Assessment of Eutrophication in the Firth of Clyde: Analysis of Coastal Water Data from 1982 to 1996

The potential for eutrophication in coastal waters of the Firth of Clyde, Scotland is assessed through statistical analysis of water quality data at one sampling station for the period 1982–1996. Monitoring data are presented for temperature, salinity, dissolved oxygen, chlorophyll a and plant nutrients (nitrate, nitrite, ammonia, phosphate and silicate). Exploratory statistical analysis is used to investigate changes in these parameters with depth and through time. This analysis provides no evidence to suggest that nutrient concentrations have changed significantly with time. There is no indication of a change in the trophic status or in the potential for eutrophication in these waters. Concentrations of the measured parameters display greater variation in surface waters than at depth due to seasonal factors such as freshwater inputs and stratification. These seasonal effects are examined through the application of nonparametric statistical techniques to pooled data. The conclusions of the study will aid the design of future survey work to monitor coastal water quality, including the deployment of a towed constant-monitoring device.