1
Development of Low Budget Survey Equipment and Techniques for Shallow
Water Ecosystems: A Case Study of the Fal Estuary Seagrass beds
Clive Pollittt and Claire Eatock
Author’s biographical information
Mr Clive Pollitt, FdSc Marine Science student. Falmouth Marine School. Falmouth, Cornwall,
UK. [email protected].
Dr Claire Eatock. FdSc Marine Science lecturer. Falmouth Marine School. Falmouth, Cornwall,
Claire Eatock is a lecturer and Clive Pollitt a foundation degree student at Falmouth Marine
school. Clive is an engineer interested in promoting marine biology to the general public.
Falmouth Marine School
Killigrew Street
Falmouth
Cornwall
TR11 3QS
United Kingdom
Tel: 01326 310 310
2
Abstract
Seagrass beds are one of the many shallow water benthic habitats that need to be regularly
monitored. This project used the seagrass beds in the Fal estuary in Cornwall UK as a test case
to develop inexpensive shallow water habitat surveying equipment that would be suitable for
colleges and amateur conservationists. It came up with four devices; a simple glass bottomed
box that could be mounted on the side of a boat; a video camera mounted on a long extending
pole that could give close-up pictures of the benthos; a photo/video-quadrat made from industrial
shelving material that could record statistical data for benthic habitats and finally an underwater
towed video monitoring system that could be used to cover large benthic areas. With these
pieces of equipment a successful baseline survey of the Fal estuary Seagrass beds was
completed.
Keywords
Benthic, Survey, Seagrass, Volunteer Bio-monitoring.
Introduction
Surveying shallow marine benthic environments is important for conservation groups,
environmental monitoring, water quality control, pollution monitoring and for monitoring global
warming and ocean acidification. (Rhoads 2004) A large amount of marine life is within the
shallow photic zone just beyond the shore and in the inter-tidal zone.
The costs associated with this type of surveying have become prohibitive due the sheer amount
of area to be covered. This has resulted in large areas being infrequently surveyed, if at all, and
environmental and planning decisions cannot be easily made with confidence if current coastal
survey data is not available. An example of this is in the Fal estuary in Cornwall, England where
a Special Area of Conservation (SAC) was established in 1992 as a result of the European
Habitats Directive. The local harbor commissioners are one of the organizations who have been
3
made responsible for environmental monitoring of the estuary but have very little current data.
This is a very typical situation in Britain and Europe at large. The reasons for this situation are
the costs involved with environmental surveying which are often outside the budget of small
environmental organizations.
The Fal estuary was made a SAC largely because of the maerl and seagrass beds that are present
within it. There is however very little current environmental habitat survey data available, the
habitat map presently in use being more than 20 years old. (Kevan Cook, Lead Advisor, Marine,
Truro, Natural England, personal communication, 23 September 2010)
Volunteer based monitoring programs have been designed and initiated by many organizations
including Seagrass Watch, (McKenzie 2002) but many have found that these programs are
difficult to sustain. This is largely due to the fact that most Seagrass is below the water for much
of the time and qualified volunteer divers are required to do the surveying. (Short 2009)
Different monitoring options are dependent on the structure and resources available, e.g.
cumbersome methods are not practical for volunteer-based monitoring networks and also the
adequacy of different methods for the various species, which requires knowledge of their growth
rates and basic ecology. (Duarte 2003)
Many types of equipment have been used to overcome the difficulty of using professionally
qualified divers. Professional surveying institutions often overcome this by the use of remotely
deployed video equipment (Potts 1982), which has become a well established tool in many areas
of marine research. (Holme 1984) Towed video sledge techniques provide a means to visually
survey large areas of seafloor without the depth or time constraints usually associated with other
techniques such as scuba diving. (Sisman 1982)
In the past, techniques such as this have been used to monitor the condition of features in
candidate Special Areas of Conservation (SAC) (Magorrian 1996) Towed video sledge data can
4
be used to estimate the relative abundance of benthic species using the Visual Fast Count (VFC)
technique. (Kimmel 1985) The main disadvantage of the towed video sledge system is the
potential damage it can cause to the fragile seafloor habitat that it is recording. (Grizzle 2008)
An alternative is to have a Drop Down Video System (DDVS) which is a camera mounted on a
frame, often associated with a quadrat. (Holt, Sanderson 2001) This is lowered to the seafloor
where it remains stationary whilst recording the benthos. The position is given by a Global
Positioning System (GPS) receiver and the equipment is then moved to a new location often on a
pre-set transect. DDVS recording techniques have been used in a variety of applications and are
appropriate for the identification of seabed habitats. (Sanderson et al. 1999)
An underwater Remotely Operated Vehicle (ROV) is a self propelled underwater camera system
often with artificial lighting capable of descending to depths unreachable by divers and is
considered suitable for biotype surveying and monitoring. (Arbour 2004) The ROV is usually
connected to a surface support vessel via a tether cable which controls the ROV’s movements
and passes the underwater video image to the operator for control and recording purposes. Due
to their maneuverability these systems are able to acquire great detail of the biotype. Together
with GPS equipment and on-board recorders these systems combine the flexibility of a diver
together with the advantages of remote control.
The disadvantage of ROV, towed and drop down video systems is the expense of the equipment
and of the support vessel, deploying equipment and tethers and the need for highly trained
personnel. (Epstein 2010) These factors usually place these survey techniques out of the reach of
small, low budget surveying organizations and volunteer initiatives. (Short 1984)
The purpose of this project was to develop inexpensive and safe shallow benthic surveying
equipment using basic skills and the recent development of inexpensive high definition digital
video cameras and recording equipment. The Seagrass beds in the Fal estuary were chosen as a
test case.
5
1) Aqua-scope
The first device developed was built along the lines of a glass bottomed boat. (See figure1) This
piece of equipment was a large wooden box 75cm high by 75cm long and 40cm wide. The
bottom of the box had a glass water-proof window installed with handles and boat attachment
points placed along the sides of the box. The inside was painted matt black and a removable top
with an observation port were added. It was named the Aqua-scope.
Deployment
When the boat had reached the right location to be surveyed the position and depth were taken
using the boats onboard fish finder and GPS. The Aqua-scope was then placed in position over
the side of the boat and secured with its fastenings. Viewing of the seafloor was simply done by
looking into the viewing port. The boat was allowed to drift and the depth, GPS positions and
benthos were noted as it did so. Still camera and video photography was possible with the
camera placed at the viewing port or lowered to the glass pane where a very wide field of view
was possible.
Results
General observation underwater to a depth of 4 to 5 meters in bright, calm conditions was
possible at slack low tide. (See figure 2) The Aqua-scope was successfully used to map the
position of the major sea-grass beds in the Fal and in particular the St. Mawes Eelgrass meadow
near the Fal entrance.
Four surveys were conducted in the summer months of June, July and September and three
during March using the Aqua-scope. It was also used in conjunction with the other surveying
equipment developed in the project to help observe the performance and deployment of the
equipment.
6
Materials and Costs (See table 1)
Capabilities and limitations
The data collected by the Aqua-scope could be considered to be equivalent to the data obtained
from surface snorkeling i.e. a general visual survey of areas of the seafloor where the benthos
type , coverage and location could be observed and recorded manually.
The main limitation of the Aqua-scope was the limited depth to which it can be used and the
inability of the boat to maneuver with it deployed. Any movement by the boat against the tide
resulted in turbulence and bubbles around the observation glass. The weather conditions had to
be bright and calm and the survey had to take place during slack tide, preferably spring low tide,
when the water had the lowest turbidity conditions.
A suggestion for its improvement would be to have a more streamlined design with strong
attachment points to the boat that would make limited maneuverability possible.
2) Scubar
In order to have a closer look at the benthos, and in this case the seagrass, observed with the
Aqua-scope it was necessary to develop a simple video system that could get within centre
meters of the seagrass. A simple all-in-one water-proof video head- camera (Oregon Scientific
Action Camera ATC-3k) was mounted on a 5 meter fiberglass extending window cleaning pole
and used to place the camera into the desired position below the boat. This system was called the
Scubar.
The camera was set to record and its timer synchronized with the boats onboard clock along with
the GPS position and depth. This was blind recording but worked well where the general
7
condition of the seagrass was required. The footage recorded was analyzed in conjunction with
the recorded depth and position afterwards by re-synchronizing the results.
An improvement of this system was to replace the head-camera with a waterproof closed circuit
television (CCTV) camera that was connected to a boat mounted monitor and recorder via a long
tether cable. A video monitor and a mini digital-video recorder were used. The monitoring and
recording could be performed by a laptop computer with basic video recording web-cam
software and video input adaptor. (The lap-top computer monitoring and recording system was
used on the Delta-wing, see later) This allowed real time monitoring and a recording for later
analysis.
Deployment
The Scubar was simply put over the side of the boat on arrival at the chosen survey location. The
pole was extended to the required depth and held above the benthos by using the boats on-board
depth meter and a graduated scale on the Scubar lowering pole. The Scubar was allowed to
record the benthos for a preset time and then raised to the surface and the boat moved to the next
location where the same procedure was repeated.
Results
This system was very simple to use and required minimal set up and preparation. Being totally
waterproof it was used on a small inflatable dinghy and canoe allowing access to areas not
normally accessible to motorboats. This system was aided by the simultaneous use of the Aqua-
scope to position and orientate the camera at the end of the pole.
The CCTV system was more complicated, requiring external power for the monitor, camera and
recorder. The length of the tether cable had an effect on the video signal quality and hence the
recorded image.
8
The Scubar was able to examine the outer limits of the Seagrass areas with more detail than with
the Aqua-scope, when it was often unclear whether the seafloor coverage was seaweed or
Seagrass. (See figure 3) The Scubar was able to positively identify the Seagrass and seaweed in
these situations. Eight successful surveys of the Fal Seagrass beds were conducted with the
Scubar in June, July, September and October in 2010 and in March 2011.
Materials and Costs (See tables 2 and 3)
Capabilities and Limitations
The data collected by the Scubar could be considered to be equivalent to the data obtained from
scuba diving down to 5 meters, i.e. a close visual survey of the seafloor where the benthos type,
coverage and position could be observed and recorded manually in detail.
The limitation of the Scubar was the inability of the boat to maneuver with it deployed.
The boat was only able to drift with the tide, as to maneuver the boat with the pole extended,
threatened to break the pole. A drifting transect was possible but not a preset transect. The
Scubar had to be used as part of a fixed point survey method where it was deployed and
recovered between preset way-points.
Another limitation of the Scubar was the limited depth to which it could be used. Like the Aqua-
scope, the weather conditions had to be bright and calm and the survey had to take place during
slack tide, preferably spring low tide, when the water had the lowest turbidity conditions. The
Scubar was also limited to the depth rating of the camera used.
A suggestion for improvement would be for a sturdier pole with a boat mounting to hold it in
position and a high definition camera with lighting to enable deeper surveys in darker
conditions.
9
3) Photo-quadrat.
In order to collect data that could be statistically analyzed a Photo-quadrat system was
developed. This survey would traditionally be undertaken by a diver with a quadrat and possibly
an underwater camera. The Photo-quadrat was a metal cage fitted with an underwater digital
stills camera, connected to a remote triggering system. The cage was lowered to the seabed and
the camera triggered from the boat above.
The cage had a 0.5m square base and was one meter tall with a grid pattern built into the base.
(See figure 4) It was constructed of galvanized metal “Dexion”, an industrial shelf rack system
that can be used for construction of framework due to its narrow (3cm) L section, long lengths
and its multiple pre-drilled mounting holes. The grid pattern was made of fine nylon cord that
was laced at measured intervals along the bottom of the cage. The cage was held together with
nuts and bolts through the multiple holes in the Dexion lengths. Small half Kilogram zinc
weights were added to the base to provide better stability.
The camera was mounted on the top of the cage using its tripod fitting and was positioned
pointing towards the base. The trigger release mechanism was a small water-proofed electric
solenoid positioned on the frame to activate the camera shutter via the solenoid’s plunger. (See
figure 5) The solenoid was connected via a long cable connected to a 12v battery and activation
trigger on the boat.
Deployment
The camera was pre-focused on the Photo-quadrat base and lowered to the seafloor whilst the
GPS position and depth were recorded from the boats instruments. Once the Photo-quadrat had
reached the bottom, it was left for a couple of minutes for any disturbed sediment to settle and
the camera trigger activated. The equipment was then raised to the surface and moved to the next
point and the process repeated.
10
A further development of the Photo-quadrat was the substitution of the still camera with an
underwater high definition (HD) video camera. This camera was attached to the Photo-qaudrat in
the same way as the stills camera and lowered to the seabed. The camera was set to record
before it was lowered as it required no trigger release mechanism and could be left on the
seafloor unattached to the boat. The lowering rope could be tied off to a buoy on the surface for
collection when the recording was complete.
This system was very inexpensive and simple to construct and was easy to adjust for cameras of
different focal lengths due the multiple fixing holes in the Dexion material.
Results
The Photo-quadrat system allowed close inspection of the seabed in high definition still image
snapshots but also close observation of the seabed in 10 minute video recordings showing
transitions and activity during that time. The GPS position, its depth and other data could be
recorded from the boats instruments as the Photo-quadrat was lowered.
The grid pattern on the Photo-quadrat base allowed accurate data collection for quantitative
statistical analysis. The percentage coverage could be measured together with individual
measurement of leaf, rhizomes and flower size and quantity. (See figure 6)
Materials and costs ( See table 4)
Capabilities/ Limitations
This system was successfully tested in two surveys in October 2010. A problem encountered
with the still camera system was the camera lens became fogged from the sunlight when the
Photo-quadrat was brought to the surface between deployments. This was remedied by placing a
dark, wet towel over the camera when it was lifted clear of the water. Another problem
encountered was that the rate of drift of the boat was often rapid, allowing insufficient time for
11
the sediment to settle around the Photo-quadrat before a photograph could be taken. This could
be rectified by having a longer cable for the trigger release mechanism.
The waterproof HD video camera system also suffered lens fogging problems between
deployments and limited camera battery life. A large battery would be required for meaningful
surveys.
4) Delta-wing
To overcome the boat maneuverability limitations of the Aqua-scope and Scubar, a towed video
camera system was developed. This allowed continuous close-up monitoring of the seabed at
greater depths, over a large area whilst travelling along a pre-set transect. This required a
waterproof CCTV camera connected to a devise that kept the camera approximately a meter
above the seabed. It was required to be stable when towed below the boat whilst being connected
to a boat mounted monitor and recorder. It was important that the devise could give accurate
GPS positions and depths of what was being recorded. In order for this to happen, the devise
needed to be towed directly beneath the boat. This devise was named the Delta-wing. This
system would give similar results to that obtained from an ROV system.
The Delta-wing was a one meter triangular wing shaped piece of 6mm ply-wood with 30cm
triangular vertical stabilizing fin and a 10 kg metal weight bolted to the underside of the wing.
(See figure 7) The camera was mounted at the front of the wing and a tow rope attached in such
a position that the Delta-wing pointed 30 degrees down from the horizontal when towed.
The Delta-wing was tested using a lap-top computer to monitor and record the benthos. The
depth of the Delta-wing was monitored from markings on the tether rope whilst the depth of the
water and position and speed were measured using the boats onboard fish finder, log and GPS.
12
Deployment
The Delta-wing was lowered over the side of the stationary boat with the tether rope together
with the electric cable. The depth of the Delta-wing was indicated by measurements on the tether
rope. The lap-top video recording was started and the depth, position and times were all noted.
The boat moved forward until the Delta-wing had orientated itself in the direction of travel and a
steady course steered along a transect at approximately 4 kph.
Results
Three successful transect surveys were conducted in March 2011 over the seagrass beds in the
Fal Estuary at approximately a meter above the seafloor. The boat was moving at approximately
4 kph and good quality images could be observed and were recorded. The boat speed had to be
adjusted when the Delta-wing was moved closer to the seafloor as the image on the monitor was
moving too rapidly for accurate identification. The advantage of the system was that when a
particular area of interest came into view the boat could stop for closer analysis and the Delta-
wing could even be lowered onto the seafloor. The Delta-wing orientated itself well in the
direction of travel and could be positioned directly below the boat at 4 kph giving an accurate
GPS position and depth. The Delta-wing could be used to cover large areas more rapidly by
raising it to give a broader field of view and increasing the boat speed. An extra light was fitted
to the Delta-wing but it was found to be unnecessary.
The value of the Delta-wing was shown by the discovery of two other wise undetected seagrass
beds. The Aqua-scope and Scubar were unable to detect these very small sparsely populated
beds using the point survey system. The Delta-wing however using continuous recording was
able to detect these thinly populated Seagrass beds easily amidst a large area of deserted seabed.
(See figure 8)
13
Materials and Costs (See table 5)
Capabilities/Limitations
The Delta-wing was heavy and cumbersome to use. Lowering and raising it was strenuous work
and the tether rope, electric cables and connections to the lap-top and battery were awkward. A
boat with sufficient deck space was necessary. It was found that for extended recording the
computer lap-top method of monitoring and recording was the most satisfactory however the
laptop needed extra battery power. Connecting this particular lap-top to the boats 12v power
source caused interference from the boats alternator which affecting the CCTV camera timing
signal.
Overall equipment comparisons (See tables 6,7,8)
Discussion
In line with the project’s objective, it has been shown that inexpensive home built surveying
equipment can be developed and used successfully for shallow benthic habitat surveying that
could be performed by colleges, enthusiasts, clubs and boatmen to a scientifically robust
standard. (Holt 2001) The costs can be kept low due to the use of equipment already available
like under water cameras, lap-top computers and standard on board boat equipment like fish
finders and GPS.
Other factors not included in this report were the size and type of boats used, the fuel and boat
costs, the detailed health and safety issues with each different system, the affect of time and
seasons on the surveys and the qualifications of the participants in the project.
The Aqua-scope was the most user-friendly, easiest to build and deploy and gave good enough
results to establish a basic presence to a depth of 5 meters on sunny days at low slack tide. The
14
Scubar made it possible to refine the perimeters of the Seagrass beds and examine the general
condition of the Seagrass but was more difficult to use. The Photo-quadrat produced quantitative
data making it possible to perform statistics on the Seagrass beds and the Delta-wing made it
possible to search larger areas for new Seagrass beds although it was the most complicated to
use. The ability of the Delta-wing was proved by the discovery of two previously undetected
seagrass beds.
The surveys conducted during this project using this equipment developed has formed a
baseline survey of the Fal estuary Seagrass beds that can be built upon by further use of the same
equipment or for more detailed professional surveys in the future.
3691 words including abstract.
15
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and management. The M&MS project. ( November 2010; www.seagrasses.org)
Epstein J. 2010. Hawkes Unveils New ROV Class. Marine Technology reporter. October 2010.
(November 2010. http://dwp.marinelink.com/pubs/nwm/mt/201010/ )
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oyster reefs as an example application. Journal of Coastal Research: volume 24.
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Kimmel J. 1985. A New species-time method for visual assessment of fishes and
its comparison with established methods. Environmental Biology of Fishes 12.
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Magorrian BH. Service M.1996. An acoustic bottom-classification survey of Strangford Lough,
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McKenzie L J. Campbell S J. 2002. Manual for Community(citizen) Monitoring of Seagrass
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Potts G W et al.1982. Scuba diver-operated low-light-level video system for use in underwater
research and survey. Journal of the Marine Biological Association of the United Kingdom , 67.
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Sanderson et al. 1999. The Human Footprint and the Last of the Wild. BioScience . Vol. 52.
Short F T.1984. Seagrass-Watch Western Pacific Manual for Community (citizen) Monitoring of
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2010. www.seagrasswatch.org)
Sisman D. 1982. The Professional Diver's Handbook. Submex. London .
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Figure 1. The Aqua-scope C Pollitt 2010
Figure 2. View through the Aqua-scope. C Pollitt 2010
18
Figure 3. Seagrass recorded by the Scubar. C Pollitt 2010
Figure 4. Photo-quadrat with still waterproof camera. C Pollitt 2010
19
Figure 5. Waterproof, still camera, trigger release mechanism. C Pollitt 2010
Figure 6. Photo-quadrat picture. C Pollitt 2010
20
Figure7. The Delta-wing C Pollitt 2011
Figure 8. The Delta-wing recording C Pollitt 2011
21
Table1. Materials and Costs of the Aqua-scope
Material Measurements Used for Number Cost Supplier
6mm, Exterior
plywood
Sheet, 1220cm
x 2440cm
Aqua-scope
body
1 £30 Hardware
supplier.
Wood
Adhesive.
Everbuild 502
250 ml £4 Hardware
supplier
Pine 12mm x 12mm
x 3m long
Body
construction
1 £10 Hardware
supplier.
Glass pane 6mm thick
60cm x 30cm
Window 1 £10 Glazier
Exterior white
Gloss Paint
1 liter Aqua-scope
exterior
1 £6 Hardware
supplier.
Silicon Sealer
Unibond 2580
310 ml Waterproofing
window
1 £8 Hardware
supplier.
Aluminum
Handles
15cm x 3cm Hand
Mounting
2 £5 Hardware
supplier.
20cm
diameter
Aluminum
tube
3m length Boat
mounting and
supports
1 £10 C&S Non-
ferrous
metals. Metal
supplier
Matt Black
Paint
750 ml Inside Aqua-
scope
1 £5 Hardware
supplier.
Wood screws 12mm Aqua-scope
Body
50 £10 Hardware
supplier.
Total cost £98
22
Table 2. Materials and costs for the basic blind Scubar system
Material Measurements Used for/in Number Cost Supplier
Extending
Fibreglass
pole
5 meters x
50mm
diameter
Underwater
camera
mounting
1 £50 Window
cleaning
suppliers
Head Camera
Oregon
Scientific
atc-3k
10cm x 5cn
diameter
Underwater
image
recording
1 £80 Sports
equipment
supplier
Extra strong
Cable ties
30cm Securing
camera to
pole
5 £3 Hardware
supplier.
Trago mills
Total cost £133
23
Table 3. Materials and costs for the real time CCTV Scubar system
Material Measurements Used for/in Number Cost Supplier
Extending
Fiberglass
pole
5 meters x
50mm
diameter
Underwater
camera
mounting
1 £50 Window
cleaning
suppliers
Swann
CCTV
camera
Color, 380 tv
lines, 1/3 inch
cmos. 12 v.
Underwater
monitoring
1 £30 Electronic
security
supplier
12v battery 12v Powering
cctv camera
1 £15 Electronic
supplier
7” color
video
monitor
Phono (RCA)
or s-video
compatible
Monitoring
cctv camera
images
1 £70 Consumer
Electroncs
supplier
DV recorder 2Gb Sd card
recording
media.
Recording
CCTV
images
1 £70 Consumer
Electroncs
supplier
3 core
13 amp
mains cable
20 meters Transferring
images from
CCTV to
monitor.
power
1 £20
Electrical
supplier
B&Q
Total cost £255
24
Table 4. Materials and costs of the Photo-quadrat
Material Measurements Used for/in Number Cost Supplier
Galvanised
Dexion
shelving
material
3cm L section Frame
construction
10 meters £50 Industrial
shelving
supplier
Dexion nuts,
bolts and
washers
1 x 50 pack
8mm x 15mm
Frame
construction
1x 50 pack £10 Industrial
shelving
supplier
12v car door
locking
solenoid
12v, generic
20mm plunger
travel
Remote
shutter
activation
1 £10 Car parts
supplier
2 Core,
5 amp cable
7 meters Remote
shutter
trigger
1 £10 Electrical
supplier
B&Q
10 mm
diameter
nylon rope
10 meters Deployment
of Photo-
quadrat
1 £10 Hardware
supplier
B&Q
Zinc weights 0.5 kg Frame base
stabilization
4 £10 Hardware
supplier
12v battery 12v, 1ah Solenoid
power
1 £15 Electronics
supplier
Total cost £115
25
Table 5. Materials and costs of the Delta-wing
Material Measurements Used for/in Number Cost Supplier
6mm
plywood
1 meter square Delta-wing
body and fins
1 £10 Hardware
supplier
Zinc
Weights
10 Kg – Boat
engine anode
stabilization
and ballast
1 £30 Boat
Chandler
Swann
CCTV
camera
Color, 380 tv
lines, 1/3 inch
cmos. 12 v.
Underwater
monitoring
1 £30 Electronics
supplier
12v battery 12v , 1ah Powering
cctv camera
1 £15 Electronics
supplier
7” colour
video
monitor
Phono (RCA)
or s-video
compatible
Monitoring
cctv camera
images
1 £70 Consumer
electronics
supplier
DV recorder 2Gb Sd card
recording
media.
Recording
CCTV
images
1 £70 Consumer
electronics
supplier
3 core 13A
cable
20 meters Transferring
images
1 £20 Hardware
supplier
Galvanised
Dexion
shelving
3cm L section Frame
construction
0.5 meters £2.50 Industrial
shelving
supplier
Dexion nuts,
bolts and
washers
I x 10 pack
8mm x 15mm
Frame
construction
1x 50 pack £2.50 Industrial
shelving
supplier
Total cost £250
26
Table 6. Comparison of Aqua-scope with Snorkeling
Aqua-scope Snorkeling
Advantages Disadvantages Costs Advantages Disadvantages Costs
General
visual
benthic
survey
Boat
Maneuverability
when deployed
£98
+ boat
General
visual
survey of
the seafloor
Trained and
Qualified
personnel
required.
Snorkel
equipment
£30
Minimal
Health and
safety, and
insurance
requirements
Weather and
tide dependant
Can be
conducted
from the
shore
Stringent
health and
safety and
insurance
requirements
No formal
training.
Large groups
possible
Limited field of
view.
Wide field
of view
Position and
depth
recording
difficult
Simply
adaptable for
non-
waterproof
video/ photo
recording
Requires
under water
photo and
video
recording
equipment
Weather and
tide
dependant
27
Table 7. Comparison of the Photo-quadrat and a diver quadrat survey
Photo-quadrat Diver Quadrat
Advantages Disadvantages Costs Advantages Disadvantages Costs
Minimal
Health and
safety, and
insurance
requirements
£115
without still
or video
camera
Accuracy Stringent
health and
safety and
insurance
requirements
£1000 for
basic diving
package
No formal
training
required
Blind quadrat
positioning
and
orientation
Preset
quadrat
positioning
and
orientation
Trained and
Qualified
personnel
required.
Large groups
possible
large groups
difficult.
Weather and
tide
dependant
Weather and
tide
dependant
28
Table 8. Comparison of the Delta-wing and an ROV
Delta-wing ROV
Advantages Disadvantages Costs Advantages Disadvantages Costs
Easily
deployed by
untrained
personnel
Depth
limitation
£250 Highly
accurate data
gathered and
recorded
Professional
trained and
qualified
personnel
required
£60 000
initial cost .
Rental £1000
per day
including
operator
Accurate,
recorded
data
Limited
maneuverability
Highly
maneuverable
Professional
Personnel
hire £300 per
day
Suitable for
detailed and
extensive
surveying
Suitable for
detailed and
extensive
surveying
Can be
modified for
other camera
systems
Can achieve
great depth
surveys