Comparison of rocky itertidal community sampling methods at northern coast of Rio de Janeiro State, Brazil

Abstract

The purpose of this study is to compare different rocky intertidal sampling methods at the northern coast of the Rio de Janeiro State. Quadrats with 50 and 100 intersection points were sampled in field and in computer using digital photos. A similarity over 90% was obtained between both methods for the intertidal zone. Cluster analysis showed that the lower sample size overestimated some indicator organisms. The zonation pattern through photo sampling was different from that in field especially in Supralitoral Fringe due to the color similarity of Chthamalus sp with bare substrate. The main advantages of the digital method are the fast abundance estimation, the possibility of comparison among researchers and the permanent community record. However, there is a potential for species misidentification with similar color morphotypes. In zonation intertidal studies, digital photograph sampling method is suggested since it is rather efficient, accurate and advantageous in relation to the field method. Such a choice might be made after the previous knowledge of local organisms and should be adequate to the final objectives.