Conceptual models for the biogeochemical role of the photic zone microbial food web, with particular reference to the Mediterranean Sea

Thingstad, T. F.; Rassoulzadegan, Fereidoun

doi:10.1016/s0079-6611(99)00029-4

Cited by 99 publications

(88 citation statements)

References 52 publications

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“…deficiency, limitation) is not necessarily readily examined, especially for natural communities of phytoplankton and bacteria. The specific affinity for a substrate is the slope of the specific uptake rate versus a substrate concentration curve, and is analogous to a specific clearance rate, the volume cleared for food (substrate) per unit biomass and unit time (Thingstad and Rassoulzadegan, 1999). Under P-depletion, bacteria and phytoplankton are known to produce alkaline phophatase (AP) which can split phosphate-monoester bonds of organic phosphorus complexes and release phosphate.…”

Section: Introductionmentioning

confidence: 99%

Availability of phosphate for phytoplankton and bacteria and of glucose for bacteria at different pCO2 levels in a mesocosm study

et al. 2008

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Abstract. Availability of phosphate for phytoplankton and bacteria and of glucose for bacteria at different pCO 2 levels were studied in a mesocosm experiment (PeECE III). Using nutrient-depleted SW Norwegian fjord waters, three different levels of pCO 2 (350 µatm: 1×CO 2 ; 700 µatm: 2×CO 2 ; 1050 µatm: 3×CO 2 ) were set up, and nitrate and phosphate were added at the start of the experiment in order to induce a phytoplankton bloom. Despite similar responses of total particulate P concentration and phosphate turnover time at the three different pCO 2 levels, the size distribution of particulate P and 33 PO 4 uptake suggested that phosphate transferred to the >10 µm fraction was greater in the 3×CO 2 mesocosm during the first 6-10 days when phosphate concentration was high. During the period of phosphate depletion (after Day 12), specific phosphate affinity and specific alkaline phosphatase activity (APA) suggested a P-deficiency (i.e. suboptimal phosphate supply) rather than a P-limitation for the phytoplankton and bacterial community at the three different pCO 2 levels. Specific phosphate affinity and specific APA tended to be higher in the 3×CO 2 than in the 2×CO 2 and 1×CO 2 mesocosms during the phosphate depletion period, although no statistical differences were found. Glucose turnover time was correlated significantly and negatively with bacterial abundance and production but not with the bulk DOC concentration. This suggests that even though constituting a small fraction of the bulk DOC, glucose was an important component of labile DOC for bacteria. SpecificCorrespondence to: T. Tanaka (tsuneo.tanaka@univmed.fr) glucose affinity of bacteria behaved similarly at the three different pCO 2 levels with measured specific glucose affinities being consistently much lower than the theoretical maximum predicted from the diffusion-limited model. This suggests that bacterial growth was not severely limited by the glucose availability. Hence, it seems that the lower availability of inorganic nutrients after the phytoplankton bloom reduced the bacterial capacity to consume labile DOC in the upper mixed layer of the stratified mesocosms.

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Section: Introductionmentioning

confidence: 99%

Availability of phosphate for phytoplankton and bacteria and of glucose for bacteria at different pCO2 levels in a mesocosm study

et al. 2008

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“…It has been proposed that primary production (Karl et al 1997;Wu et al 2000;Sañudo-Wilhelmy et al 2001) as well as bacterial production (Thingstad and Rassoulzadegan 1999;Van Wambeke et al 2002) are controlled by the availability of phosphate. There is thus need for a better understanding of the photic P cycle in marine systems.…”

mentioning

confidence: 99%

“…Maximum specific uptake rates (V max ) were calculated by dividing the maximum uptake rates by particulate phosphate concentration; for the Ͼ2-m size fraction, rates were divided by half of the particulate phosphate concentration to take into account P in zooplankton (Thingstad and Rassoulzadegan 1999). Affinity (␣) was calculated from f/(T B)…”

mentioning

confidence: 99%

Does competition for nanomolar phosphate supply explain the predominance of the cyanobacterium Synechococcus?

Moutin¹,

Thingstad²,

Wambeke³

et al. 2002

Limnology & Oceanography

201

112

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Abstract-Experimental work during a cruise along a W-E transect in the Mediterranean Sea suggests that (1) orthophosphate concentrations in the upper photic zone show a decreasing trend from the west to the east reaching levels well below 1 nM and (2) microorganisms in the 0.6-2-m size fraction, probably Synechococcus, have, in addition to high affinity for orthophosphate, significantly higher maximum uptake rates than heterotrophic bacteria or eukaryotic algae. These specific advantages concerning orthophosphate uptake at low (Ͻ5 nM) as well as at relatively high (5-25 nM) concentrations could explain both general Synechococcus abundance in P-depleted environments and transient blooms of this species in the open ocean where episodic orthophosphate nanopulse events are likely to occur.

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“…Our steady state assumptions allow us to disregard predator biomass. However, in a dynamical model, it is imperative to consider explicit population of predators as part of the N and P would be channelled into predator biomass and would remain unavailable to osmotrophs (Thingstad and Rassoulzadegan, 1999). However, considering zooplankton explicitly also required detailed knowledge on their growth rate and stoichiometry.…”

Section: Discussionmentioning

confidence: 99%

“…Saying that bacteria are more competitive than phytoplankton is the same as saying that α β max > α ϕ max . For a spherical cell, and assuming that all the molecules reaching the cell through molecular diffusion are captured, the theoretical expression for α max has also been given by (Thingstad and Rassoulzadegan, 1999):…”

Section: Uptake Of Nutrientsmentioning

confidence: 99%

Accumulation of DOC in Low Phosphate Low Chlorophyll (LPLC) area: is it related to higher production under high N:P ratio?

2011

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Abstract. The biogeochemistry of carbon and nutrients (N,P) in the surface layer of the ocean strongly depends on the complex interactions between primary producers (phytoplankton) and remineralizers (heterotrophic bacteria). To understand how these interactions impact the overall DOC dynamics in the surface layer of the Mediterranean Sea, we implemented, using Eco3M (Ecological Mechanistic Modular Modelling tool), a multi-element model with a mechanistic description of primary production. We studied the model steady state results under various nutrient conditions and fixed cell abundances. By doing so, we show how the bottom up control of osmotrophs growth can impact the overall DOC dynamics in the system. Based on our set of parameters, the biogeochemical characteristics displayed by the model appear realistic when compared to literature data for the Mediterranean basin. Differences in DOC dynamics between N and P limited systems in the model, lead to the conclusion that the unusually high N:P ratio of the Mediterranean Sea may favour the uncoupling between growth and carbon production leading to higher DOC accumulation compared to systems with lower N:P ratio.

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Conceptual models for the biogeochemical role of the photic zone microbial food web, with particular reference to the Mediterranean Sea

Cited by 99 publications

References 52 publications

Availability of phosphate for phytoplankton and bacteria and of glucose for bacteria at different <i>p</i>CO<sub>2</sub> levels in a mesocosm study

Availability of phosphate for phytoplankton and bacteria and of glucose for bacteria at different <i>p</i>CO<sub>2</sub> levels in a mesocosm study

Does competition for nanomolar phosphate supply explain the predominance of the cyanobacterium Synechococcus?

Accumulation of DOC in Low Phosphate Low Chlorophyll (LPLC) area: is it related to higher production under high N:P ratio?

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Conceptual models for the biogeochemical role of the photic zone microbial food web, with particular reference to the Mediterranean Sea

Cited by 99 publications

References 52 publications

Availability of phosphate for phytoplankton and bacteria and of glucose for bacteria at different &lt;i&gt;p&lt;/i&gt;CO&lt;sub&gt;2&lt;/sub&gt; levels in a mesocosm study

Availability of phosphate for phytoplankton and bacteria and of glucose for bacteria at different &lt;i&gt;p&lt;/i&gt;CO&lt;sub&gt;2&lt;/sub&gt; levels in a mesocosm study

Does competition for nanomolar phosphate supply explain the predominance of the cyanobacterium Synechococcus?

Accumulation of DOC in Low Phosphate Low Chlorophyll (LPLC) area: is it related to higher production under high N:P ratio?

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Availability of phosphate for phytoplankton and bacteria and of glucose for bacteria at different <i>p</i>CO<sub>2</sub> levels in a mesocosm study

Availability of phosphate for phytoplankton and bacteria and of glucose for bacteria at different <i>p</i>CO<sub>2</sub> levels in a mesocosm study