A study of offshore benthic communities in natural areas and in areas affected by dredging and dredged material disposal.

Biological, hydrological, and geological samples were collected monthly for twelve months, from May, 1975, through April, 1976, at six stations offshore Galveston, Texas. A total of 170 species, including 67 polychaetous annelids, 37 crustaceans, 19 bivalves, and 12 gastropods, were collected during the study. The most abundant organism was the enteropneust Balanoglossus sp., while the most ubiquitous species were the polychaetes Prionospio pinnata and Magelona sp., the nemertean Cerebratulus lacteus, and the gastropod Nassarius acutus. Two-dimensional and multidimensional cluster analyses were utilized to delineate site and species groups. Three site and five species groups were constructed from the two-dimensional data, while eight site-time and seven species groups were constructed from the multidimensional data. A Thalassema community, composed of the echiuroid Thalassema hartmani, the commensal bivalve Paramya subovata, and the commensal brachyuran Pinnixa lunzi, was also found during the study.