Taxonomic level sufficient for assessing pollution impacts on the southern california bight macrobenthos—revisited

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Abstract
Taxonomic sufficiency is the pragmatic concept of identifying organisms only to the taxonomic level necessary and sufficient to meet a study's objectives. Sufficient taxonomy was determined for detecting differences in macrobenthic taxa richness, a dominance index, and three diversity indices between a reference and two pollution‐impacted stations in the Southern California Bight using a wide variety of sampling protocols. A higher taxonomic level was deemed sufficient for a given measure and sampling protocol if the statistical power of t tests performed on data grouped to it was essentially the same as that when tests were performed on data grouped to all lower taxa. The sufficient taxon for the optimum sampling protocol was phylum except when assessing biological stimulation based on differences in mean log10(number of taxa) where it was species. Generic dominance and diversity indices were sufficient independent of the sample units tested (0.02, 0.06, and 0.1 m2) and sample size (n ≥ 2). We recommend family level identification of specimens collected using the optimum sampling protocol when assessing macrobenthic community impacts in the study area because familial analyses are very likely to be sufficient. Confounding effects of sampling variables need to be accounted for when determining the true cost efficiency of and the underlying reason(s) for the sufficiency of higher taxonomy.