Planktonic encounter rates with non-spherical encounter zones

Andersen, A.; Dölger, Julia

doi:10.1098/rsif.2019.0398

Cited by 6 publications

(9 citation statements)

References 24 publications

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“…Individual behaviour can be modulated by triggers acting at different scales [40]. When both organisms involved in the interaction are moving, the shape of the encounter zone may impact the effective encounter rate [67]. The assumption of a spherical encounter zone for C. typicus , however, can be considered a valid oversimplification at least in the framework of the process-oriented model here outlined.…”

Section: Discussionmentioning

confidence: 99%

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Homeostatic swimming of zooplankton upon crowding: the case of the copepod Centropages typicus

Uttieri

Hinow

Pastore

et al. 2021

J. R. Soc. Interface.

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Crowding has a major impact on the dynamics of many material and biological systems, inducing effects as diverse as glassy dynamics and swarming. While this issue has been deeply investigated for a variety of living organisms, more research remains to be done on the effect of crowding on the behaviour of copepods, the most abundant metazoans on Earth. To this aim, we experimentally investigate the swimming behaviour, used as a dynamic proxy of animal adaptations, of males and females of the calanoid copepod Centropages typicus at different densities of individuals (10, 50 and 100 ind. l −1 ) by performing three-dimensional single-organism tracking. We find that the C. typicus motion is surprisingly unaffected by crowding over the investigated density range. Indeed, the mean square displacements as a function of time always show a crossover from ballistic to Fickian regime, with poor variations of the diffusion constant on increasing the density. Close to the crossover, the displacement distributions display exponential tails with a nearly density-independent decay length. The trajectory fractal dimension, D 3D ≅ 1.5, and the recently proposed ‘ecological temperature’ also remain stable on increasing the individual density. This suggests that, at least over the range of animal densities used, crowding does not impact on the characteristics of C. typicus swimming motion, and that a homeostatic mechanism preserves the stability of its swimming performance.

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Section: Discussionmentioning

confidence: 99%

Section: Adapting To Crowding: Ecological Implicationsmentioning

confidence: 99%

Homeostatic swimming of zooplankton upon crowding: the case of the copepod Centropages typicus

Uttieri

Hinow

Pastore

et al. 2021

J. R. Soc. Interface.

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“…The model builds on experimental data to derive a general framework that can be applied to other species with intermittent motion. Being semi-empirical, it avoids relying on simplifying assumptions that are common to most existing theoretical formulations, for instance that organisms have a constant ballistic or diffusive motion [27,50]. The model only requires empirical quantities that are easy to measure, ensuring its applicability beyond the species and experimental conditions considered in this work.…”

Section: Predicting Plankton Encounter Rates In Turbulencementioning

confidence: 99%

Efficient mate finding in planktonic copepods swimming in turbulence

Michalec,

Fouxon,

Souissi

et al. 2020

Preprint

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Zooplankton live in dynamic environments where turbulence may challenge their limited swimming abilities. How this interferes with fundamental behavioral processes remains elusive. We reconstruct simultaneously the trajectories of flow tracers and calanoid copepods, the most abundant metazoans in the ocean, and we quantify their ability to find mates when ambient flow impose physical constrains on their motion and impairs their olfactory orientation. We show that copepods achieve higher encounter rates in turbulence than in calm water due to the contribution of advection and vigorous swimming. Copepods further convert encounters within the perception radius to contact events via directed motion toward nearby organisms. Inertial effects do not result in preferential concentration, reducing the geometric collision kernel to the clearance rate, which we model accurately by superposing turbulent velocity and organism motion. We suggest that this behavioral and physical coupling mechanism accounts for the ability of copepods to reproduce in turbulent environments.

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“…Within this approach the rotation induced by the flow on the particles can be computed by the Jeffery's equations [16]. Scientists have studied various aspects of these models as a function of shape, motility, and the turbulent flow [17,19,23,24,36,38,72,101,[104][105][106]. In our case we contributed to the current scientific knowledge by carrying out systematic measurements of rotation rates and transport properties of microswimmers in turbulence as a function of their shape and motility.…”

Section: Dispersion Statistics and Collision Rates Of Motile Ellipsoi...mentioning

confidence: 99%

“…In cloud microphysics [57,102,103], for example, shape and size dependent collision rates play a big role in particle clustering and growth, leading to rain droplet formation and growth. When studying the collision rates of planktonic organisms the effect of motility turned out to be critical in determining collision rates [104,105], while at the same time, the geometry of the colliding particles plays a crucial role in fixing collision rates [106]. Despite this extensive range of works, a comprehensive analysis of the effect of both shape and motility on collision rates and dispersion statistics is currently missing.…”

Section: Introductionmentioning

confidence: 99%

Physical modeling of motile and sedimenting plankton: from simple flows to turbulence

Leiva¹

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Planktonic microorganisms play a fundamental role in oceanic ecology and chemical cycles. Different planktonic species are found at various levels of the oceanic trophic chain, ranging from photosynthetic organisms to grazing species higher in the food chain. Many planktonic species have developed migration strategies to aid their survival. This includes motility and density regulation. Physical aspects, such as transport and collision rates, have a direct impact on planktonic survival and are influenced by the planktonic migration strategies. Furthermore, collision rates between planktonic organisms also play an important role in the formation of macroscopic plankton blooms. These have a direct effect on the ecology of oceans and lakes. In this dissertation we use physical modeling to study motile and sedimenting microorganisms in a fluid flow. We aim at shedding light on the key features of microorganism dynamics in fluid flows as a function of their key parameters: shape, motility, and density offset.In chapter 1 we introduce the biological setting of plankton, and give a very brief overview of the physical modeling approaches for plankton in fluid flows. Subsequently in chapter 2 we introduce the theoretical framework of turbulence and the methodology of our numerical simulations.In chapter 3 we start by examining microswimmers in a simple two-dimensional toy-model. We use methods from dynamical systems theory to uncover the role played by shape and motility in determining the microorganism dynamics in this simple setting. We explicitly identify the Hamiltonian dynamics followed by spherical microswimmers. Additionally, we find that elongated microswimmers more easily escape simple vortex structures than other shapes. In chapter 4 we then move on to ellipsoidal microswimmers in realistic mild turbulent flows. We analyze transport and rotation rates of motile ellipsoids. We find that elongated microswimmers have an advantage in transport, which is in part due to shape-dependent rotation rates. We also investigated the collision rates of motile spheres, and we were able to extract a master curve interpolating between the passive and motile limits for different sized spheres. We quantified the effect of motility and found that even very small motility greatly enhances collision rates.In chapter 5 we study of sedimentation of elongated microorganisms in mild turbulence. We measure the collision rates of elongated microorganisms in terms of size, energy dissipation rate, and aspect ratio. We then find a master curve interpolating between a passive particle and a sedimentation dominated limit. We characterize the role played by shape, which increases collision rates of elongated microorganisms in comparison with equal-volume spheres. This shape-induced enhancement helps to explain the timescales for formation of blooms of elongated planktonic species. In summary, in this dissertation we study the effect of shape, motility, and density regulation on physical models of planktonic microorganisms. Our findings help to ...

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Planktonic encounter rates with non-spherical encounter zones

Cited by 6 publications

References 24 publications

Homeostatic swimming of zooplankton upon crowding: the case of the copepod Centropages typicus

Homeostatic swimming of zooplankton upon crowding: the case of the copepod Centropages typicus

Efficient mate finding in planktonic copepods swimming in turbulence

Physical modeling of motile and sedimenting plankton: from simple flows to turbulence

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