USING PREHISTORIC FORAMINIFERAL ASSEMBLAGES TO ASSESS REMEDIATION OF HALIFAX HARBOUR AFTER 250 YEARS OF DEGRADATION

Analysis of benthonic foraminifera in sediment cores from a domestically impacted estuary in Maritime Canada (Halifax Harbour) was helpful to reconstruct the pre-impact environment of the area to determine a “target” for remediation. High diversity, dominant calcareous record, very low deformities and association of other fossil groups (e.g. ostracods, pelecypods, echinoids, etc) characterize foraminiferal assemblage of pre-impact times. However large changes in the foraminiferal assemblages from prehistoric times to the present occurs as a consequence of organic enrichment from pollutants dumped in the harbour in the last 250 years. The results show a slight decrease in both foraminiferal diversity and total abundance upward in the sediment cores with the light input of organic waste. There is a dramatic change in foraminiferal record representing the transition from moderate to heavy pollutants discharge times (before1960s and 1960-present) as a result of the huge growth of the city of Halifax in the second half of 20th century. The heavy pollution rate that took place after 1960s is indicated by the dominance of high organic tolerant species such as Eggerella advena, and Reophax scottii in the upper part of sediment cores. Additionally there is a large decrease to a complete absence of calcareous tests, leaving only organic inner linings, resulting from the dissolution of carbonate due to the high OC concentration in sediments. Shell deformities with variable modes and intensities are also related to the increase of pollutants.