Larval Settlement of Corals in Flowing Water using a Racetrack Flume

2002 ◽  
Vol 36 (1) ◽  
pp. 76-79 ◽  
Author(s):  
S. Harii ◽  
H. Kayanne
Keyword(s):  
Reef Flat ◽  
Marine Invertebrates ◽  
Larval Settlement ◽  
Flow Speed ◽  
Flowing Water ◽  
Pocillopora Damicornis ◽  
Settlement Rate ◽  
Ishigaki Island ◽  
Digitally Controlled ◽  
Flow Speeds

Although the larvae of marine invertebrates settle in currents, few studies have examined settlement under flow. We studied the settlement of two brooding coral larvae with different behavior in a flow using a small racetrack flume made of polycarbonate and acrylic (58 cm long). Flow was generated using a digitally controlled gear-motor-driven paddle wheel. The settlement rates of the larvae, Heliopora coerulea and Pocillopora damicornis, were observed at three flow speeds: 1.6, 4.4, and 9.8 cm/sec, which correspond to the currents at low, mean, and ebb or flood tides, respectively, at Shiraho Reef flat, Ishigaki Island, Japan. The settlement rate of H. coerulea larvae decreased with increasing flow speed (20% at 1.6 cm/sec, 2% at 9.8 cm/sec). In contrast, the settlement rate of P. damicornis larvae was high at all flow speeds (> 50% at all flow speeds). This difference in the larval settlement rates of the two species is in accordance with the current conditions in which the adult corals are distributed.

I Feel That! Fluid Dynamics and Sensory Aspects of Larval Settlement across Scales

2018 ◽  
Keyword(s):  
Fluid Dynamics ◽  
Marine Invertebrates ◽  
Larval Settlement ◽  
External Environment ◽  
Life Cycles ◽  
Decision Making Process ◽  
Larval Biology ◽  
Sea Floor ◽  
External Cues ◽  
Juvenile Habitat

A commonality among oceanic life cycles is a process known as settlement, where dispersing propagules transition to the sea floor. For many marine invertebrates, this transition is irreversible, and therefore involves a crucial decision-making process through which larvae evaluate their juvenile habitat-to-be. In this chapter, we consider aspects of the external environment that could influence successful settlement. Specifically, we discuss water flow across scales, and how larvae can engage behaviors to influence where ocean currents take them, and enhance the likelihood of their being carried toward suitable settlement locations. Next, we consider what senses larvae utilize to evaluate their external environment and properly time such behavioral modifications, and settlement generally. We hypothesize that larvae integrate these various external cues in a hierarchical fashion, with differing arrangements being employed across ontogeny and among species. We conclude with a brief discussion of the future promises of larval biology, ecology, and evolution.

scholarly journals Large amplitude, short wave peristalsis and its implications for transport

2015 ◽  
Author(s):  
Lindsay D Waldrop ◽  
Laura A. Miller
Keyword(s):  
Fluid Flow ◽  
Large Amplitude ◽  
Compression Wave ◽  
Wave Speed ◽  
Flow Direction ◽  
Short Wave ◽  
Flow Speed ◽  
Biological Pumps ◽  
Flow Speeds ◽  
Flow Compression

Valveless, tubular pumps are widespread in the animal kingdom, but the mechanism by which these pumps generate fluid flow are often in dispute. Where the pumping mechanism of many organs was once described as peristalsis, other mechanisms, such as dynamic suction pumping, have been suggested as possible alternative mechanisms. Peristalsis is often evaluated using criteria established in a technical definition for mechanical pumps, but this definition is based on a small-amplitude, long-wave approximation which biological pumps often violate. In this study, we use a direct numerical simulation of large-amplitude, short-wave peristalsis to investigate the relationships between fluid flow, compression frequency, compression wave speed, and tube occlusion. We also explore how the flows produced differ from the criteria outlined in the technical definition of peristalsis. We find that many of the technical criteria are violated by our model: fluid flow speeds produced by peristalsis are greater than the speeds of the compression wave; fluid flow is pulsatile; and flow speed have a non-linear relationship with compression frequency when compression wave speed is held constant. We suggest that the technical definition is inappropriate for evaluating peristalsis as a pumping mechanism for biological pumps because they too frequently violate the assumptions inherent in these criteria. Instead, we recommend that a simpler, more inclusive definition be used for assessing peristalsis as a pumping mechanism based on the presence of non-stationary compression sites that propagate uni-directionally along a tube without the need for a structurally fixed flow direction.

Effects of Shield Gas Flow on Meltpool Variability and Signature in Scanned Laser Melting

2020 ◽  
Author(s):  
David C. Deisenroth ◽  
Jorge Neira ◽  
Jordan Weaver ◽  
Ho Yeung
Keyword(s):  
Additive Manufacturing ◽  
Aspect Ratio ◽  
Flow Velocity ◽  
Process Monitoring ◽  
Gas Flow ◽  
Laser Energy ◽  
Flow Speed ◽  
Powder Bed ◽  
Flow Speeds ◽  
Gas Flow Velocity

Abstract In laser powder bed fusion metal additive manufacturing, insufficient shield gas flow allows accumulation of condensate and ejecta above the build plane and in the beam path. These process byproducts are associated with beam obstruction, attenuation, and thermal lensing, which then lead to lack of fusion and other defects. Furthermore, lack of gas flow can allow excessive amounts of ejecta to redeposit onto the build surface or powder bed, causing further part defects. The current investigation was a preliminary study on how gas flow velocity and direction affect laser delivery to a bare substrate of Nickel Alloy 625 (IN625) in the National Institute of Standards and Technology (NIST) Additive Manufacturing Metrology Testbed (AMMT). Melt tracks were formed under several gas flow speeds, gas flow directions, and energy densities. The tracks were then cross-sectioned and measured. The melt track aspect ratio and aspect ratio coefficient of variation (CV) were reported as a function of gas flow speed and direction. It was found that a mean gas flow velocity of 6.7 m/s from a nozzle 6.35 mm in diameter was sufficient to reduce meltpool aspect ratio CV to less than 15 %. Real-time inline hotspot area and its CV were evaluated as a process monitoring signature for identifying poor laser delivery due to inadequate gas flow. It was found that inline hotspot size could be used to distinguish between conduction mode and transition mode processes, but became diminishingly sensitive as applied laser energy density increased toward keyhole mode. Increased hotspot size CV (associated with inadequate gas flow) was associated with an increased meltpool aspect ratio CV. Finally, it was found that use of the inline hotspot CV showed a bias toward higher CV values when the laser was scanned nominally toward the gas flow, which indicates that this bias must be considered in order to use hotspot area CV as a process monitoring signature. This study concludes that gas flow speed and direction have important ramifications for both laser delivery and process monitoring.

scholarly journals Experimental Study on the Effects of a Vertical Jet Impinging on Soft Bottom Sediments

2020 ◽  
Vol 12 (9) ◽  
pp. 3775 ◽  
Author(s):  
Wei Fan ◽  
Weicheng Bao ◽  
Yong Cai ◽  
Canbo Xiao ◽  
Zhujun Zhang ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Side Effects ◽  
Field Experiments ◽  
Sediment Resuspension ◽  
Ecological Engineering ◽  
Phosphorus Release ◽  
Flow Speed ◽  
Critical Conditions ◽  
Water Tank ◽  
Flow Speeds

Artificial downwelling, which is an ecological engineering method, potentially alleviates bottom hypoxia by bringing oxygen-rich surface water down below the pycnocline. However, the downward flow is likely to disturb sediments (or induce sediment resuspension) when reaching the bottom and then have unwanted side effects on the local ecosystem. To evaluate this, our paper presents a theoretical model and experimental data for the sediment resuspension caused by artificial downwelling. The theoretical model considers the critical conditions for sediment resuspension and the scour volume with the downwelling flow disturbing sediment. Experiments with altered downwelling flow speeds, discharge positions relative to the bottom, and particle sizes of sediment were conducted in a water tank, and the results were consistent with our theoretical model. The results show that the critical Froude number (hereinafter Fr) for sediment resuspension is 0.5. The prevention of sediment resuspension requires the downwelling flow speed and the discharge position to be adjusted so that Fr < 0.5; otherwise a portion of sediment is released into the water and its volume can be predicted by the derived formulation based on the Shields theory. Furthermore, sediment resuspension has side effects, such as a water turbidity increase and phosphorus release, the magnitudes of which are discussed with respect to engineering parameters. Further study will focus on field experiments of artificial downwelling and its environmental impacts.

Calcified macroalgae and their bacterial community in relation to larval settlement and metamorphosis of reef-building coral Pocillopora damicornis

2020 ◽  
Vol 97 (1) ◽  
Author(s):  
Fangfang Yang ◽  
Jiahao Mo ◽  
Zhangliang Wei ◽  
Lijuan Long
Keyword(s):  
Bacterial Community ◽  
Community Composition ◽  
Bacterial Community Composition ◽  
Larval Settlement ◽  
Pocillopora Damicornis ◽  
Principal Coordinates Analysis ◽  
Principal Coordinates ◽  
Coral Reef Ecosystems ◽  
Settlement And Metamorphosis ◽  
Invertebrate Larvae

ABSTRACT Calcified macroalgae play an important role in the settlement and metamorphosis of invertebrate larvae in coral reef ecosystems. However, little is known about the algal-associated bacterial communities and their effects on larval settlement. In this study, the responses of larvae of the coral Pocillopora damicornis to calcified algae (Porolithon onkodes, Halimeda cylindracea, Halimeda opuntia and Amphiroa fragilissima) were evaluated. The results revealed that Por. onkodes and H. cylindracea significantly enhanced the rates of settlement and metamorphosis, whereas fewer larvae settled on Am. fragilissima and H. opuntia. Amplicon pyrosequencing of the V3–V4 region of 16S rDNA was applied to investigate the relationship between algal bacterial community and larval settlement. Principal coordinates analysis demonstrated that the bacterial community composition of H. opuntia was more similar to that of Am. fragilissima, but clearly distinct from those of H. cylindracea and Por. onkodes. Furthermore, the relative abundances of bacteria were highly diverse among different algae. H. opuntia had higher percentages of Thalassobius, Pelagibius and SM1A02, whereas the abundances of Mycoplasma and Suttonella were significantly higher in H. cylindracea than other algae. Our results showed that larval settlement/metamorphosis was strongly correlated with the bacterial community composition and with the relative abundance of a few operational taxonomic units.

scholarly journals Bacterial Nucleobases Synergistically Induce Larval Settlement and Metamorphosis in the Invasive MusselMytilopsis sallei

2019 ◽  
Vol 85 (16) ◽  
Author(s):  
Jian He ◽  
Qi Dai ◽  
Yuxuan Qi ◽  
Pei Su ◽  
Miaoqin Huang ◽  
...  
Keyword(s):  
Marine Invertebrates ◽  
Larval Settlement ◽  
Aquatic Systems ◽  
Substrate Selection ◽  
Content Type ◽  
Dreissenid Mussels ◽  
Settlement And Metamorphosis ◽  
Environmental Bacteria ◽  
Fouling Organisms ◽  
Chemical Mediators

ABSTRACTMarine bacterial biofilms have long been recognized as potential inducers of larval settlement and metamorphosis in marine invertebrates, but few chemical cues from bacteria have been identified. Here, we show that larval settlement and metamorphosis of an invasive fouling mussel,Mytilopsis sallei, could be induced by biofilms of bacteria isolated from its adult shells and other substrates from the natural environment. One of the strains isolated,Vibrio owensiiMS-9, showed strong inducing activity which was attributed to the release of a mixture of nucleobases including uracil, thymine, xanthine, hypoxanthine, and guanine into seawater. In particular, the synergistic effect of hypoxanthine and guanine was sufficient for the inducing activity ofV. owensiiMS-9. The presence of two or three other nucleobases could enhance, to some extent, the activity of the mixture of hypoxanthine and guanine. Furthermore, we determined that bacteria producing higher concentrations of nucleobases were more likely to induce larval settlement and metamorphosis ofM. salleithan were bacteria producing lower concentrations of nucleobases. The present study demonstrates that bacterial nucleobases play an important role in larval settlement and metamorphosis of marine invertebrates. This provides new insights into our understanding of the role of environmental bacteria in the colonization and aggregation of invasive fouling organisms and of the metabolites used as chemical mediators in cross-kingdom communication within aquatic systems.IMPORTANCEInvasive species are an increasingly serious problem globally. In aquatic ecosystems, invasive dreissenid mussels are well-known ecological and economic pests because they appear to effortlessly invade new environments and foul submerged structures with high-density aggregations. To efficiently control exotic mussel recruitment and colonization, the need to investigate the mechanisms of substrate selection for larval settlement and metamorphosis is apparent. Our work is one of very few to experimentally demonstrate that compounds produced by environmental bacteria play an important role in larval settlement and metamorphosis in marine invertebrates. Additionally, this study demonstrates that bacterial nucleobases can be used as chemical mediators in cross-kingdom communication within aquatic systems, which will enhance our understanding of how microbes induce larval settlement and metamorphosis of dreissenid mussels, and it furthermore may allow the development of new methods for application in antifouling.

scholarly journals Formation of Kinneyia via shear-induced instabilities in microbial mats

2013 ◽  
Vol 371 (2004) ◽  
pp. 20120362 ◽  
Author(s):  
Katherine Thomas ◽  
Stephan Herminghaus ◽  
Hubertus Porada ◽  
Lucas Goehring
Keyword(s):  
Microbial Mats ◽  
Flow Speed ◽  
Glass Beads ◽  
Flowing Water ◽  
Flow Conditions ◽  
Theoretical Predictions ◽  
Laboratory Analogue ◽  
Littoral Habitats ◽  
Over Time ◽  
Ripple Pattern

Kinneyia are a class of microbially mediated sedimentary fossils. Characterized by clearly defined ripple structures, Kinneyia are generally found in areas that were formally littoral habitats and covered by microbial mats. To date, there has been no conclusive explanation of the processes involved in the formation of these fossils. Microbial mats behave like viscoelastic fluids. We propose that the key mechanism involved in the formation of Kinneyia is a Kelvin–Helmholtz-type instability induced in a viscoelastic film under flowing water. A ripple corrugation is spontaneously induced in the film and grows in amplitude over time. Theoretical predictions show that the ripple instability has a wavelength proportional to the thickness of the film. Experiments carried out using viscoelastic films confirm this prediction. The ripple pattern that forms has a wavelength roughly three times the thickness of the film. This behaviour is independent of the viscosity of the film and the flow conditions. Laboratory-analogue Kinneyia were formed via the sedimentation of glass beads, which preferentially deposit in the troughs of the ripples. Well-ordered patterns form, with both honeycomb-like and parallel ridges being observed, depending on the flow speed. These patterns correspond well with those found in Kinneyia, with similar morphologies, wavelengths and amplitudes being observed.

Drop Generation in Cross-Flow of Liquid Rotating in Rigid Body Motion

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Haipeng Zhang ◽  
Sangjin Ryu
Keyword(s):  
Rigid Body ◽  
Cross Flow ◽  
Continuous Phase ◽  
Flow Speed ◽  
Rigid Body Motion ◽  
Body Motion ◽  
Drop Diameter ◽  
Liquid Drops ◽  
Syringe Needle ◽  
Flow Speeds

Abstract Various methods have been developed to generate monodisperse drops of a dispersed phase (DP) liquid in an immiscible continuous phase (CP) liquid, which include the membrane emulsification method and the microfluidic drop generation. This study proposes an easy-to-adopt drop generation method using cross-flow: a DP liquid is injected through a stationary vertical syringe needle into a CP liquid rotating in rigid body motion. The developed method was tested and characterized using de-ionized water as the DP liquid and mineral oil as the CP liquid. Drops were generated mainly either in the dripping mode or the jetting mode, and the former resulted in higher monodispersity. Smaller drops were generated when a thinner syringe needle was used, the average flow speed of the DP liquid through the needle was decreased, or the linear flow speed of the CP liquid at the needle location was increased. Especially, the power–law relationship was observed between the drop diameter and the flow speeds, and the dripping-to-jetting transition (DJT) was observed when the Weber number of the DP liquid was about 5.

scholarly journals Effect of morphology on the large-amplitude flapping dynamics of an inverted flag in a uniform flow

2019 ◽  
Vol 874 ◽  
pp. 526-547 ◽  
Author(s):  
Boyu Fan ◽  
Cecilia Huertas-Cerdeira ◽  
Julia Cossé ◽  
John E. Sader ◽  
Morteza Gharib
Keyword(s):  
Large Amplitude ◽  
Free Edge ◽  
Flow Speed ◽  
Uniform Flow ◽  
Analytical Theory ◽  
Natural Occurrence ◽  
Fluid Forces ◽  
Elastic Sheet ◽  
Divergence Instability ◽  
Flow Speeds

The stability of a cantilevered elastic sheet in a uniform flow has been studied extensively due to its importance in engineering and its prevalence in natural structures. Varying the flow speed can give rise to a range of dynamics including limit cycle behaviour and chaotic motion of the cantilevered sheet. Recently, the ‘inverted flag’ configuration – a cantilevered elastic sheet aligned with the flow impinging on its free edge – has been observed to produce large-amplitude flapping over a finite band of flow speeds. This flapping phenomenon has been found to be a vortex-induced vibration, and only occurs at sufficiently large Reynolds numbers. In all cases studied, the inverted flag has been formed from a cantilevered sheet of rectangular morphology, i.e. the planform of its elastic sheet is a rectangle. Here, we investigate the effect of the inverted flag’s morphology on its resulting stability and dynamics. We choose a trapezoidal planform which is explored using experiment and an analytical theory for the divergence instability of an inverted flag of arbitrary morphology. Strikingly, for this planform we observe that the flow speed range over which flapping occurs scales approximately with the flow speed at which the divergence instability occurs. This provides a means by which to predict and control flapping. In a biological setting, leaves in a wind can also align themselves in an inverted flag configuration. Motivated by this natural occurrence we also study the effect of adding an artificial ‘petiole’ (a thin elastic stalk that connects the sheet to the clamp) on the inverted flag’s dynamics. We find that the petiole serves to partially decouple fluid forces from elastic forces, for which an analytical theory is also derived, in addition to increasing the freedom by which the flapping dynamics can be tuned. These results highlight the intricacies of the flapping instability and account for some of the varied dynamics of leaves in nature.

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