EFFECT OF BARITE ON MEIOFAUNA IN A FLOW-THROUGH EXPERIMENTAL SYSTEM

The effects of barite (94-96% BaSO4), a major constituent of drilling muds used in marine oil drilling operations, on meiofauna were studied in an experimental flow-through system. Aquaria containing sand or varying proportions of barite and sand received a continuous supply of unfiltered seawater from Santa Rosa Sound, Florida, for ten weeks. At the end of this period the composition, biomass and vertical distribution of the meiofauna were determined. Most of the meiofauna (>99%) occurred in the highly aerobic upper 2 cm portion of the substratum. Rotifera, Foraminifera, Hydrozoa, Turbellaria, Ostracoda, Polychaeta and Bivalvia did not exhibit significant differences between control and experimental aquaria. However, the densities of Nematoda, Copepoda and Copepoda nauplii varied with the substrate composition. The meiofaunal densities in the aquaria containing 1:10 or 1:3 mixtures of barite and sand were greater than that in aquaria containing sand alone. A marked decrease in meiofaunal density was evident in aquaria containing 5·5 cm of sand covered with a 0·5 cm layer of barite. © 1979.