RECONSTRUCTION OF POLLUTION HISTORY AT MILL COVE, BEDFORD BASIN USING BENTHIC FORAMINIFERA

Abstract

The comparison of data from two cores collected in Bedford Basin, adjacent to the Mill Cove Sewage Treatment Plant, in August 1998, to data from 1968, 1993 and 1996, allows the impact of pollution to be determined. Benthic foraminiferal distributions respond to changing environmental conditions allowing these changes to be recorded in the fossil record. Species diversity and abundance decreased dramatically from 1968 to 1993, and continued to decrease up to 1996. Degradation of the benthic community is the result of increased organic matter pollution. Remediation of the environment at this location is probable, as foraminiferal diversity increases with a decrease in organic matter. The abundance of Eggerella advena, a species indicative of pollution, has decreased since 1993, confirming a reduction in organic matter. Near normal conditions, determined by the presence of calcareous species, \Vere noted at the bottom of core 1C, at 57-59cm depth. Increased pollution resulted in low oxygen conditions, determined by the abundance of organic linings in the top 12cm of sediment. Organic linings are remnants of calcareous tests, which have dissolved due to low oxygen and pH conditions in the sediments. Lower organic matter concentrations in the 1998 samples and higher species diversity and abundance indicate that the benthic community is returning as the environmental conditions improve. These improvements follow a large outfall event in 1996 from the sewage treatment plant at Mill Cove.

Key Words: benthic foraminifera, estuarine environment, Mill Cove, organic matter, pollution impact, carbonate dissolution, recolonization.