Surrogates are used in marine conservation planning when there is limited information on the distribution of biodiversity, and representation of species and assemblage diversity are conservation goals. With prior confirmation of their relationship to spatial variation in biodiversity, habitat classification schemes are a potentially useful surrogate.
Polychaetes can comprise over one-third of species of benthic infaunal assemblages, they are the most frequent and abundant marine metazoans in benthic environments, and they are a reliable surrogate for other macrobenthic taxa. It was tested whether polychaete biodiversity differed among six estuarine habitat classes defined for conservation planning in the Port Stephens–Great Lakes Marine Park, New South Wales, Australia: subtidal sand, mud, muddy sand, and seagrass beds comprising Posidonia australis, Zostera capricorni and mixed Posidonia/Zostera. Polychaetes were sampled from replicate sites in each habitat and differences among habitat classes in species richness, abundance, and assemblage structure were examined. Several environmental variables, known to be important determinants of polychaete distribution, were also quantified at each site. Ninety-five species of polychaetes (belonging to 35 families) were identified. Species richness and abundance did not differ among the habitat classes. Polychaete assemblages of subtidal sand differed from assemblages in both mud and muddy sand, however, assemblages in all other habitats were not different. A combination of some of the measured environmental variables (distance to the estuary entrance, depth, sediment grain size) was a more important determinant of assemblage variation than the habitat classes. Using these predictors, an alternative habitat classification scheme to the scheme currently utilized in marine park planning is proposed. This study demonstrates the critical importance of testing assumptions about surrogacy and an approach for refining surrogates.