Scientific Diving Sampling Techniques. Sources Heine, J. N. 1999. Scientific Diving Techniques. Best...

Scientific Diving Sampling

Techniques

SourcesHeine, J. N. 1999. Scientific Diving Techniques. Best Publishing Company, Flagstaff, Arizona.

Norton, S. 2000. Lecture - Diving in Biological Research.

History of Scientific Diving

1953 – scuba diving in support of science authorized at the University of California. First in U.S.

1956 – research conducted using scuba first published

Aleem, Anwar Abdel, Quantitative underwater study of benthic communitiesinhabiting kelp beds off California. (1956) Science. 123(3188)1956:

Scientific diving has been conducted in a wide variety

of environments…Coral reefsMangrovesKelp forestsRocky shoresSoft bottom habitatsPolar environmentsOpen ocean/blue water environments

Offshore platformsEstuariesHot springsHypersaline environmentsCavesLakesRivers

…and been used in many different sciences

ChemicalGeologicalBiological

PaleontologicalArchaeological

Chemistry – diving has been used to support research such as determining the chemical ecology of invertebrates and collecting marine organisms for the extraction of chemical compounds.

Geology – divers may obtain core samplesof rock and sediment…

…or dig holes to examine depositional history

Scuba is very useful for visual identification of sediments – and for collecting representative and relatively undisturbed samples

Biology – Divers may perform a wide variety of tasks such as measuring various community structural parameters like fish density, algal density, macroinvertebrate density, percent cover of benthic algae and invertebrates, etc…, or measuring physiological responses of organisms in natural environments.

Paleontology – divers recover fossils from the underwater realm…

Dinosaur fossils from the waters off the Isle of Wight

Of course, diving is integral to the study of underwater archaeology…

Excavation of 4th – 6th century A.D. harbor site in Malta.

Serçe Liman1 excavation - 11th Century Byzantine Shipwreck - Diver hovers above grid used to mark locations of artifacts

Serçe Limanl excavation – Diver raises fragile hull timber using a lifting box.

Scientific Diving - GeneralThe diversity of disciplines involved in scientific diving, and the varied environments where this diving is performed, has necessitated the development of a wide variety of techniques for observing and sampling underwater.

Recording Information - Slates

Almost every scientific project requires that data be recorded underwater. Slates are a simple tool for doing this.The best material for a slate is a white polycarbonate or acrylic. This material is strong, waterproof, and negatively buoyant. It will not corrode when exposed to salt water, and is available in sheets, which can be easily cut to the desired size.

Diver using slate to record organisms found in artificial reef


Slate size and form may vary - large or small, single or multiple sheets, flat or curved to fit around the wrist.


For archaeology, it is recommended that the minimum dimensions of a slate should measure approximately 10” x 12” x ¼”, to 12” x 14” x ¼”. Much smaller and the diver has inadequate space for detailed recording. Larger slates are useful, but can be difficult to handle under certain conditions.


A wooden or mechanical pencil is attached to the slate by a string, cord, or rubber tubing. Bic brand mechanical pencils have been found to work the best due to the hardness of the lead, but the mechanics of the pencil are not always reliable when repeatedly exposed to water. Regardless of the pencil chosen, always carry at least one spare. A pencil may be used to write directly on the plastic of a slate, or to write on material attached to a slate.


Mylar is often attached to slates and drawn on underwater. It is a thin plastic film (or sheet) frosted on one or both sides. Mistakes are easily erased using a standard eraser. Mylar is available from drafting supply stores in rolls, which are easily cut to size with scissors or a paper cutter. Since drawing is done on the frosted side, double frosted Mylar alleviates the problem of which side to draw on. The Mylar sheet is secured to the slate using strips of Duct Tape. It is important that the sheet is secured properly so that several hours/days work is not lost by having the sheet come off underwater

Locating, Relocating, and Marking Sites

Locating, relocating, and adequately marking a study site are critical. Many methods may be employed.

Compass bearingsUse compass bearings towards readily identifiable objects on landFor greater accuracy, use shore lineups, where pairs of objects that are in a straight line can be used to triangulate a position.

Disadvantage – shore markers may not always be visible


Global Positioning Units (GPS)Relatively inexpensive, portable, and accurateCan store multiple points (waypoints), give the heading, distance, time to each waypoint from your present position and store multiple routes with many legs on each route

Sonar (depth finders) Tell water depth, or distance underwater to structures


BuoysPerhaps the best and easiest method for relocating a site from the surfaceMay be inexpensively made from plastic bottlesTorpedo shaped buoys minimize chances of entanglement with kelpMay be connected to the bottom with chain, cable, or linesMay be tied to structure on bottom – length of garden hose may help to avoid chafing – or weighted on bottomIn sandy or soft-bottom areas, sand, earth, or fence anchors can be screwed into the bottom Disadvantages – take time to install correctly, and are subject to loss from storms, theft, entanglement in boat propellers, or mauling by marine animals.


Underwater marking – may be necessary once the surface location of a site is established.

Variety of items may be driven into the substrate NailsTent stakesRebarRailroad spikesPitons

Marking tags may be placed on theseCable tiesVinyl roll flagging tapePieces of PVC


To properly mark an area, it may be necessary to drill holes

Star Drill – hammered in by hand. The drill is held with pliers and is rotated slightly with each blow of the hammer.

Time consuming and tiring. Not practical if large number of holes must be drilled.


Pneumatic drill or hammer – good for making numerous holes, especially in hard rock - or for more permanent fastening.

May be fitted to work off a scuba tankDisadvantages:

May use a great deal of airVery loudRequire considerable maintenance after use

Hydraulic systems Advantages - Quieter and more efficient than pneumatic toolsDisadvantages – More expensive – requires a link with control station on surface


Cement and epoxy may also be used to adhere items to the substrate.

Generally work best on a clean substrateMay be packed into cracks, crevasses, or drilled holesMarine putties or underwater patching compounds have been usedA mixture of four parts Type II Portland cement and one part molding plaster combined with seawater may be carried underwater in plastic bags. This mixture can be packed into holes before placement of eyebolts or stakes.

Geological Measurements and collections

Collection of sediments - Coring devices – useful for stratigraphy determination or grain size analysis. A wide variety of corers are available.

Coffee can with plastic lidRemove bottom and replace with fine mesh screen. Insert corer into substrate and push lid under lip of corer to seal it before removing.Very inexpensive

Piston corer May be constructed from PVC, designed to collect a complete and undisturbed sample


Small Ekman grabs and box corers

May be manually inserted and tripped by divers, insuring proper and complete samples are collected.


Box corers may be fitted with a slide hammer for driving into the sediment.

Some corers also have sliding doors – grooves along the open side of the corer guide the removable door down the open face once the corer is in place in the sediment. This eliminates the need to excavate and expose the lower surface of the corer to install a lower plate before removing a sample from the sediment.

Box corer filled with sediment

Slide hammer

Sliding door


Vibrocoring (vibracoring) – collecting cores of unconsolidated material by driving a tube with a vibrating device (vibrohead).

3 types of vibrators:PneumaticHydraulicElectric

Pneumatic vibrocorers – can be made to work underwater with very few adjustments and don’t involve the use of electrical current. They work best in relatively shallow water because of increased air consumption at depth. They also require a cumbersome compressor, and the hose becomes an impediment in swift or choppy waters.

Hydraulic vibrocorers – Do not share depth limitations with pneumatic corers, but do require a hydraulic power plant and an umbilical hose.

Hydraulic corer

Electric vibracorers – are more efficient (have a better force/weight ratio) than other types, and do not require umbilical hoses or large compressors or power plants.


Heavy cores may be brought to the surface with lift bags

Measuring TemperatureHand held thermometer

Generally encased in stainless steel or plastic

Temperature data loggersLong termMay be downloaded to computer after retrieval or in situ.

Fouling organisms may be issue – users often wrap download connection points with tape or encase thermometer in PVC

Multiparameter instruments

Conductivity, Temperature, and Depth units (CTD’s)

May measure other parameters such as salinity, fluorescence, pH, turbidity and oxygen and may take water samples from different depthsMay be small enough for divers to swim with them underwater to collect discreet data from precise locations.

A NOAA CDT

Measuring water motionMay be difficult and complex to measure

PlasterBlocks of plaster are weighed, affixed to some sort of framework and deployed. The plaster dissolves in water – faster or slower depending on water velocity. After recovery, the plaster is dried and weighed again. Differences in weight give a relative measure of water motion.

Plaster attached to cards (referred to as “Clod cards”). The one on the left has not been deployed – the other two have. Note the size difference

Measuring water motion Fluorescent dye

useful for determining current direction and velocity - may be released and visually tracked and timed, or recorded on a video camera with a timer.

Measuring water motion

Current metersSmall hand-held flow meters

Different rotor size for different water velocity ranges

Measuring water motionCurrent meters may also be attached:

Taut- line mooring – current meter is attached to a line that is weighted, anchored, or fixed to a sand anchor in soft sediment

Under a strong current, however, the meter will be deflected

Rigid mooring – will prevent deflection of current meter

Inexpensive option: concrete block with four out-riggers for stability, and a vertical pole with a swivel on top for the current meter

Rigidly moored current meter on tripod.

Measuring LightA variety of light meters are available.

Divers may use hand held light meters for measuring light in precise locationsLight meters may also be deployed for long periods of time in specific locations

Light meter

Diver uses handheld light meter to determine level of light reflected from coral

SoundMeasuring sound underwater often requires the deployment by divers of transducers (for transmitting sound) and hydrophones (for listening to sound emitted from both biological and physical sources) – these are sometimes quite large

Biologist using video and hydrophone to record fish sounds

Diver deploying transducer

Chemical measurementsMay range from simply collecting water in a plastic container to using sophisticated collection techniques and analyzing devices…

Van Dorn Bottle –May be mounted on scuba cylinders and tripped by diver at precise time and location to collect discreet water sample for analysis.

Sediment oxygen demand chamber – may be positioned by divers at specific locations – used to measure sediment oxygen demand.

Underwater ArchaeologyUnderwater archeologists locate, draw, excavate, and recover material objects in order to better understand history and culture. Divers are integral to this process.

Archaeologyand Low Visibility

Because many sites of archeological interest are located in coastal environments, estuaries, or rivers, a great deal of underwater archaeology takes place in locations with poor water visibility. Frank Cantelas

dredging during 1992 Maple Leaf expedition.

Low Visibility - Measuring

Clear ziplock plastic bags (“Brody Bags”) filled with water may be used to view measuring tapes in low visibility situations. The bag is placed on the tape and a flashlight is used for illumination.

The bag may be made more secure by applying duct tape to the sealed portion of the bag.

Before recording measurements, it is always a good idea to have a diver swim the tape to ensure it is not snagged somewhere.

Archaeology – MappingMapping is how locations are recorded in two or three dimensions. This is done by taking measurements.

Site maps are two dimensional plan views looking down from above, using an X and Y coordinate system. The third dimension, or Z coordinate, provides depth or elevation data. Profile views use the Z coordinate to record cross sections that show the vertical components of a site. A 2-dimensional and 3-

dimensional coordinate system

Archaeology – MappingEstablish a number of fixed points (datums) across the site – measurements are taken from these datums which are used as reference points. An intact wreck may have only 2 datums – bow and stern Datums:

Must not moveMust be precisely located (if using more than one datum, and you usually are, they must be precisely located in reference to each other in order for your site map to be accurate) Datums should be high enough not to be obstructed when taking measurements.

Archaeology – MappingFix a baseline (usually a tape or line marked in regular increments) between datums. Baselines allow three things to be done:

1) Mapping of features that fall under the baseline2) Making measurements away from the baseline3) Creating a mapping grid over the site.

1) 2) 3)

Archaeology – Mapping – Horizontal Offsets

Involves taking measurements at right angles to the baseline. This method is best suited to document objects located near the baseline.

The accuracy of this method relies on judging right angles. A useful technique is to place the zero end of the tape on the point to be plotted and to move the other end along the datum line until the shortest distance is noted, thus giving a line perpendicular (i.e. 90 degrees) to the baseline.Offsets must be taken in the horizontal plane.

Archaeology – Mapping – Horizontal Offsets

1) Taking an offset measurement from the baseline to a target object. 2) Establishing a 90-degree right angle. 3) Plotting the offset measurement on the site map.

Archaeology – Mapping – Vertical Offsets

Vertical offsets are generally taken from a level baseline. The baseline can be made level using a simple and inexpensive mason’s line level. A tape positioned close to, and parallel to, the baseline proper provides a reference for vertical measurements. Vertical measurements are taken from the level baseline, not the reference tape. A tape can not be adequately leveled. Vertical measurements can be taken by using a plumb bob and scaling rod dropped from the baseline along the reference tape to take measurements down to the object to be documented.

Archaeology – Mapping – Vertical Offsets

Diver recording vertical offset measurements from a horizontal baseline.

Archaeology – Mapping - Trilateration

Trilateration (or triangulation) involves using the sides of a triangle to map.

Distance measurements are taken from fixed datum points 1 and 2 to the target to be surveyed. A third measurement is taken from datum point 3 for precision accuracy.


Distance measurements are taken from two datum points whose positions are known (Previous slide) to the target being mapped (For best results – datum points should surround the object.). When plotted by hand, the intersection of these two distance lines (arcs centered on the datum points) locates the target point. For precision surveying a measurement from a third known point should be taken, as this will provide an immediate check. If an error is made using two measurements, the two arcs drawn as described below will usually intersect; with three arcs plotted they cannot intersect unless accurately measured and drawn.


Trilateration may also be done from the baseline.

Distance measurements are taken from the baseline to four points along the mast labeled A, B, C, and D.

Distance Line


The intersection for the distance lines is generally best kept between 60 and 120 degrees – not too obtuse or acute.Advantages of Trilateration

Accurate over greater lengths than other types of measurements

Disadvantages of TrilaterationAll measurements should be taken in a horizontal plane (problematic given that most sites are uneven). A commonly used method to deal with this is to establish a horizontal line using a mason’s line level, and stretch a tape along the line; a plumb line can then be used to line up the object to be surveyed

Archaeology – Combining Trilateration and Vertical

Offsets

Mapping objects usually requires the use of both trilateration and vertical offset techniques.Distance measurements are taken from two or three fixed datum points to the target to be surveyed. When plotted by hand, the intersection of these distance lines (arcs centered on the datum points) locates the target. The measurements should be taken horizontally to ensure that a true distance is recorded.

Archaeology – Combining Trilateration and Vertical

OffsetsTo document the target’s vertical position, a plumb bob (weighted tape measure or scaling rod) is dropped from the intersection of the datum measurements down to the surface of the target itself. It is imperative for an accurate vertical measurement that the horizontal datum measurement lines are kept as level as possible. Each target point measured should yield two (or three) distances from datum points and one vertical offset distance. (See following slide).

Archaeology - Combining Trilateration and Vertical

Offsets

Object

Horizontal Measurement Line

Horizontal M

easurement Line

Baseline

Vert

i cal O

ffse

t d

ista

nce

Archaeology – Removing Sediment

Tools such as trowels, shovels, brushes, etc…are impractical underwater. Hand fan - can move loose sediments but is slow.

Archaeology – Removing Sediment

Water induction dredge (see diagram on following slide) - good for moving large amounts of sediment. It consists of a long tube with a bend at one end. High-pressure water (from a water pump) is injected into the tube. The flow of water along this pipe causes an induced suction at the working end. A flexible tube may be added to the suction end to increase mobility of the dredge.

Water Induction Dredge

Induction Dredging

Archaeology - Removing Sediment

Airlift (see diagram on following slide) - also good for moving large amounts of sediment. Pressurized air is introduced into the bottom of a tube. As the air rises up the tube, it expands and this expansion causes suction at the lower end of the tube. The greater the volume of air and the greater the vertical rise from one end of the pipe to the other, the greater the suction. (Shallow water requires greater volume.) Because the airlift is buoyant when in operation, the lower end will have to be anchored or weighted down.

Air compressor

Weighted induction tube

Airlift

Valve – allows diver to control airflow

Airlifts

Biological Research

Before the advent of scuba in the 1940’s, marine biologists relied solely on technologies such as trawls, dredges, grabs, and plankton nets for research – somewhat akin to putting your hand into a dark sack and pulling out an unknown sample. These techniques made it:

Hard to sample specific areasHard to assess variabilityImpossible to manipulate/ do controlled experiments

Scuba made possible what was heretofore difficult or impossible

Biological ResearchActivities of biologically oriented divers include:

Observation – making raw or semi-processed recordings of biological phenomena (behavior, abundance, etc…)

Counting, measuring, observing individuals etc…

Collection – obtaining specimens (dead or alive) for examination/experimentation

For observing behavior in lab, fecundity estimates, physiological experiments etc…

Manipulation – altering the marine environment for a controlled experiment

Territories, cages, outplants, etc…

Biological ResearchMajor areas of underwater biological interest:

Ecology – the factors influencing the distribution and abundance of organismsBehavior – actions and responses of organisms to stimulationPhysiology – internal functions of organisms and their responses to internal and external influencesOther fields – biochemistry, pharmacology, evolution

Biological Research- Observation

Semi-processed observations – The diver makes counts or size measurements while underwater.

Sampling SchemesQuadrats – used to intensively analyze a fixed areaTransects –rectangles/strips used for measuring abundance in a set area

Biological Research - Quadrats

Typically used for small, non-motile or slow moving organisms that are reasonably abundant within a manageable quadrat size.

Size – typically 0.1m2, 0.25m2 , or 0.5m2

Construction – aluminum, welded rebar, or PVC pipe.

Typically 4 sided, but 3 sided are good if dealing with thick algal cover.

Quadrats

Diver using 3 sided quadrat – note transect line

Typical rectangular quadrats arrayed on a transect line

Point contact quadrats (% cover)Strung with lines creating squares

Where the lines cross – record the species under that point

Circular quadratsUse a weight attached to a line to circumscribe an area

Effective in areas of high algal cover



Random point contactA weighted bar with a string of knots tied to each end is dropped in a quadrat. Each species or group under the string, or above it to a specified height, is recorded.

Biological Research -Transects

Typically used for larger, more mobile or less abundant organismsMaterials

Fiberglass transect tapesNylon line marked with tape, heat shrink tubing, lead sleevesPermanent leaded core lines secured with anchors

Transects may be laid ahead of survey - or distance of transect may be assessed after completion.

A Diver moves along a transect

Diver counting lobsters found within 2m of a 150m transect.

Biological Research -Transects

Determining the dimensions of a transect (length x width = area) is done by measuring, using a stiff rod, or estimation.

The length and width of the transect must be scaled according to the abundance and size of the organisms in question

Observations can be biased by organisms that avoid divers or are attracted to themTimed observations:

Record the number of target individuals passing by a specific pointRecord the arrival of target species

Biological Research- Observation

Raw Observations – Observations are recorded underwater and counts or size measurements are done later.Photoquadrats

Application – Most useful for documenting the abundance of non-motile or slow-moving organisms

Photoquadrat images

Divers using photoquadrats – note framers made of PVC

Biological Research – Observation – photo

quadratsFramers – Underwater framers allow reliable, repeatable pictures. The framer usually supports the camera and flash and indicates the area being filmed.

May be made from aluminum stock or even PVC pipe.Often have scale bars to allow absolute measurements to be made.

Strategies for analysisProject the slides or digitize the slides and analyze the data via computer programs for:

CountsRandom point intercept (% cover)Measurements of area

Biological Research – Observation – Underwater

videoMost often used for documenting the abundance of motile organismsMethodology – video may be shot along a fixed transect for a fixed amount of timeConcerns:

Visibility must be measuredSome mobile organisms avoid divers, others are attracted

Analysis:Project video on monitorDigitize video and analyze with computer programs

Divers recording video along transect lines

Still from video transect – images may be quantified

Assessing aquatic populations

Non-mobile organismsCorers for soft sediments

Coffee can corersCut off both ends Drive into sedimentPut one lid on the topDig out one side and slip another lid on the other openingGood for large area samples

Suction corerUse 1” –2” PVC tubingSharpen the edgeDrive into the sedimentPlug the exposed end with a rubber stopperPull the tube from the substrate, place into plastic bag


Airlifts for hard-substrate organismsAirlift design

Typically a long PVC tube (4-8” diameter) connected to a separate air tank via a first stage and a low pressure port.Air enters the tube near the opening and expands as it rises, creating suction at the openingA sample bag is attached to the far end. This bag must be secured to the end, but be easy to release and seal

ProcedureMark out area with a quadratGo over the area quickly to remove loose material and semi-mobile organismsScrape the surface with a wire brush


Mobile organismsTraps

Baited and unbaited traps can be laid out and then recovered after a set period of time

Slurp gunsEffective when capturing small fish or invertebrates


Spear guns/pole spearsSpear guns are effective for larger fish, multi prong pole spears are more effective with smaller fish (easy to rearm if you miss).

Hand netsMade from seine material – rugged, but high drag and slowMade from gill net mesh – less rugged, but less resistance and faster


Anesthetics/poisonsPoisons include Rotenone (root of South American plant), pronox and chem fish.Anesthetics include

MS-222 – dissolves in waterQuinaldine – dilute to 10% with EtOH or acetone or isopropanol

Hard to get rid of smellBenzocaine2-phenozyethanol

Mix a dye (flouroscene) so that the target area can be monitoredApplication

Place in plastic bag – puncture and squeezePlace in several large syringesPlastic squeeze bottle

Scientific Diving Sampling Techniques. Sources Heine, J. N. 1999. Scientific Diving Techniques. Best...

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Transcript of Scientific Diving Sampling Techniques. Sources Heine, J. N. 1999. Scientific Diving Techniques. Best...