Seasonal variation of bacterial production, respiration and growth efficiency in the open NW Mediterranean Sea

Lemée, Rodolphe; Rochelle‐Newall, Emma; Wambeke, F. Van; Rinaldi, Paula Cristina Natalino

doi:10.3354/ame029227

Cited by 119 publications

(114 citation statements)

References 46 publications

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“…[dFe] [Bonnet and Guieu, 2006], TChla [Marty et al, 2002], BA [Lemée et al, 2002] and DOC [Avril, 2002] .85 nM-eqFe) were of the same order of magnitude as the July value in our study (4.9 nM-eqFe). Seasonal variations of organic speciation have been demonstrated for copper [Croot, 2003] but, to our knowledge, this is the first report of the temporal variability of iron binding ligands at a yearly scale.…”

Section: Temporal Variation Of Iron Binding Ligand Concentrationssupporting

confidence: 67%

Dust iron dissolution in seawater: Results from a one‐year time‐series in the Mediterranean Sea

Wagener¹,

Pulido-Villena²,

Guieu³

2008

Geophysical Research Letters

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[1] A better comprehension of atmospheric iron dissolution in seawater would be a key advance in understanding the atmospheric supply of iron to the ocean and its role on marine biogeochemistry. So far, different studies have demonstrated that dissolution of atmospheric iron depends on physical and chemical properties of the particles, which can be modified during their transport from the source. Here, based on a one-year time-series in the Western Mediterranean Sea, we show that dissolution of iron from a Saharan desert dust sample in seawater follows the seasonal trend of the dissolved organic carbon (DOC) variability in the surface layer. As part of the DOC pool, the role of iron binding ligands, probably derived from bacteria activity, has also been investigated. The dust iron dissolution rates are found to be linearly dependent on iron binding ligands and dissolved organic carbon concentrations (r 2 > 0.65, p < 0.01, n = 9).

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Section: Temporal Variation Of Iron Binding Ligand Concentrationssupporting

confidence: 67%

Dust iron dissolution in seawater: Results from a one‐year time‐series in the Mediterranean Sea

Wagener¹,

Pulido-Villena²,

Guieu³

2008

Geophysical Research Letters

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“…This, however, was not possible in the low-UVR lake, since autotrophic picoplankton and bacteria co-existed in the < 3 µm fraction. Therefore, BCD in this lake was estimated by assuming that BR values lie within two limits: (i) a conservative value of 75 % of TPR, which is an average value based on data reported for oligotrophic waters (Lemeé et al, 2002), and (ii) a potential minimum value of 50 % of TPR (Robinson, 2008), comparable with direct measurements made in this study on the TPR vs. BR in La Caldera (Herrera et al, unpublished data).…”

Section: Analysis Of Biotic Functional Variablessupporting

confidence: 55%

“…It has also been demonstrated that UVR exposure in the upper layers of the water column can increase the proportion of photosynthate released as exudates (Carrillo et al, 2008;Korbee al., 2012), which would stimulate the growth of UVR-resistant bacteria (Xenopoulos and Schindler, 2003) and give rise to a coupled phytoplankton-bacteria relationship in clear oligotrophic lakes . Coupling between phytoplankton and bacterioplankton has been defined as the capacity of the carbon (C) released by phytoplankton to support the bacterial carbon requirement (Morán et al, 2002) and will therefore differ depending on (i) the availability of alternative (allochthonous or autochthonous) carbon sources (Gasol et al, 2009) and (ii) the supply of inorganic nutrients (Medina-Sánchez et al, 2010;López-Sandoval et al, 2011). Although the bacterial dependence on C released by phytoplankton is a well-established paradigm in aquatic microbiology (Cole et al, 1988), it is currently under renewed debate.…”

Section: P Carrillo Et Al: Synergistic Effects Of Uvr and Simulatedmentioning

confidence: 99%

“…Our study offers a quite precise estimate of the BCD, because both HBP and BR were directly measured in the high-UVR lake, due to the absence of size overlap between auto-and heterotrophic organisms. In the low-UVR lake, where segregation between both biological fractions was not feasible, BR was estimated from direct measurements of TPR and the reported percentages of the latter variable accounted for BR (i.e., 50 and 75 %; Lemeé et al, 2002;Robinson, 2008). This procedure brought about a min-max range where the actual BR should safely fall.…”

Section: Uvr and Increased Stratification Effect On The Commensalistimentioning

confidence: 99%

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Synergistic effects of UVR and simulated stratification on commensalistic phytoplankton–bacteria relationship in two optically contrasting oligotrophic Mediterranean lakes

et al. 2015

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Abstract. An indirect effect of global warming is a reduction in the depth of the upper mixed layer (UML) causing organisms to be exposed to higher levels of ultraviolet (UVR, 280-400 nm) and photosynthetically active radiation (PAR, 400-700 nm). This can affect primary and bacterial production as well as the commensalistic phytoplankton-bacteria relationship. The combined effects of UVR and reduction in the depth of the UML were assessed on variables related to the metabolism of phytoplankton and bacteria, during in situ experiments performed with natural pico-and nanoplankton communities from two oligotrophic lakes with contrasting UVR transparency (high-UVR versus low-UVR waters) of southern Spain. The negative UVR effects on epilimnetic primary production (PP) and on heterotrophic bacterial production (HBP), intensified under increased stratification, were higher in the low-UVR than in the high-UVR lake, and stronger on the phytoplanktonic than on the heterotrophic bacterial communities. Under UVR and increased stratification, the commensalistic phytoplankton-bacteria relationship was strengthened in the high-UVR lake where excretion of organic carbon (EOC) rates exceeded the bacterial carbon demand (BCD; i.e., BCD : EOC(%) ratio < 100). This did not occur in the low-UVR lake (i.e., BCD : EOC(%) ratio > 100). The greater UVR damage to phytoplankton and bacteria and the weakening of their commensalistic interaction found in the low-UVR lake indicates that these ecosystems would be especially vulnerable to UVR and increased stratification as stressors related to global climate change. Thus, our findings may have important implications for the carbon cycle in oligotrophic lakes of the Mediterranean region.

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“…On an optimistic note, it should also be stressed that, in spite of all the problems and uncertainties mentioned, we have been able to identify patterns for some of the ecological key variables. As an example, pronounced seasonal dynamics in BP and BGE have been reported (Lemée et al 2002. If the current methods were not methodologically robust, we would not find such consistent patterns.…”

Section: How Accurately Are We Measuring Bacterial Activities?mentioning

confidence: 67%

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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Seasonal variation of bacterial production, respiration and growth efficiency in the open NW Mediterranean Sea

Cited by 119 publications

References 46 publications

Dust iron dissolution in seawater: Results from a one‐year time‐series in the Mediterranean Sea

Dust iron dissolution in seawater: Results from a one‐year time‐series in the Mediterranean Sea

Synergistic effects of UVR and simulated stratification on commensalistic phytoplankton–bacteria relationship in two optically contrasting oligotrophic Mediterranean lakes

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

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