New Zealand Journal of Marine and Freshwater Research abstracts
Calcification rates of rapidly colonising bryozoans in Hauraki Gulf, northern
New Zealand
ABIGAIL M. SMITH*
CAMPBELL S. NELSON
Department of Earth Sciences
University of Waikato
Private Bag 3105
Hamilton 2001, New Zealand
*Present address: Department of Marine Science, University of Otago, P.O. Box
56, Dunedin, New Zealand
Abstract Very little is known about calcification rates of
bryozoans, despite their importance in modern temperate-latitude shelf
carbonate sediments and in temperate limestones. Here we report the carbonate
production rates for 19 species of bryozoans over 3, 9, and 12-month periods
from a settling experiment in 14 m water depth at Cape Rodney, Hauraki Gulf.
Based on the larger bryozoan colonies, estimates of calcification rate range
from 25 to 740 mg CaCO3 y-1. Extrapolation of calcification rate to overall
bryozoan sediment production is not straightforward, but a value of 24-240 g
CaCO3 m-2 y-1 for the sample site has been determined, equivalent to a sediment
accumulation rate of 4-40 cm per 1000 years (ky). In reality, over a large
shelf region both dilution by other organisms and a patchy areal distribution
of living bryozoans would reduce these values to only a few cm ky-1. The
relatively low rates of accumulation deduced here are mainly consistent with
the few other studies of bryozoan sedimentation in temperate waters, and also
with those typically reported (1-3 cm ky-1) for many occurrences of temperate
bryozoan-rich limestones from the rock record.
Keywords Bryozoa; calcification rate; carbonate sediments;
sedimentation rate; Hauraki Gulf; New Zealand
PDF file of entire paper: medium quality (500K); (scanned from paper original: notes about this process)
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