Is there a link between the type of habitat and the patterns of abundance of holothurians in shallow rocky reefs?

Abstract

The presence of a mosaic of habitats, largely determined by sea urchin grazing, across\nshallow rocky reefs may potentially influence in differences in the distribution patterns\nof invertebrates. The aim of this paper was to assess, using a correlative approach,\nwhether the type of habitat influences the abundance patterns of holothurians in the\neastern Atlantic. We hypothesized that abundances of large (> 10 cm) holothurians\nvaried among four types of habitat (3 vegetated habitats with low abundances of the sea\nurchin D. antillarum versus ?barrens? with hyperabundances of sea urchins), and that\nthese differences were consistent at a hierarchy of spatial scales, including two islands\nand several replicated sites within each type of habitat and island. Three species of large\nholothurians were found, accounting for a total of 300 specimens. We found remarkable\ndifferences in abundances of holothurians between the ?barrens? and the three vegetated\nhabitats. This pattern was strongest for the numerically dominant species, Holothuria\nsanctorii. Total abundances of holothurians were between 5 ? 46 times more abundant\nin ?barrens? compared with the vegetated habitats. Inter-habitat differences were\nspecies-specific with some inconsistent patterns from one island to the other. The total\nabundances of holothurians tended to increase with the abundance of sea urchins within\n?barrens?. Our study suggests that there may be a link, at least for the dominant species\nHolothuria sanctorii, between the distribution and abundances of large holothurians and\nthe habitat across shallow-waters of the eastern Atlantic.