METHODOLOGY 



As pointed out above, conventional sampling techniques can neither prevent 

 nor account for changes which may occur as a sample of sea water is 

 brought from its native environment to the surface. Special sample bottles 

 capable of this were designed by one of us (RWC) and approximately 100 

 bottles were fabricated for use on this project. Figure 1 is a picture of 

 one such bottle which has a volume of approximately 225 milliliters. The 

 bottles are made of polyvinyl chloride (PVC) tubing with a screw cap at 

 either end. (The openings on both ends are to facilitate flushing of the 

 bottle at the sample site.) The screw caps are made of plastic with an 

 inner lining of PVC and an 0-ring to assure sealing. A hole is drilled into 

 the side of the bottles and a small piece of PVC is then sealed into it; 

 finally, a rubber septum is fitted into and over the small piece of PVC tub- 

 ing for the addition of reagents "in situ". The reagents are added by means 

 of disposable syringes which are inserted into the septum, injected into the 

 bottles, and then withdrawn. 



In order to facilitate the taking of large numbers of samples, a special 

 back-pack was developed that would fit over double scuba tanks as shown in 

 Figure 2. With each of two divers wearing a back-pack containing 14 

 sample bottles, a total of 28 samples could be taken during a given dive. 

 In addition to housing the sample bottles, the back-packs contained the 

 disposable syringes with fixing agents, additional venting needles for the 

 injection process, and a thermometer which allowed each diver to record the 

 temperature at which the sample was taken. 



Three sample stations were selected: the first of these was located in the 

 heart of the lush reef where plant and animal life abounded; the second 

 station was located on a barren sand flat; and, a third was chose at the 

 edge of the reef and the sand flat. A total of four dives per 24-hour 

 period were scheduled: two divers of the habitat team would take samples 

 at 0600, 1200, and 1800, and the surface support team would make one dive 

 per day, i.e., at 2400. Approximately half of the 800 analyses performed in 

 our Mission 1-50 were carried out in the laboratory setup in the wet room 

 of the habitat: the other half were carried out in a topside laboratory 

 located at the College of the Virgin Islands Ecological Research Station on 

 St. John. 



The salinity determinations were made on the surface with a Hytech portable 

 salinity bridge; calcium and magnesium determinations were carried out in the 

 habitat laboratory using the conventional EDTA titration; pH measurements 

 were made on the surface as well as in the habitat with Beckman Expando- 

 matic pH meters. The oxygen analyses were performed both on the surface and 

 inside the habitat. Originally, plans called for use of an oxygen meter 

 (Beckman Instruments) as well as the standard Winkler titration. Due to a 

 malfunction of the meter, all oxygen samples were analyzed by the Winkler 

 method. Unfortunately, no reliable data were obtained on phosphate 

 concentrations; all phosphate reagents were ruined in a "pot transfer" from 

 the surface into the habitat. 



VI-17 



