Fluids

Editorial

Jump to: Research, Review

4 pages, 1506 KiB

Open AccessEditorial

Fluid Mechanics of Plankton

by Hidekatsu Yamazaki and J. Rudi Strickler

Fluids 2021, 6(2), 56; https://doi.org/10.3390/fluids6020056 - 27 Jan 2021

Viewed by 1741

Abstract

These first lines of Hensen’s article (Figure 1) in the “Fünfter Bericht” (1887) translate as follows [...] Full article

(This article belongs to the Special Issue Fluid Mechanics of Plankton)

► Show Figures

Figure 1

Research

Jump to: Editorial, Review

15 pages, 2730 KiB

Open AccessFeature PaperArticle

An Elastic Collision Model for Impulsive Jumping by Small Planktonic Organisms

by Houshuo Jiang

Fluids 2020, 5(3), 154; https://doi.org/10.3390/fluids5030154 - 5 Sep 2020

Cited by 4 | Viewed by 2441

Abstract

Many small marine planktonic organisms converge on similar propulsion mechanisms that involve impulsively generated viscous wake vortex rings, and small-scale fluid physics is key to mechanistically understanding the adaptive values of this important behavioral trait. Here, a theoretical fluid mechanics model is developed [...] Read more.

Many small marine planktonic organisms converge on similar propulsion mechanisms that involve impulsively generated viscous wake vortex rings, and small-scale fluid physics is key to mechanistically understanding the adaptive values of this important behavioral trait. Here, a theoretical fluid mechanics model is developed for plankton jumping, based on observations that the initial acceleration phase for a jumping plankter to attain its maximum speed is nearly impulsive, taking only a small fraction of the viscous timescale, and therefore can be regarded as nearly inviscid, analogous to a one-dimensional elastic collision. Flow circulation time-series data measured by particle image velocimetry (PIV) are input into the model and Froude propulsion efficiencies are calculated for several plankton species. Jumping by the tailed ciliate Pseudotontonia sp. has a high Froude propulsion efficiency ~0.9. Copepod jumping also has a very high efficiency, usually >0.95. Jumping by the squid Doryteuthis pealeii paralarvae has an efficiency of 0.44 ± 0.16 (SD). Jumping by the small medusa Sarsia tubulosa has an efficiency of 0.38 ± 0.26 (SD). Differences in the calculated efficiencies are attributed to the different ways by which these plankters impart momentum on the water during the initial acceleration phase as well as the accompanied different added mass coefficients. Full article

(This article belongs to the Special Issue Fluid Mechanics of Plankton)

► Show Figures

Graphical abstract

13 pages, 2701 KiB

Open AccessArticle

Jellyfish and Fish Solve the Challenges of Turning Dynamics Similarly to Achieve High Maneuverability

by John O. Dabiri, Sean P. Colin, Brad J. Gemmell, Kelsey N. Lucas, Megan C. Leftwich and John H. Costello

Fluids 2020, 5(3), 106; https://doi.org/10.3390/fluids5030106 - 30 Jun 2020

Cited by 16 | Viewed by 4150

Abstract

Turning maneuvers by aquatic animals are essential for fundamental life functions such as finding food or mates while avoiding predation. However, turning requires resolution of a fundamental dilemma based in rotational mechanics: the force powering a turn (torque) is favored by an expanded [...] Read more.

Turning maneuvers by aquatic animals are essential for fundamental life functions such as finding food or mates while avoiding predation. However, turning requires resolution of a fundamental dilemma based in rotational mechanics: the force powering a turn (torque) is favored by an expanded body configuration that maximizes lever arm length, yet minimizing the resistance to a turn (the moment of inertia) is favored by a contracted body configuration. How do animals balance these opposing demands? Here, we directly measure instantaneous forces along the bodies of two animal models—the radially symmetric Aurelia aurita jellyfish, and the bilaterally symmetric Danio rerio zebrafish—to evaluate their turning dynamics. Both began turns with a small, rapid shift in body kinematics that preceded major axial rotation. Although small in absolute magnitude, the high fluid accelerations achieved by these initial motions generated powerful pressure gradients that maximized torque at the start of a turn. This pattern allows these animals to initially maximize torque production before major body curvature changes. Both animals then subsequently minimized the moment of inertia, and hence resistance to axial rotation, by body bending. This sequential solution provides insight into the advantages of re-arranging mass by bending during routine swimming turns. Full article

(This article belongs to the Special Issue Fluid Mechanics of Plankton)

► Show Figures

Graphical abstract

10 pages, 3197 KiB

Open AccessArticle

Impacts of Microplastics on the Swimming Behavior of the Copepod Temora turbinata (Dana, 1849)

by Caroline H. Suwaki, Leandro T. De-La-Cruz and Rubens M. Lopes

Fluids 2020, 5(3), 103; https://doi.org/10.3390/fluids5030103 - 30 Jun 2020

Cited by 18 | Viewed by 4185

Abstract

Zooplankton are prone to the ingestion of microplastics by mistaking them for prey. However, there is a lack of knowledge about the impacts of microplastic availability on zooplankton behavior. In this study, we investigated the effects of polystyrene microbeads on swimming patterns of [...] Read more.

Zooplankton are prone to the ingestion of microplastics by mistaking them for prey. However, there is a lack of knowledge about the impacts of microplastic availability on zooplankton behavior. In this study, we investigated the effects of polystyrene microbeads on swimming patterns of the calanoid copepod Temora turbinata under laboratory conditions. We acquired high-resolution video sequences using an optical system containing a telecentric lens and a digital camera with an acquisition rate of 20 frames per second. We estimated the mean speed, NGDR (Net-to-Gross Displacement Ratio, a dimensionless single-valued measure of straightness) and turning angle to describe the swimming behavior in three different treatments (control, low and high concentration of microplastics). Our results revealed that swimming speeds decreased up to 40% (instantaneous speed) compared to controls. The NGDR and turning angle distribution of the organisms also changed in the presence of polystyrene microbeads, both at low (100 beads mL⁻¹) and high microplastic concentration (1000 beads mL⁻¹). These results suggest that the swimming behavior of Temora turbinata is affected by microbeads. Full article

(This article belongs to the Special Issue Fluid Mechanics of Plankton)

► Show Figures

Figure 1

18 pages, 3432 KiB

Open AccessFeature PaperArticle

Nutrient Patchiness, Phytoplankton Surge-Uptake, and Turbulent History: A Theoretical Approach and Its Experimental Validation

by Mathilde Schapira and Laurent Seuront

Fluids 2020, 5(2), 80; https://doi.org/10.3390/fluids5020080 - 22 May 2020

Cited by 1 | Viewed by 2613

Abstract

Despite ample evidence of micro- and small-scale (i.e., millimeter- to meter-scale) phytoplankton and zooplankton patchiness in the ocean, direct observations of nutrient distributions and the ecological importance of this phenomenon are still relatively scarce. In this context, we first describe a simple procedure [...] Read more.

Despite ample evidence of micro- and small-scale (i.e., millimeter- to meter-scale) phytoplankton and zooplankton patchiness in the ocean, direct observations of nutrient distributions and the ecological importance of this phenomenon are still relatively scarce. In this context, we first describe a simple procedure to continuously sample nutrients in surface waters, and subsequently provide evidence of the existence of microscale distribution of ammonium in the ocean. We further show that ammonium is never homogeneously distributed, even under very high conditions of turbulence. Instead, turbulence intensity appears to control nutrient patchiness, with a more homogeneous or a more heterogeneous distribution observed under high and low turbulence intensities, respectively, under the same concentration in nutrient. Based on a modelling procedure taking into account the stochastic properties of intermittent nutrient distributions and observations carried out on natural phytoplankton communities, we introduce and verify the hypothesis that under nutrient limitation, the “turbulent history” of phytoplankton cells, i.e., the turbulent conditions they experienced in their natural environments, conditions their efficiency to uptake ephemeral inorganic nitrogen patches of different concentrations. Specifically, phytoplankton cells exposed to high turbulence intensities (i.e., more homogeneous nutrient distribution) were more efficient to uptake high concentration nitrogen pulses (2 µM). In contrast, under low turbulence conditions (i.e., more heterogeneous nutrient distribution), uptake rates were higher for low concentration nitrogen pulses (0.5 µM). These results suggest that under nutrient limitation, natural phytoplankton populations respond to high turbulence intensities through a decrease in affinity for nutrients and an increase in their transport rate, and vice versa. Full article

(This article belongs to the Special Issue Fluid Mechanics of Plankton)

► Show Figures

Graphical abstract

12 pages, 7396 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Rotational Maneuvers of Copepod Nauplii at Low Reynolds Number

by Kacie T. M. Niimoto, Kyleigh J. Kuball, Lauren N. Block, Petra H. Lenz and Daisuke Takagi

Fluids 2020, 5(2), 78; https://doi.org/10.3390/fluids5020078 - 21 May 2020

Cited by 7 | Viewed by 3628

Abstract

Copepods are agile microcrustaceans that are capable of maneuvering freely in water. However, the physical mechanisms driving their rotational motion are not entirely clear in small larvae (nauplii). Here we report high-speed video observations of copepod nauplii performing acrobatic feats with three pairs [...] Read more.

Copepods are agile microcrustaceans that are capable of maneuvering freely in water. However, the physical mechanisms driving their rotational motion are not entirely clear in small larvae (nauplii). Here we report high-speed video observations of copepod nauplii performing acrobatic feats with three pairs of appendages. Our results show rotations about three principal axes of the body: yaw, roll, and pitch. The yaw rotation turns the body to one side and results in a circular swimming path. The roll rotation consists of the body spiraling around a nearly linear path, similar to an aileron roll of an airplane. We interpret the yaw and roll rotations to be facilitated by appendage pronation or supination. The pitch rotation consists of flipping on the spot in a maneuver that resembles a backflip somersault. The pitch rotation involved tail bending and was not observed in the earliest stages of nauplii. The maneuvering strategies adopted by plankton may inspire the design of microscopic robots, equipped with suitable controls for reorienting autonomously in three dimensions. Full article

(This article belongs to the Special Issue Fluid Mechanics of Plankton)

► Show Figures

Figure 1

11 pages, 2996 KiB

Open AccessArticle

Fluid and Predator-Prey Interactions of Scyphomedusae Fed Calanoid Copepods

by Zachary Wagner, John H. Costello and Sean P. Colin

Fluids 2020, 5(2), 60; https://doi.org/10.3390/fluids5020060 - 25 Apr 2020

Cited by 7 | Viewed by 3020

Abstract

The feeding current of scyphomedusae entrains and transports surrounding fluids and prey through trailing tentacles to initiate encounters with prey. After contact, most prey are retained for ingestion. However, the probability that a contact will occur depends on several factors including capture surface [...] Read more.

The feeding current of scyphomedusae entrains and transports surrounding fluids and prey through trailing tentacles to initiate encounters with prey. After contact, most prey are retained for ingestion. However, the probability that a contact will occur depends on several factors including capture surface morphology, prey size and behavior. We examined how hydrodynamics, capture surface morphology and prey behavior affect the capture probability of copepods. To do this, we documented medusa-copepod interactions of four species of scyphomedusae (two semeostomes and two rhizostomes) possessing different capture surface morphologies. We tracked the movement and behavior of entrained copepods throughout the feeding process to quantify prey behavior effects upon capture efficiency (# captures/# encounters). The feeding currents generated by all the medusan species generated fluid shear deformation rates well above the detection limits of copepods. Despite strong hydrodynamic signals, copepod behavior was highly variable and only 58% of the copepods reacted to entrainment within feeding currents. Furthermore, copepod behavior (categorized as no reaction, escape jump or adjustment jump) did not significantly affect the capture efficiency. The scale and complexity of the feeding current generated by scyphomedusae may help explain the poor ability of copepods to avoid capture. Full article

(This article belongs to the Special Issue Fluid Mechanics of Plankton)

► Show Figures

Graphical abstract

11 pages, 4282 KiB

Open AccessFeature PaperArticle

Chemical Signaling in the Turbulent Ocean—Hide and Seek at the Kolmogorov Scale

by Erik Selander, Sam T. Fredriksson and Lars Arneborg

Fluids 2020, 5(2), 54; https://doi.org/10.3390/fluids5020054 - 21 Apr 2020

Cited by 3 | Viewed by 3002

Abstract

Chemical cues and signals mediate resource acquisition, mate finding, and the assessment of predation risk in marine plankton. Here, we use the chemical properties of the first identified chemical cues from zooplankton together with in situ measurements of turbulent dissipation rates to calculate [...] Read more.

Chemical cues and signals mediate resource acquisition, mate finding, and the assessment of predation risk in marine plankton. Here, we use the chemical properties of the first identified chemical cues from zooplankton together with in situ measurements of turbulent dissipation rates to calculate the effect of turbulence on the distribution of cues behind swimmers as well as steady state background concentrations in surrounding water. We further show that common zooplankton (copepods) appears to optimize mate finding by aggregating at the surface in calm conditions when turbulence do not prevent trail following. This near surface environment is characterized by anisotropic turbulence and we show, using direct numerical simulations, that chemical cues distribute more in the horizontal plane than vertically in these conditions. Zooplankton may consequently benefit from adopting specific search strategies near the surface as well as in strong stratification where similar flow fields develop. Steady state concentrations, where exudation is balanced by degradation develops in a time scale of ~5 h. We conclude that the trails behind millimeter-sized copepods can be detected in naturally occurring turbulence below the wind mixed surface layer or in the absence of strong wind. The trails, however, shorten dramatically at high turbulent dissipation rates, above ~10⁻³ cm² s⁻³ (10⁻⁷ W kg⁻¹) Full article

(This article belongs to the Special Issue Fluid Mechanics of Plankton)

► Show Figures

Graphical abstract

26 pages, 3346 KiB

Open AccessArticle

Feeding of Plankton in a Turbulent Environment: A Comparison of Analytical and Observational Results Covering Also Strong Turbulence

by Hans L. Pécseli, Jan K. Trulsen, Jan Erik Stiansen and Svein Sundby

Fluids 2020, 5(1), 37; https://doi.org/10.3390/fluids5010037 - 19 Mar 2020

Cited by 3 | Viewed by 2781

Abstract

The present studies address feeding of plankton in turbulent environments, discussed by a comparison of analytical results and field data. Various models for predator-prey encounters and capture probabilities are reviewed. Generalized forms for encounter rates and capture probabilities in turbulent environments are proposed. [...] Read more.

The present studies address feeding of plankton in turbulent environments, discussed by a comparison of analytical results and field data. Various models for predator-prey encounters and capture probabilities are reviewed. Generalized forms for encounter rates and capture probabilities in turbulent environments are proposed. The analysis emphasizes ambush predators, exemplified by cod larvae Gadus morhua L. in the start-feeding phase (stage 7 larvae) collected in shallow waters near Lofoten, Norway. During this campaign, data were obtained at four sites with strongly turbulent conditions induced by tidal currents and long-wave swells, and one site where the turbulence had a lower level in comparison. The guts of the selected cod larvae were examined in order to determine the number of nauplii ingested. Analytically obtained probability densities for the gut content were compared with observations and the results used for estimating the rate of capture of the nauplii. This capture rate was then compared with analytical results using also data for the surroundings, such as measured prey densities and turbulence conditions, as quantified by the specific energy dissipation rate. Different from earlier studies, the presented data include conditions where the turbulence exceeds the level for optimal larval encounter-capture rates. Full article

(This article belongs to the Special Issue Fluid Mechanics of Plankton)

► Show Figures

Graphical abstract

11 pages, 1681 KiB

Open AccessCommunication

Changes in Vertical Distribution of Zooplankton under Wind-Induced Turbulence: A 36-Year Record

by Mamoru Tanaka

Fluids 2019, 4(4), 195; https://doi.org/10.3390/fluids4040195 - 25 Nov 2019

Cited by 7 | Viewed by 2656

Abstract

A multidecadal record of a local zooplankton community, stored in an open-access database, was analyzed with wind data to examine the impact of wind-induced turbulence on vertical distribution of zooplankton. Two major findings were made. First, the abundance of zooplankton assemblage (composed of [...] Read more.

A multidecadal record of a local zooplankton community, stored in an open-access database, was analyzed with wind data to examine the impact of wind-induced turbulence on vertical distribution of zooplankton. Two major findings were made. First, the abundance of zooplankton assemblage (composed of copepods, cladocerans, etc.) in the upper layer (<10 m deep) decreased with increasing turbulence intensity, suggesting turbulence avoidance by zooplankton. Second, when focusing on each species, it was found that ambush (sit-and-wait) feeders showed statistically significant changes in response to turbulence, whereas suspension (filter) feeders did not. This is the first clear evidence that ambush feeders change vertical distribution in response to turbulence. Full article

(This article belongs to the Special Issue Fluid Mechanics of Plankton)

► Show Figures

Figure 1

Review

Jump to: Editorial, Research

28 pages, 4940 KiB

Open AccessEditor’s ChoiceReview

Kinematic and Dynamic Scaling of Copepod Swimming

by Leonid Svetlichny, Poul S. Larsen and Thomas Kiørboe

Fluids 2020, 5(2), 68; https://doi.org/10.3390/fluids5020068 - 11 May 2020

Cited by 24 | Viewed by 4156

Abstract

Calanoid copepods have two swimming gaits, namely cruise swimming that is propelled by the beating of the cephalic feeding appendages and short-lasting jumps that are propelled by the power strokes of the four or five pairs of thoracal swimming legs. The latter may [...] Read more.

Calanoid copepods have two swimming gaits, namely cruise swimming that is propelled by the beating of the cephalic feeding appendages and short-lasting jumps that are propelled by the power strokes of the four or five pairs of thoracal swimming legs. The latter may be 100 times faster than the former, and the required forces and power production are consequently much larger. Here, we estimated the magnitude and size scaling of swimming speed, leg beat frequency, forces, power requirements, and energetics of these two propulsion modes. We used data from the literature together with new data to estimate forces by two different approaches in 37 species of calanoid copepods: the direct measurement of forces produced by copepods attached to a tensiometer and the indirect estimation of forces from swimming speed or acceleration in combination with experimentally estimated drag coefficients. Depending on the approach, we found that the propulsive forces, both for cruise swimming and escape jumps, scaled with prosome length (L) to a power between 2 and 3. We further found that power requirements scales for both type of swimming as L³. Finally, we found that the cost of transportation (i.e., calories per unit body mass and distance transported) was higher for swimming-by-jumping than for cruise swimming by a factor of 7 for large copepods but only a factor of 3 for small ones. This may explain why only small cyclopoid copepods can afford this hydrodynamically stealthy transportation mode as their routine, while large copepods are cruise swimmers. Full article

(This article belongs to the Special Issue Fluid Mechanics of Plankton)

► Show Figures

Graphical abstract

12 pages, 1819 KiB

Open AccessReview

Numerical Simulations of Flow around Copepods: Challenges and Future Directions

by Iman Borazjani

Fluids 2020, 5(2), 52; https://doi.org/10.3390/fluids5020052 - 17 Apr 2020

Cited by 4 | Viewed by 2656

Abstract

Copepods are small aquatic creatures which are abundant in oceans as a major food source for fish, thereby playing a vital role in marine ecology. Because of their role in the food chain, copepods have been subject to intense research through different perspectives [...] Read more.

Copepods are small aquatic creatures which are abundant in oceans as a major food source for fish, thereby playing a vital role in marine ecology. Because of their role in the food chain, copepods have been subject to intense research through different perspectives from anatomy, form-function biology, to ecology. Numerical simulations can uniquely support such investigations by quantifying: (i) the force and flow generated by different parts of the body, thereby clarify the form-function relation of each part; (ii) the relation between the small-scale flow around animal and the large-scale (e.g., oceanic) flow of its surroundings; and (iii) the flow and its energetics, thereby answering ecological questions, particularly, the three major survival tasks, i.e., feeding, predator avoidance, and mate-finding. Nevertheless, such numerical simulations need to overcome challenges involving complex anatomic shape of copepods, multiple moving appendages, resolving different scales (appendage-, animal- to large-scale). The numerical methods capable of handling such problems and some recent simulations are reviewed. At the end, future developments necessary to simulate copepods from animal- to surrounding-scale are discussed. Full article

(This article belongs to the Special Issue Fluid Mechanics of Plankton)

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Fluid Mechanics of Plankton

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Published Papers (12 papers)

Editorial

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI