Performance of the line-intercept transect in the coral reef habitat, accuracy, precision, errors and their control

grantor: University of TorontoThe dominant coral reef survey method, the line intercept transect (LIT), was imported from terrestrial plant ecology in 1971 to solve survey problems, especially on the reef slope. Results of the few field tests conducted are mixed and vaguely described methods cannot be replicated. This thesis aims to: define the most commonly used LIT protocols; elucidate problems and possible correctives; explore error sources and their control. Methods: authors of works testing or applying the LIT were surveyed; the dominant LIT protocol and an alternative were field tested. Accuracy was assessed using digitized and geometric model area estimates of every coral on one site. The thesis argues that: Parallax effects, and attempts to overcome them, constitute the major threats to LIT validity. The problem increases as topographic relief increases and is greatest on the reef slope. The dominant protocol produces data of very low precision and uncertain meaning. The alternative allows lower cost, high precision estimates of vertically projected cover, repeatable for particular colonies, and can therefore provide some insight into mosaic recycling as well as community change. Variation in reef topographic relief remains a major obstacle and must be carefully factored into all inter-site comparisons. Topographic character as a stratifying criterion in sampling programs may mitigate the problem for comparisons across similar strata depending on information needs and budgetary constraints.M.Sc