Impacts and Direct Effects of Sand Dredging for Beach Nourishment on the Benthic Organisms and Geology (West Florida Shelf Benthic Repopulation Study)

Over the course of three years, this study examined an area that has undergone dredging to determine the extent of benthic organism repopulation after dredging was completed and the effects dredging had on bottom geology. Through coordination with the U.S. Army Corps of Engineers, dredge sites off the Tampa/St.Petersburg area were selected for study. These sites are in sandy sediments and were used to restore several beach areas off the west coast of Florida. The study was accomplished by way of a cooperative agreement with the University of South Florida - Department of Marine Science, with a subcontract to Mote Marine Laboratory in Sarasota, Florida. The Florida Institute of Oceanography provided overall program management, research vessels, and equipment.

The baseline collection phase of the study prior to the actual dredging of the sites began in July 1992. Post-dredging cruises were conducted in January and September 1993 and May 1994. The sampling plan involved two sites within each dredge area and a control site outside the influence of each dredging operation.

In general, the dredged areas underwent rapid recolonization. The only adverse effects noticed in the collected data are dredge holes left behind during operation of a clamshell dredge. A final report, Impacts and Direct Effects of Sand Dredging for Beach Nourishment on the Benthic Organisms and Geology of the West Florida Shelf, MMS 95-004, is available from the address below:

Minerals Management Service
381 Elden Street
Herndon, VA 22070-4817
(703) 787-1300

East Florida Shelf Benthic Repopulation Study

In support of the negotiated agreement with the City of Jacksonville, Florida, the U.S. Army Corps of Engineers agreed to fund a small-scale study to examine the effects of the dredging operation within the borrow area on the on the macro-infauna, or marine organisms. Five cores at three closely spaced areas, both within and outside the dredge site, were to be collected for analysis. A baseline cruise was completed in June 1995 before dredging operations started; the first post-dredging cruise was completed in February 1996. Reports are available that describe the sampling methodology and the data collected. (Order reports from the address given above.)

The initial analyses indicated that the sampling scheme needed to be modified and that additional samples needed to be collected to represent the resident benthic population adequately. The post-dredging sampling completed in February 1996 incorporated the changes in the sampling methodology. Analysis of the data indicates that seasonal variations were more important than the effects of dredging on the bottom populations. Four additional samplings are scheduled at 6-month intervals.

Sand and Gravel Mining Projects

MMS's Sand, Shell and Gravel Program, provides the policy direction and guidance for the development of marine hard-mineral resources on the Federal OCS.

Valuable, non-energy OCS resources, including sand and gravel, have become increasingly important especially to coastal States for beach renourishment efforts.