Optimum macrobenthic sampling protocol for detecting pollution impacts in the Southern California Bight.

The optimum macrobenthic sampling protocol [sampling unit, sieve mesh size, and sample size (n)] was determined for detecting ecologically important pollution impacts in the Southern California Bight, U.S.A. Cost, in laboratory processing time, was determined for samples obtained using fourteen sampling units (0.005-0.1 m(2) surface area) and two sieve mesh sizes (1.0 and 0.5 mm). Statistical power analyses for t-tests of means were performed to estimate the minimum sample size (n min) needed to reliably (α=0.05, 1-β≧0.95) reject the null hypothesis of no difference between a reference and both a stimulated and a degraded station on twelve measures of community structure. The optimum sampling protocol for detecting impacts was determined as that with the lowest total cost ×n min on most measures.Five replicate, 0.02 m(2)×5 cm deep, 1.0 mm mesh samples per station could reliably distinguish reference from impacted conditions on nine or ten measures of community structure at less than one quarter of the cost of the standard sampling protocol of 5 replicate, 0.1 m(2), 1.0 mm mesh samples per station. About 5 replicate, small (<0.1 m(2)), 1.0 mm mesh samples per station may often be optimal for detecting important structural changes in macrobenthic communities with naturally high species richness and abundance.