Field test of a novel, low-cost, scanner-based sediment profile imaging camera

Abstract

Sediment profile imagery (SPI) is a well-established technique for mapping benthic habitat quality in soft marine sediments, but several limitations exist in the apparatus employed, particularly the degree of penetration achieved by the sampling device into more compacted subtidal sands and capped sediments. To address this problem and others, such as the high cost of purchasing and maintaining commercially available instruments and illuminating the area to be photographed, a novel scanning sediment profile camera was designed and constructed. This prototypic system was deployed alongside the existing technology in a survey along an established gradient of organic enrichment and in an area of dredge spoil disposal in Galway Bay on the west coast of Ireland. The results of the survey revealed that the novel system, termed SPIScan, achieved a greater degree of penetration than the digital SPI while losing none of the image quality. Although it addresses most of the limitations of existing SPI technology, the new system has one drawback: it is not suitable for deployments in deeper water because of an air-filled space in the imaging module. This disadvantage is offset by the incorporation of an air reservoir attached to the prism. The volume of the reservoir is the dependent factor limiting the operating depth of the system. It is important to note, however, that the SPIScan is a prototype, and the problem of depth limitation can be solved completely with further development of the instrument.