Temporal and spatial distribution of enterococcus in sediment, shellfish tissue, and water in a New Zealand harbour

Enterococci, a group of faecal bacteria commonly found in stormwater discharges, were used to trace the spatial and temporal impact of waste streams from an outfall in the Whangateau Harbour, northeastern New Zealand. A seasonal trend in levels of enterococci in two infaunal bivalves, Austrovenus stutchburyi (Gray in Wood 1828) and Macomona liliana (Iredale 1915) was detected, with maximum contamination correlating with high winter rainfall. Rainfall events were also shown to affect stormwater and harbor water significantly. Median enterococci levels in A. stutchburyi were higher at the putative impact site compared to the reference site, and were higher than M. liliana at both sites. Bacterial levels in surficial sediment and A. stutchburyi tissue declined with distance from the stormwater outfall and the stormwater channel. Enterococci were effective for determining the spatial and temporal patterns of stormwater discharge in this harbor, and may have general applicability as an indicator of such discharges.