New Zealand Journal of Marine and Freshwater Research abstracts
Minimal impact from long-term dredge spoil disposal at a dispersive site in
Tasman Bay, New Zealand
RODNEY D. ROBERTS
BARRIE M. FORREST
Cawthron Institute
Private Bag 2
Nelson, New Zealand
email: rodney@cawthron.org.nz
Abstract The effects of dredge spoil disposal on contaminant
concentrations and benthic macrofauna were examined at a shallow marine
disposal site used for c. 20 years. The site had received c. 50 000
m
3 yr
-1 of maintenance dredgings annually, from the Port
of Nelson. Port sediments were contaminated to varying degrees with some trace
metals, organochlorine pesticides, polychlorinated biphenyls, and polycyclic
aromatic hydrocarbons. They showed mildly elevated toxicity in laboratory
bioassays, and their macrofauna was dominated by small-bodied polychaetes.
Despite this, there was very little indication of impact in the spoil disposal
area. The disposal area, spoil spreading zone and control sites were all
similar in terms of sediment contaminants, sediment toxicity, neogastropod
imposex, and macrofauna. The lack of discernible impact is probably because of
the dynamic sedimentary environment in the disposal area, which disperses
dumped dredgings and mixes them with ambient sediment.
Keywords benthos; bioassay; contaminants; dredge spoil;
environmental impact; toxicity
M98072
Received 2 October 1998; accepted 16 June 1999
PDF file of entire paper: medium quality (1310K); (scanned from paper original: notes about this process)
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