GULF-II SEMIAUTOMATIC PLANKTON SAMPLER FOR INBOARD USE Marine Biological Laboratory WOODS HOLE, MASS. SPECIAL SCIENTIFIC REPORT- FISHERIES No. 199 UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE EXPLANATORY NOTE The series embodies results of investigations, usually of restricted scope, intended to aid or direct management or utilization practices and as guides for administrative or legislative action, it is issued in limited quantities for official use of Federal, State or cooperating agencies and in processed form for economy and to avoid delay in publication. United States Department of the Interior, Fred A. Seaton, Secretary Fish and Wildlife Service GULF-II SEMIAUTOMATIC PLANKTON SAMPLER FOR INBOARD USE By Albert Collier Fishery Research Biologist Special Scientific Report- -Fisheries No. 199 Washington, D. C, February 1957 ABSTRACT The Gulf -II semiautomatic plankton sampler was developed for study- ing heterogeneous plankton distribution in the Gulf of Mexico . By means of a circular rotating trough, eight consecutive hourly samples are collected on removable disks of bolting silk. The sampler collects continuously re- gardless of sea conditions, the intake being through the hull of the vessel at the lowest point possible. Water flow through the sampler is metered directly. Construction details and specifications are provided. CONTENTS Page Description General The filtering pan and filters The tray Channel frame and fittings Preservative dispenser 2 The flow diagram 2 Miscellaneous 2 Notes on operation 2 Remarks 3 Literature cited 3 GULF -II SEMIAUTOMATIC PLANKTON SAMPLER FOR INBOARD USE The Gulf-II semiautomatic plankton sampler was used during a combination biolog- ical and oceanographic survey of the Gulf of Mexico by M/V ALASKA in the years 1951-53 . TTie study of the distribution of plankton organ- isms was a part of this program, and three methods of sampling planKton were developed. Two of these have been described previously (Arnold and Gehringer, 1952) . Heterogeneous plankton distribution, or "patchiness, has long been recognized (Lucas, 1940), and 1 felt that an attempt should be made to study it along with the other plankton work contemplated. The best and most widely known study of plankton distribution was that of Hardy (1939) which culminated in developmait of the Continuous PlanKton Recorder. Because this machine was not available to us, the apparatus described here was developed as a substitute method. By comparison with the Continuous Plankton Recorder it had certain shortcomings, but it also had some virtues. • DESCRIPTION General Basically, this sampler is a circular trough divided into 8 equal segments, each of which passes under a stream of water. The trough, or filtering pan, is rotated in the horiz- ontal plane by a synchronous clock motor at the rate of 1 revolution in 8 hours . Each segment, or compartment, requires 1 hour to pass under the stream . The partitions have the effect of breaking the stream into hourly components, and since each compartment has a filter to catch the plankton, the plankton is separated into hourly samples . The filters are removable disks of bolting silk which are replaced each 8 hours. The apparatus receives the water from a pump situated near the keel of the vessel, with the intake throu^ the SKin of the ship at the low- est point possible. The construction and specifications are shown in the accompanying figures. The following description will be con- fined to points needing clarification relative to operation. The Filtering Pan and Filters (figures 1 and 2) The construction of the filtering pan is shown in figure 1, and its profile with an at- tached filter assembly on figure2. The 1/4- inch -square head setscrew shown at the hub of the pan (fig. 1) provides a means of adjusting the angular setting of the pan. I found that filtering tubes 12 inches long provided sufficient hydrostatic pressure to overcome the resistance of the silk aijd accumu- lated plankton organisms, except dense phytoplankton . The U-tube welded to the bottom section of the filter assembly served to keep the liquid level above the silk; filters, and so kept the sample moist. Before the filters (#1 bolting silk disks, 1-1/2 in. in diameter) were removed by loosening the hinged bolt, the fluid in the U- section was drained by removing the 1/4 -inch rubber plugs. The Tray (Figure 3) The filtrate fell into the tray and by means of a drain and connecting hose was car- ried to laboratory sink, and thence, overboard. The tray was kept in place by a monel strip ex- tending across the bottom and into the cavity of the channel frame on either side. This arrange- ment enabled the tray to be raised if necessary (see fig. 4 ) . The center of the tray was fitted with a permanently attached tube extending to a point flush with the top. The shaft of the filter- ing pan ran through this tube to the lower journal box. Channel Frame and Fittings (Figures 4 and 5) The shaft was in 2 sections and coupled as indicated in the drawing. This permitted convenient disassembly when necessary. The upper end of the shaft was drilled lengthwise to accommodate the shaft of the synchronous clock motor, and a setscrew affixed to complete the connection. These details are not shown be- cause they vary according to the type of driving unit supplied. The journal boxes were designed to provide a bearing assembly which would mini- mize friction resulting from both rolling and pitching motions of the vessel. Preservative Dispenser (Figure 6). A pump and microswitch system was in- tegrated with a synchronous motor which was set in phase with the filtering cycle of the samp- ler. Thus after each hour of filtering a given compartment of the filtering pan was flooded and rinsed with preservative, which also covered the silk disk and sample until removal. This dispensing system is simple in principle and of course is subject to many variations according to the need and facilities of the individual investigator. The Flow Diagram (Figure 3> This diagram indicates the flow of water from intake to waste. The intake was at an average level of 10 feet below sea surface. A stainless -steel pump powered by a 1/3-horse- power motor discharged a total of approximately 450 gallons an hour through the system, about one -fourth of which passed through the sampler. The flow could be distributed either to the waste or the sampler as desired by adjusting the 2 valves. The total discharge went through the first water meter, and the portion drawn through the sampling apparatus passed through the second water meter. This system permitted the pump to pull water from the sea at a maximum rate, thus increasing the ability of the system to entrain plankters at the intake. The 2 meters permitted a comparison of the amount of water filtered by the sampler with the total water pumped through the system . rate of 20 gallons a minute. The manufacturer's stated error at the flow which we used was less than 1 percent. The meters were calibrated while in operation aboard ship by catching the flow in containers of known volume and no error could be detected. It is likely that a small error might have been found if facilities had permitted calibration for great quantities. The synchron- our motor driving the apparatus was a small timing motor with a shaft rotation of 1 revolution in 8 hours. A mercury manometer was con- nected to the water supply near the discharge of the sampling stream . This provided a guide for adjusting the pressure from one run to the next. Notes on Operation When the vessel cleared the dock and there was no sign of harbor sediments and detritus the pump was started. While the system was allowed to clear itself by discharging through the first water meter only, the silk disks were placed in the filter assemblies, with the excep- tion of one. When this was done the compartment for this last filter was held under the sampling stream and the water was allowed to run through to clear the line and second meter of possible contaminants. Following this the last silk was placed in the filter assembly and the apparatus was started by setting the forward partition (in the direction of rotation) for the first com- partment to just clear the sample stream . At this point the setscrew connecting the filtering pan shaft to the shaft of the synchronous motor was tightened, thus setting the filtering pan in motion . The water meter readings, the time of starting, and the manometer readings were recorded. In my experience dense masses of phyto- plankton occasionally caused the silK to clog and a compartment to overflow . The operator should be on the alert for this and other difficulties so that proper entries can be made in the notes. There were times when clogging could be avoid- ed by reducing the rate of flow of water through the apparatus, but this was avoided if possible. Miscellaneous The water meters were tropic -type disk meters, 5/8 x 3/4 inch, with a safe maximum After the apparatus ran 8 hours (1 hour for each compartment) it was stopped for re- placing the silk filter disKS. The plugs in the U -tubes were removed to permit the fluid to be drained The sides of the tubes were washed down with water, and then the silk disks and sample were removed and placed in a small vial of preservative without attempting to separate the captured organisms from the silk . The labels placed in the tubes carried the date, run number, and hour. These data were sufficient to locate the sample on the vessel's cruise track. New silk disks were placed in the filter assemblies, and the apparatus started again . Remarks The sampler described is not an ideal apparatus for quantitative plankton sampling, but it does supply us with a record of the gener- al distribution of some of the larger plankton organisms of the Gulf of Mexico which we would not have otherwise obtained. Its advantages are that it collects continuously regardless of sea conditions, it is simple to operate, and the water flow through the apparatus is metered directly. Table 1 represents an hourly break- down of a typical run . The disadvantages are: Samples can be taken from only one depth; turbulence and other influences from the ship's hull have an unknown effect on quantitative collection; clogging might give trouble in more fertile waters heavily laden with plankton; the turbulence of the pump probably destroys or mutilates more fragile organisms although there was no evidence of excessive damage; the filtering rate is limited by the maximum hydrostatic head available in the tubes, hence the mesh of the silk and the flow is limited by the practical lengths of these tubes. By way of comparison, it is illuminating to plot some results from the G-II along with some from the G-IA high-speed sampler. The latter was described by Arnold and Gehringer (1952) . It was towed between hydrographic stations without removal from the water and was provided with a meter for measuring water filtered. For comparison, the hourly values from the G-11 data which corresponded to a given G-IA tow were selected and accumulated (fig. 7) . As has been pointed out, the G-II sampled con- stantly at approximately 10 feet below the surface as contrasted to a sampling depth of 3 to 20 meters for the G-IA. This factor alone makes comparisons of the 2 sets of data invalid, but with the extreme differences in design and operation of the two Kinds of apparatus in mind the general parallelism of the 2 sets of data is striking. 1 would like to suggest that the internal mechanism of the Hardy Continuous Plankton Recorder could be adapted to inboard use and would be superior to, although more complex than the apparatus described here. Such an arrangement operating continuously would con- tribute much to our knowledge of the relation of plankton aggregates to the congregation of fishes. LITERATURE CITED Arnold, E. L., Jr. 1952. A high speed plankton sampler (Model Gulf I-A) . U.S. Fish and Wildlife Serv., Sp. Sci. Rept. 88, pp. 1-6. Gehringer, J. W. 1952. An all-metal plankton sampler (Model Gulf III) . U.S. Fish and Wildlife Serv., Sp. Sci. Rept. 88, pp. 7-12. Hardy, A. C. 1939. Ecological investigations with the continuous plankton recorder: Object, plan and methods . Hull Bull . of Mar . Ecol . Ul):l-57. Lucas, C. E. 1940. Ecological investigations with the continuous plankton recorder: The phytoplankton in the southern North Sea, 1932-37. Hull Bull, of Mar. Ecol. J_(3): 73-170. Table 1. — June $, 19$1. Run 2, UU6.2 gallons for eight hour period. Mean $6 gallons per hour. Catch, organisms per m3. Hour Copepods Saigitta Append! cul aria Fish eggs aher 1 ^ 1 ^ ^ ^^ 2 8 2 ^ 1 3 35 . ^ ^ 2 h 23 ^ ^ 2 2 5 6 2 ^ 1 6 29 1 ^ ^^ 2 7 13 2 2 1 8 16 3 M «• INT.-DUP. SEC. WASH., D.C. 12709 5 SQUARE HEAD SET SCREW 3 4 5 TOP SECTION FILTERING PAN INCHES DETAIL FILTERING PAN |"H0LES,8 CENTERED IN EACH COMPARTMENT RADIAL PARTITIONS 8 EQUALLY SPACED^ MONEL WELD. CONSTRUCTED OF M0NEL(I5 GAUGE ) FIGURE I FILTER ASSEMBLY- ' RUBBER GASKET- RUBBER PLUi RADIAL SUPPORTS WELDED TO HUB FILLET ON BOTH SIDES r MONEL FLOW PIPE 8 EQUALLY SPACED 12 3 4 5 INCHES SECTION A-A OF FILTERING UNIT MONEL 13 GAUGE J ca lo. Vi", TOP SECTION BOTTOM SECTION DETAIL FILTER ASSEMBLY 3_" 16 H 1^ T -t=n WING NUTS ON ALL BOLTS M%V^D 3" BRASS BOLTS END VIEW -II — I p=i INCHES FIGURE 2 0. T q: < 1 (- < 10 hi Ll.l ^ O •.•> S LJ r _1 -|t> < I < z o I- o llJ V) 5 UJ a: < IT < o q E t lu z I- 3 n UJCS Z3 o< 20 -lUJ UJC9 §i 2® i. ..^ - r ^= r . 11'+ + + + 1 "•" *l + t + +- + V| OJ r _l -I CC Q + + DRILL 1 r-tco w CM Pi I 1 1 + + 1 ' ^r 1,-f + + + 1 + + 4- + t* 1..Z >- < q: 3"C 4,1* -K. SYNCHRON CLOCK MOTOR ^OTOR MOUNT(DETAIL) -JOURNAL BOX(DETAIL) -15 DRILL I HOLE -CENTERED IN WEB 2 ALLEN SET SCREWS. 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