Toxic marine diatoms of Hong Kong:A paleoecological study

To determine whether toxic diatoms in Hong Kong's Victoria Harbour have become more common during the last four decades,a gravity core was taken from the anaerobic sediments of Kowloon Bay in the harbour. Analysis of these sediments from a depth of 0-1cm,4-5cm and 9-10cm indicated that 6.4%,2.4% and 1.5% of the diatoms observed at each of these three respective depths belonged to the genus Pseudonitzschia. The abundance of Pseudonitzschia frustules in the surface sediments of Victoria Harbour was significantly higher(p<0.05)than it was in the harbour's deeper and older(ca.1965)sediments. The increase in potentially toxic diatom species over the last 30 years was attributed to a variety of factors including the addition of large amounts of nutrients to Hong Kong's coastal waters as a re- sult of man's activities.