A proposed method for coral cover assessment: A case study in Abrolhos, Brazil

Abstract

One of the methods most often used to evaluate reef community coverage are line intercept transects (LIT). However, collection of cover data using LIT has drawbacks. The optimization of data collecting permits an increase in number of replicates, allowing a more adequate quantification of the community and comparison among different sites/times. It was assumed that a LIT is composed of several adjacent data points and the number of data points necessary to 'describe' a whole line was investigated. Several LIT were deployed in the Abrolhos Archipelago, Brazil. The variation of the stand error for percent cover in relation to a varying number of points drawn from each LIT was evaluated. A relatively stable condition was reached with 500 (out of 2000) points. This procedure (point intercept transects - PIT) needed much less effort for two reasons: (1) time per transect (up to 62.5% reduction); and (2) for each point the diver can just mark species/categories in a ticklist, so less underwater skills are needed. We also demonstrate and discuss the necessity for line replicates. Species with less than 2% cover were detected in LIT and PIT.