Zonation of inshore benthos off a sewage outfall in Hawke Bay, New Zealand

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Abstract
Benthos was sampled quantitatively on a rectangular grid perpendicular to shore directly off a sewage outfall. Faunal samples were washed through a 0.5 mm sieve, and resulting species frequency data subjected to the ‘flexible’ classification. Crustacea and Polychaeta contributed most of the 100 species; most individuals were polychaetes. Five groups of species were found. Five faunal zones parallel to shore and progressively wider further offshore were distinguished. Community structure increased offshore, and faunal density decreased offshore from the second zone. Inshore zones were obviously polluted, with the capitellid Heteromastus filiformis occurring in densities up to 36 950 per square metre 500 m from shore. Furthest from shore, the fauna was more ‘normal’ with Heteromastus densities of 6000 per square metre. Unique to New Zealand shores is a dense (440 per square metre) zone of holothurians at 8–10 m depth. Deposit‐feeders dominated all stations with mean sediment sizes finer than 1.0 , whereas suspension feeders dominated the benthos of coarser sediments.