The benthic fauna of Pine Harbour Marina

Abstract

An investigation into the benthic ecology of Pine Harbour Marina, Beachlands was undertaken over the period June 1994 - February 1996. The primary purpose was to provide a broadscale examination of the benthic fauna of the area, and to assess the effects of dredge spoil dumping on benthic organisms. The subtidal benthic ecology to the immediate north-west of the marina was also examined. Behavioural experiments were carried out in the laboratory to evaluate the abilities of the common cockle (Austrovenus stutchburyi) to rebury if left on the surf ace and to resurface if buried under sediment. The intertidal benthic ecology of the area was diverse, with 89 taxa being identified. The 10 most common taxa accounted for 66% of the 39125 individuals recorded. The assemblage composition was similar to other low energy intertidal areas. The taxal assemblages were reasonably stable in time, with seasonal fluctuations in assemblage composition being related to recruitment phases. Spatially, there was variation between the transects, however the transects close to the approach channel to the marina were similar. Mid and low tide sites had similar mollusc assemblages, which changed similarly through time. High tide sites however were distinct. The dumpground faunal assemblage changed post-dumping. Not all taxa were affected and within 6 months the dumpground was recolonised to pre-dumping levels. The subtidal area to the west of Motukaraka Island was dominated numerically by the introduced bivalve Theora lubrica. Species diversity changed in an onshore/offshore direction, with a higher species diversity closer to shore. In laboratory experiments cockles were able to resurface through sediment at burial depths of up to 10 cm, and rebury when left on the surface, in under 15 hours.