Seasonal variability of salinity, temperature, turbidity and suspended chlorophyll in the Tweed Estuary

Results are presented from a campaign of measurements that were undertaken to examine seasonal variability in physical and chemical fluxes and processes within the Tweed Estuary during the period September 1996–August 1997. The study utilised monthly surveys, each of approximately 1 week duration. This article interprets a subset of the salinity, temperature, turbidity [suspended particulate matter (SPM) levels] and chlorophyll a data. Measurements discussed here were obtained throughout the estuary during high-speed transects that covered the region between the tidal river and the coastal zone. Longitudinal distributions of surface salinity depended strongly on freshwater runoff. During high runoff the surface salinity was low and the freshwater–saltwater interface (FSI) was located close to the mouth. The reverse was true at times of low runoff. Salinity stratification was generally strong. During the surveys, river runoff temperatures ranged from approximately 2 to 18°C and coastal waters (∼33 salinity) from approximately 6 to 15°C. Turbidity was low throughout the campaign (SPM