Mesoscale Turbulence, Plankton and the Marine Ecosystem (original) (raw)
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Mesoscale vortices and the paradox of the plankton
Proceedings of the Royal Society B: Biological Sciences, 2000
Coexistence of competitive species is severely limited by the availability of resources and the characteristics of the environment. In particular, the so-called`competitive exclusion principle' states that, at equilibrium, the number of coexisting species cannot be larger than the number of resources for which they compete. However, many in situ observations have revealed prolonged coexistence of a large number of competitive plankton species, a phenomenon known as`the paradox of the plankton' . Here we investigate this problem and show that ocean mesoscale vortices generate transport barriers and incomplete horizontal mixing, allowing for a prolonged survival of the less-¢t species, even for fully homogeneous resource distributions. In such a situation, the temporarily less-¢t plankton species are protected from competition by the action of the vortices.
Effects of small-scale turbulence on lower trophic levels under different nutrient conditions
2010
Small-scale turbulence affects the pelagic food web and energy flow in marine systems and the impact is related to nutrient conditions and the assemblage of organisms present. We generated five levels of turbulence (2*10 29 to 1*10 24 W kg 21) in landbased mesocosms (volume 2.6 m 3) with and without additional nutrients (31:16:1 Si:N:P mM) to asses the effect of small-scale turbulence on the lower part of the pelagic food web under different nutrient conditions. The ecological influence of nutrients and small-scale turbulence on lower trophic levels was quantified using multivariate statistics (RDA), where nutrients accounted for 31.8% of the observed biological variation, while 7.2% of the variation was explained by small-scale turbulence and its interaction with nutrients. Chlorophyll a, primary production rates, bacterial production rates and diatom and dinoflagellate abundance were positively correlated to turbulence, regardless of nutrient conditions. Abundance of autotrophic flagellates, total phytoplankton and bacteria were positively correlated to turbulence only when nutrients were added. Impact of small-scale turbulence was related to nutrient conditions, with implications for oligotrophic and eutrophic situations. The effect on community level was also different compared to single species level. Microbial processes drive biogeochemical cycles, and nutrient-controlled effects of small-scale turbulence on such processes are relevant to foresee altered carbon flow in marine systems.
Marine Ecology-progress Series, 2000
From the literature we obtained experimental data on the effects of small-scale turbulence on plankton at the organism scale. Normalized rates in response to turbulence were calculated in the present study for parameters related to growth, ingestion and energy expenditure. Growth rates are, in general, negatively affected by turbulence. Nevertheless, the data are highly biased towards a specific group of organisms, dinoflagellates, which could have peculiar physiological impediments under turbulence. Ingestion rates seem to be increased by turbulence, especially at low and intermediate levels.
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Deep Sea Research Part II: Topical Studies in Oceanography, 2001
The intensive "eld observational phase of JGOFS in the North Atlantic Ocean has shown the importance of oceanic mesoscale variability on biogeochemical cycles and on the strength of the ocean biological pump. Mesoscale physical dynamics govern the major time/space scales of bulk biological variability (biomass, production and export). Mesoscale eddies seem to have a strong impact on the ecosystem structure and functioning, but observational evidence is rather limited.
Influence of turbulence variability on osmotrophic plankton dynamics in a coastal area
La turbulència és el fenomen pel qual la majoria d'aquesta energia mecànica, que entra al sistema a escales grans, es transfereix a escales petites rellevants per als organismes planctònics. L'estudi dels efectes de la turbulència en el plàncton és enormement complex, i per tant científicament estimulant. Combina la complexitat dels sistemes biològics amb el què ha estat descrit pel premi Nobel Richard Feynman (1918-1988) com "el problema irresolt més important de la física clàssica". La turbulència és un procés ubic, amb un rang d'escales espacials i temporals més ampli encara que el del plàncton. Per tant els seus efectes sobre els organismes planctònics van més enllà de la redistribució de nutrients i fitoplàncton de què hem parlat, i afecta tots els seus processos (fig.1). Després de vàries dècades d'estudi ara comencem a tenir una noció conjunta Descomposició de la component nort del senyal de velocitat de l'aigua davant del Port Olímpic de Barcelona. A, senyal original, B intensitat mitja, C, component de l'onatge, D, senyal turbulent d'alta freqüència. La suma dels tres senyals a B, C i D dóna el senyal orginal.
Analysis of the effect of small scale turbulence on the phytoplancton dynamics in the upper ocean
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Theories" and techniques for observing turbulence in the ocean euphotic zone
With growing recognition of the important roles which turbulence plays in the functioning of marine food webs, interest in the tools and techniques of measuring turbulence in the ocean has spread from the physical to the biological oceanographic community, for which this paper is intended. The subject of ocean turbulence and its measurement is introduced, with emphasis on the euphotic zone of both deep ocean and coastal environments. A discussion of important characteristics of turbulence and the various means by which turbulence may affect components of the biological system is followed by a simplified outline of the mathematical means used to describe scales of variability produced by turbulent fields. Existing and developing techniques for field measurements of turbulence variables are described, with discussion of the "theories" which are often necessary to transform those variables which we can measure into those we actually wish to know.