ABSTRACT

The influence of shell dredging in San Antonio Bay, Texas, on the Aransas National Wildlife Refuge and surrounding bays was investigated for an Environmental Impact Statement by a team from Texas A&M University. More than sixty scientists and technicians from the Wildlife & Fisheries, Biology, Meterology, Geology, and Oceanography Departments were involved.

In addition to a sedimentological and subbottom study, the geologists undertook most of the circulation, flushing, remote sensing, foraminiferal and chemical studies. Some of them were also heavily involved in investigating economics, reef silting, and dredge discharge.

San Antonio Bay has an average depth of four feet and contains numerous large and small reefs. As a result of the bay's shallowness, the circulation and flushing are contolled primarily by wind and river discharge and patterns of these aspects are, therefore, erratic. Nevertheless, certain consistent sediment patterns can be distinguished on the bay bottom as well as in the shallow subsurface. Heavy mineral distributions and clay mineral studies present complementary information. The distribution of modern reefs differs little from that of buried reefs. These distributions and several borings reveal the gross topography of the buried Pleistocene surface.

It is clear that in such an Environmental Impact Study, a thorough investigation of the geological, physical, and economical aspects is just as important as understanding the biological aspects of a coastal ecosystem.