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A Suction Sampler for QuantitativelySampling Benthos on Rocky Substratesin RiversWilliam F. Gale a & J. Douglas Thompson aa Ichthyological Associates, Inc., R. D. 1, Berwick, Pennsylvania,18603, USAVersion of record first published: 09 Jan 2011.

To cite this article: William F. Gale & J. Douglas Thompson (1975): A Suction Sampler forQuantitatively Sampling Benthos on Rocky Substrates in Rivers, Transactions of the AmericanFisheries Society, 104:2, 398-405

To link to this article: http://dx.doi.org/10.1577/1548-8659(1975)104<398:ASSFQS>2.0.CO;2

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A Suction Sampler for Quantitatively Sampling Benthos on Rocky Substrates in Rivers •

WILLIAM F. GALE AND J. DOUGLAS THOMPSON Ichthyological Associates, Inc.

R. D. 1, Betwick, Pennsylvania 18603

ABSTRACT

The dome (suction) sampler is a self-contained unit that consists of five main parts: (i) a transparent acrylic hemisphere to enclose an area of the river bottom; (ii) a bilge pump to vac- uum organisms out of the sampler; (iii) a net to collect organisms as they are pumped out; (iv) a bag for collecting large stones; and (v) a band to seal the space between the dome and the substrate.

The dome sampler was designed to be used by a SCUBA diver to sample benthos quantita- tively on 0.18 m 2 of cobble-gravel substrate in the North Branch of the Susquehanna River. The sampler was used throughout the year, often under such adverse conditions as strong currents, cold water, and poor visibility. The sampler can be used in water 0.4-1.0 m deep without SCUBA.

Eighty-two percent of the organisms released inside the sampler were recovered during efficiency tests. Most organisms collected with the sampler were in identifiable condition. Ten minutes pumping per sample was required for best results. The sampler was more efficient than the Petersen, Ekman, and Ponar grabs, a corer, and the Surber sampler in collecting benthie macroinvertebrates from substrates in our study.

Twenty-two families of benthie invertebrates were collected in dome and artificial substrate (Bar-B-Q basket) samples. Only 12 families occurred in both and there were major differences in the relative abundance of some of them. Population trends formulated with data from the two samplers did not agree.

Direct samphng of rocky bottoms of riv- ers and deep streams has sometimes proven so difficult that many researchers have resorted to artificial substrates, in spite of their many shortcomings. Grabs, corers, dredges, etc. were not designed for rocky substrates, such as those in the North Branch of the Susquehanna River. Therefore, we developed a dome (suction) sampler to quantitatively sample benthos on rocky substrates in water 1-10 m deep. The sampler was operated by a SCUBA diver in clear and in turbid water, from 0 to 28 C with currents up to 1.7 m/s.

Brett (1964) was the first of several in- vestigators (Emig and Lienhart 1967; Bar- nett and Hardy 1967; True, Reys, and De- lauze 1968; Mass• 1970) to sample marine benthos with a suction device. Suction has

been used to sample freshwater benthos (Finnish IBP-PM group 1969; Christie and Allen 1972; Aare0ord 1972; Zimmermann and Amb'fihl 1970) and to collect fish eggs

•The sampler was designed for use in a com- prehensive study of the North Branch of the Sus- quehanna River in the vicinity of Berwick, Pennsyl- vania. The study was supported by Pennsylvania

(Manz 1964; Novak and Sheets 1969; Vogele, Boyer, and Heard 1971). Only the sampler of Zimmermann and Ambfihl (1970) sampled rocky river bottoms.

MATERIALS AND METHODS

Construction

The dome sampler consists of five main parts (Figs. 1, 2): (i) an acrylic hemisphere, 45 cm in diameter, to enclose the sample; (ii) a bilge pump (powered by a 12-volt bat- tery) to vacuum organisms out of the dome, (iii) a net to collect organisms as they are pumped out; (iv) a bag for collect- ing large stones; and (v) a band to seal the space between the dome and the sub- strate.

The acryhc hemisphere or dome is transparent, strong, easily worked, and commercially available. Arm-holes in the dome are 15-cm diameter circles with cen-

ters about 15 cm from the lower edge of the acryhc hemisphere and about 40 cm from each other. Five holes (4.5-cm diame- ter) in the dome just above the band per- mit refilling as water is pumped out. Brass

Power and Light Company. screen (250 micron openings) is fastened 398

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GALE AND THOMPSON--SUCTION SAMPLER 399

FIGURE 1.--Dome sampler with serrated band (rear view) and polyurethane cylinder band (side view). a. eye bolt. b. bilge pump. c. net bag. d. handle. e. battery. f. arm-hole cover. g. self-adjusting contour rod. h. screened port. i. rock bag.

over the inside of the holes to prevent or- ganisms from entering or escaping.

Either of two types of bands for sealing the dome to the substrate may be used. A serrated stainless steel band works well in unconsolidated sediments; large teeth permit easier penetrations of coarse substrates. A band of individually spring- loaded, polyurethane-foam cylinders pro- vides a better seal on solid, irregular bot- toms. About 8 kg of lead was added to the inside of either band, in a long flat belt, to hold it in place in strong currents. Overall,

the sampler weighed 27 kg, but less weight could have been used in moderate cur- rents.

Dome samplers can be purchased com- mercially (Aquatic Specialties, P.O. Box 65, Berwick, Pennsylvania) or can be as- sembled following detailed construction plans available from the authors. Compo- nents cost about $250 to 300.00.

Operation

A SCUBA diver can take 2 to 6 samples per hour. Preparation of the sampler for a day's sampling takes about 30 minutes.

The sampler is lowered by a helper to the river bottom; the SCUBA diver moves the sampler upriver from himself and posi- tions it on an undisturbed area.

When the serrated band is used (in small cobbles and finer substrates) the sampler can be rotated back and forth to help penetration. When the band with self-adjusting foam cylinders (Fig. 2F) is used, the diver presses down on top of the aluminum suppoa rods before sampling, so that all foam cylinders are tight against the substrate. Then, the diver activates the bilge pump and reaches inside the sampler to vacuum the substrate surface with the

intake nozzle (Figs. 1, 2F). Large quantities of sand and pebbles (about 10 mm or less in diameter) are pumped into the net bag. After thoroughly cleaning the substrate surface, individual stones can be dis- lodged, vacuumed to remove clinging or- ganisms, and then pushed through a rock por• into the rock bag. About 15-20 kg of substrate (Fig. 2A) can be removed in 5 minutes. Substrates should be removed to within 2-3 cm of the band to a depth of about 10 cm. Finally, the entire inner sur- face of the dome should be vacuumed; the area around the band should be cleaned at least twice.

Sampler components which might need changing underwater can be easily re- placed by a diver, even when wearing thick neoprene mittens. The battery can be removed by withdrawing a hitch-pin and disconnecting the plug to the pump (Figs. le, 2B); the impeller can be in-

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400 TRANS. AMER. FISH. SOC.. 1975, NO. 2

E ---, F' FIGURE 2.--Dome sampler and components. A. dome sampler with net and rock bag contents. B. battery being

removed. C. impeller with bilge pump snapped off. D. net bag friction fitting. E. arm-hole, foreground; rock bag being placed over rock-hole collar. background. F. polyurethane cylinder assembly and screened intake nozzle.

spected by snapping the pump housing from the pump base (Fig. 2C). The net bag, intake nozzle, and the intake hose are joined by friction fittings for quick re- moval. The rock bag is held to the sampler by an elastic cord sewn into the upper end (Figs. li, 2E) and is closed by tightening a belt sewn to it.

FIELD TESTS

Dome Efficiency Tests '•4"--four field tests were con-

ducted to determine dome sampler

efficiency. The sampler was placed on 5-10 cm of pre-cleaned, sand-cobble sub- strate in plastic wading pools submerged about 1 m in the river. Substrates were ar- ranged to simulate natural river bottom. Test organisms were collected from the general vicinity and kept in cool, oxygen- ated water prior to use. A known number of organisms was released inside the dome and allowed 15 minutes to acclimate. The

interior of the sampler was then vac- uumed. Most of the substrate was removed during the first 5 minutes. Three of the

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GALE AND THOMPSON--SUCTION SAMPLER 401

TABLE 1.---Numbers of organisms released and re- covered in 4 efficiency tests "A" with the dome sampler (3 trials in the North Branch Susquehanna River; 1 trial in Little Wapwallopen Creek)

Organisms

Taxa released recovered

Oligochaeta 3 2 Hirudinea 4 4 Crustacea

Isopoda 11 11 Amphipoda 1 1 Decapoda 2 1

Insecta Perlidae 17 10 Baetidae 30 17 Caenidac 2 2

Ephemeridae 4 4 Ephemerellidae 1 1 Heptageniidae 69 58 Leptophlebiidae 1 Aeschnidae 1 1

Coenagrionidae 1 1 Corydalidae 3 0 Hydropsychidae 114 114 Leptoceridae 27 15 Psychomyiidae 11 7 Elmidac 32 23

Gyrinidae 1 1 Psephenidae 18 15 Chironomidae 3 3

Gastropoda Physidae 6 6

Pelecypoda Sphaeriidae 34 27

Total 396 325

four efficiency tests were conducted in the river; the other test was in the mouth of a creek in July 1973.

In tests "A", 77% of the organisms re- leased in the sampler with the serrated band and 83% of those released in the

sampler with the foam cylinder band, were recovered (Table 1). How close these per- centages reflected actual efficiency achieved during systematic field sampling was difficult to determine for two reasons.

First, handling stress may have increased the vulnerability of test organisms to vac- uuming and second, some organisms may have escaped or hidden on the interior sur- face of the dome during the 15-minute ac- climation period. Snails (Physa sp.), for example, floated to the top of the dome sampler when released and began crawling on its interior surface. If the snails had not

been observed floating to the top they could have easily been missed, whereas,

snails on the river bottom would be easily caught.

Organisms such as hellgrammites and crayfish that were too large to pass through the screened intake nozzle posed the greatest problem, because they could not be felt by the diver wearing foam neoprene mittens and, as a consequence, probably would be missed.

The low percentage of recapture of some types of animals suggest they avoided the intake nozzle. Baetids, for example, can dart from rock to rock, and it was not sur- prising that 43% were missed in tests "A". That 28% of the adult elmids, which ap- peared slow and clumsy, would escape capture was more surprising. More tests might establish whether certain kinds of organisms avoid the intake nozzle.

Tests "B"--during systematic sampling of the natural river bottom in August 1973, pumping time for four samples was in- creased from 5 to 15 minutes to determine

how many more organisms could be col- lected by pumping longer. The substrate inside the sampler was not vacuumed dur- ing the two extra 5-minute periods, to avoid deeper than usual penetration. Water inside the sampler was swirled by hand movements during the last two periods to place organisms into suspension so they could be collected by the vacuum.

In tests "B", 85% of the organisms were collected during the first 5-minute period and an additional 11% were collected in

the second 5-minute period (Table 2). It is doubtful if longer pumping in our study would be worthwhile, unless the depth of penetration was increased.

Comparison to Other Samplers The dome sampler collected many more

organisms per square meter than other samplers. The Ekman grab and a core sampler obtained no substrate and no or- ganisms in 12 attempts. Three of 15 at- tempts with the Petersen grab yielded sub- strate, but a total of only five stones was collected. The ponar grab performed in about the same way as the Petersen grab.

The Surber "square-foot" sampler, with a #76 mesh net sewn inside, was tested in

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402 TRANS. AMER. FISH. SOC., 1975, NO. 2

TABLE 2.---Numbers of organisms collected in 4 efficiency tests "B" (2 trials in the North Branch Susquehanna River and 2 trials in Big Wapwallopen Creek)

River Creek

Taxa 0-5 5-10 10-15 0-5 5-10 10-15 minutes

Nematoda 2 0 0 108 43 15 Ohgochaeta 40 0 0 56 17 12 Ephemeroptera

Baetidae 0 0 0 8 1 1 Caenidae 6 0 0 0 3 0

Heptageniidae 2 0 0 16 4 3 Megaloptera

Sialidae 0 0 0 4 0 0 Trichoptera Hydropsychidae 25 2 0 0 2 0 Psychomiidae 0 0 0 12 2 0

Coleoptera Elmidae 9 1 0 44 1 0

Diptera Chironomidae 3310 549 187 6546 731 232 Empididae 207 24 6 36 5 0 Simuhidae 2 2 1 0 0 0 Rhagionidae 1 0 0 0 0 0

Pelecypoda Sphaeriidae 1 0 0 0 0 0

Total 3605 578 194 6830 809 263 Percent 82 13 4 86 10 3

about 1 m of water early in 1973 at low river level; the diver and sampler were forced downstream by the current. Prob- lems with the Surber sampler would be more acute at moderate and high river levels. Even if the Surber net could be

held in place, some organisms might be lost because animals escape over the top when the sampler is completely inundated (Chutter 1972).

Artificial substrate samplers are a com- mon alternative to conventional benthic

sampling methods on rocky substrates. We used "Bar-B-Q" baskets (Mason, Anderson, and Morrison 1967) filled with stones or cement spheres (Jacobi 1971) in our study for about two years. ^ series of baskets, each with a detritus deflector over the up- stream end, was attached to a line on the river bottom. A SCUBA diver retrieved the

baskets in individual cloth bags after five weeks (Gale and Thompson 1974a). The basket's performance prompted the build- ing of the dome sampler.

Large quantities of detritus accumulated in the baskets creating a unique habitat for invertebrate colonization. The detritus also made the measurement of surface area

available for colonization impractical and

density values for basket samplers are provided in Table 3 with reluctance.

Twenty-two families of organisms were collected by one or both samplers (Table 3). Six families occurred only in baskets, 4 families were only in dome samples, and 12 families were in both. In some in-

stances, baskets contained organisms such as ancylids that were lacking or extremely rare on the natural substrate. Ancylids are fairly common transients in fall, drifting downriver on vegetation broken free in less polluted waters upstream. Baskets fre- quently caught such vegetation, and lim- pets probably reached them in this way.

Empidids were scarce in baskets but they were common in dome samples. Bas- kets, on the other hand, contained large numbers of simuliids and dome samples had relatively few. Inspection of the river bottom by a SCUBA diver revealed that there were few simuliids on the natural substrate.

Population trends did not agree, either. Results of basket sampling indicated that the population of invertebrates was maxi- mal in summer and minimal in winter, whereas, dome sampler results indicated that the population peaked in winter.

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GALE AND THOMPSON--SUCTION SAMPLER 403

TABLE 3. •9rganisms/m 2 in dome and basket samples from the North Branch of the Susquehanna River about 11 km upstream from Berwick, Pennsylvania, in 1972-1973. Stone curvature was not considered in calculation of dome sampling area; the surface areas of rocks in basket samplers was approximated but detrital surface areas were not included. Numbers of samples are given parenthetically in the heading

October February June Percent Percent Smnpler Basket Dome Basket Dome Basket Dome of of total total

Taxa No. of samples (6) (2) (5) (2) (3) (3) (baskets) (dome) Annelida

Oligochaeta Naiadidac Tubificidae

Arthropoda Crustacea

Amphipoda Talitridae

lnsecta

Plecoptera Perlidae Nemouridae

Ephemeroptera Baetidae

Ephemerellid ae Ephemeridae Heptageniidae

Odonata

Coenagrionidae Libellulidae

Trichoptera Hydropsychidae Leptoceridae Phklopota•nidae Psychomyiidae

Coleoptera Elmidac

Hydrophilidae Diptera

C hironomidae

Empididae Simuliidae Unidentifiable

Mollusca

Gastropoda Ancylidae

Pelecypoda Sphaeriidae

Total

7 132 225 578 221 7.9 7.5 17 53 129 28 1.7 1.2

28

7 11 1

26 14 34

3

799 660 25

196 11 17

4

17 1059 918

1 2 < 0.1 < 0.1

141

10 0.1 1 <0.1

1 52 51 0.7 0.8 5 0.1

1 25 3 110 0.1 2.1 1 93 62 45 0.8 2.0

3 0.2 0.2 <0.1

126 23 6 1.8 1.6 2 < 0.1

17

6 171 3

95 2770 562

0.1 0.2

16 34 0.4 2.4 < 0.1

2232 2291 53.5 74.4 15 30 0.2 6.8

1974 24 31.8 0.5 0.5

0.1

0.2

4048 5099 2844 100.0 99.9

Clearly, different conclusions would be drawn from the two sampling systems.

CRITIQUE

We used the dome sampler under a va- riety of adverse conditions during 1972-73: in almost total darkness; in water as cold as 0 C; and in substantial currents. Use of a submersible raft (Gale and Thompson 1974b) facilitates transport of the sampler to the river bottom in strong currents.

The dome sampler could be used on all substrates with one of the two bands. The

sampler was especially valuable on coarse pebble-cobble substrates that other sam- plers could not handle. On muddy sub-

strates the collection net tended to clog with silt, unless it was shaken frequently. Where vegetation was present, organic matter sometimes had to be removed from the intake nozzle.

The foam cylinder band could be im- proved by modifying it to accommodate more irregular substrates. It is recom- mended that a sampler with a serrated band be tested before construction of

the complicated foam cylinder band is at- tempted. The possibility of using a sim- pler, inflatable rubber collar on the bot- tom of the sampler might be considered.

The acrylic hemisphere held up fairly well under heavy use. The foam cylinders

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404 TRANS. AMER. FISH. SOC., 1975, NO. 2

deteriorate from contact with battery acid and the battery should be removed when the sampler is idle. When the bilge pump was new, shreds of the pump body and impeller, abraided away by coarse parti- cles, were found in benthic samples. Rate of pump wear, however, decreased as the space between the impeller and pump body increased; pumping efficiency was not greatly reduced. The pump body and the impeller are replaceable. A new "Bilge King" pumped 66 hters of water per min- ute through the sampler (about 81% efficiency); the equivalent of emptying the sampler about 1.4 times per minute. Other bilge pumps were not tested, but only those that snap open (for removal of large gravel) should be used.

Motorcycle batteries performed well without being enclosed in watertight com- partments. High-capacity batteries (12-14 ampere-hours) were better suited to sam- phng than low-amperage batteries, which fatigued quickly in cold water. Batteries can be recharged with small, inexpensive chargers. Only well charged batteries should be used in cold water because

pumping rate varies with battery strength. The battery can be used to illuminate the interior of the dome with a 12-volt sealed- beam headlamp. We tested such a light, but visibility in turbid. water was little im- proved.

The sampler enclosed 0.18 m 2, but smaller and larger acrylic hemispheres are available commercially and other sizes of samplers could be built. We selected the largest size that one person could handle in the current. One sampler cannot be of optimal size to sample all organisms; the dome sampler was too small for efficient sampling of widely scattered organisms, such as mussels and crayfish, and at the same time, was too large for very abun- dant organisms, such as chironomids, which had to be subsampled. In general, however, the sampler yielded adequate numbers of most types of organisms.

Most organisms collected with the sam- pler were in identifiable condition and many were unharmed; a few were badly mutilated. Organisms may have been dam-

aged during sampling (by digging, by the impeller, or by sand and stones in the net bag) or later, during sample transport and washing. Probably most damage occurred in the net bag. Damage could be reduced by changing the net bag two or three times when taking a sample (to prevent overfilling) or by constructing a larger net.

Few, if any, organisms were found in the rock bag or on large stones returned to the laboratory and it might be better to leave the stones at the sampling site. Rocks that get in the way during sampling could be removed through the arm-hole. Sampler construction would be simplified by eliminating the rock port.

Two of the dome sam pier's disadvan- tages are: (1) it cannot sample rocky sub- strate deeper than about 30 cm and (2) it requires a SCUBA diver for sampling in water over a meter deep. Use of a SCUBA diver, however, provides extra benefits, such as visual inspection of the substrate at the sampling site.

The dome sampler appears to be the most efficient, self-contained quantitative sampler available for rocky substrates in shallow to moderately deep rivers; its efficiency in small streams needs assess- ment. The dome sampler was no more difficult to use than "Bar-B-Q" basket samplers in the North Branch. The dome sampler is superior to artificial substrate samplers in that it yields an immediate sample of the naturally occurring benthic community and does not require a coloni- zation period.

LITERATURE CITED

AAREFJORD, F. 1972. The use of an air-lift in fresh- water bottom sampling. A comparison with the Ekman bottom sampler. Verh. Internat. Verein. Limnol. 18: 701-705.

BARNETT, P., AND B. HARDY. 1967. A diver-operated quantitative bottom sampler for sand mac- rofaunas. Helgolander wiss. Meeresunters. 15: 390-398.

BaETT, C. 1964. A portable hydraulic diver-operated dredge-sieve for sampling subtidal macrofauna. J. Mar. Res. 22(2): 205-209.

CHRISTIE, N., AND J. ALLEN. 1972. A self-contained diver-operated quantitative sampler for inves- tigating the macrofauna of soft substrates. Trans. R. Soc. S. Afr. 40(4): 299-307.

CHUTTER, F. 1972. A reappraisal of Needham and

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GALE AND THOMPSON--SUCTION SAMPLER. 405

Usinger's data on the variability of a stream fauna when sampled with a Surber samplerß Limnol. Oceanogr. 17(1): 139-141.

EMIG, C., AND R. LIENHART. 1967. Un nouveau moyen de recolte pour leg substrats meubles in- fralittoraux: 1' aspirateur sous-marin. Rec. Trav. St. Mar. End. Bull. 42: 115-120.

FINNISH IBP/PM GROUP. 1969. Quantitative sampling equipment for the littoral benthog. Int. Rev. Ges. Hydrobiol. 54(2): 185-193.

GALE, W., AND D. THOMPSON. 1974a. Placement and retrieval of artificial substrate samplers by SCUBA. Progr. Fish. Cult. (To appear in Oc- tober 1974)

__, AND_ 1974b. Aids to benthie sampling by SCUBA divers in rivers. Limnol. and Oceanogr. 19(6): 1004-1007.

JACOBI, G. 1971. A quantitative artificial substrate sampler for benthie macroinvertebrates. Trans. Amer. Fish. Soc. 100(1): 136-138.

MANZ, J. 1964. A pumping device to collect walleye eggs from offshore spawning areas in Western

Lake Erie. Trans. Amer. Fish. Soc. 93(2): 204-206ß

MASON, W., J. ANDERSON, AND g. MORRISON. 1967. A limestone filled artificial substrate sampler-float unit for collecting macroinverte- brates in large streams. Progr. Fish-Cult. 29: 74.

MASSt•, H. 1970. La suceuse hydraulique, bilan de quatre ann•es de •mploi sa manipulation, ses avantages et incov•nients. Peupleuments benth- iques. Tethys 2(2): 547-556.

NOVAK, P., AND W. SHEETS. 1969. Pumping device used to collect smallmouth bass fry. Progr. Fish. Cult. 31(4): 240.

TRUE, M., J. REYS, AND H. DELAUZE. 1968. Progress in sampling the benthog; the benthie suction sampler. Deep-Sea Res. 15(2): 239-242.

VOGELE, L., R. BOYER, AND W. HEARD. 1971. A por- table underwater suction device. Progr. Fish- Cult. 33(1): 62-63.

ZIMMERMANN, V., AND H. AMB•HL. 1970. Zur- methodik der quantitativen biologischen prob- enahmen in stark str6omenden f16ssen. Schweiz. Z. Hydrol. 32(1): 340-344.

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