REEF MONITORING TECHNIQUES

The monitoring and research of local coral reefs is one of the most vital first steps to be taken for any reef manager. Coral reef Monitoring essentially answers the following questions:

What is on our reefs (Abundance, biodiversity, etc)?
What species are special or important for our area?
What is the current health of our reef?
What changes are being seen over time?
What is causing any declines in health?
What can be done to stop declines in reef health or abundance?
Are the reef management techniques being used effective and efficient?

There are in fact many research and monitoring techniques available to local reef managers. Some are very simple, and can be conducted by swimmers or divers with only a half hour of training, others are very complex or expensive and are usually only used at the University or professional research level. In the case of the more broadly accessible methods, the basic techniques are the same, but each location or group will alter them slightly to fit their needs or unique location.

Generally monitoring will be both for the living organisms and for the physical conditions of the area (i.e. water sampling analyses). This article is more focused on how divers and local reef managers can evaluate the health, biodiversity, and abundance of their reefs. You can also click here if you want to learn more about water testing techniques.

The list below gives an overview of some of the general techniques used in coral reef monitoring and research, as well as some of the applications of each. Readers more interested in actually practicing these techniques would be advised to also visit the GEFCORAL website which has many great manuals freely available for download by reef managers.

ROVING DIVER SURVEY

This survey can be conducted while either snorkeling or diving, and only requires the surveyor to have a slate and pencil. The surveyor then swims along the reef for a set distance or time, or evaluates a reef area of predetermined size (i.e. 10m x 10m). The surveyor records their observational data on a slate, such as that of Reef Watch or Greenfins.

APPLICATIONS

Easy survey for non-professionals, non-divers, kids, etc.
Survey covers a large area – necessary for unfamiliar areas or when evaluating organisms which are not very abundant (giant clams, Crown of Thorns, etc)
Data can be easily collect in many locations and collected in a global database

WEAKNESSES OF TECHNIQUES

Data tends to be subjective and involve estimations
Surveyors often choose, or ‘Cherry-Pick’, locations to observe
Data is not easily compared over time

WHEN WE USE THIS TECHNIQUE AT THE NHRCP

Greenfins/Coral Watch Survey
Coral Health Watch Survey
Shark Population Monitoring
Conservation activities for kids
Crown of Thorns abundance Surveys
Seahorse population Studies

QUADRAT

Quadrat surveys involving placing a grid over the area being surveyed to either estimate percentage cover or ease the counting of a targeted organism. The size of the grid can be varied depending on the goals of the survey, but often a 1m x 1m grid broken into 10 columns and rows is used for divers. The quadrants can either be randomly thrown out, haphazardly placed, or permanent.

APPLICATIONS

Allows for an accurate estimation of percent coverage
Facilitates the counting of small organisms
Is easily coupled with photographic techniques
Requires little training

WEAKNESSES OF TECHNIQUES

Generally does not cover large areas of the reef
Must be used carefully to reduce the chance of harming the research area or organisms being studied.

WHEN WE USE THIS TECHNIQUE AT THE NHRCP

Tracking growth at the Hin Fai Biorock
Drupella Snail Monitoring
Coral Disease Surveys
Recruitment Studies
Assessing Artificial Reefs

TRANSECT LINES

Transect lines is a technique whereby a surveyor will lay out a measuring tape, and record all data or observations in relation to that line. The line can be laid out randomly, or can be laid in the same place each time using permanent marking points. Surveyors may use multiple short lines, or a single long transect line, depending on their survey design. The transect line survey is the technique most commonly used in our program, under the techniques of the Save Koh Tao Ecological Monitoring Program.

APPLICATIONS

Transect lines reduce the subjectivity of surveys and increase the accuracy in counting or observing marine life
Data collected along permanent transects can be compared over time
The technique is highly adaptable to a wide range of survey goals or logistical considerations

WEAKNESSES OF TECHNIQUES

Requires trained surveyors, using specific techniques that often cannot be entered into global databases
Requires more time and materials

WHEN WE USE THIS TECHNIQUE AT THE NHRCP

Our monthly surveys around the island as part of the Koh Tao Ecological Monitoring Program for fish, corals, and invertebrates
Drupella Snail Monitoring
Coral Disease Surveys
Recruitment Studies
Assessing Artificial Reefs
Seahorse Populations studies

THE MANTA TOW

Manta Tow is a survey technique whereby skin divers will towed slowly behind a boat, recording their observation of the reef below. Often, this can be done to survey large areas, with the boat generally trying to maintain a constant depth profile in its course. The observations are taken in 1-2 min cycles, and the route of the boat is tracked using GPS. Many government groups in Thailand, such as the Department of Marine and Coastal Resources, utilize this technique to survey the islands in the Gulf.

APPLICATIONS

Surveying large areas in a limited amount of time
Search and recovery or other exploratory needs
Yearly or less frequent monitoring

WEAKNESSES OF TECHNIQUES

Data tends to be subjective and relies on estimations
Technique is physically demanding and requires good water skills
Often is is difficult to follow a constant depth profile with the boat

WHEN WE USE THIS TECHNIQUE AT THE NHRCP

Identifying new research/restoration locations urvey
Search and Recovery activities (for moorings, anchors, reef damage, etc)
Joint activities with the Department of Marine and Coastal Resources