Procedures for Scientific Dives 9 SECTION PAGE SECTION PAGE 9. 0 GENERAL ..........................................9- 1 9.8.6 Collecting Techniques......................9-17 9. 1 SITE LOCATION..................................9- 1 9.8.7 Specimen Preparation 9.1.1 Traditional Methods........................9- 1 and Preservation.............................9-18 9.1.2 Electronic Methods .........................9- 2 9. 9 ARTIFICIAL REEFS/HABITATS ............9-19 9. 2 UNDERWATER SURVEYS ....................9- 2 9.10 GEOLOGY..........................................9-20 9.2.1 Direct Survey Methods.....................9- 2 9.10.1 Mapping .....................................9-20 9.2.2 Indirect Survey Methods ...................9- 3 9.10.2 Sampling.....................................9-25 9.2.2.1 Underwater Photographic 9.10.3 Testing .......................................9-28 Survey...............................9- 3 9.10.4 Experimentation ...........................9-28 9.2.2.2 Underwater Acoustic 9.11 PHYSICAL OCEANOGRAPHY...............9-29 Surveys ..............................9- 4 9.11.1 Deployment, Inspection, 9. 3 UNDERWATER RECORDING Maintenance, and Recovery METHODS ..........................................9- 5 of Instruments..............................9-29 9. 4 BIOLOGICAL SURVEYS .......................9- 6 9.11.2 In situ Sampling of Currents and 9.4.1 Estimating Population Densities.........9- 6 Waves by Divers...........................9-31 9. 5 BIOLOGICAL SAMPLING.....................9- 7 9.11.3 Water Samples..............................9-31 9.5.1 Plankton Sampling ..........................9- 8 9.11.4 Undersea Laboratories....................9-32 9.5.2 Benthic Organism Sampling...............9- 8 9.12 ARCHEOLOGY ...................................9-32 9.5.3 Airlift Sampling..............................9-10 9.12.1 Site Location................................9-33 9.5.4 Midwater Sampling .........................9-10 9.12.2 Site Documentation .......................9-34 9.5.5 Estimating Density of 9.12.3 Site Testing..................................9-36 Planktonic Aggregations ...................9-11 9.12.4 Partial and Full-Site Excavation........9-37 9. 6 SHELLFISH STUDIES ...........................9-11 9.13 ANIMAL CAPTURE TECHNIQUES ........9-39 9.6.1 Collecting Techniques......................9-12 9.13.1 Nets ...........................................9-39 9. 7 TAGGING AND MARKING 9.13.2 Seines.........................................9-39 TECHNIQUES .....................................9-13 9.13.3 Trawls........................................9-39 9. 8 BOTANICAL SAMPLING ......................9-16 9.13.4 Diving on Stationary Gear...............9-39 9.8.1 Field Procedures .............................9-16 9.14 THE USE OF ANESTHETICS IN 9.8.2 Macro-Photogrammetric Method ........9-17 CAPTURING AND HANDLING FISH......9-40 9.8.3 Herbivory Assays............................9-17 9.14.1 Response to Anesthetics..................9-40 9.8.4 Palatability Experiments...................9-17 9.14.2 Selecting an Anesthetic ...................9-40 9.8.5 Nutrient Enrichment Assays 9.14.3 Application of Anesthetics ..............9-43 and Primary Productivity..................9-17 9.14.4 Diver-Operated Devices..................9-45 Procedures for Scientific Dives 9 9.0 GENERAL to be investigated. In geological mapping of the seafloor, a Scientific diving has been widely performed since 1952 scale of 1 inch to 200 yards (2.5 cm to 183 m) is adequate to observe underwater phenomena and to acquire scientific for reconnaissance surveys. In archeological and some bio- data. The use of diving has led to significant discoveries in logical studies, a much more detailed base map, with a the marine sciences. Placing the trained scientific eye scale of 1 inch to 30 ft. (2.5 cm to 9 m), may be required. If under water is, in some instances, the only method that existing charts do not contain the proper scale or sounding can be used to make valid observations and take accurate density, it may be necessary to use echosounder survey measurements. Scientific diving is occasionally also used techniques to construct a bathymetric map of the bottom to compliment submersible work, remote sensing, or sur- before starting the dive. Gross features can be delineated face ship surveys. Regardless of the project or the role that and bottom time used more efficiently if the diver has a diving plays, marine research using diving as a tool has good bathymetric map of the study area. If published topo- been important in understanding the ocean, its organisms, graphic charts are inadequate, the sounding plotted on orig- and its dynamic processes. inal survey boat sheets of a region (made by NOAA’s The scientific diver’s working time is measured in min- National Ocean Service) can be contoured and will usually utes and seconds instead of hours (unless the saturation div- provide adequate bathymetric control for regional dive sur- ing mode is used). The cost-effectiveness of scientific diving veys. If the survey plan requires bottom traverses, it will be therefore depends on how efficiently scientists can perform necessary to provide some means of locating the position of their tasks. Efficiency under water requires good tools, reli- the diver’s samples and observations on the base chart. able instruments that can be set up rapidly, and a well- Techniques used to search for underwater sites fall into thought-out dive plan. In the scientific community there is a two general categories: visual search techniques and elec- fair amount of standardization of the equipment and meth- tronic search techniques. Divers must verify the results ods used to perform research under water, yet in many from the latter after the specific site has been located. cases, the instruments, tools, and techniques are improvised Hand-held dive sonars or vessel fathometers are useful in and advanced by individual scientists to meet the specific determining water depth prior to initiating the dive. needs of the project. Through necessity, scientists who work under water must be proficient in their scientific discipline 9.1.1 Traditional Methods and as divers, inventors, and mechanics. Most scientific diving is carried out in nearshore The purpose of this section is to describe some of the waters where surface markers (fixed by divers over strate- procedures used in scientific diving projects. These meth- gic points of the work site) may be surveyed from the shore ods are intended as guidelines and should not be construed using well-established land techniques, or from the sea as the best or only way to perform underwater surveys or using bearings from a magnetic gyro compass, Loran C, or to gather data. Global Positioning System (GPS) coordinates. At the other extreme in terms of complexity is a site 9.1 SITE LOCATION relocation method used successfully by many scientists; in To study any region carefully, it is necessary to plot on this method, landmarks on shore are sighted visually, a base map the precise location from which data will be without the use of artificial aids. Basically, once the site is obtained (Holmes and Mclntyre 1971). This is especially located and the boat anchored over it, scientists take a important if there is a need to return to the same location number of sightings of various nearshore landmarks (such several times during a study. The scale of the base map as trees, hills, and power poles) and align them visually so depends on the detail of the study and the size of the area that when the site is revisited in the future, the landmarks 9-1 9.2 UNDERWATER SURVEYS A variety of methods are used to survey the underwa- ter landscape; these include direct and indirect surveying methods. Direct methods require scientific divers to mea- sure distances themselves, while indirect approaches use photography, underwater sonars, or acoustic means to determine distances, angles, and other features. 9.2.1 Direct Survey Methods With the exception of long distance visual triangula- tion, many of the methods used in land surveying can also be used under water. A review of a standard college text on surveying will provide the scientist with some basic surveying concepts. Woods and Lythgoe (1971) give an excellent description and review of methods that have FIGURE 9.1 been devised specifically for work under water. In most Fiberglass Measuring Tape diving surveys, distances are measured with a calibrated line or tape (the use of an expensive steel tape is unneces- sary). Most ropes or lines will stretch and should be used line up the same way. The only drawbacks to this method are only if the measurement error resulting from their use is that the work must be conducted near shore and the visibility acceptable. A fiberglass or vinyl measuring tape that has a must be good in order for the shoreside landmarks to be seen. minimum of stretch and is marked in feet and inches on When several lineups have been established and proven, they one side and meters and centimeters on the other is com- should be diagrammed in a notebook that is kept in the boat. mercially available (see Figure 9.1). If exact calibration is These methods allow divers to establish the locations of a concern, a steel tape is recommended. These tapes come major features in the working area accurately. If buoys are in an open plastic frame with a large metal crank to wind used for location, particular care is needed to ensure that the the tape back onto the reel. They are ideal for most pur- surface floats used during the initial survey be directly over poses and require no maintenance except for a freshwater the weights anchoring them to the selected underwater fea- rinse and lubrication of the metal crank. No matter what tures; the best plan is to wait for a calm day at slack tide. Rec- measuring method is used, especially if long distances are ognize that surface buoys may disappear at any time or may involved, the lines or tapes must be kept on reels to pre- be repositioned over time. vent tangling or fouling. In clear waters, optical instru- In some cases it may be advisable to leave the seabed ments can and have been used to measure both distance anchors in place after the floats have been cut away.