Bryozoan-dominated benthos of Otago shelf, New Zealand: its associated fauna, environmental setting and anthropogenic threats

Abstract

The epibenthos of Otago shelf (south-eastern New Zealand, 45°S, 170°E) is locally dominated by bryozoans that generate habitat both as living colonies and after death as sediment. Differences in physico-chemical conditions across Otago shelf relate to the properties of different water masses and to shore-parallel sediment facies. From 70 m water depth to the shelf break, large, heavily calcified bryozoans are abundant, and dominate an area of about 110 km2 on the mid-shelf, providing habitat at a range of scales. The presence of these bryozoans indicates a stable substratum, low levels of sediment input, relatively high mean water flow, and productive waters. Evidence indicates that bryozoans, particularly on the outer-shelf, are vulnerable to disturbance from bottom fishing. A better understanding of how bryozoans function as habitat is necessary to predict effects of fishing impacts on these assemblages and we suggest ways this understanding might be attained.