Journal ArticleDOI
Phytoplankton, light, and nutrients in a gradient of mixing depths: field experiments
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In this article, the effects of mixing depth and background turbidity on phytoplankton biomass, light climate, and nutrients in two field enclosure experiments designed to test predictions of a dynamical model were investigated.Abstract:
We studied the effects of water column mixing depth and background turbidity on phytoplankton biomass, light climate, and nutrients in two field enclosure experiments designed to test predictions of a dynamical model. In 1997 and 1998, we created gradients of mixing depth by enclosing the 100-μm-filtered phytoplankton community of a phosphorus-deficient lake in cylindrical plastic bags of varying depth (1.5–15 m) which were continuously mixed. To mimic different levels of background turbidity, we surrounded the transparent enclosure walls with a layer of opaque white (1997) or black (1998) plastic. The experiments were run for 4 wk (1997) and 6 wk (1998). The results supported two key assumptions of the model: specific production and specific sedimentation losses both decreased with increasing mixing depth. At all mixing depths, fast-sinking diatoms dominated the communities. In accordance with model predictions, algal biomass concentration and standing stock (summed over the mixed layer) showed a unimodal relationship to mixing depth when background turbidity was high (1998). When background turbidity was lower (1997), only the ascending limbs of the corresponding relationships were found, which supports the prediction that the mixing depth at which biomass peaks (i.e., becomes predominantly limited by light) increases with decreasing background turbidity. Also in accordance with predictions, light intensity at the bottom of the mixed layer decreased with increasing mixing depth and with increasing background turbidity. Finally, the data supported only the ascending limbs of the predicted inverse unimodal relationships among mixing depth and dissolved inorganic and total water column phosphorus. The absence of descending limbs in these relationships at low mixing depths was probably due to deviations of the experimental systems from two model assumptions. First, the remineralization rate of sedimented phosphorus may have been too slow to equilibrate with sedimentation losses over the experimental periods. Second, biomass yield per unit nutrient (the ratio of seston carbon to phosphorus) was not constant, but decreased with increasing mixing depth. To our knowledge, these are the first field experiments in which the effects of mixing depth on phytoplankton and its resources have been investigated systematically along a large gradient.read more
Citations
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Journal ArticleDOI
Changes in turbulent mixing shift competition for light between phytoplankton species
Jef Huisman,Jonathan Sharples,J. Stroom,Petra M. Visser,W. Edwin A. Kardinaal,Jolanda M. H. Verspagen,Ben Sommeijer +6 more
TL;DR: Competition theory is developed that predicts how changes in turbulent mixing affect competition for light between buoyant and sinking phytoplankton species, and warns that changes in the turbulence structure of natural waters, for instance driven by climate change, may induce major shifts in the species composition of phytopsized communities.
Journal ArticleDOI
Phytoplankton response to a changing climate
Monika Winder,Ulrich Sommer +1 more
TL;DR: In this paper, the authors review mechanistic links between climate alterations and factors limiting primary production, and highlight studies where climate change has had a clear impact on phytoplankton processes.
Journal ArticleDOI
Consumer versus resource control of producer diversity depends on ecosystem type and producer community structure.
Helmut Hillebrand,Daniel S. Gruner,Elizabeth T. Borer,Matthew E. S. Bracken,Matthew E. S. Bracken,Elsa E. Cleland,James J. Elser,W. Stanley Harpole,Jacqueline T. Ngai,Eric W. Seabloom,Jonathan B. Shurin,Jennifer E. Smith +11 more
TL;DR: It is indicated that system productivity and producer evenness determine the direction and magnitude of top-down and bottom-up control of diversity and may reconcile divergent empirical results within and among ecosystems.
Journal ArticleDOI
Lake diatom responses to warming: reviewing the evidence
TL;DR: This article examined the role that climate-mediated alterations in inter-related lake processes have played on diatom community composition, dynamics and size structure, with particular attention to the recent success of planktonic diatom species relative to heavier tychoplanktonic and small benthic diatoms.
Journal ArticleDOI
Scale-dependent carbon:nitrogen:phosphorus seston stoichiometry in marine and freshwaters
Robert W. Sterner,Tom Andersen,James J. Elser,Dag O. Hessen,James M. Hood,Edward McCauley,Jotaro Urabe +6 more
TL;DR: In this article, the authors used.2,000 observations of the chemistry of particulate matter from small and large lakes, as well as near and off-shore marine environments, and found that the best model to describe seston stoichiometry depended on the scale of analysis.
References
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Journal ArticleDOI
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TL;DR: In this paper, the main aim is to describe the counting-chamber method and the numerous difficulties encountered in quantitative plankton research are discussed and ways of avoiding them are described together with improvements of technique that save time.
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Journal ArticleDOI
Simulated response of the ocean carbon cycle to anthropogenic climate warming
TL;DR: In this article, a coupled atmosphere-ocean model of global warming was used to examine the effect of ocean circulation and biology changes on the ocean carbon cycle and found that increased rainfall leads to surface freshening and increased stratification in a vast region of the Southern Ocean.