"Seasons in the Sun: A Year in the Hong Kong Intertidal"

Gray A. Williams
The Swire Institute of Marine Science
& Department of Ecology & Biodiversity,
The University of Hong Kong,
Hong Kong, SAR China

Friday, 30th January 2004: 2.30-3.30pm

DBS Conference Room
Blk S3 Level 5, Dept. Biological Sciences,
The National University of Singapore
Science Drive 4

Visitors may park at Carpark 10
See map

Host: Dr Ruth O'Riordan

About the talk
Hong Kong lies within the tropics, yet experiences a strongly seasonal climate resulting in a wet/hot, tropical summer, and a cool/dry temperate winter, which greatly affect rocky shore assemblages. In winter, shores are covered by algal mats and ephemeral blooms of algae. Herbivorous molluscs are active over the entire shore and grazing by these molluscs and herbivorous crabs set algal distribution patterns. With the onset of summer, however, algae, grazers and many sessile species die-back or are restricted to refuges from physical stress. This transition can be quite sudden, associated with increasing air temperatures and a shift in tidal patterns.

Typhoons also impact shores in summer, often scouring the rock surface clean. As a result shores can appear bare in summer, the only autotrophs being encrusting algae and cyanobacteria. Many grazers migrate down shore and are restricted to refuges (cracks and crevices). As such, biotic factors such as grazing pressure become relatively less important, except low on the shore, or under shade, where physical stress is reduced. With the onset of winter, as conditions ameliorate, algae recruit and grow rapidly, and biotic interactions become more important as grazers become less reliant on refuges. Small scale disturbance events within the seasons, therefore, have little long term effect on these shores, which appear controlled by physical changes in season.

This strong climatic variation, therefore, has a great effect on the importance of biological processes and subsequent assemblage structure providing an interesting contrast to processes on less seasonal tropical shores.

About the speaker
Dr Gray A. Williams is the Hon. Director of The Swire Institute of Marine Science, The Department of Ecology & Biodiversity, The University of Hong Kong. He joined the university in 1989 after a brief Post-doctoral Fellowship at Port Erin Marine Laboratory, the University of Liverpool, Isle of Man. Since then he has established a research group working on the community ecology of tropical rocky shores. They work on a variety of intertidal organisms, but maintain a focus on algal (especially cyanobacteria) - herbivore interactions and the role of herbivore behaviour influencing rocky shore community structure.

ALL ARE WELCOME!  

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