QUANTITATIVE APPROACH TO THE "PHYSIOGNOMIC ASSESSMENT OF HARD BOTTOM MARINE BENTHIC COMMUNITIES" METHOD: PRECISION ANALYSIS

Abstract

The “Physiognomic Assessment of Hard Bottom Marine Benthic Communities” (PCM) method proposes the use of operational units called `settlements`, allied to photographic sampling. The aim of this study is to detect variations on the precision of the quantitative approach of the method when performed by a) different researchers, and b) by the same researcher on different occasions. Thirty digital images were taken from Moela Island and Ponta do Munduba Munduba - Santos, São Paulo state, on the Brazilian southeastern coast, at depths between zero and five meters. Three researchers analyzed the images. One of the researchers did the analysis on two different occasions six months apart, while the other two did the analysis once. One of the researchers was unaware of the research objectives. Settlement Richness values varied from 13 to 19, generating Sørensen Similarity values between the different observers of always higher than 80%. The correspondence analysis (CA) on percent cover data showed no significant differences between the values found for Axes I, II, III and IV (corresponding to 42.8% of data variability) when compared by ANOVA (P being respectively 0.963; 0.975; 0.867; 0.894). The results here presented indicate that the quantitative approach of the PCM method is little researcher-dependentt, consequently making the cooperation between different researchers to describe large areas possible.