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A History of Flow Simulation Studiesat St. Andrews Biological Station

D. J. Wildish

Biological StationSt. Andrews, N. B. EOG 2XO

December 1991

Canadian anuscript Repor ofFisheries and Aquatic Sciences

0.2134

Canada=====~===--============================:=:::::-;::::===-=

Canadian Manuscript Report ofFisheries and Aquatic Sciences

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Canadian Manuscript Report of

Fisheries and Aquatic Sciences 2134

December 1991

A HISTORY OF FLOW SIMULATION STUDIES AT

ST. ANDREWS BIOLOGICAL STATION

by

D. J. Wildish

Department of Fisheries and Oceans

Biological Sciences Branch

Biological Station

S1. Andrews, N. B. EOG 2XO Canada

ii

© Minster of Supply and Services Canada 1991

Cat. No. Fs 97-4/2134E

Correct citation for this publication:

ISSN 0706-6473

Wildish, D. J. 1991. A history of flow simulation studies at St. Andrews Biological Station. Can.Manuscr. Rep. Fish. Aquat. Sci. 2134: 25 p.

iii

ABSTRACT

Wildish, D. J. 1991. A history of flow simulation studies at St. Andrews Biological Station. Can. Manuscr.Rep. Fish. Aquat. Sci. 2134: iii + 25 p.

An historical perspective of flow studies at the St. Andrews Biological Station is presented withemphasis on the equipment used. Flow simulators, inclusive of flumes, growth tubes or respirometers,were either originally designed or taken from literature sources and built for specific experimental purposes.Six flow simulators built or used in the period 1981-91 are described and their purpose, capabilities andcharacteristics are discussed. The flow simulation lab, 1991 vintage, is described in detail inclusive of waysused to measure environmental variables (velocity, seston concentration and temperature) during anexperiment, how the data are collected, stored and analyzed. Possible improvements to the lab are alsodiscussed.

RESUME

Wildish, D.J. 1991.~Ahistory of ,flow simulation studies at SLAndrews. Biological Station. Can. Manuscr.Rep. Fish. Aquat. Sci. 2134: iii + 25 p.

Ce document trace I'historique des etudes de debit realisees a la station biologique de St. Andrews,en insistant sur Ie materiel utilise. Les simulateurs de debit, comprenant des canalisations, des tubes deculture ou des respirometres, ont ete congus apartir de zero ou encore construits aux fins experimentalesspecifiques selon des modeles provenant de sources documentaires. Ce document decrit six simulateursde debit, construits ou utilises de 1981 a 1991, et explique leurs objectifs, leurs capacites et leurscaracteristiques. On y decrit en details Ie laboratoire de simulation du debit, version 1991, Y compris lesmethodes utilisees pour mesurer les variables ecologiques (Ia velocite, la concentration de seston et latemperature) au cours d'une experience. On decrit aussi comment les donnees sont recueillies,emmagasinees et analysees et on discute des possibilites d'ameliorer Ie laboratoire.

INTRODUCTION

It is fitting that tidal energy as a keyenvironmental variable should be studied at theSt. Andrews Biological Station. S1. Andrews issituated at the mouth of the Bay of Fundy - amacrotidal estuary reputed to have one of thelargest tidal ranges in the world. Thetremendous tidal energy dissipated within the Bayhas resulted in various attempts to harness it asa renewable source of electrical power. Thisbegan in the 1920's when Passamoquoddy Baywas the focus (Huntsman 1952) and again in the1970s at many possible locations, with a favoredoption being the upper Bay - Chignecto Bay orMinas Basin (Daborn 1977; Gordon and Dadswell1984). Economic factors forced abandonment ofthe tidal power project on each occasion,although in 1984 a small demonstration tidalpower facility was installed at Annapolis Royal.This 17.8 MW capacity plant on the Nova Scotiashore is still in operation today. As the supply offossil energy. diminishes, the.Bay.oLFundy tidesmay again be considered as a source ofelectrical power for the Maritimes.

Early in the twentieth century manyinvertebrate fisheries biologists had noticed thatbivalve molluses grew faster, or larger, whereseawater tidal currents were more rapid (e.g.Belding 1912; Fraser and Smith 1928; Kerswill1949). The latter author, Dr. C. J. Kerswill,worked at the S1. Andrews Biological Station firstas a student (1938-41) doing bivalve graduatestudies at the University of Toronto. Later hewas employed at the Station (1942-46) as abivalve biologist, returning for a second period(1949-63) as principal scientist in charge ofsalmon investigations. Jim Kerswill conductedsome original field experiments to test the effectof "water circulation" on growth of quahaugs(Mercenaria mercenaria L.) and oysters (Ostreavirginica L.). This work was done near theBiological Station, Ellerslie, Prince Edward Islandin 1939-40. The results (Table 1) clearly showthat water circulation affects the growth rate ofboth bivalves over a summer-fall growing period,although direct measures of velocity or volumetric

" flow were.no1.available. In.tray.experiments withsediment, the growth of quahaugs wasreasonable with growth limitation :s. 0.8 m above

Table 1. C. J. Kerwsill's 1940 field experiments with quahaugs in trays (73 animals per tray) 60 x 120 cmwith 15 cm sides, filled with sand or oysters, and quahaugs in boxes 60 x 11 cm with 30 cm sides. Eachbox was divided into 3 layers with 1.25 cm galvanized wire with 10 cm depth between each. Twocompartments (60 x 45 cm) were present in each layer with 73 quahaugs in one and 75 oysters in theother.

Height above Initial Final Specificsediment-water mean height mean height growth

interface ± SE ±SE Growth L1-LaType of equipment m mm mm mm .100--

La

Trays with 2.3 31.4 ± 0.6 40.4 ± 0.5 9.0 28.7sediment and 1.5 31.0 ± 0.7 39.6 ± 0.6 8.6 27.7quahaugs 0.8 31.8 ± 0.7 39.2 ± 0.6 7.4 23.3

0 30.8 + 0.9 38.1 + 0.6 7.3 23.7

Boxes with Box openingsquahaugs only Open end 31.1±0.8 35.7 ± 0.6 4.6 14.8

Slatted ends 30.8 ± 0.8 34.3 ± 0.5 3.5 11.4Solid end/few 31.6±0.7 33.0 ± 0.6 1.4 4.4

holes

Boxes with oysters Box openingsonly Open end 24.7 ± 0.3 48.9 ± 0.7 24.2 98.0

Slatted ends 24.7 ± 0.3 47.6 22.9 92.7Solid end/few 24.7 ± 0.3 28.1 3.4 13.8

holes

the sediment, suggestive of benthic boundarylayer limitation. In boxes lacking sediment butcontaining quahaugs, growth was much lessbecause they grow poorly unless properlyburrowed into the sediment. By contrast, oystersgrew extremely well on wire mesh, although theflow-limited oysters (solid end/few holes) werealso slow growing. In the latter case, the causeof growth limitation was almost certainly due toseston depletion and starvation as 34 of the 75oysters died during the experiment. These, andsimilar, experiments confirm that some bivalvepopulations grow faster when exposed to highervelocities, but do not explain why.

In 1971, a large hydraulic flume wasconstructed at the St. Andrews Biological Station.It was of wood with acrylic viewing windows andtwo side-by-side, 15-m long channels. Onechannel was 119 cm and the other 92 em widewith wall heights of -120 em. Flow wasconditioned at either end of the channel wheredividers ,were absent, and. included two, low­speed propellors to recirculate water at velocitiesup to 150 cm·s· l

. The flume was used in thedevelopment of underwater instruments by theFishing Gear Engineering research section and insimulating juvenile salmon stream habitats at 50­70 cm·s· l for studies involving territoriality andfeeding (Symons 1973). This flume wasdismantled in 1979.

My own interest in tidal energy as a keyvariable in benthic ecology grew with a study ofL'Etang inlet beginning in 1970. The primarypurpose of this work was to document the benthiceffects of organic pollution by pulp mill wastesdischarging into the upper L'Etang. One couldnot avoid noticing the dominant effect of tidalvelocities in the shaping of functional groups ofbenthic animals found there. With a change indirection of my work to determine the benthicbiological effects of the previously mentioned1970's tidal energy project (Wildish 1977a) and achance to attend an international conference,which required a publishable manuscript, themoment was right to marshal ideas on tidalcurrents and benthic ecology. The conferencewas organized by Dr. Otto Kinne (InternationalHelgoland Symposium "Ecosystem Research")and took place on the island of Helgoland from26 September-1 October 1976. The paperpresented (Wildish 1977b) hardly aspired to theecosystem level of the conference, since it waslimited to subtidal sediments. A publication list

2

including all flow-related work published since,inclusive of papers in preparation to the end of1991, is shown at the end of the Reference list.

Professor David D. Kristmanson of theChemical Engineering Dept. of the University ofNew Brunswick, who had collaborated with me inthe L'Etang work, also became interested in tidalvelocity as a control for suspension feedingmacrofauna. Professor Kristmanson hascontributed a detailed knowledge of the physicsof flow and an ability to represent complex ideasin terms of mathematical formalism to our jointwork. My own thinking is visual and literate andhas caused an interaction which is aptlydescribed in a poem by Robert Graves (1961):

In Broken Images

He is quick, thinking in clear images:I am slow, thinking in broken images.

He becomes dull, trusting to his clear images;I become sharp, mistrusting my broken images..

Trusting his images, he assumes their relevance;Mistrusting my images, I question their relevance.

Assuming their relevance, he assumes the fact;Questioning their relevance, I question the fact.

When the fact fails him, he questions his senses;When the fact fails me, I approve my senses.

He continues quick and dull in his clear images;I continue slow and sharp in my broken images.

He in a new confusion of his understanding;I in a new understanding of my confusion.

David Kristmanson was also largely responsiblefor the design of two of the flow simulators (#1and #3) used in experimental work (see Table 2).

It is the purpose here to present a briefdescription of the flow simulators used in 1981­91, their design, purpose and limitations. Alsopresented is a description of the flow simulationlab as it existed in 1991, with a discussion ofsome possible future developments.

3

Table 2. Flow simulators built or used in the period 1981-91 at the St. Andrews Biological Station

VolumeSimulator capacitynumber Name Type L Reference

1 Single channel flume Flow-through FULL - 1125 Wildish and Kristmanson20 cm (1984)depth - 500

2 Kirby-Smith growth tube Flow-through 1 tube - 165 Kirby-Smith (1972)8 tubes-1319 Wildish and Kristmanson

(1985)

3 Multiple channel flume Flow-through FULL - 1670 Wildish et al. (1987)20 cm Wildish and Kristmansondepth - 740 (1988)

Wildish and Saulnier (inpress)

4 Blaika respirometer Re-circulating 50 Beamish (1978)Wildish et al. (1987)

5 Modified Vogel flume Re-circulating 90 Vogel (1981)Wildish and Miyares(1990)

6 Mini Flow Tank Re-circulating 200 Saunders and Hubbard(1944)

FLOW SIMULATORS, 1981-91

Six flow simulators were built or used atthe Biological Station (Table 2) in the 10-yrperiod ending in 1991. Other flow simulatorsproved to be unsuitable and were discarded (e.g.Appendices 1 and 2).

1) SINGLE CHANNEL FLUME

The first flow simulator to be built wasmade with marine, resin-coated, plywood by theStation workshop (Fig. 1). Its purpose was todetermine whether or not a seston depletioneffect could occur downstream of a mussel bed.The flume was deployed on the shore side of themain building at the top of the intertidal region,was provided with a roof for weather protection,and had working section dimensions of 5 m x 0.5m. Unfiltered seawater was pumped by a 4 H.P.submersible pump located just above bottomnear the wharf. The maximum flow possible was- 5 cm'S". Velocity measurements were madewith an hydrogen bubble generator apparatus, or

Out let

Fig. 1. Single channel flume #1.

volumetrically with a simple orifice meter andwater manometer. This flume was eventuallygiven to Kee Muschenheim of the Dept. ofOceanography, Dalhousie University, andtransported there aboard the RN ALFREDNEEDLER. This was near the beginning of Kee'sgraduate studies and must have provided astimulus to build a better flume (seeMuschenheim et al. 1986).

2) KIRBY-SMITH GROWTH TUBE

For longer-term measures of the growthrate of bivalves, Kirby-Smith (1972) designed agrowth tube apparatus which was used in ourstudies of giant scallop growth (Wildish andKristmanson 1985). The construction of theheadtank and outflow boxes was of marineplywood in the Station workshop (Fig. 2).Seawater supply to the constant head tank wasfrom the same pump as used for the singlechannel flume. Experimental bivalves weresupported in the centre line of the 1.5-m longacrylic tubes by plastic mesh inserts. Bulk flowvelocities were determined from timed volumetricflows divided by the area of tube cross section(=38.47 cm2

) thus:

bulk flow velocity cm.s -1. volumetric flow rate, cm3 -s -I, 38.47

Pipe flows are complex with maximum velocitiesat the pipe centre line where velocities, when fullydeveloped, are 2x the mean, or bulk, velocity.Thus bulk velocities underestimate velocitiesexperienced by bivalves at the tube centre line.Although it is possible to insert velocity probesthrough the tube walls in rubber bungs, this wasnot done during our experiments (Wildish andKristmanson 1985).

- ,II

---I -----,,- I _

'-----"'-- ...L.::..;:....c..:~__'''"---''=___=_;1-=

4

experiments. The four channels of the multiple­channel flume which are run concurrently thusmean that four treatments at the same sestonconcentration (and quality) can have varyingvelocities (versus eight in the Kirby-Smith growthtube).

The multiple channel flume (Fig. 3) wasbuilt in the Station workshops from a design byD. D. Kristmanson. It occupies a semi­permanent position near the Biological Stationtide pool and is protected from weather by awooden building which is wired for electricalpower. The working part of the flume is 5 m longwith a downstream flare (from 64-85 cm wide).The flume is divided by plywood walls into fourequal channels, each 15 cm wide at the inlet,and 20 cm wide at the outlet end. The seams ofthe channels were caulked to prevent seawaterexchange between them. Velocities in eachchannel could be adjusted by removing rubberbungs in a perforated bulkhead which terminatedthe working· section (Fig.3). Originally, theunfiltered seawater for the flume was supplied by'a separate 3" line and 8 H.P. submersible pumplocated near the wharf. A maximum flow of-15cm-s· 1 in one of the flume channels waspossible with this arrangement. More recently,unfiltered seawater for the multiple channel flumehas been supplied direct from the small reservoirfrom the main seawater supply before it passesthrough a sand filter.

One advantage of the multiple-channelflume over the growth tube in that it permits amore realistic simulation of flow with a flumeboundary layer present during the experiment.The flume also allows better access to determinevelocity profiles near the experimental bivalves,e.g. with a Nixon Stream Flo probe (see p.11).

4) BLAZKA RESPIROMETER

Fig. 2. Kirby-Smith growth tube apparatus #2.

3) MULTIPLE CHANNEL FLUME

In using unfiltered seawater in bivalvegrowth studies, velocity as the primary variablecan only be compared within each experimentalrun. This is because seston concentration andquality will be variable for consecutive

1+1.--_ 1 m ----.j.1 Outlet

IIIWith flow-through devices, designed to

measure bivalve growth, it is practicallyimpossible to adjust the seston concentration andquality. This is because of the large volumesinvolved and great cost in providing sufficientamounts of cultured microalgae. Thus, forinstance, in the multiple channel flume, thevolumetric flow required would be 444 Umin at amodest flow of 5 cm-s" and flume depth of 20cm. In order to examine velocity concurrentlywith seston concentration and quality, it wasnecessary to minimize the volume of seawater

5

Perforated Bulkheadtake Perforated Plywood

, - 0, 1, : ~ 00 .. 64

~\ : ~em 0

• u 1. :tfJ/"I : 0

- 'j ...-In

86em

~_ ,.sm--_'I_'----------Sm ·1·30.~elmI Inl!ke

T

-,-S3.3em

1jer,lorated Bulkhead

Ho'. DIameters000 1.9. 2.S. 3.B emo 0 5.0. 2.S emo 0 2.5.1.2cm

Fig. 3. Multiple channel flume #3. Top· plan view; bottom· elevation view.

used and to employ a recirculating system. Suchan approach dictates that only short-termexperiments are feasible. This is because of thebuildUp of excretory products in seawater withtime, and hence a short-term measure, feeding,rather thangrowthrate,-is too method of choice.

A closed, recirculating device, the Blaika,Volf and Cepala respirometer (see in Beamish1978), became available from the BiologicalStation laboratory of Dr. R. W. Saunders. TheBlaika respirometer consisted (Fig. 4) of an innerand outer acrylic tube with machined end walls ofacrylic to maintain smooth flows. The impellerwas positioned in the inner tube and caused areturn flow in the outer tube. The respirometerhad been constructed in the University of TorontoWorkshop and could reach a velocity -75 cmes·'.The apparatus was designed for swimmingperformance experiments with fish (see also Smit1965) and was not ideal for bivalves. The chiefdifficulty was that without further modification itwas impossible to measure velocities near theanimals which were slJpported in our experiments(Wildish et al. 1987) on plastic mesh in the mid,centre line of the fish chamber. A Nixonstreamflo probe could be inserted through thesampling tube at one end of the apparatus (Fig.4) but was distant from the bivalve experimentalsubjects.

Sampling

l~r-o"'''' \r'~ inlet

____ 1.= - - Irr - 0- -lr () 1F - - - t~

Fig. 4. Blazka respirometer #4. Redrawn from Smit(1965).

5) MODIFIED VOGEL FLUME

The flow pattern in the Blaikarespirometer was that of a pipe, unlike theboundary layer flow that bivalves wouldexperience in the natural environment.Consequently a design was sought which couldprovide a flume boundary layer environment.The flume design chosen was from Vogel (1981).The St. Andrews Biological Station version wasconstructed of 6" diameter plastic plumbers pipeand corner ells with 82 x 18.5 x 15 cm workingsection of acrylic (Fig. 5). Instead of mountingthe propeller in the vertical position as in Vogel(1981), it was mounted horizontally with a driveshaft sealed into the lower section of the flume.

Table 3. Mini Flow tank calibration on 31 July1991 using Stream Flo probe #1330 positioned8.5 cm above the flume floor.

Fig. 5. Modified Vogel flume #5.

The motor was of 3/4 H.P. capacity (Leeson DCpermanent magnet motor Model C4D17FK3C)and was adjusted by a Motor Master 100rheostat. In practice this flume was satisfactoryup to a flow velocity of <40 cm_s· 1 but beyondthis, entrainment of air bubbles and waveformation limited its usefulness. The flow profilesin this flume were not uniform.

6) MINI FLOW TANK

6

Impellor MeanSettings Velocity-turns cm_s· 1

\ 201/

2 253/ 304

1 3511

/4 3913

/4 4521

/ 4 5523

/ 4 6231

/ 4 7433

/ 4 93

Observations

clear

Few bubblesMany bubbles

The requirement in feeding/growthstudies with bivalves to provide ambient flowconditions >75 cm_s· 1 led to a further search fora recirculating flume capable of these flows. Mr.Mark Chin-Yee, Head of the MechanicalEngineering group at the Bedford Institute ofOceanography located a reference (Saundersand Hubbard 1944) from which it appearedpossible .to .achi.eve this. The flume is of castacrylic throughout and was constructed byPlastics Maritime Ltd, Armdale, NS, according toa detailed design prepared by Mark Chin-Yee.The mini flow tank (Fig. 6) differed from theVogel flume in having a trap from whichentrained air bubbles were removed by vacuumsuction, and a collimator and throat section forflow forming at the entrance to the 65 cm long by23 cm wide working section. A different methodof driving the impeller was also used - apneumatic system with an air compressor andpressure storage tank located in a separatebuilding. This arrangement minimized electricalnoise and hence interference with acousticmethods used in the laboratory to determineanimal physiological or behavioral responses.

The initial calibration results (Table 3)show that -75 cm-s" could be achieved. With afew minor changes to the angle of attack of theturning vanes near the impellor shaft, which wasshedding air bubbles, this was improved to -100cm_s· 1

• Impeller settings at low velocities werenot reproducible - this might be improved by use

of a variable pitch propellor. Stream Flo probeprofiles in vertical (Table 4) and horizontal (Table­S) planes show that velocities are uniform with aslight tendency to be 'Iess near the centre(presumably because of lower acceleration forcesthere than near the throat walls). Flumeboundary layers on walls and floor arecompressed to within 2 em or less and flows herecan only be resolved with thermistor beadvelocimeter observations. A satisfactory flumeboundary layer of -8 cm high can be simulatedby placing a 1-cm diameter acrylic cylinderacross the entrance to the working section.

HYDRODYNAMIC CONSIDERATIONS

Ambient velocities in the Bay of Fundy for1978 ranged from Umax =40-150 cm-s" (see inWildish and Peer 1983) and are complex, inter­acting in shallow water with wind/wave effects. Insimulating these flows in the lab it has beennecessary to simplify so that in all of the devicesdescribed here only a unidirectional flow wascreated. In only three of the simulators (thesingle channel flume #1, multiple channel flume#3 and Mini Flow Tank #6) has a reasonably welldeveloped boundary layer been simulated withinthe working section. Thus the flume boundarylayer at the downstream end of the workingsection of flumes 1 and 3 with adequateroughness (consisting of live or dead musselbeds) was >20 cm in height. These flumes could

7

9

f

ec

•

.----~----b--- ....·I

Q f I®

I---

b e 0~I

l-

I- I-

Fig. 6. Mini Flow Tank #6. a. propellor; b. flume working section with false floor; c. flow depth; d. flap forcontrolling surface flow; e. throat section; f. exit hole for air removal; g. collimator; h. turning vanes.

8

Table 4. Mini Flow Tank vertical flow profiles observed with streamflo probe #1330 on 1.8. 1991. Averageof six replicated samples (10-s integrations) as cm-s". The probe samples 2.5 mm above bottom and sincethe rotor diameter is 11.6 mm the lowest sample is (11.6 + 2.5)/2 = 7.1 mm above bottom. The probe ispositioned in the flume centre line at 35 em in from the entrance.

Compressed air controlDistance from bottom

em 1/4 turn 2 turns 3 turns

0.7 19.9 50.9 69.91.7 20.2 51.5 71.62.7 19.9 - 69.33.7 19.8 49.9 67.64.7 19.5 48.8 66.15.7 19.5 - 65.46.7 19.4 47.2 -7.7 - - 64.58.7 19.6 47.7 66.29.7 20.0 - 68.1

10.7 20.8 48.9 69.111.7 20.7 - -12.7 21.2 50.5 71.913.7 21.6 50.4 72.5

Table 5. Mini Flow Tank horizontal flow profile at 8.7 ern-above bottom and 35-cmin from the entranceas cm-s". Stream Flo probe #1330 measurements (average of six 10-s integrations). Flume width =23 em.

Compressed air controller

Distance from wall. em 1/8 turn 1 3/4 turn 3 turns

0.7 17.9 47.9 67.81.7 17.6 47.0 67.72.7 17.7 47.7 67.23.7 17.7 46.31 68.34.7 17.5 47.2 68.55.7 17.5 47.1 68.46.7 17.2 48.7 69.17.7 17.2 48.2 68.48.7 17.3 48.3 67.49.7 - - -

10.7 16.9 45.5 67.7

meet the exacting requirements detailed byNowell and Jumars (1987) for studies involvingseston distribution and capture by bivalves or indetermining the initial motion conditions forsuspending sedimentary particles.

The two pipe flow devices (#2 and 4)have complex flows with wall drag dominatingand maximum flows at the centre line where theexperimental subjects were positioned duringexperiments.

As long as the actual velocities near thebivalve inhalant can be measured and thevelocity conditions replicated then the Mini FlowTank method is satisfactory for bivalve feeding,and single and multiple channel flumes forbivalve growth studies.

An open channel solution in a relativelysmall recirculating flume «200 L volume) wassought because of ease in placing velocitymeasuring probes. The first attempt - a modifiedVogel type flume - produced non-uniform flows at10-15 cm_s· l and a flow maximum of <40 cm_s· l

before air bubbles appeared in the flow. Theflume conditions are influenced by the poordesign for both entrance and exit conditionswhich do not reduce the instabilities introducedby the impellor blade stroke and in forcing theflow around four corners. Air may be entrainedat either end of the flume depending on whichway the flow is directed. The latest flume (#6)has a much more uniform flow profile in theworking section with boundary layers on wallsand floor of <2 cm thick. The entrance conditionsincluded a collimator and throat section whicheffectively smoothed the flow in the workingsection. Cavitation caused by the revolvingimpellor resulted in an upper useful limit of -100cm_s· l

.

FLOW SIMULATION LABORATORY IN 1991

GENERAL

A new laboratory was built at the southend of the Solarium wing of the Main Building.The floor plan is shown in Fig. 7. The labincludes a control room with two 1 x 1 m, one­way glass windows for viewing the wet lab., orflume room which is supplied with cold, filteredseawater, cold fresh water and air. A separate

9

supply line is connected to a 1000-L capacityround tank situated on the floor above the laband is supplied with filtered or unfiltered seawaterwith a cooling device (Mini-cool) for temperaturecontrol. Its purpose is to rapidly fill the flumesincluding the 1000-L capacity Maxi Flow Tankplanned for installation in 1992.

The wet lab is illuminated by seven 100watt bulbs placed behind glass covers. Theelectrical system is connected to a control panelwith facilities for dimming the lights and alsocontrolling on/off settings to simulate, forexample, natural photoperiods (Suntracker,Paragon Electric Canada Ltd, 221 Evans Avenue,Etobicoke, Ontario, M8Z 1JS). The control panelalso regulates a heater and Xpelair fan in theoffice and an air conditioner (Electrohome, 5,000BTU rating) by on/off switch in the lab. An on/offswitch for the air compressor which is housed inan adjacent shed is also provided.

The modified Vogel flume (#5) was usedin the lab. until the end of July when the newMini Flow Tank (#6) was installed. At this timethe #5 flume was removed for storage and a 3'diameter round tank placed in the lab forexperiments with salmon smolts (Fig. 7). Thereis a video camera system, data logger and PCwith 10 separate relays in place connecting it andthe flume wet lab.

A three-di mensional positionerconstructed of Unislide Assemblies parts(Velmex, Inc., East Bloomfield, N.Y. 14443,U.S.A.) was made by the Mechanical Engineeringgroup at the Bedford Institute of Oceanography.It carried velocity or temperature probes (up tofour at a time) in custom made quick clip on/offassembles. The positioner fitted over the flumewalls and could be secured with plastic screws.One hundred units on each of the Unislideknurled knobs was equal to 1 mm in slidemovement.

FLOW VELOCITY

Velocity control In the Mini Flow Tank

Compressed air is supplied from a 10H.P. Webster model 811-1 air compressor andpressure storage tank located in a small shed

10

G

Printer

....~

E ..J::

OJ0 III0

ex:

0~-C0

U

A"ConditIOner

1m

I IoI I

Flume

Cali brator

Fig. 7. Plan view of the St. Andrews Biological Station flow simulation laboratory In 1991.

close to the lab. The air is supplied in a 1/2"plastic pipe through a Wilkerson CBO-03-000D90 air trap and pressures gauge (set at 70 psi)and oil lubricator (Wilkerson L16-04-000 K90) tothe drive head of the impeller shaft. The settingson the threaded controller (throat valve)correspond to velocities as shown in Table 3.Exhausted air is carried in a second hose outsidethe building to waste.

Velocity calibrator

The apparatus was designed andconstructed in the Chemical Engineeringlaboratory at the University of New Brunswick. Itconsisted of a 20-cm diameter acrylic tube andoverflow tank (Fig. 8). Two in-line f10wmeters(Blue White Industries, Westminster, CA, U.S.A.)could adjust the flow over the range up to 40Umin (LPM) which is equivalent to -32 cm-s·'.Sea water entered the tube at the bottom passingthrough flow forming elements and a 5-cm

e

Fig. 8. Velocity calibrator. a. flowmeter CF45750(4-40 LPM); b. flowmeter CF45500 (1.8-18 LPM); c.velocity control; d. test probe position; e. flowforming elements; f. seawater drain valve.

11

diameter exit hole before passing up the tubeand over flowing into a tank and going to waste.Test probes were introduced at 51 cm above theexit hole in a rubber bung which had beensagitally halved and bored to take the probediameter. It was necessary to ensure that theprobe was positioned centrally above the exithole, so that the Stream Flo probe was normal tothe flow.

Velocity measurement

Two systems were available to measurevelocities - Stream Flo velocity meters, andthermistor bead velocimeters.

The Stream Flo system is manufacturedby Nixon Instrumentation, Charlton KingsIndustrial Estate, Cirencester Road, Cheltenham,Gloucestershine, U.K. GL53 8 DZ. On hand aresix model 403 probes (Numbers 896,1329,1330,1473, 1474, 1487) and two model 412 digitalindicators, 115v 60 cycles (Numbers 3066 and3303). The model 403 probes are 46.8 cm long'and have a rotor protected by a metal ring withprojecting bars. The five-bladed, PVC rotor is ona hard stainless steel spindle mounted in conicalpivots with a 1-mm Vee Jewel bearing. Aninsulated gold wire in the probe terminates at 0.1mm from the rotor tips. During operation, thepassage of the blades past the gold INtre variesthe impedance, causing the indicator current togenerate a square wave signal whose pulse rateis proportional to the rotor speed and henceambient velocity. The indicators have a 3-digitLED display in hertz (Hz). One-, 10-s orcontinuous sampling is possible for the indicatorwith output for a recorder (0-200 IJA).

The rotor diameter is 11 mm and sointegrates flow in an area of 95 mm2

. Because ofthe protective metal ring, the tips of the rotor cancome only -2.5 mm away from a hard surface.

Although Nixon Instrumentation providesa calibration chart with each model 403 probe, ithas been found useful to regUlarly calibrate eachprobe in use because this helps to identify anyproblems in velocity measurement with it. I havefound the Stream Flo system to be trouble-free touse, although macro particles in the seawater(e.g. hair, bivalve faeces) may interfere with thefree turning of the rotor. We routinely view therotor under a low power binocular microscopeand remove foreign particulates with a fine pair of

12

Fig. 9. Streamflow probe calibration plot.

forceps or by treatment in a sonic bath. Afterevery use, the probe head is cleaned with 100%ethanol and rinsed with deionized water.Occasionally we have had trouble with faultyelectrical connections, but this is usually obviousby the performance of the digital indicator. 40

The calibrator is used to check eachmodel 403 probe weekly during regular use or atthe beginning of new use of a probe. Afterturning on the seawater flow to the calibrator theprobe is positioned in it as described on p. 11and the flowmeters adjusted to a range ofvelocities (Table 6). The velocity (U) indicated bythe calibrator in Umin (LPM) can be converted tocm_s· l by:

U, em_s· l = -0.0759 + 1.313 x LPM-1.26 x 10.2 x LPM2

A plot of mean Hz on U (Fig. 9) is linearexcept below 5 cm_s· l

. The quoted range of the403 Stream Flo probe is 2.5-150 cm-s· l

, althoughas mentioned the velocity calibrator can onlydetermine velocities to a maximum of 32.28cm_s· l

. It is assumed that projections of theregression line beyond the upper limit of thecalibrator give reasonable prediction of the 403probes output in the higher range.

30

en

E 20u

10 20Hz

30 40

Table 6. Calibration for Stream Flo probe #1330 using the 10 second integration option.

EquivalentLPM Hz Mean Hz cm_s· l

3 1.2, 1.2, 1.0, 1.1, 1.2 1.14 3.66 2.5, 2.4, 2.5, 2.5, 2.4, 2.5, 2.5, 2.42 2.45 7.19 4.9, 4.9, 4.8,4.9, 4.8, 4.9 4.85 10.8

12 7.4, 7.5, 7.4, 7.5, 7.5, 7.6, 7.5, 7.6 7.5 14.020 13.4, 13.3, 13.14, 13.4, 13.3, 13.4 13.35 21.116 10.5, 10.5, 10.5, 10.5, 10.5 10.5 18.724 16.2,16.1,16.0,16.1,16.1 16.1 25.312 7.5, 7.7, 7.5, 7.6, 7.5 7.55 14.0

6 2.6, 2.5, 2.5 2.55 7.13 1.5,1.0,1.1,1.0,1.0 1.1 3.6

The thermistor bead velocimeter currentlyon hand was manufactured in the University ofNew Brunswick, Dept. of Chemical EngineeringFredericton, NB, E3B 5A3, from a design byVogel (1981). The circuit diagram given on p.312 of Vogel (1981) was followed (see alsoKristmanson 1991) with minor modifications. Thethermistor used was from the Victory EngineeringCorporation, Springfield, New Jersey, U.S.A.07081, Veco model #21 A14 with sensing headdiameter of 1.326 mm.

13

velocity (-15 cm-s") and voltage measurementsacross the external resistance made with avoltmeter (Fluke 87 True RMS multimeter, FlukeElectronics Canada Inc, 400 Briltania Rd. East,Unit #1, Mississauga, Ontario, L4Z 1X9) to 0.1mV. The pen position (0-100) on a millivoltrecorder (Brinkmann 2544, BrinkmannInstruments (Canada) Ltd, 50 Galaxy Blvd,Rexdale, Toronto, Ontario) was also noted withthe linear mode operational. Using these data,the terms e and f are evaluated in:

The equation used in the velocimetercalibration (from Kristmanson 1991) is:

u -I '1 -1f£ - Cl"y2

0.2912 ...................(1)

where d is the number of recorder divisions.

The velocimeter probe was thencompared with the Stream Flo 403 probe asstandard (U, cm-s") in estimating Win two ways:

where U =a =~' =t>.V' =

velocity in cm-s"the. probe constanta circuit plus probe constantat>.vo + b, where the amplifieroutput is at>.vo and a and barecircuit parameters to bedetermined.

(0.2912)'12 _ L _Cl (2)

U "V,2

13' - [( 0.~12r + Cl] (9(M)2 ........(3)

The coefficient 0.2912 was measured ata temperature of 7.8°C and a probe diameter of1.326 mm - any departure from these parametersmust be corrected for as in Kristmanson (1991).

It is necessary to determine a probeconstant (a) for each new probe used (seeKristmanson 1991). For the probe currentlyavailable velocimeter probe #1 a = 1.5398.

The thermistor bead probe was carried ina steel tube and during calibration this wasmounted in the flume alongside a previouslycalibrated Stream Flo 403 probe so that bothexperienced the same velocity (e. g. equal heightabove the bottom) but did not interfere with theflow patterns of each other. The temperaturecompensating thermistor of the velocimeter wasplaced in the flume flow and sufficient timeallowed for it to equilibrate.

The flume flow was reduced to 0 andwhen it had stopped circulating, thepotentiometer was set so the micrometerindicates -10 microamperes. The flume wasthen run at a low (5 cm-s") followed by a higher

If the values of (2) and (3) were within±2%, the average value was used to calculate Uby the equation (1). If the values are not close,a third determination is made and the worst valuediscarded.

The above calculations are made with aprogram written for an IBM compatible PC usingthe spread sheet Quattro Pro (Kristmanson1991). Typical results with velocimeter probe #1are shown in Fig. 10. The curvilinear responseshows that velocities > 20 cm_s· l cannot bemeasured by the probe because the responsehas peaked. The useful range for this probe isthus -2 - 20 cm-s".

TEMPERATURE

It is important during flume experimentsto maintain a constant seawater temperature sothat this variable does not influence bivalvefeeding rates.

14

In the flow-through, mUltiple-channelflume the seawater supplied is unfiltered naturalseawater taken from bottom water near the endof the Station wharf and supplied to the flumebefore it is filtered. Hence, growth studies can beconducted to closely reflect the growth potentialof natural local seawater for bivalves. Filteredseawater is usually employed in bivalve feedingexperiments if cultured microalgae are added.Knowing the volume of seawater and the densityof microalgal cells in the culture, it is possible to'adjust the initial density of microalgae in theflume. The volume of cultured microalgaerequired is often quite large, e. g. to obtain a celldensity of 106 Chroomonas salinus cells/L in theMini Flow Tank; since the maximum culturedensity attainable is -109 cells/L and the totalvolume in the flume = 200 L, we require 200 x107 cells/L = 20 Lx 109 cells. Thus we require allof the culture solution or 20 L to achieve thedesired density. Local blooms of microalgae (e.g. Nitzschia pseudodelicatissima) reach maximumdensities of 2.8 x 108 cells/L (Martin and Wildish1990).

Microalgal culture methods employed arestandard (see Guillard 1984) for easily culturedmicroalgae, such as Chroomonas salinus,although specialized techniques (or greenthumbs) are required for some species (e.g. N.pseudodelicatissima) .

It is well established in the literature ofthe subject (e. g. Brand 1991) that feeding andgrowth are controlled by seasonal changes in theconcentration and quality of seston as a foodsource.

Packard Thermometer System 2802-A operatingand service manual for details.

Seston supply

SESTON

25

•

10 15 20Ve 10 e i I Y (em· s")

54 50 L..-__L.....__..L-__...l..-__...l-_----.J

o

Temperature measurement

The solution was an in-flume cooling coilof titanium supplied with circulating Freon from aremote source (so the pump motor did notinterfere with acoustic measurements). Thepump was controlled by a temperature regulatingcircuit (Appendix 3) designed and built byLaurence White of the NB Community College,St. Andrews. Cooled water could also besupplied to the flume from the overhead 1000-Lcapacity head tank which contained a refrigeratedtitanium cooling coil (Mini Cool). ..

Fig. 10. Thermistor bead velocimeter #1 calibrationplot.

Temperature control

In the new flow simulation lab, it washoped that the air conditioner would maintain lowenough wet lab air temperatures to avoid heatingthe flume water during 2 h long experiments.This proved not to be the case; for instance, inApril, incoming filtered seawater was 4'soC andduring a 2-h experiment in the modified Vogelflume (80 L), it heated 2.5°C at a wet lab air

. temperature of 14°C.

480

(J)-0>

:; 4.70

~::J

0~

~ 460

a.E

<:t:

A Hewlett Packard 2802 A thermometer(#1213 A06922) and temperature probe(HP 16642 - 2209 M) were mounted in the flumeflow. The probe was 6 mm in diameter at the tipand 13 em long. Calibration of this instrumentwas probe specific and required calibration ofboth digital and analogue outputs at O°C bymeasuring the probe in a Dewar flask containingice shavings and water. See the Hewlett·

Seston concentration

Two methods are routinely used indetermining the concentration of microalgaepresent in the seston seawater samples. Afluorometric method involves extraction ofchlorophyll a from the filtered sample andmeasurement in a Turner III fluorometercalibrated with known quantities of chlorophyll a.The other method involves direct microscopic

counting on a slide fitted with a counting chamberof known volume (haernocytometer of 0.01 mLcapacity).

To measure chlorophyll a, take aseawater sample of appropriate and measuredvolume, and filter in a Millipore vacuum systemwith a Whatman GFC filter in place. Removeand fold the drying filter paper and grind in amortar containing a few grains of sea sand anddrops of 90% acetone. Pour the contents into agraduated centrifuge vial and make up to 10 mLwith 90% acetone washings from the mortar.The vial is stored in the dark for a 2-h periodbefore centrifuging for 5 min (half speed in anIEC clinical centrifuge). After diluting some of thesupernate appropriately (usually 1:100) withfurther 90% acetone, the blank sample is readyfor analysis. After warming up, the fluorometer iszeroed with a 90% acetone blank and theunknown sample read. The method is calibratedagainst pure chlorophyll a purchased from SigmaChemical Co.

To measure cell numbers a small aliquot(5 mL) of seawater is removed from the flumeand placed in a vial with a drop of formalin-aceticacid for fixing the cells. After thorough shaking,an aliquot is withdrawn in a Pasteur pipet andused to load the 0.01 mL capacityhaemocytometer. With a Carl Zeiss microscopefitted with a Neofluar 25/0.60 objective and 8 xeyepiece, all cells in the 16 x 16 grid arecounted. When 25 adjacent grids have beencounted, the numbers are totalled and this equalscell number/mL x 104

.

A recent calibration involving cell density(x) and chlorophyll a (y) content as Ilg/L (Table 7)yields a regression of:

y =6.19E - 4x + 7.868, ~ =0.995, n =28.

The mean of each of the x and ycolumns with the standard error as a percentageof the mean gives an estimate of the variability ofeach measure (Table 8). This analysis showsthat the cell density measurement and chlorophylla determination seem equally variable (standarderrors < 1-5%) except in the most dilute solutionanalyzed for chlorophyll a (standard error of11.3%).

15

Seston quality

No routine measurement of seston quality- by which Ultimately is meant its ability topromote growth in a specified bivalve - isavailable.

During preliminary studies with filtrationrate measurements of blue mussels at varyingambient flow velocities (Wildish and Miyares1990), it was noticed that two major factorsinfluenced the filtration rate of Mytilus edulis:velocity (with r? = 0.45) and initial chlorophyll alevel (with ~ = 0.2). Since the mussels were alloffered the same initial cell concentration of acultured microalga (104 celis-mL'l of C. salina)and fed more rapidly on cells with higherchlorophyll a, the initial chlorophyll a per cellcould be used as an indicator of the palatability(but not necessarily growth promotioncapabilities) of that particular species ofmicroalga. The mean initial chlorophyll a

. concentration._used inour..experiment was: 1.5pg-celr' with 2X standard error as 7%. Theactual range of levels recorded over 40 separateexperiments was 0.72-1.84 pg-celr'. Althoughsatisfactory if a unialgal culture is fed to bivalves,when a mixed culture or natural seston is offered,the method may become invalid. This is becausedifferent microalgae may have different quantitiesof chlorophyll a per cell or affect palatability (e.g.the presence of toxins resulting in differentialingestion). Despite this, MacDonald and Ward(1991), using mg chlorophyll almg seston inscallop feeding experiments, claim it to besatisfactory.

The question of food quality in freshwaterand marine studies was considered at the 1991annual meeting of the American Society ofLimnology and Oceanography, held at S1. Mary'sUniversity in Halifax. Bowen (1991), studyingfish, thought that protein and energy contentswere required to characterize the growth potentialof food for Tilapia aurea. Enzymatically availableprotein has been proposed as a measure of thefood of deposit feeding macrofauna (Meyer 1991)and the method could readily be used on sestonpellets. Harrison and Thompson (1990) showedthat the diatom Thallassosira pseudonana grownunder enhanced light conditions produced bettergrowth and survival rates of Pacific oyster larvae(Crassostrea gigas) apparently due to increasedlevels of carbohydrates in the cell.

16

Table 7. Cell density (x) and chlorophyll a content as Ilg/L (y) for a seawater dilution series of Chroomonassalinus culture.

Replication 1:1.000,000 1:10,000 1:1000 1:100 1:10 0# x y x y x y x y x y x y

1 5.4 .0083 109 .0568 860 .6231 7800 8.374 79,000 83.74 1,220,000 705.2

2 5.2 .0061 105 .0568 800 .5901 7200 8.925 76,000 80.43 1,190,000 762.5

3 6.1 .0061 89 .0623 860 .6231 7200 8.594 76,000 79.33 1,220,000 727.2

4 .0094 98 .0557 1010 .6121 7600 7.713 73,000 81.53 1,210,000 793.3

5 112 .0169 1030 .6341 7300 7.602 86,000 81.53 1,200,000 785.3

Table 8. Mean cell density (x) and chlorophyll a content (y) with standard error (SE) as a percentage ofthe mean.

Dilution x±% SE n y±% SE n

0 1.208 x 106 ± 0.5 5 754.68 ± 2.2 5

10 7.800 X 104 ± 2.8 5 81.31 ± 0.9 5

10.2 7.420 x 103 ± 1.6 5 8.24 ± 3.1 5

10.3 9.120 X 102 ± 5.0 5 0.617± 1.2 5

10.4 1.030 X 102 ± 4.0 5 0.059± 2.4 5

10.5 5.570 ± 4.9 3 0.008± 11.3 4

VIDEO CAMERA

The video camera system availableconsists of:

an RCA TV camera (TC2855C) with azoom lens (12.5-75 mm, from Cosmicar,Model C621218M3-2),a remote lens controller (from FOR-A Co,model M2-6B),an Electrohome video cassette recorder,andtwo black and white Rostech videomonitors, one in the wet lab and theother in the control room.

The equipment was ageing and surplus to therequirement of the now defunct BRUTIV (BottomReferencing Underwater Towed Instrument

Vehicle) development project at the BiologicalStation.

Use of the camera has clearlydemonstrated the utility of a video system inbivalve feeding studies. In our June/July studiesof giant scallops in the modified Vogel flume (Fig.11), the camera was focused on the exhalantopening while flow rates were varied. Scallopsare very sensitive to light changes but byscreening one side of the flume it was possible toadjust flows without disturbing the scallops.Exhalant opening areas could then be monitoredon undisturbed scallops by making measure­ments directly on the screen. These resultsprovided the first evidence that the degree ofopening of the exhalant was directly related tothe ambient velocity (Wildish and Saulnier, inpress).

17

Fig. 11. Experimental setup for June-July 1991 with the Vogel flume to determine the mechanism of velocityin giant scallops.

DATA LOGGING AND ANALYSIS

The data logger was obtained from AlphaControls and 361 Steelcase Rd.,West, Unit 3, Markham, Ontario, L3R 3V8 andconsisted of:

PC A-48 Aquistor to handle up to 48input channels of 0.3 microvolts to 10volts.Options obtained include: menu-drivensoftware, signal conditioning (to providetemperature referencing and linearizingfor thermocouples), printer-driver (to givereal time printout), multi-tasking software(to allow simultaneous use of the PCwhile it is recording input data fromexperiments), a 10 relay output (forcontrol of equipment by the PC Aquistor),RS-232 serial interface and high speeddata storage facility.

The computer (PC) used withthe data logger was an IBM compatible, with 31

/ 2

and 51// disk drives, a 40 meg hard disc and 1

meg of The multi-mode was aPanasonic KX-P1180.

PREPARATION OF ASEXPERIMENTAL ANIMALS

Bivalves are preferably collected by hand,ie. at low tide by digging for clams or by removalfrom rocky surfaces as in the case of bluemussels. For giant scallops, this meanscollection by we havealso used undamaged scallops collected bydredging. In transporting the bivalves back to thelab, the aim is to avoid temperature shocks andpreferably to keep them in running seawater atambient seawater temperature.

Once back at the lab, the bivalves wereimmediately transferred to holding conditionswhere they experience low current velocities andnatural seston concentration and quality. Theywere held either in lantern nets fromthe Biological Station wharf pontoon, or placed in

18

IMPROVEMENTS

the multichannel flume through which non-filteredseawater was flowing at -5 cm-s- 1

.

Individual bivalves of adult size can beidentified a small, numbered plastictag from Hallprint Pty Ltd., 27Jacobson Crescent, Holden Hill, South Australia5088, Australia) with a cyanoacrylate adhesivethat is available from Satellite City PTO, P.O. Box836, Simi, California, 93062, USA.

For the reasons mentioned in theappropriate section, the measurement of sestonquality by chlorophyll a per cell or per unit weightof seston are unlikely to be sufficient for manyfuture uses. Hence, a method should be cali­brated which will compare protein:carbohydrateor chlorophyll a:carbohydrate contents in sestonicfood of known dry weight.

LONG~ERMIMPROVEMENTS

Improvements required for the videosystem include: replacement of the VCR systemto provide a better cassette editor so· thatstopped images can be analyzed for shape, area,and number, a video digitizing board andsoftware for the PC to enable automated analysisof shapes, area, etc.

One goal of the last few years has beento devise an automated system for addingcultured microalgae to the flume in such a waythat the rate of addition is a direct indication ofthe feeding rate of a single bivalve or group ofbivalves. Winter (1973) originally used such asystem in a gently stirred tank (10-L capacity)containing a group of blue mussels. Aphotometric system was used to detect the lossof light caused by absorption by the microalgaepresent. By suitable relays and switches, it waspossible to have the increasing light level(caused by the bivalves consuming themicroalgae) switch on a dosing valve connectedto a microalgal culture kept suspended by amagnetic stirrer. This system was not specificsince any particles present would reduce the lightreaching the photoelectric cell, and hence couldnot be used with natural seston in seawater.Modern liquid particle monitoring systems (Le.that produced by Met One, 481 CaliforniaAvenue, Grants Pass, OR, 97526, USA) do notseem adaptable to this purpose (J. Hunt, pers.commun.) for the same reasons.

LAB: THE FUTURE

It is difficult to predict how the lab will beset up next year, let alone in 5 yr time. Never­thedes:s, there are some obvious improvements tomethods used in the present system as describedin the sections (short-termimprovements for which solutions appear to beavailable) as well as novel objectives and/orimprovements for which solutions seem to beless clear (long-term improvements).

For the purpose of flume holding, thethree wall dividers were removed as well as thetwo fine mesh screens which tend to clog upduring use. Calculations were made (Le.assuming adult sized scallops pump 10 L_h-1

,

and adult blue mussels 2 L"h-1) to ensure that a

downstream seston depletion effect was absentwith the densities present.

The feeding history must be knownbefore experimentation involving bivalve filtrationfeeding. This is usually achieved by starving thebivalves for 24-48 h by placing them in a holdingtank receiving filtered seawater. In growth'studies which are of longer duration (few weeksor more versus few hours for feeding), thefeeding is less critical, althoughdefinitive studies will require this

An obvious improvement to the flowcalibrator is to provide it with flowmeters whichincrease its to the upper rangeachieved the Mini Flow tank. Flowmeters canbe purchased and, as as there is sufficientpressure in the should enable the highervelocity to be calibrated.

The ideal solution seems to be in flowcytometry because this technique simultaneouslymeasures cell volume, density, and thefluorescent properties of the microalgae present.With this method it should be possible to identifyindividual species of microalgae in a complex,natural, seawater sample. Because of the highinitial cost of the flow cytometer, it has not beenconsidered for use in the flow simulation lab.A cheaper and somewhat less satisfactorymethod is by flow fluorometry, in which the

natural fluorescence of microalgae is directlymonitored (Fig 12). Limitations of this methodare currently being investigated, in particular thehigh concentration quenching and/or absorptionof light by the microalgae. Bayne et al (1977)have used flow fluorometry to measure feedingrates of blue mussels; the method wassatisfactory with monoalgal cultures but not with

oc

d

o 0 0 0

f

. L- f ---

g

Fig. 12. Possible setup for a flume with automatedaddition of microalgae to monitor bivalve feedingrates. a. metering pump controlled by c; b. aeratorto mix mlcroalgal culture; c. data logger withswitch relays; d. microcomputer; e. Turner flowfluorometer; f. sampling pump.

natural phytoplankton in seawater. The Turnerfilters used are a primary 5-60 and secondary 2­64 giving excited light at 430 nm and emittedlight at 650 nm. Provided the flowmeter issufficiently sensitive to measure small changes influorescence (maximum of 0.04% per min,l)based on one scallop filtering with 100%efficiency at 10 L.h,l in a total of 200 Lthroughout the experiment, it will be necessary toadd a stock microalgal culture (= initialconcentration) at 75 mL·min'l.· If the stockmicroalgae culture is 10x more concentrated, itsaddition rate can be reduced to 7.5 mL·min"l.

Future objectives ar~ to run feedingexperiments with natural microalgae collectedbeforehand in a plankton net or in a newlydesigned continuous collecting device. Themicroalgae could be metered into the flume bythe automated method outlined above with the

19

rate of addition indicating the effect of knownharmful microalgae on bivalve feeding rate.

It is also hoped to study salmon smoltphysiology and behavior challenged by toxicmicroalgae using an implanted ECG monitorwhich has been developed. Experiments areplanned in which the smolts are exercised byexposure to controlled velocities. This will requireconstruction of a larger flume of 1000 L capacity(the maxi flow tank #7) based on the present MiniFlow Tank design.

An immediate future requirement inbivalve growth studies is that the experimentalsubjects should be of known genetic stock. Withthe recent development in many parts of theworld in culturing bivalve spat and thedevelopment of successful methods to grow themout to juvenile stage in commercial hatcheriesthis is already feasible.

,.._. DISCUSSION

The St. Andrews Biological Station isideally situated to support a flow simulationlaboratory because of the high quality of thelocally available, St. Croix estuary seawater.There is a general lack of industrial activity, apartfrom forest industry-related (i.e. saw and pUlpmills) and-absenc-e of ~Atensiv-e agriculturethroughout the St. Croix River catchment. Highseawater quality is one reason why a UnitedStates group of investors, in 1991, beganinvestigating the feasibility of a land-basedsalmonoid culture facility at Robbinston, Maine,just across the estuary from the BiologicalStation. The facility would include seawater growout of smolts in raceways.

There is growing evidence that tidalcurrents, as flow direction and velocity, arefundamentally important in shaping both the typeof benthic community and the production ofsuspension-feeding members of the community(e.g. Wildish and Peer 1983). It is not surprisingtherefore that other levels of biologicalorganization, such as the behavior andphysiology of suspension feeders are profoundlyaffected by flow direction and velocity. Nor is theeffect of flow on benthic ecology limited to theesoteric since practical fisheries or aquacultureproblems (ie. how to predict the carrying capacityof an area for blue mussel culture) or ecological

problems (ie. predicting changes caused by tidalpower development) requires this knowledge.

In fact, a wide range of questions, atmany levels of biological organization and with adiverse range of taxa, can only be solved by useof flow simulation experiments. Anyoneinterested in this field - animal experimentationinvolving flow simulation methods - is encouragedto contact the author.

ACKNOWLEDGMENTS

My interest in benthic biology led me intosome unfamiliar areas of the physics of flow. Iwas very fortunate in having Professor DavidKristmanson, Department of ChemicalEngineering, UNB, Fredericton, NB as my guideand teacher in this field. David has collaborateddirectly in many of the experiments, been patientwhen "I was slow, thinking in broken images",and any scientific rigour in our work regarding thephysics of flow is. due. to .his..insistence that thebiology must fit the physics (and not the otherway round).

The Biological Station workshop hastalented people able to transform plans intoreality. Many of the earlier flumes (#1-4) weremade under the direction of Herb Small (retired1987). Latterly, Brian Kohler was responsible forconstruction of the new flow simulation lab andrefurbishing the multiple channel flume and itsbuilding. Flume work also requires pipes andfittings; and expert advice and craftsmanshipwere always available. Initially this was from ArtCarson (retired 1987) and now from his sonRichard Carson. Many of the measurements andobservations in the flow lab are made withelectronic equipment and I have relied onassistance from Sam Polar when problems arose.Sam was also responsible for the design of theelectrical circuits and fittings in the new flow lab.It is a pleasure to acknowledge the help receivedfrom Mark Chin Yee (#6 flume) and GeorgeSteeves of the Management Services Branch,Bedford Institute of Oceanography, Bedford, NS,in getting the new lab equipped and running.

I wish also to acknowledge the experttechnical assistance provided by Ms. AlineSaulnier (nee Decoste) and Ms. MichelleRinguette in many of the experiments describedin the papers included at the end of the reference

20

list. Aline has worked with me for 9 yr andMichelle for 4 yr. I thank Ms. Jennifer Martin forhelp and advice in cultivating microalgae and ArtWilson for assistance in field collection ofbivalves. Frank Cunningham prepared thefigures for this publication and, over the years, heand Bill McMulion (retired 1991) have providedexcellent graphics facilities both for publicationsand illustrated talks. I wish to thank Brenda Bestand Elaine Maillet who prepared this publicationfor printing and Drs. Richard Peterson andShawn Robinson for critically reviewing an earlierversion.

REFERENCES

Bayne, B. L., J. Widdows, and R. I. E. Newell.1977. Physiological measurements onestuarine bivalve molluses in the field, p.5-68. ill B. F. Keegan, P. 6. Ceidigh,and P. J. S. Boaden (ed.) Biology ofBenthic Organisms. Pergamon Press,Oxford.

Beamish, F. W. H. 1978. Swimming capacity, p.101-187. ill W. S. Hoar and D. J.Randall (ed.) Fish physiology. AcademicPress, New York.

Belding, D. L. 1912. A report upon the guahaugand oyster fisheries of Massachusetts.Commonwealth of Massachusetts,Boston, 112 p.

Bowen, S. H. 1991. Dietary protein, energy andtheir interaction: consumer response iningestion and its significance for growth,p. 10-11. In Abstracts of Papers for the1991 Annual Meeting, ASLO. Publishedby BIO, Dartmouth, N.S.

Brand, A. R. 1991. Scallop ecology: distributionand behaviour, p. 517-584. ill S. A.Shumway (ed.) Scallops: biology,ecology and aquaculture. Elsevier,Amsterdam.

Daborn, G. R. [Ed.]. 1977. Fundy Tidal Powerand the Environment. Acadia UniversityInstitute, Wolfville, 304 p.

Fraser, C. M., and G. M. Smith. 1928. Notes onthe ecology of the butter clam,

Saxidomous giganteus Deshayes.Trans. Roy. Soc. Can. 22: 271-282.

Gordon, D. C., and M. J. Dadswell. [Ed.]. 1984.Update on the marine environmentalconsequences of tidal powerdevelopment in the upper beaches of theBay of Fundy. Can. Tech. Rep. Fish.Aquat. Sci. 1256: 686 p.

Graves, R. 1961. Poems selected by himself.Penguin Books, London, 222 p.

Guillard, R. R. L. 1984. Culture of phy1o­plankton for feeding invertebrates, p.108-132. !!l C. J. Berg (ed.) Culture ofmarine invertebrates. Hutchinson Ross,Stroudsbury, Pennsylvania.

Harrision, P. J., and P. Thompson. 1990.Effects of light intensity on the nutritionalvalue of phy1oplankton to bivalve larvae.!!lU.B.C. Dept.of Oceanography, AnnualReport, Vancouver, B.C.

Huntsman, A G. 1952. The production of life inthe Bay of Fundy. Trans. Roy. Soc. Can.46: 15-38.

Kerswill, C. J. 1949. Effects of water circulationon the growth of guahaugs and oysters.J. Fish. Res. Board Can. 7: 545-551.

Kirby-Smith, W. W. 1972. Growth of the bayscallop: the influence of experimentalwater currents. J. Exp. Mar. BioI. Ecol.8: 7-18.

Kristmanson, D. D. 1991. The thermistor beadvelocimeter. A report prepared for theDFO, Biological Station, St. Andrews,N.B. Unpublished.

MacDonald, B. A, and J. E. Ward. 1991.Variation in food quality and particleselection in Placopecten magellanicus, p.58. !!l Abstract of Papers for the 1991Annual Meeting, ASLO. Published byBIO, Dartmouth, N.S.

Martin, J. L., and D. J. Wildish. 1990. Algalblooms in the Bay of Fundy salmonaquaculture region. Bull. Aquacult.Assoc. Can. 90-4: 19-21.

21

Meyer, L. 1991. Nutritional quality of sedimentsbased on kinetics of nutrient release, p.61. !!l Abstracts of Papers for the 1991Annual Meeting, ASLO. Published byBIO, Dartmouth, N.S.

Muschenheim, D. K., J. Grant, and E. L. Mills.1986. Flumes for benthic ecologists:theory, construction and practice. Mar.Ecol. Prog. Ser. 28: 185-196.

Nowell, A R. M., and P. A Jumars. 1987.Flumes: theoretical and experimentalconsiderations for simulation of benthicenvironments. Oceanogr. Mar. BioI. Ann.Rev. 25: 91-112.

Saunders, H. E., and C. W. Hubbard. 1944.The circulating water channel of theDavid W. Taylor Model Basin. Soc.Naval Architects and Marine Engineers,Transactions 52: 325-364.

Smit, H. 1965. Some experiments of theoxygen consumption of goldfish(Carassius auratus L.) in relation toswimming speed. Can. J. Zool. 43: 623­633.

Symons, P. E. K. 1973. Territorial behaviour ofjuvenile Atlantic salmon reducespredation by brook trout. Can. J. Zool.52: 677-679.

Vogel, S. 1981. Life in moving fluids: thephysical biology of flow. Willard GrantPress, Boston, 352 p.

Wildish, D. J. 1977a. The marine and estuarinesublittoral benthos of the Bay of Fundyand Gulf of Maine, p. 160-163. !!l G. R.Daborn (ed.) Fundy tidal power and theenvironment. Acadia Univ. Institute,Wolfville.

Wildish, D. J. 1977b. Factors controlling marineand estuarine sublittoral macrofauna.Helg. wiss. Meeresunters 30: 445-454.

Wildish, D. J., and D. D. Kristmanson. 1984.Importance to mussels of the benthicboundary layer. Can. J. Fish. Aquat. Sci.41: 1618-1625.

Wildish, D. J., and D. D. Kristmanson. 1985.Control of suspension-feeding bivalveproduction by current speed. Helg. wiss.Meeresunters 39: 237-243.

Wildish, D. J., and D. D. Kristmanson. 1988.Growth response of giant scallops toperiodicity of flow. Mar. Ecol. Prog. Ser.42: 163-169.

Wildish, D. J., D. D. Kristmanson, R. L. Hoar,A. M. Decoste, S. D. McCormick, andA. W. White. 1987. Giant scallopfeeding and growth responses to flow. J.Exp. Mar. BioI. Ecol. 113: 207-220.

Wildish, D. J., and M. P. Miyares. 1990.Filtration rate of blue mussels as afunction of flow velocity: preliminaryexperiments. J. Exp. Mar. BioI. Ecol.142: 213-219.

Wildish, D. J., and D..Peer.1983.,,,-Tidal currentspeed and production of benthicmacrofauna in the lower Bay of Fundy.Can. J. Fish. Aquat. Sci. 40 (Suppl. 1):309-321.

Wildish, D. J., and A. M. Saulnier. 1992. Theeffect of velocity and flow direction on thegrowth of juvenile and adult giantscallops. J. Exp. Mar. BioI. Ecol. (inpress).

Winter, J. E. 1973. The filtration rate of Mytilusedulis and its dependence on algalconcentration, measured by a continuousautomatic recording apparatus. Mar. BioI.22: 317-328.

22

Additional flow-related publications of D. J.Wlldish published or in preparation by 1991

Wildish, D. J., and D. D. Kristmanson. 1979.Tidal energy and sublittoral macrobenthicanimals in estuaries. J. Fish. Res. BoardCan. 36: 1197-1206.

Wildish, D. J. 1985. Geographical distribution ofmacrofauna on sublittoral sediments ofcontinental shelves: a modified trophicratio concept. J. Mar. BioI. Assoc. U.K.65: 335-345.

Emerson, C. W., J. C. Roff, and D. J. Wildish.1986. Pelagic-benthic energy coupling atthe mouth of the Bay of Fundy. Ophelia26: 165-180.

Wildish, D. J. 1991. The flow simulationlaboratory at St. Andrews BiologicalStation. Can. Manuscr. Rep. Fish .

..•.AquaLSCi. 2134: iii +.25 p.

Wildish, D. J., D. D. Kristmanson, and A. M.Saulnier. 1991. Interactive effect ofvelocity and seston concentration ongiant scallop feeding inhibition. J. Exp.Mar. BioI. Ecol. (in press).

Wildish, D. J., and A. M. Saulnier. 1992. On thecauses of valve closure in the giantscallop. In preparation.

Bouvet, F., and D. J. Wildish. 1993. Modellingconsequences of the "seston depletioneffect" in turbulent flow, suspensionfeeding bivalves. In consideration.

23

APPENDIX I. Recirculating flume for suspended sediment studies. Upper - side view, lower - plan view.Flume channel flow was from left to right.

T

.L

oI

,,,,• 1,

1mI

",""",.,.

~.t

o

o

24

APPENDIX II. Recirculating flume designed to replace the Vogel flume.

~1O'~ .......c---------- 40'-'-----.--.1.1

III @ :: f" 7 ;[J~Collimator1 II~ Centres

~ HP Lightnln VariableSpeed Mixing Motor

6" PVC

-.--" 'I 'T 11' II •6i2 II ....... : ...

J. - II '-L.- L...-,r--.;:'I:--'T""""-'-----------------....L...-L.·--JI--........../- II

"II"IIII

"\:~:) +Reducing ~-~

Flange4" PVC

Drain

25

APPENDIX III. Parts list and wiring diagram of the cooling system used in the Mini Flow Tank.

Condensing Unit Copeland Unit Model MGBH00205AA2

Compressor Compressor Model ARD10020 SAA200

@]SIN 91 B031949

Evaporator 12 f1 5/8" titanium

Metering Device Alco balanced port thermostatExpansion valve BF1/4FC

§JPenn digital thermostatModel A350 Johnston control

Temperature Control[f2] clw Penn low voltage (24V) power pac

Model Y350 Johnston control

Low Pressure Control

E9Rance low pressure

Protection Model 010-1402

L1 Potential 120 Volt AC

Switch SW1 is in/ Blue Panel of Lab

SW1 I.C. PC./ - -2; C

TemperatureThermistor inFlume Water

L2