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Keywords:

  • sublittoral;
  • monitoring;
  • new techniques;
  • photomosaics;
  • benthos;
  • macrophytes;
  • invertebrates;
  • growth;
  • recruitment;
  • mortality

ABSTRACT

  1. In marine temperate waters, the diverse epibenthic communities of hard substrata require robust, efficient, high-resolution methods to better understand community dynamics and biological processes, such as growth, recruitment and mortality that drive changes within communities.
  2. The epibenthic community of a harbour wall was monitored from fixed stations over three seasons in 2009 to evaluate the utility of a high-resolution photomosaic method. The community was described by visually estimating cover and abundance of taxa within the photomosaics. In addition, areas occupied by the solitary cup coral Caryophyllia smithii, the encrusting sponge Hymeniacidon perleve, and the red macroalga Plocamium cartilagineum were digitized and their seasonal growth, recruitment and mortality estimated over the study period.
  3. Significant changes occurred to the community in every season. The fewest number of taxa and the lowest total taxa cover was observed in the winter. In the spring, there was significant growth of red macroalgae, brown macroalgae, and ascidian taxa. In the summer there was significant growth of green macroalgae and turf taxa, while red macroalgae experienced photoinhibition, and ascidians significantly declined in abundance.
  4. The photomosaics enabled the extraction of data at a high taxonomic resolution, reduced the effects of water-column turbidity, and through digitization, enabled estimation of the seasonal growth, recruitment, and mortality of C. smithii, H. perleve and P. cartilagineum. However, the spring and summer canopies of macroalgae and turf obscured the detection of many understory taxa, and thus, limited the accuracy of understorey assessments. Provided the limitations of photomosaics are recognized, the method demonstrated in this study has many potential benefits of advantage for fixed-station monitoring studies in temperate waters.

    Copyright © 2011 John Wiley & Sons, Ltd.