Benthic Polychaeta of the West Flower Garden Bank



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The West Flower Garden Bank, a submerged coral reef — possibly the northernmost living coral reef in waters contiguous to the mainland United States -- 174 km SSE of Galveston, Texas, was the site of a baseline faunal survey which, among others, included the benthic polychaetous annelids. As the only known living coral reef in the northwestern Gulf of Mexico, the West Flower Garden Bank (WFG) might be expected to yield a divergent community of benthic polychaetes from previous studies in the otherwise soft-bottom northwestern Gulf. Gathered in depths ranging from 20-140 m, the benthic polychaetes of WFG were collected primarily by SCUBA-equipped divers on the upper reef where the hard coral substrate was predominant. Collections from deeper depths were gathered by manned submersible, grabs and dredges, in addition to SCUBA-equipped scientists. Eighty-seven species of polychaetes, representing 26 families, were gathered during the course of this study. Almost 37% of the species collected are first records for the Gulf of Mexico and 57.5% are extensions of range into the northwestern Gulf. Seventeen genera are first records for the Gulf of Mexico herein. The families Eunicidae and Syllidae were best represented, each with 15 species, and the sedentariate Serpulidae included 13 species. Several worms are probable new species and are classified only to their genera. The serpulid Spirobranckus giganteus was found to be ubiquitous on the upper reef and its population on the 13.6 hectare area of the upper reef zone is estimated to range from 353,803 to 730,549 individuals. A significant correlation was found to exist between the abundance of S. gigantaus and the percentage of living coral and, in particular, the presence of the coral species Montastrea annularis on the upper reef. It is speculated that the clumped distribution of S. giganteus on coral reefs throughout its range has evolved to assure reproductive advantage by synchronizing release of reproductive products and, furthermore, to assure simultaneous maturation and condition. It is theorized that S. gigantaus may have the ability to bore within the corals to extend its tubicolous dwelling.