The exhalant jet of mussels Mytilus edulis

Abstract

The exhalant jet flow of mussels in conjunction with currents and/or other mussels may strongly influence the mussels' grazing impact. Literature values of mussel exhalant jet velocity vary considerably and the detailed fluid mechanics of the near-mussel flow generated by the exhalant jet has hitherto been uncertain. Computational modelling of this phenomenon depends on knowledge of the velocity distribution near the exhalant siphon aperture of mussels to provide appropriate boundary conditions for numerical flow models. To be useful such information should be available for a range of mussel shell lengths. Here, we present results of a detailed study of fully open mussels Mytilus edulis in terms of filtration rate, exhalant siphon aperture area, jet velocity, gill area and body dry weight, all as a function of shell length (mean ± SD) over the range 16.0 ± 0.4 to 82.6 ± 2.9 mm, with the corresponding scaling laws also presented. The exhalant jet velocity was determined by 3 methods: (1) measured clearance rate divided by exhalant aperture area, (2) manual particle tracking velocimetry (PTV) using video-microscope recordings, and (3) particle image velocimetry (PIV). The latter provides detailed 2-component velocity distributions near the exhalant siphon in 5 planes parallel to the axis of the jet and the major axis of the oval aperture, and hence estimates of momentum and kinetic energy flows in addition to mean velocity. Data obtained on particles inside the exhalant jet of filtered water was verified by the use of titanium dioxide seeding particles which were de-agglomerated by ultrasound to a size range of 0.7 to 2 µm prior to addition, to avoid retention by the gill filter of the mussels. We found that exhalant jet velocity was essentially constant at ~8 cm s −1 , and independent of shell length. Based on geometric similarity and scaling of mussel pump-system characteristics we found that these characteristics coincide approximately for all sizes when expressed as pressure head versus volume flow divided by shell length squared. KEY WORDS: Filtration rate · Exhalant siphon area · Particle image velocimetry · Particle tracking velocimetry · Exhalant jet velocity · Velocity field · Allometric equation · Scaling law Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 437: [147][148][149][150][151][152][153][154][155][156][157][158][159][160][161][162][163][164] 2011 will influence the grazing impact and thus the concentration distribution of food particles reaching the inhalant aperture; hence affecting the feeding conditions of the mussel. Of particular interest is the undesirable phenomenon of re-filtration where part of the once filtered and exhaled water reaches the inhalant aperture of either the same or other mussels. This has been studied to some extent for mussel beds where a number of attempts have been made to model phytoplankton concentration gradients caused by dense beds of filter-feeding bivalves in relatively strong currents with a high ...

Magnetic resonance imaging analysis of water flow in the mantle cavity of live Mytilus galloprovincialis

“…When M. edulis is stimulated by algal cells, the mussel remains fully open and exploits the filtration potential. The maximum flow rate has been estimated as 2.8 l h −1 for the shell length of 33.5 mm at 11.6°C (Riisgård et al, 2011). Another study (Yamamoto et al, 2013) showed that the maximum flow rates for M. galloprovincialis were almost constant when they were acclimatized at 15, 20 and 24°C.…”

“…Intensive studies have been conducted to measure the filtration rate, using either particle clearance or direct measurements of inhalant and exhalant flows (Bayne, 1976;Kiøboe et al, 1980;Riisgård, 2001). The exhalant jet velocity of mussels has been reported in a range of 80-30 mm s −1 for Mytilus (Maire et al, 2007;MacDonald et al, 2009;Riisgård et al, 2011). The introduction of video endoscopy (Ward et al, 1991) has made it possible to conduct in vivo observation of the gills inside the shell, and also to estimate the water flow from movement of microspheres in the seawater.…”

Hydrodynamics and energetics of jumping copepod nauplii and copepodids

“…The camera was fitted with an inverted 20 mm focal length lens (Nikon Corporation, Tokyo, Japan) and a magnifying bellows tube to achieve a field of view ranging between 3.0 and 20.5 mm 2 . For PTV and PIV seeding, we prepared a suspension of TiO 2 particles by suspending a small amount of TiO 2 powder in ethanol and diluting it with filtered sea water, followed by treatment with ultrasound for 1 h, yielding particles smaller than 2 μm (Riisgård et al, 2011). We then added a small amount of the suspension to the aquarium to achieve an appropriate seeding density.…”

Effect of Salinity-Changing Rates on Filtration Activity of Mussels from Two Sites within the Baltic <i>Mytilus</i> Hybrid Zone: The Brackish Great Belt (Denmark) and the Low Saline Central Baltic Sea

“…The clearance rate (F CR ) was determined from the exponential decrease in algal concentration as a function of time using the formula (e.g. Riisgård et al [29]):…”

“…During this laps of time, the decrease (or increase) of the salinity was considered near linear so that the dilution rate (or strengthening rate) was given by the slope of a straight line for salinity versus time in the experimental period where the filtration rate was affected. The mussel shell opening degree (SOD), defined as the distance between the shells just below the exhalant siphon aperture [29], was measured manually from a digital photo by using a ruler placed on the glass wall of the experimental aquarium close to the mussel. Blue mussels, Mytilus edulis, were collected in Great Belt, Denmark, and kept in the nearby Marine Biological Research Centre (SDU) in aerated flow-through tanks supplied with seawater (18 ± 1 psu) until the experiments were performed.…”