Acorn Barnacles (Balanus sp.)
Sengkang Riverside Park, 27th November 2010
These empty shells of Acorn Barnacles were found on a concretised section of the riverbank at Sungei Punggol. In the past, this stretch would have been subject to the ebb and flow of the tides, and the water must have been sufficiently salty to sustain some marine organisms. However, with the subsequent damming of the river mouth to form Punggol Reservoir, the salinity has presumably dropped, killing off those organisms unable to survive in freshwater. These dead barnacles, and the mangroves that still grow along the riverbank, hence represent a time not very long ago, when the sea still exerted significant influence over aquatic life in the former estuary.