Report: TR2006/09

Author: Kay C. Vopel, Greig Funnell (NIWA)

Abstract

Sediment profile imaging (SPI) was developed more than two decades ago as a rapid reconnaissance tool for characterising physical, chemical, and biological sediment properties. Because the sediment column is a good time-integrator of short- and long-term perturbations in the water column and/or the seafloor, this technology allows researchers to deduce dynamics from sediment images using the same inverse methods approach that paleoecologists and sedimentologists use to reconstruct past environmental conditions.

This report details the findings from a test of the applicability of SPI for future resource consent monitoring of the seafloor around mussel farms in Wilson Bay, Firth of Thames, using the prototype SPITwo system (Benthic Science Ltd).

SPITwo is a portable device that can be deployed to the seabed in waters of up to 30 m depth. Imaging of the sediment is by a specialized scanner that physically penetrates into the sediment and produces a vertical image of the top 10 to 20 cm of the sediment.

To assess its performance, NIWA deployed the prototype SPITwo system, from a small inflatable alloy-hull boat, to the seafloor in Wilson Bay, Firth of Thames, at five sites near Area A of the Wilson Bay Aquaculture Management Area.

The tests showd great potential of the SPITwo systems for the assessment of the Wilson Bay seafloor. The instrument can be cost-effectively deployed from a small boat to rapidly produce high-quality profile images of soft sediment. Minor changes to the designs of the instrument frame and the cable-instrument link are suggested in the report.

Wilson Bay Sediment Profile Imaging: 1 Instrument Test : July 2005 [PDF, 138 KB]