Aquatic Sciences Meeting, Albuquerque 2001

SS33 Human Impacts and Activities on Riverine Ecosystems (Science and Society Connections)

Date: Thursday, February 15, 2001, Time: 9:45:00 AM

Location: Galisteo

Nayar, S, , National University of Singapore, , Singapore, scip8370@nus.edu.sg

Goh, B, , National University of Singapore, , Singapore, dbsgohb@nus.edu.sg

Chou, L, M, National University of Singapore, , Singapore, dbsclm@nus.edu.sg

EFFECT OF DREDGING ON THE SIZE FRACTIONATED PRIMARY PRODUCTION AND BIOMASS IN AN IMPACTED ESTUARY IN SINGAPORE.

Size fractionated (0.2-2 u, 2-20 u, 20-200u and >200u) primary productivity, pigment concentrations and biomass were estimated on a fortnightly basis in Ponggol estuary on the northeastern coast of Singapore. Large scale dredging and reclamation, besides recreational boating from a nearby marina impact this estuary. Preliminary results show phytoplankton of size class 2-20u dominating the assemblage in terms of productivity and pigment concentrations, contributing up to 58% of total productivity. In terms of biomass, the smallest size class of 0.2-2u accounted for 36% of total biomass. However, bacterioplankton accounted for a bulk of this biomass (92%). Since 60-80% of the bacteria are metabolically inactive, it can be concluded that only 12% of the total biomass of the 0.2-2u size class were involved in carbon fixation. Dredged areas in the estuary recorded lower production rates, pigment concentrations and biomass. Cells of the larger size class of 20-200u dominated, accounting for 40% of total production. Light reduction up to 95% in the water column as a result of resuspension of particulate material during dredging is thought to be responsible for the larger size class dominating the assemblage.

This Session Listing

Aquatic Sciences Meeting, Albuquerque 2001

Quicklinks