The production of dissolved organic matter by phytoplankton and its importance to bacteria: Patterns across marine and freshwater systems

Baines, Stephen B.; Pace, Michael L.

doi:10.4319/lo.1991.36.6.1078

Cited by 625 publications

(501 citation statements)

References 36 publications

(39 reference statements)

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“…Baines and Pace (1991) reviewed 16 studies and 225 measurements of PER in marine and freshwater systems and found that PER averaged 13% of particulate PP (95% confidence intervals 2-50%). Recently Teira et al (2001) made a comprehensive series of measurements along a productivity gradient off the Spanish Coast, finding PER was a mean of 7% of PP in the coastal upwelling area and 28% in offshore, oligotrophic waters.…”

Section: Discussionmentioning

confidence: 99%

The magnitude of spring bacterial production in the North Atlantic Ocean

Ducklow

Kirchman

Anderson

2002

Limnology & Oceanography

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Dissolved organic carbon (DOC), a major reservoir in the ocean carbon cycle, is produced by a profusion of plankton sources and processes but is consumed mainly by bacterioplankton. Thus bacterial metabolism regulates the entry of DOC into the longer scale global carbon cycle. Bacterial production (BP) is the routinely measured quantity for evaluating the roles of bacteria in carbon cycling. However BP cannot be measured directly and instead is estimated from related metabolic processes requiring the use of poorly constrained conversion factors. BP, and thus the total carbon utilization, are potentially uncertain by a factor of two or more. In the North Atlantic Bloom Experiment (NABE), BP was estimated to be about 30% of the simultaneous particulate primary production (PP), with some daily estimates exceeding 50%. Here we reassess these estimates, synthesizing knowledge and understanding of plankton dynamics gained since the 1989 NABE study. Daily BP derived from six different conversion factors averaged 20% of PP but ranged from 3 to 68%. The coupling of BP to PP was not consistent with either short-term cycling of labile DOC (hours) nor with much longer term cycling of semilabile DOC (seasons). Trophodynamic processes, including release of DOC from phytoplankton, by themselves could have maintained BP at about 15% of PP. Use of decomposing POC or previously accumulated semilabile DOC could each have supported some additional increment of BP for brief periods. Both reconsideration of observations and model results indicated that higher estimates of BP exceeding 20% of PP could not be supported without extraordinary and prolonged inputs of allochthonous carbon. Recent assertions of high BP in the tropics and other oceanic regimes should be considered carefully, especially if external subsidies are not obvious.

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Section: Discussionmentioning

confidence: 99%

The magnitude of spring bacterial production in the North Atlantic Ocean

Ducklow

Kirchman

Anderson

2002

Limnology & Oceanography

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“…As PAR increases (up to a saturating level), biomassspecific rates of photosynthesis will also increase. Extracellular DOC excretion is correlated with increases in particulate primary production or POC production in both marine and freshwater ecosystems (Baines and Pace 1991). Although these broad patterns in DOC excretion rates exist across ecosystem nutrient gradients, mechanistic insights can also be gained by examining the response of extracellular DOC release to changing light availability within a given ecosystem or community.…”

Section: Light-nutrient Interaction Experiments-skaneatelesmentioning

confidence: 99%

Nutrient and light availability regulate the relative contribution of autotrophs and heterotrophs to respiration in freshwater pelagic ecosystems

Roberts

Howarth

2006

Limnol. Oceanogr.

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In this study, two main hypotheses were addressed. (1) Bacteria contribute proportionally less than autotrophs to ecosystem respiration as trophic status increases. This hypothesis was examined in a pond phosphorus-fertilization experiment and two microcosm nutrient-fertilization experiments. (2) The relative contribution of autotrophs to ecosystem respiration, at a given nutrient availability, increases as light availability increases. This hypothesis was tested in three light by nutrient factorial microcosm experiments. Rates of total plankton community, bacterial (Ͻ1 m fraction), and phytoplankton (total Ϫ bacterial) respiration all increased as nutrient availability increased. The contribution of bacteria to community respiration ranged between ϳ10 and 90%, with the highest contribution occurring under the most oligotrophic conditions. As light availability increased within each nutrient availability treatment, there was a similar decline in the contribution of bacteria to community respiration. Under oligotrophic conditions bacteria are better competitors for nutrients that limit both autotrophs and heterotrophs, but as nutrient availability increases, conditions become increasingly favorable for larger celled phytoplankton that have higher maximal nutrient uptake rates. As light availability increases, the relative contribution of phytoplankton to ecosystem respiration also increases. Light and nutrient availability are important regulators of the relative contributions of autotrophs and heterotrophs to ecosystem respiration, but the observed patterns are primarily driven by changes in phytoplankton production rates.

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“…4b and Web Appendix 1). According to Laws (1991), the ratio of GP( 18 O) to gross carbon fixation is 1.1, and about 13% of P( 14 C) are excreted in dissolved organic carbon as DO 14 C (Baines and Pace 1991;Laws et al 2000). This will explain ϳ21% of the 47% difference between GP( 18 O) and P( 14 C).…”

Section: Net Production-inmentioning

confidence: 99%

Evaluation of community respiratory mechanisms with oxygen isotopes: A case study in Lake Kinneret

Luz

Barkan

Sagi

et al. 2002

Limnology & Oceanography

125

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Gross and net O 2 production between May 1996 and February 1999 was determined in bottle incubation experiments with H 2 18 O spike and from the change in O 2 concentration. Carbon fixation rates were obtained from 14 C incubations. In general, production rates determined using the H 2 18 O-spike were about twice the primary production determined by the 14 C method, where the latter was close to net oxygen evolution. These relationships are similar to results for the open ocean. During the spring bloom, when the dinoflagellate Peridinium was abundant, the ratio of gross O 2 production to carbon fixation was about 7.5, and net O 2 production was greater than carbon fixation. The difference between O 2 gross production and carbon fixation results, at least in part, from uptake by Mehler reaction and from recycling of the 14 C tracer by dark respiration and the alternative oxidase (AOX). We used the difference in isotopic discrimination against 18 O, occurring during O 2 consumption by various biological pathways, to place constraints on the relative engagement of these pathways. We estimated the overall discrimination against 18 O in the lake from O 2 isotopic mass balance as 20.5-29‰. The only mechanism that can explain the strong overall fractionation in the lake is AOX, which strongly discriminates against 18 O (ϳ31‰). Our results show, for the first time, that uptake by AOX is widespread and quantitatively important to oxygen consumption in aquatic systems.Oxygen exchange by photosynthesis and respiration is the largest biogeochemical cycle in aquatic systems. In order to understand this cycle, it is necessary to know the gross rates of the major processes involved in oxygen production and uptake. Production of O 2 is known to occur in one process in photosystem II, but O 2 consumption in aquatic organisms is possible by several reactions. These include ordinary respiration through the cytochrome oxidase pathway, respiration by the alternative oxidase pathway, Mehler reaction, and photorespiration. The first two processes take place in light as well as in dark conditions, whereas the latter two occur only under illumination. Although the presence of the above mechanisms has been established in different studies, their quantitative importance in the overall O 2 uptake in aquatic systems is not well known, and it is necessary to assess their role in natural environments. In this respect, ordinary O 2 incubation methods, which are very useful for the assessment of photosynthetic production from light-and dark-incubation experiments (e.g., Williams and Purdie 1991), do not provide the necessary information. The main drawback of these methods is their inability to measure the rate of O 2 AcknowledgmentsWe thank Y. Geiffman and the Mekorot Watershed Unit for provision of wind data and extend special thanks to the Kinneret Limnological Laboratory skipper M. Hatab. We are grateful

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The production of dissolved organic matter by phytoplankton and its importance to bacteria: Patterns across marine and freshwater systems

Cited by 625 publications

References 36 publications

The magnitude of spring bacterial production in the North Atlantic Ocean

The magnitude of spring bacterial production in the North Atlantic Ocean

Nutrient and light availability regulate the relative contribution of autotrophs and heterotrophs to respiration in freshwater pelagic ecosystems

Evaluation of community respiratory mechanisms with oxygen isotopes: A case study in Lake Kinneret

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