Long-term comparison of dissolved nitrogen species in tropical estuarine and coastal water systems

Lim, Joon Hai; Wong, Yi You; Lee, Choon Weng; Bong, Chui Wei; Kudo, Isao

doi:10.1016/j.ecss.2019.04.008

Cited by 13 publications

(1 citation statement)

References 44 publications

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“…For example, the Can Gio estuary downstream of Ho Chi Minh City (Vietnam) receives high inputs of wastewater nutrients, but the inorganic N pool is dominated by nitrate (because wastewater ammonia is nitrified within the estuary), and dissolved inorganic N : P ratios are generally low (Taillardat et al, 2020). In contrast, the Klang River estuary downstream of Kuala Lumpur (Malaysia) has an inorganic N pool dominated by ammonia from riverine inputs, but peaks in ammonia concentration during periods of high river flow are not always accompanied by peaks in phosphate concentration, leading to very variable N : P ratios (Lim et al, 2019;Lee et al, 2020). Jakarta Bay (Indonesia) also receives high nutrient inputs from urban wastewater via rivers, with low N : P ratios in river water and hypereutrophic conditions near to the shore.…”

Section: Introductionmentioning

confidence: 99%

Distribution of nutrients and dissolved organic matter in a eutrophic equatorial estuary: the Johor River and the East Johor Strait

Cheong,

Annammala,

Yong

et al. 2024

Biogeosciences

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Abstract. Estuaries have strong physicochemical gradients that lead to complex variability and often high rates of biogeochemical processes, and they are also often impacted by humans. Yet, our understanding of estuarine biogeochemistry remains skewed towards temperate latitudes. We examined seasonal and spatial variability in dissolved organic matter (DOM) and nutrients along a partly eutrophic, agricultural–urban estuary system in Southeast Asia: the Johor River and the East Johor Strait. Dissolved organic carbon (DOC) and coloured DOM (CDOM) showed non-conservative mixing, indicating significant DOM inputs along the estuary. The CDOM spectral slopes and CDOM : DOC ratios suggest that terrigenous, soil-derived DOM dominates along the Johor River, while phytoplankton production and microbial recycling are important DOM sources in the Johor Strait. CDOM properties were not unambiguous source indicators in the eutrophic Johor Strait, which is likely due to heterotrophic CDOM production. Nitrate concentrations showed conservative mixing, while nitrite concentrations peaked at intermediate salinities of 10–25. Ammonium concentrations decreased with salinity in the Johor River but increased up to 50 µmol L−1 in the Johor Strait, often dominating the dissolved inorganic nitrogen (DIN) pool. Phosphate concentrations were low (<0.5 µmol L−1) throughout the Johor River but increased in the Johor Strait, where DIN : phosphate ratios were typically ≥ 16 : 1. This suggests that the Johor Strait may experience phosphorus limitation and that internal recycling is likely important for maintaining high nutrient concentrations in the Johor Strait. Overall, our results indicate that the Johor River and Johor Strait are clearly not part of the same estuarine mixing continuum and that nutrient recycling processes must be quantified to understand nutrient dynamics in the Johor Strait. Moreover, our results highlight the need for better techniques for DOM source tracing in eutrophic estuaries.

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Section: Introductionmentioning

confidence: 99%