Ecological studies of selected level-bottom macro-invertebrates off Galveston, Texas

Abstract

The substrate preference and temporal distribution of 64 species of marine macro-invertebrates were studied. All species inhabit the shallow, nearshore (3-11 m) bottom off Galveston, Texas. Ecological and behavioral notes are given for several species which were brought into the laboratory and maintained aquaria. Temperature, salinity and turbidity data from the study area are included. The seasonal distributions of 5 sediment fractions, viz coarse shell, fine shell, fine sand, very fine sand and "mud" are analyzed. Numerical dominance and restricted substrate preference were used as criteria for selecting species characteristic of the 3 bottom types in the study area, sandy, mixed and muddy. On sandy bottoms dominant forms included the mollusks Tellinia iris, Mulinialateralis, Olivella mutica, and Pyramidella crenulata, the polychaetes Onuphis eremita oculata and Owenia fusiformis and the crustaceans Isocheles wurdemanni (young) and Anicus depressus. On mixed bottoms, the mollusk Terebraprotexta was the only species with a large enough population to be considered dominant. On muddy bottoms, the mollusk Nuculana concentrica and the polychaete Diopatra cuprea were the dominant forms. A mollusk, Nassarius acutus, was the most abundant species in the study area. It was not restricted to a particular bottom type.