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<p>This study investigates the spatial and temporal dynamics of dissolved organic carbon (DOC) and particulate organic carbon (POC) in the Terengganu River Estuary (TRE), Malaysia, under neap and spring tidal conditions. Surface water samples were collected during longitudinal surveys at 22 stations, including both freshwater and coastal sites, across diurnal cycles. These samples were analyzed to assess DOC and POC concentrations, to evaluate their conservative and non-conservative behavior, and to identify their potential sources. Results showed significantly higher DOC concentrations [(284 ± 103) µmol/L] and POC concentrations [(89 ± 38) µmol/L] during spring tides compared with neap tides [(218 ± 67) µmol/L] and [(53 ± 15) µmol/L], respectively, attributed to tidal turbulence resuspending organic-rich bottom sediments. Diurnal variations revealed DOC and POC followed tidal cycles at a freshwater station (Sta. S22), with peaks during flood phases. In contrast, a coastal station (Sta. S5) exhibited inverse trends due to seawater dilution and retention near a breakwater. Both DOC and POC displayed non-conservative behavior, dominated by net additions along the salinity gradient, indicating the estuary acts as a source. Percentage concentration of low molecular weight (LMW) [molecular weight cut-off (MWCO) &lt; 10 kDa] DOC was more prevalent during spring tides (60%) than during neap tides (40%), suggesting enhanced resuspension of labile organic matter. No significant correlation was found between Percentage concentration of LMW DOC and chlorophyll <i>a</i> (Chl <i>a</i>) concentration, implying phytoplankton contributed minimally to DOC dynamics. This study highlights tidal forcing as a key driver of DOC/POC variability in tropical estuaries, with implications for understanding carbon cycling and pollutant transport. Further research is needed to identify specific anthropogenic and natural sources of organic carbon in the TRE.</p>

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Tidal influence on the spatial and temporal dynamics of dissolved and particulate organic carbon in a tropical riverine estuary

  • 期刊论文

  • 发表日期：

    2026年1月1日

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  • Azyyati Abdul Aziz,
  • Edmand Andrew Bedurus,
  • Suhaimi Suratman,
  • Sadeq Abdullah Abdo Alkhadher,
  • Lariyah Mohd Sidek

摘要

This study investigates the spatial and temporal dynamics of dissolved organic carbon (DOC) and particulate organic carbon (POC) in the Terengganu River Estuary (TRE), Malaysia, under neap and spring tidal conditions. Surface water samples were collected during longitudinal surveys at 22 stations, including both freshwater and coastal sites, across diurnal cycles. These samples were analyzed to assess DOC and POC concentrations, to evaluate their conservative and non-conservative behavior, and to identify their potential sources. Results showed significantly higher DOC concentrations [(284 ± 103) µmol/L] and POC concentrations [(89 ± 38) µmol/L] during spring tides compared with neap tides [(218 ± 67) µmol/L] and [(53 ± 15) µmol/L], respectively, attributed to tidal turbulence resuspending organic-rich bottom sediments. Diurnal variations revealed DOC and POC followed tidal cycles at a freshwater station (Sta. S22), with peaks during flood phases. In contrast, a coastal station (Sta. S5) exhibited inverse trends due to seawater dilution and retention near a breakwater. Both DOC and POC displayed non-conservative behavior, dominated by net additions along the salinity gradient, indicating the estuary acts as a source. Percentage concentration of low molecular weight (LMW) [molecular weight cut-off (MWCO) < 10 kDa] DOC was more prevalent during spring tides (60%) than during neap tides (40%), suggesting enhanced resuspension of labile organic matter. No significant correlation was found between Percentage concentration of LMW DOC and chlorophyll a (Chl a) concentration, implying phytoplankton contributed minimally to DOC dynamics. This study highlights tidal forcing as a key driver of DOC/POC variability in tropical estuaries, with implications for understanding carbon cycling and pollutant transport. Further research is needed to identify specific anthropogenic and natural sources of organic carbon in the TRE.