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

Roberts, Brian J.; Howarth, Robert W.

doi:10.4319/lo.2006.51.1.0288

Cited by 30 publications

(36 citation statements)

References 56 publications

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“…Total respiration tends to increase with lake trophy, and respiration by autotrophs becomes an increasing part of total respiration as lakes become more eutrophic (del Giorgio and Peters, 1993;Biddanda et al, 2001;Roberts and Howarth, 2006). A literature review by del Giorgio and Peters (1993) suggests that autotrophic respiration may contribute 35% in oligotrophic systems and over 60% in eutrophic systems.…”

Section: Sensitivity Analysismentioning

confidence: 99%

Phosphorus sources and demand during summer in a eutrophic lake

et al. 2009

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In pelagic systems, phytoplankton biomass may remain abundant or near equilibrium while concentrations of the limiting nutrient are below detection. In eutrophic lakes, it has been thought that episodic algal blooms are due to mixing events that break down this equilibrium by adding nutrients to the mixed layer. Alternatively, rapid rates of biotic recycling among primary producers and heterotrophic consumers could maintain high phytoplankton biomass, yet the recycling process has been difficult to observe in situ. Here we use free-water oxygen measurements and an associated metabolic model to infer rates of phosphorus (P) uptake and biotic mineralization in the epilimnion of a eutrophic lake. The rates of uptake and mineralization were compared to "external" sources of P such as loading and entrainment. Also, model results were assessed using sensitivity analysis. We found that the majority of phytoplankton P demand during the period of low P availability could be accounted for by biotic mineralization, but that it was important to consider the effects of entrainment in order to account fully for P uptake. These general results were relatively insensitive to model parameterization, though the relative C:P ratio of material taken up versus mineralized was an important consideration. This study integrates modeling and measurement tools that monitor ecosystem processes at finer temporal resolution than has previously been possible, complementing other studies that use experimental incubation and elemental tracers. Extension of this approach could enhance models that aim to integrate biological and physical processes in assessment of water quality and prediction of phytoplankton biomass.

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Section: Sensitivity Analysismentioning

confidence: 99%

Phosphorus sources and demand during summer in a eutrophic lake

et al. 2009

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“…Several studies have indicated that the contribution to community respiration of bacteria relative to phytoplankton decreases with increasing nutrient availability because of increases in phytoplankton respiration (Biddanda et al 2001, Chan et al 2004). Furthermore, Roberts & Howarth (2006) found that the bacterial contribution to respiration is lower when light availability for photosynthesis increases. According to the results of nutrient addition experiments performed by Roberts & Howarth (2006), the variability patterns of community respiration following nutrient enrichment are related to the higher metabolic needs of phytoplankton growing actively, while bacterial respiration remains more stable.…”

Section: Changes In Bacterial Metabolism and Plankton Community Respimentioning

confidence: 99%

“…Furthermore, Roberts & Howarth (2006) found that the bacterial contribution to respiration is lower when light availability for photosynthesis increases. According to the results of nutrient addition experiments performed by Roberts & Howarth (2006), the variability patterns of community respiration following nutrient enrichment are related to the higher metabolic needs of phytoplankton growing actively, while bacterial respiration remains more stable. In our experiments, the main factor contributing to variability of RR was light (Table 1), supporting the hypothesis that the changes in RR were related to changes in phytoplankton respiration (direct effects of irradiance level on bacterial respiration can be discarded).…”

Section: Changes In Bacterial Metabolism and Plankton Community Respimentioning

confidence: 99%

Effect of CO2, nutrients and light on coastal plankton. II. Metabolic rates

Mercado¹,

Sobrino²,

Neale³

et al. 2014

Aquat. Biol.

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photosynthetic organisms and the subsequent sinking of POC which is sequestered in deep waters (the so-called biological pump) are 2 of the main organism-mediated processes that are involved in this CO 2 sink effect. In pelagic ecosystems, a large proportion of the POC produced by the phytoplankton is re - ABSTRACT: We conducted a microcosm experiment aimed at studying the interactive effects of high CO 2 , nutrient loading and irradiance on the metabolism of a planktonic community sampled in the Western Mediterranean near the coast of Málaga. Changes in the metabolism of phytoplankton and bacterioplankton were observed for 7 d under 8 treatment conditions, representing the full factorial combinations of 2 levels each of CO 2 , nutrient concentration and solar radiation exposure. The initial plankton sample was collected at the surface from a stratified water column, indicating that phytoplankton were naturally acclimated to high irradiance and low nutrient concentrations. Nutrient addition combined with high irradiance resulted in a significant increase in primary production. Nitrate uptake by phytoplankton was also stimulated under high nutrient conditions. High nutrients, high irradiance and the combination of low CO 2 and high irradiance positively affected bacterial production. Light was the main factor affecting the respiration rates of the community, which were higher at the high light level. After 7 d of incubation, nutrient loading was the only factor that significantly affected the amount of particulate organic carbon (POC) accumulated in the microcosms. Therefore, the changes in metabolic rates produced at high CO 2 had no effect on net production of particulate organic matter. If these results are extrapolated to the natural environment, it could be hypothesized that high levels of CO 2 will have a limited impact on biological pump activity in the northern Alboran Sea since it is assumed that POC export towards deeper layers determines the potential for carbon sequestration.

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“…Such a change in light climate is of great importance to the local ecosystem. Light availability has recently been pointed out as the main controlling factor of the relative contribution of the phytoplankton and bacteria on total community respiration (Roberts and Howarth 2006). While bacterial respiration rates remain roughly constant under differing light conditions, increased light intensity can increase the respiration rates of the phytoplankton to over 90% of the total planktonic respiration (Roberts and Howarth 2006).…”

Section: Discussionmentioning

confidence: 99%

Dissolved oxygen response to wind‐inflow interactions in a stratified reservoir

Botelho

Imberger

2007

Limnology & Oceanography

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Results of a field campaign and numerical simulations are used to show how physical mechanisms impose length scales and timescales that determine the dominant biogeochemical process. As an example, the dynamics of the Snake River inflows into Brownlee Reservoir is investigated to explain the onset and maintenance of an oxygen-depleted region (the oxygen block) in the surface layer of the upstream part of the reservoir. The oxygen block was located in a region of the reservoir in which the surface layer was warmer as a result of smaller wind stresses and reduced evaporation rates. Numerical simulations reproduced the hydrodynamic field observations resulting from inflow, outflow, wind stress, and atmospheric heat fluxes. When the wind stress opposed the inflow, the surface layer was arrested, forming a zone of convergence, stagnating the fluid and allowing the biological oxygen demand in the water to deplete the dissolved oxygen (DO) in the surface water; direct measurements showed that vertical mixing was small and contributed only marginally to the oxygen depletion. Net DO production in the water column was consistent with the observed variation with the buoyant inflow pattern, that is, a sink during overflows and overcast days and a source during interflows and intense sunlight. These observations provided further evidence that the water in this region was biologically isolated as confirmed by a scaling analysis. Modern numerical hydrodynamic simulations have reached a level of accuracy where they may be used to identify and quantify ecological niches.

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

Cited by 30 publications

References 56 publications

Phosphorus sources and demand during summer in a eutrophic lake

Phosphorus sources and demand during summer in a eutrophic lake

Effect of CO2, nutrients and light on coastal plankton. II. Metabolic rates

Dissolved oxygen response to wind‐inflow interactions in a stratified reservoir

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