CRAMP RAT Other Benthic Protocols

Numerous methods have been used to evaluate benthic environments. Selection criteria for benthic sampling methods should include the population of interest, statistical power, accuracy, precision, sources of variability, the focus of the study and the spatial scale involved. Time, cost and effort must also be evaluated.

Benthic sampling methods used in coral reef investigations
Method	Type	Description	Limitations
Presence/ Absence	Qualitative	Lists species	No abundance data. Records species only.
Relative abundance	Semi-Qualitative	Categories ranging from common to rare	No absolute data
Quadrat	Quantitative	% cover of substrate types are recorded	High observer variability
Planar Point Intercept	Quantitative	Substrate type under each intersection is recorded	No absolute value can be calculated
Line Transect	Quantitative	Lengths of substrate types underlying the transect line are recorded	Small or rare species can be missed
Nearest Neighbor	Quantitative	Distance of organism from random transect point is recorded	Determines only abundance of target species
Point-Quarter	Quantitative	Coral colony measurements are taken from a haphazardly determined point	Greater variance. Vertical overlap possible
Photographic Transect	Quantitative	Video or digital still images	Resolution

CRAMP has compared nine methods widely used in Hawai‘i. Data on coral coverage has been taken by different methods and by different individuals over a period of many years. The methods involved vary due to the needs of specific investigations. Constraints on time, differences in questions being asked (intensive or extensive), and utility of sampling regimes under various field conditions led to employment of different methods that undoubtedly will continue to be used in the future. These methods vary in the amount of time required in the field and time required to process the field data. There is a high cost for the specialized hardware and software needed to process the information for some of the techniques. Thus a comparison of these methods was undertaken in order to determine whether or not results of different techniques could be combined in an analysis of coral cover in Hawai‘i.

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CRAMP Rapid Assessment. Other Benthic Survey Techniques