A Rapid Ecological Assessment (REA) Quantitative Survey Method for Benthic Algae Using Photoquadrats with Scuba

摘要

The challenge of assessing seldom-visited, benthic substrates hascreated the need for a method to describe benthic communities quickly and efficiently.Macroscale rapid ecological assessments (REAs) of algal assemblagesprovide managers of coral reefs and other benthic ecosystems with the fundamentaldescriptive data necessary for continued yearly monitoring studies. Thehigh cost of monitoring marine communities, especially remote sites, coupledwith the time limitations imposed by scuba, require that statistically valid data becollected as quickly as possible. A photoquadrat method using a digital camera,computer software for photographic analysis, and minimal data collection inthe field was compared with the conventional method of point-intersect (grid)quadrats in estimating percentage cover in subtidal benthic communities. Intimed studies, photoquadrats yielded twice the number of quadrats (and an almostinfinite number of data points) as conventional methods, provided permanenthistorical records of each site, and minimized observer bias by having onlyone observer identifying algae in the field. However, photoquadrats requiredmore post-collection computer analyses of digital photographs than conventionalmethods. In the manual method, observer bias in algal identification can occurdepending on the degree of experience of individual divers. On the other hand,photoquadrats rely on one observer in the field and one observer in the laboratory,standardizing algal identification. Overall, photoquadrats do not yield thefiner resolution in diversity that was found using point-intersect quadrats but doprovide a more precise estimate of percentage cover of the abundant species, aswell as establishing a permanent visual record in the time allowed by work withother teams.