Evaluation of techniques used in the assessment of subtidal epibiotic assemblage structure

Abstract

A comparative study was carried out to evaluate the efficiency of a number of techniques commonly used for assessing the structure of subtidal epifaunal communities. Assessments were made of the epifaunal assemblages fouling two substrata: concrete and PVC plastic. Where possible, each technique was undertaken in three ways, namely, in situ underwater, in the laboratory and using image analysis on photographs taken in situ. Comparisons were also made of biomass estimates made on samples taken in situ and in the laboratory. All method and technique combinations assessed detected differences in the epibiotic communities associated with the two fouling substrata. Sampling in situ, in the laboratory and using image analysis gave similar estimates of percent cover. However, there were significant differences in measurements made for most taxa with respect to abundance and frequency counts depending on how the technique was carried out. Laboratory-based sampling of abundance and frequency counts and biomass determinations, rather than in situ or image-analysis based sampling, are recommended for use in future studies of epifaunal fouling.

Keywords:

• Technique evaluation
• fouling
• epifauna
• biomass
• abundance
• frequency
• percent cover

Acknowledgements

The authors thank the SAMS diving unit (the NERC Facility for Scientific Diving) and the crew of the RV Seol Mara for assistance with diving activities. MT Burrows provided advice on statistical analyses. The authors also thank two anonymous referees for helpful comments and criticism on the manuscript. This work contributes to NERC studentship NER/S/A/2002/1055.