Carbon isotopes and fatty acids analysis of the sediments of Negro Harbour, Nova Scotia, Canada

Fatty acid (FA) ratios are here intercalibrated with stable isotopes (δ13C) to characterize the sediments of a Nova Scotian estuary which receives mixed terrestrial input (peat, higher plants).Salinity records indicate a stronger river influence in 1985 compared to 1984. The isotopic signature in the sediments is in contradiction with these records implying a lesser terrestrial input in 1985. Total (%) organic carbon (TOC) and fatty acid concentrations were higher in 1985. The C24C14 and C24C16 fatty acid ratios both agree with the salinity records.Percentages of terrestrial organic matter in the sediments, calculated from both isotopes and fatty acid ratios through a mixing equation, decreased seaward as expected. Both FA ratios give essentially the same % terrestrial organic carbon at each site. Percentages calculated from δ13C and fatty acid ratio are similar at least in the upper part of the estuary. However, changes in the relative contribution of peat compared to higher terrestrial plants are more readily noticed using fatty acid ratios than with isotope ratios.