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

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Title:A Rapid Ecological Assessment (REA) Quantitative Survey Method for Benthic Algae Using Photoquadrats with Scuba
Authors:Preskitt, Linda B.
Vroom, Peter S.
Smith, Celia M.
Date Issued:Apr 2004
Publisher:University of Hawai'i Press
Citation:Preskitt LB, Vroom PS, Smith CM. 2004. A rapid ecological assessment (REA) quantitative survey method for benthic algae using photoquadrats with scuba. Pac Sci 58(2): 201-209.
Abstract:The challenge of assessing seldom-visited, benthic substrates has
created the need for a method to describe benthic communities quickly and efficiently.
Macroscale rapid ecological assessments (REAs) of algal assemblages
provide managers of coral reefs and other benthic ecosystems with the fundamental
descriptive data necessary for continued yearly monitoring studies. The
high cost of monitoring marine communities, especially remote sites, coupled
with the time limitations imposed by scuba, require that statistically valid data be
collected as quickly as possible. A photoquadrat method using a digital camera,
computer software for photographic analysis, and minimal data collection in
the field was compared with the conventional method of point-intersect (grid)
quadrats in estimating percentage cover in subtidal benthic communities. In
timed studies, photoquadrats yielded twice the number of quadrats (and an almost
infinite number of data points) as conventional methods, provided permanent
historical records of each site, and minimized observer bias by having only
one observer identifying algae in the field. However, photoquadrats required
more post-collection computer analyses of digital photographs than conventional
methods. In the manual method, observer bias in algal identification can occur
depending 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 the
finer resolution in diversity that was found using point-intersect quadrats but do
provide a more precise estimate of percentage cover of the abundant species, as
well as establishing a permanent visual record in the time allowed by work with
other teams.
Appears in Collections: Pacific Science Volume 58, Number 2, 2004

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