Appraisal of visual assessments of habitat complexity and benthic composition on coral reefs

Mar Biol (2007) 151:10691076 DOI 10.1007/s00227-006-0538-3

RESEARCH ARTICLE

Appraisal of visual assessments of habitat complexity and benthic composition on coral reefs

S. K. Wilson N. A. J. Graham N. V. C. Polunin

Received: 18 July 2006 / Accepted: 30 October 2006 / Published online: 21 November 2006 Springer-Verlag 2006

Abstract Visual assessments of topographic habitat structure and benthos on coral reefs were appraised using quantitative data collected from 16 replicate surveys within each of 21 sites on Seychelles reefs. Results from visual assessments of reef benthos were similar to those obtained using techniques frequently used to assess benthic complexity and composition. Visual estimates of habitat topography were correlated with rugosity, reef height and holes of 1070 cm diameter, whilst visual estimates of benthic composition were very similar to those obtained from line intercept transects. Visual estimates of topography correlated strongly with species richness of Wsh communities and explained 42% of the variation in these data. The relationship between visual estimates of topography and species richness is strongest with Wsh 1030 cm total length (TL), abundance of Wsh within this size category also correlating positively with topographic visual assessments. Visual techniques are prone to observer bias, however with regular training they can be used to quickly provide a reliable and eVective means of assessing habitat complexity and benthos on coral reefs.

Introduction

Structure and heterogeneity of benthic habitat are known to aVect the composition of Wsh communities. At a large spatial scale certain Wsh assemblages are characteristic of habitat types such as mangroves, sea-grass beds or coral reefs (Chittaro et al. 2005; Wilson et al. 2005), whilst at smaller spatial and taxonomic scales some Wsh species are habitat specialists and are closely associated with speciWc microhabitats (e.g. Munday et al. 1997). The relationship between habitat complexity and Wsh communities has been particularly well researched, previous studies demonstrating positive correlations between complexity and abundance (Lawson et al. 1999) or biomass (Jennings et al. 1996) of individual Wsh species. Similarly, at the community level, habitat complexity has been positively correlated with diversity and total abundance (Luckhurst and Luckhurst 1978; Sano et al. 1984; Caley and St John 1996; Friedlander and Parrish 1998; Gratwicke and Speight 2005a, b) or biomass (Grigg 1994; Friedlander and Parrish 1998) of Wsh assemblages....