Distribution Of Water Physico-Chemical Parameters And Biogenic Elements In Setiu Lagoon During Monsoon Events As Indicator For Primary Productivity

Abstract

he study was conducted in the Setiu Lagoon, Terengganu involving three sampling periods, namely in May 2007 (post-monsoon), September 2007 (pre-monsoon) and January 2008 (monsoon). Samples of nutrients (NO3 - - - + N, NO2 -3 -N, NH4 -N, PO4 -P), primary productivity, chlorophyll-a and physico-chemical parameters of water were collected during low and high tides from 6 stations in the lagoon area and 6 stations in the riverine area except for primary productivity where samples were taken during the pre- monsoon and monsoon seasons only during high tide. Data obtained were analyzed to assess the variations of water quality within Setiu lagoon spatially and temporally subjected to monsoonal events and tidal changes. From the results, the N:P ratio indicated that the study area was mostly N limited especially in the lagoon area. Correlation analysis indicated that phytoplankton consumed more NO3 - -N during low tide in the post- monsoon (p<0.01) and pre-monsoon season (p<0.05) but during high tide, PO4 -P more favorable to phytoplankton in the post-monsoon (p<0.01) and pre-monsoon season (p<0.01). Factor analysis showed that monsoonal event affects the phytoplankton productivity in the study area compared to tidal event. Temperature was the primary factor while nutrients concentration and salinity were the secondary factors. These indicated that monsoonal events coupled with tidal events contribute to the nutrient supply into the study area. Non-point sources and natural sources were the contributer for the nutrient enhancement in the study area. The study area was still not polluted with nutrients loading and did not exhibit any sign of eutrophication. The nutrient level did not exceed the standard of MWQCS (2010). The physico-chemical parameters and nutrients can be a good indicator for primary productivity in the Setiu lagoon.