WALLACE RESOURCE LIBRARYWALLACE RESOURCE LIBRARYLecture 05 – How to Survey a Coral Lecture 05 – How to Survey a Coral
ReefReef
WALLACE RESOURCE LIBRARYWALLACE RESOURCE LIBRARYLecture 05 – How to Survey a Coral Lecture 05 – How to Survey a Coral
ReefReef
This is an ‘example’ of a lecture that is given to A level students as part of their academic lecture series whilst on their expedition.It has been produced for the exclusive use of the lecturer conducting the series and is solely intended for educational purposes.Most of the material comes from Operation Wallacea sources and any other material that has been used has been credited (as far as is possible) to the appropriate author wherever possible.
This lecture is only to be used for EDUCATIONAL purposes.
WALLACE RESOURCE LIBRARYWALLACE RESOURCE LIBRARYLecture 05 – How to Survey a Coral Lecture 05 – How to Survey a Coral
ReefReef
WALLACE RESOURCE LIBRARYWALLACE RESOURCE LIBRARYLecture 05 – How to Survey a Coral Lecture 05 – How to Survey a Coral
ReefReef
Lecture 5 – How to survey a coral reefLecture 5 – How to survey a coral reef
Summary
• Why do we survey coral reefs?• Which method(s) to use?• Rapid habitat surveys• Benthic and invertebrate assessment techniques• Fish assessment techniques• Measuring abiotic factors (remember those??)• The use of technology• The Operation Wallacea reef monitoring program
Why do we survey coral reefs?Why do we survey coral reefs?
According to the “Status of Coral Reefs of the World: 2008”…• 19% of the world's reefs are effectively lost already•15% are seriously threatened with loss in the next 10-20 years•20% are under threat of loss in the next 20-40 years.
Surveying and monitoring allows researchers and conservation managers to quantify the state of a coral reef, and decide what
action, if any, is needed
Assessing a coral reefAssessing a coral reef• One of the most commonly carried out assessment of reefs is a Rapid
Environmental Assessment (RAE) – known as a Survey• Aims to determine the overall community diversity and health of a particular reef
system at a particular time
• By repeating environmental assessments regularly, ecosystem change can be identified – this is known as ecosystem Monitoring
• Operation Wallacea programme is a great example of this
Gradient of ecosystem healthGradient of ecosystem health
Choosing the best method will depend on…Choosing the best method will depend on…
Technique used depends
upon…
The Site:A more remote site will
mean extra considerations about the surveying options
available to you
The objectives of the study:What questions are you trying to answer? Is there an aspect
of the coral reef which you are particularly interested in?
The time available for the study:The more time you have, the
more in depth surveying you can do. You need to maximise the
amount of data you collect
The experience of the researchers:Some techniques require a higher
level of expertise, and so the level of training researchers have had is an
important consideration
Funding:Some methods cost more than
others, plus remember that time costs money!
Manpower:How many people are available to you? How can you use their
time most effectively?
Broad habitat surveysBroad habitat surveys
• For rapid characterisation of general habitat characteristics i.e. a “look see”
• Large area surveyed quickly but data is low quality
• Suitable for inexperienced researchers
• Often used to identify areas worth surveying in more detail
Site: Buoy 1, AustraliaDate: 1st August 2012Reef depth estimate: 4 – 30m
Hard coral cover: 60%Soft coral cover: 20%Sand cover: 10%
Dominant coral growth type: MassiveSigns of bleaching? NoSigns of damaged coral? Yes
No. Diadema: 21No. CoTs: 35No. giant clams: 5
Example data sheet for broad habitat survey
Broad habitat survey: Manta towBroad habitat survey: Manta tow
• A snorkeller is pulled behind a slow moving boat using a manta board
• The distance covered is noted
• Researcher notes key features of the reef below them
Fun technique – which helps Fun technique – which helps encourage people to get encourage people to get
involved!involved!
Broad habitat survey: Spot surveysBroad habitat survey: Spot surveys
• These involve descriptive surveys of reef habitats as recorded on set timed spot dives
• The information gained is broad but enables key locations to be identified for further study
Spot survey results from Puerto Rico, Caribbean
(Morelock et al. 2001)
Benthic surveysBenthic surveys
• Benthic means ”living on the sea bottom”
• This includes things like coral and algae, and also those fish and invertebrates that live on the bottom
• In terms of surveys, it generally refers to space competitors (hard coral, soft coral, benthic algae, sponge etc.)
Working close to the reef – considerations!Working close to the reef – considerations!
Diver damage can be one of the biggest threats to coral reefs Important we think while we dive – we are trying to make Important we think while we dive – we are trying to make
things better not worse!things better not worse!
• Good buoyancy – will allow you to ‘hover’ above the reef without contact• Horizontal swimming – helps prevent kicking the reef while finning• Dangling equipment – keep all kit tucked in, so it doesn’t hit the reef• Never touch the reef unless you have to – if you have no choice, only
use one finger on bare rock to push yourself away• Bubble awareness – bubbles can damage the reef, so avoid swimming
under overhangs or into caves• Dangerous organisms – be aware when near the reef, and waft before
using the ‘one finger rule’• Buddy contact – maintain good buddy contact at all times
Benthic transectsBenthic transects
Transects
1. Line Intercept Point: Transect is laid out (10 - 50m long) which is marked at set intervals (10 - 100cm) along the transect. At each interval the substratum type underneath each interval is recorded
2. Continual: Substratum type lying under every part of the tape is recorded. Any change is recorded as transition points
Note that both of these can be done using videography, where a recording of the
transect is taken and analysed later
Benthic transectsBenthic transects
20cm
20cm
20cm
20cm
20cm
20cm
TransectTransectSoft Coral
Hard Coral
Soft Coral
Sand
Soft Coral
Soft Coral
Soft Coral
Line Intercept Point
Sand (30cm)
Soft Coral (13cm)
Soft Coral (47cm)
Soft Coral (8cm)
Hard Coral (22cm)
Continuous
Methods of assessmentMethods of assessment
Quadrats• Obtain quantitative data• Size and number of replicates depends on
habitat, time available and target organisms
• Example: 1m x 1m to calculate % benthic cover using photo analysis
Benthic quadratsBenthic quadrats
?%
?%
?%
?%
?%
?%
Benthic quadratsBenthic quadrats
Specific benthic monitoring – coral bleachingSpecific benthic monitoring – coral bleaching
• Bleaching is a major problem on reefs (discussed in a later lecture)
• Coral Watch Health Charts provide a basic method of identifying bleaching
• Users upload results into a central database which monitors global patterns in bleaching
• Great tool to raise awareness and provide basic data
• However, there are some limitations to this technique e.g. assumes all bleaching is lethal
Fish surveysFish surveys
This is an example of swimming along a reef – how would you This is an example of swimming along a reef – how would you recommend the fish community could be ACCURATELY surveyed?recommend the fish community could be ACCURATELY surveyed?
Methods to survey fishMethods to survey fish
Destructive
Destructive techniques remove fish and generally kills them
Traps, nets, hook and line, rotenone (anaesthetic)
Useful for some technical data (e.g. growth Useful for some technical data (e.g. growth rates), but not used otherwise as it requires rates), but not used otherwise as it requires fish to be killed. Sometimes fishermen will fish to be killed. Sometimes fishermen will
allow their catches to be examined.allow their catches to be examined.
Non-destructiveNon-destructive techniques do not
remove or harm fish in any way
Underwater visual census- divers, video cameras
Limits the data available, but has little or no Limits the data available, but has little or no impact on the fish community or the reef impact on the fish community or the reef
itself. This is therefore the preferred itself. This is therefore the preferred approach.approach.
VS
Fish survey: Spot surveysFish survey: Spot surveys
• For larger pelagic species, which will tend to disappear soon after the arrival of the survey team
• First person in the water immediately looks for and records the presence of pelagic fish species (for a set time)
• Often such spot surveys are completed prior to a more detailed survey
Fish transects (also for invertebrates)Fish transects (also for invertebrates)
1. Belt transects: Transect laid down and organisms survey either side of the transect for a set distance e.g. 2m either side and above
2. Time restricted transects: These do not use a transect tape, but involve swimming along the reef at a constant speed for a set time, noting down all fish seen. An estimate of the area covered is then made
25m2m
2m
A transect (black) with the imagined “belt” (red)
Stereo-videoStereo-video
• Recent development to survey fish
• Twin video camera to provide a stereo-recording
• Allows species ID and fish lengths to be analysed post-dive (fish lengths are important to calculate biomass)
• Expensive but highly accurate
• High quality data can be collected without much experience or expertise
Stereo-video – Specialised softwareStereo-video – Specialised software
Stereo-video VS Underwater Visual Census (UVC)Stereo-video VS Underwater Visual Census (UVC)
UVC Stereo-videoAbundance data ✓ ✓
Diversity data ✓ ✓
Length data ✗ ✓
Per m2 data (true) ✗ ✓
Cross checking data ✗ ✓
Length error Up to 30-40% < 5%
Survey boundary ✗ ✓
Multiple observers Increases Error ✓
Field time More ($$$) Less ($)
Equipment cost Less ($) More ($$$)
Transects per dive 2-4 10-12 +
Post dive analysis Simple data entry Lengthy analysis
Permanent record ✗ ✓
Lets not forget our abiotic factors…
• So far in the lectures, you should have noticed how coral reefs are hugely dependent on environmental factors
• These include light, temperature, sedimentation and nutrients
• These factors can also be monitored using various techniques
Monitoring abiotic factorsMonitoring abiotic factors
Water Quality• Inorganic nutrients such as nitrate,
phosphate and ammonium can stimulate algal growth
• Simple tests can be used to measure the levels of these nutrients in the water
Temperature and Light• HOBO loggers (right) can be cemented to
the reef, and they will take a temperature and light reading every second for several years!
• They can then be brought up and the data downloaded onto a computer
Monitoring abiotic factorsMonitoring abiotic factors
Turbidity
• Can be measured by filtering large volumes of water and weighing the amount of sediment present
• Using a secchi disk (right top) – this is lowered into the water until the pattern is no longer visible, and the depth noted
Sedimentation
• Sedimentation rates are usually determined by placing sediment traps in the survey area
Technology: Remote sensingTechnology: Remote sensing
• Remote sensing utilises satellite photographs of the area under survey
• Scientists ground-truth the images by visiting and fixing the position of different habitat types
• Software can then match all similar habitat types on the satellite image (by colour)
• Therefore the area coverage and exact location can be identified by the map alone
Pollution source??Pollution source??
Technology: GIS in marine monitoringTechnology: GIS in marine monitoring
GIS can help us identify candidate
MPA sites
Questions?Questions?