Recent changes in sedimentation regime in Cienfuegos Bay, Cuba, as inferred from 210Pb and 137Cs vertical profiles

Dating techniques based on the natural and anthropogenic radionuclides 210Pb and 137Cs were applied to the study of the sedimentation regime in Cienfuegos Bay, Cuba. Core samples were collected from different locations in the bay and analysed to evalute the accumulation rate. Results evidenced significant changes in the sedimentation rate during the last 40 years: the recent sediment accumulation rates (0.47–0.50 g cm−2 yr−1) in the Northen basin are almost double those estimated before 1965 (0.30 g cm−2 yr−1). The 210Pb profiles show significant deviations from a simple exponential decline and abrupt variations between 1966 and 1970. These irregularities match closely periods of changes in land use (intense de-forestation and regimentation of the Arimao and Caonao rivers in the late 1960s and early 1970s) and exceptional natural events (Hurricane “Camille” in 1969 and the intense rainfall of 1988) which occurred in Cienfuegos. The 137Cs and chlorite minerals profiles validate the results obtained from 210Pb dating and confirm the effect of exceptional events and changes in the natural hydrological regime of the bay during the past 40 years.