station (10 30 0 N, 64 40 0 W) in the southeastern Caribbean Sea between 2005 and 2012. Marked seasonal variability in DOC concentrations was observed, with lower values (~66 mM) in the upper water column (<75 m) during the upwelling season (December-April) due to the injection of cool, DOC-impoverished Subtropical Underwater from the Caribbean Sea. During the rainy season (May-November) waters were stratified and upper layer DOC concentrations increased to~71 mM. Interannual variability in surface (1 m) concentrations of DOC was also observed in response to the variable strength in upwelling and stratification that the Cariaco Basin experienced. DON and DOP showed no such seasonality. At depths >350 m, DOC concentrations were 56 AE 4.7 mM, roughly 10 mM higher than those in the Caribbean Sea over the same depth range. DON and DOP showed similar vertical profiles to that of DOC, with higher concentrations (6.8 AE 1.2 mM N and 0.15 AE0.09 mM P) in the upper water column and invariant, lower concentrations at depth (4.8 AE 1.6 mM N and 0.10 AE 0.08 mM P). Wind-driven advection of surface DOC out of the Cariaco Basin was estimated to support a net export~15 Gmol C yr À1 into the Caribbean Sea; this rate is comparable to the flux of settling particulate organic carbon to depths >275 m within the basin.

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Rates of dissolved organic carbon production and bacterial activity in the eastern North Atlantic Subtropical Gyre during summer

Cited by 44 publications

References 85 publications

The percentage of living bacterial cells related to organic carbon release from senescent oceanic phytoplankton

The percentage of living bacterial cells related to organic carbon release from senescent oceanic phytoplankton

Dissolved organic matter (DOM) release by phytoplankton in the contemporary and future ocean

Spatial and seasonal variability of dissolved organic matter in the Cariaco Basin

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