Power-Cost Efficiency of Eight Macrobenthic Sampling Schemes in Puget Sound, Washington, USA

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Abstract
Power-cost efficiency (PCEi = (n .times. C)min/(ni .times. ci), where i = sampling scheme, n = minimum number of replicate samples needed to detect a difference between locations with an acceptable probability of Type I (.alpha.) and Type II (.beta.) error (e.g. .alpha. = .beta. = 0.05), c = mean "cost," in time or money, per replicate sample, and (n .times. C)min = minimum value of (n .times. c) among the i sampling schemes) is the appropriate expression for comparing the cost efficiency of alternative sampling schemes having equivalent statistical rigor when the statistical model is a t-distribution for comparisons of two means. PCEs were determined for eight macrobenthic sampling schemes (four sample unit sizes and two sieve mesh sizes) in a comparison of a reference site versus a putative polluted site in Puget Sound, Washington. Laboratory processing times were, on average, about 2.5 times greater for the .gtoreq. 0.5- than the .gtoreq. 1.0-mm samples. The 0.06-m2, 0- to 8-cm-deep sample unit size and 1.0-mm sieve mesh size was the overall optimum sampling scheme in this study; it ranked first in PCE on 8 and second on 3 of 11 measures of community structure. Rank order by statistical power of the 11 measures for this scheme was Infaunal Index > log10 (mollusc biomass +1) > number of species > log10 (numerical abundance) > log10 (polychaete biomass + 1) > log10 (total biomass +1) > log10 (crustacean biomass + 1) > McIntosh''s Index > 1 - Simpson''s Index > Shannon''s Index > Dominance Index.