Statistical characteristics of chlorophylla concentration in Hong Kong’s coastal waters |
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Authors: | Chen Xiaoling Yok Sheung Li Li Zhilin |
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Institution: | (1) Dept. of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hong Kong, China;(2) National Laboratory for Information Engineering in Surveying, Mapping and Remote Sensing (LIESMARS), Wuhan University, 430072 Wuhan, China;(3) Dept. of Land Surveying & Geo-Informatics, The Hong Kong Polytechnic University, Hong Kong, China |
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Abstract: | In this paper seven of the ten Water Control Zones (WCZs) in Hong Kong’s coastal waters with monthly or bi-weekly sampling
data of 17 parameters collected at 37 monitoring stations from 1988 to 1999 were selected to analyze the spatial and temporal
variations of chlorophyll-a and its influencing factors. Cluster analysis was employed to group the monitoring stations based
on the structure of the data set. Multiple step regression was employed to determine the significant influencing factors of
chlorophyll-a level. The results suggest that all the monitoring stations could be grouped into two clusters. Cluster I with
frequent red tide incidents comprises two WCZs which are semi-enclosed bays. Cluster II with less red tide occurrence comprises
the other five WCZs in an estuarine environment in the west. For both clusters, the organic contents indicator, BOD5, was
a common significant influencing factor of the chlorophyll-a level. Nitrogen and light penetration condition related to turbidity,
total volatile solids and suspended solids had more influence on the cholophyll-a level in Cluster I than in Cluster II, while
phosphorus and oceanographic conditions associated with salinity, temperature, dissolved oxygen and pH were more important
in Cluster II than in Cluster I. Generally, there was a higher average chlorophyll-a level in winter and autumn in a year.
The chlorophyll-a level was much higher in Cluster I than in Cluster II among all seasons. Although the chlorophyll-a concentration
had great variations from place to place in Hong Kong’s coastal waters, it seemed to have a common long term fluctuation period
of 8–10 years with a high-low-high variation in the period in the whole region, which might be influenced by other factors
of global scale. |
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Keywords: | Hong Kong’ s coastal waters chlorophyll-a concentration spatial-temporal variations |
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