Identification of patch structure within marine benthic landscapes using a remotely operated vehicle

The spatial scale of megafaunal assemblage variation in apparently homogeneous subtidal sediment was investigated using quantitative observations from a remotely operated vehicle (ROV). Quantitative abundance estimates of surface-dwelling megafauna and biotic sediment features associated with burrowing megafauna were derived from video images using the Automated Benthic Image-Scaling System (ABISS), a novel method of applying scale to images collected by ROVs. Spatially referenced images were collected with a maximum sample separation of 400 m within a broader area of apparently homogeneous sediment in Plymouth Sound (Devon, UK) during May 2000 and March 2001. Rank-correlograms were constructed to examine the extent and form of the megafaunal spatial structure. The megafaunal assemblage was neither uniformly distributed nor temporally stable. A hierarchy of spatial structure was detected within the megafaunal assemblage, whereby patches with minimum radius between 123 and 163 m were nested within patches up to 400-m radius. The approach described in this paper offers ways forward to address how variation of megafaunal spatial structure affects macrofaunal assemblage structure and to discuss the application of remote imaging to map and predict the conservation value of subtidal soft sediments. (C) 2002 Elsevier Science B.V. All rights reserved.