Spatial and temporal variations in the copper and zinc concentrations of two green seaweeds from Otago Harbour, New Zealand.

Copper and zinc concentrations of the cosmopolitan green seaweeds Enteromor pha intestinalis and Ulva lactuca were obtained for the first time from var ious sites within Otago Harbour, southern New Zealand. Spatial variation in the concentrations of both metals was found, with increasing levels at sta tions in the upper harbour basin. While temporal fluctuations were apparent , a significant seasonal trend was evident only for zinc in U, lactuca; con centrations varied from approximately 10 mu g g(-1) dry weight in winter to 2 mu g g(-1) in summer. Over four consecutive years of sampling there was little change in metal concentrations of either species. Concentrations of both metals were invariably higher in E. intestinalis than U. lactuca, at a ll sampling stations and at all sampling times. These results are compared with those from other studies employing the same two green seaweed genera a nd are discussed in the context of the value of seaweeds as biomonitors of trace metal pollution. The levels of copper and zinc recorded in both speci es indicate that Otago Harbour is relatively free of trace metal contaminat ion. This conclusion concurs with that reached in previous studies of disso lved copper and zinc concentrations in the surface waters of the harbour. ( C) 1999 Elsevier Science Ltd. All rights reserved.