Long-term changes in water quality and phytoplankton characteristics in Port Shelter, Hong Kong, from 1988-1998

This study analysed monthly physico-chemical and phytoplankton data collect ed from 10 marine monitoring stations in Port Shelter Hong Kong, from 1988 to 1998. Cluster analysis based on all water quality parameters measured sh ows that the 10 monitoring stations can be grouped into three clusters: Clu ster I consists of stations located in Outer Port Shelter; Cluster II consi sts of stations located in Inner Port Shelter and Cluster III consists of a single station in Hebe Heaven, a well-sheltered Bay in Inner Port Shelter. Factor analysis shows high positive loadings for nutrients and nutrient ra tios in the first two factors of the three clusters, which indicates that t he stations of the three clusters were primarily grouped according to their respective nutrient conditions. In Inner Port Shelter, and particularly St ation PM5 in the sheltered Hebe Haven, the influence of surface runoff and pollution loading from the surrounding catchment area was apparent. Five st ations located along a transect from Inner to Outer Port Shelter were selec ted for trend analysis. An increasing trend for temperature and a decreasin g trend for pH are observed in all Stations except PM10 which is at the mou th of Port Shelter. The results of canonical analysis revealed that tempera ture and pH could also play an important role in determining the density an d biovolume of the minor algal groups in Port Shelter. (C) 2001 Elsevier Sc ience Ltd. All rights reserved.