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 



