Correlation of live mollusks with sediment and bathymetry on the Texas inner shelf.
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An extensive survey of the macroinvertebrate populations of the Gulf of Mexico on the inner shelf of the Texas coast was initiated in 1976. The focus of this inventory was (1) the identification and enumeration of the macrofauna, (2) description of faunal communities, and (3) correlation of distribution and abundances, including sediment and faunal relationships. This report summarizes the mulluscan data from that survey. Although other inventories of mollusks on the inner shelf have been undertaken, this is the most extensive regional survey conducted on the Texas Gulf Coast. One hundred forty-one species of mollusks ( 82 Gastropods, 56 bivalves, and 3 scaphopods) were found in 554 benthic samples from stations located 1-11 miles (1.6-17.6 km) offshore from Sabine Pass to Brownsville, Texas. Both numbers of species and numbers of individuals of gastropods, bivalves, and scaphopods are greater on the South Texas inner shelf (Brownsville to Corpus Christi) than in areas northeast of Corpus Christi. Cluster analysis separated the fauna into three assemblages - a nearshore assemblage, characterized by sandy substrates, a transitional assemblage characterized by substrates of sandy mud, and an outer assemblage characterized by substrates of less sandy mud. All three are found on the inner shelf except in the Port Lavaca and Beaumont-Port Arthur areas. Faunal-sediment associations indicate that more molluscan species occur in sand than in mud, and the most abundant species are found where the sand fraction is high (80-100% sand). Analysis of the bathymetric distribution of mollusks shows that the mean number of species is highest in a depth range of 18-60 feet (6-18m). Many species are most abundant at either shallower-water stations (stations from 18.0-36.1 ft or 5.5-11.0 m deep) or deeper-water stations (stations from 47.9-60.0 ft or 14.6-18.3 m deep).