Seasonal changes in phytoplankton species composition at Port Shelter,Hong Kong, China (1998-1999)

by Tang, Senming

Abstract (Summary)
(Uncorrected OCR) Abstract of thesis entitled SEASONAL CHANGES IN PHYTOPLANKTON SPECIES COMPOSITION AT PORT SHELTER, HONG KONG, CHINA (1998-1999) Submitted by Tang Senming for the degree of Doctor of Philosophy at The University of Hong Kong in November 2000 This study had been carried out at three sites along a transect in Port Shelter, in the eastern part of Hong Kong, for 24 months from December 1997 to November 1999. Based on the weekly collection of net phytoplankton samples (mesh size, 10 urn), and data including temperature, salinity, pH, dissolved oxygen and Secchi disc transparency in the surface water layer, the seasonality of phytoplankton abundance, species composition and their relationships with the environmental factors were studied. Two major red tides, caused by Gymnodinium mikimotoi and Ceratium furca, occurred in spring and summer of 1998, respectively. There were no dinoflagellate blooms, only diatom blooms, in 1999. Compared with central Port Shelter and the much enclosed shallower waters of Hebe Haven, diatoms dominated over dinoflagellates in Hebe Haven whereas dinoflagellate blooms were favoured in central Port Shelter. The absence of dinoflagellate blooms in 1999 was considered to be associated with several tropical cyclone events, which resulted in decreased water stability. This study supports the hypotheses that dinoflagellate blooms were prone to form in stratified water columns and that they could out-compete diatoms using their swimming strategy when the surface water was depleted of nutrients. The study also shows that central Port Shelter, which was less stressed by eutrophication and anthropogenic activities than Hebe Haven, had higher biodiversity (H'). Four major phytoplankton populations were found in Port Shelter in 1998 and 1999. Two of them were diatom populations, which formed distinctly in the summer and winter monsoons, respectively. In conjunction with these, there were diatom transitional and dinoflagellate transitional groups, which were characterised by their greater variety in species composition. These were potential red tide causative species, which occurred during December to May the following year. The species found in Port Shelter indicated that water masses from the distant coasts of southwest and northeast Guangdong could invade Port Shelter more than was expected from the results of previous investigations. Using multiple regression, this study also shows that the algal blooms are associated with changes in environmental conditions. For example, blooms of Noctiluca scintillans increased the water transparency and blooms of the diatoms Chaetoceros or Skeletonema increased the pH of the water.
Bibliographical Information:


School:The University of Hong Kong

School Location:China - Hong Kong SAR

Source Type:Master's Thesis

Keywords:phytoplankton china hong kong port shelter


Date of Publication:01/01/2001

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