Chapter 10 Environmental Effects of a Natural Brine Seep at the East Flower Garden Bank, Northwestern Gulf of Mexico

Abstract

This chapter describes anoxic sulfide-rich brine of nearly ambient temperature, which percolates from the sea floor, forming a small, shallow lake of dense water in a depression at the eastern margin of the East Flower Garden (EFG) bank. Residence time for the brine in the lake is less than one day. Brine overflows the lake and is substantially mixed with seawater in the axis of a 60 m long canyon extending from the lake to the bank edge, where dilutions are greater. The chemical composition of the brine indicates that it is a product of dissolution of the salt by seawater percolating through cracks, faults or permeable strata. Sulfide-oxidizing bacteria are abundant at the brine seawater interface and on the canyon floor where mixing brine and entrained seawater flow in a recognizable stream along the bottom. The EFG seep provides an example of a possible management technique for brine discharges.