Physico-biochemical controls on dissolved oxygen dynamics in the Eastern Upper Gulf of Thailand: field observations and numerical modeling

Hypoxia poses an increasing threat to coastal ecosystems, particularly in semi-enclosed estuarine systems such as the Upper Gulf of Thailand (UGoT). This study investigates the spatiotemporal dynamics of dissolved oxygen (DO) along the eastern UGoT, with a focus on the Siracha area, by integrating field observations with a coupled three-dimensional hydrodynamic–biochemical model. Temporal and spatial measurements in 2020 revealed pronounced seasonal and vertical variability in DO, with hypoxic events closely associated with strong salinity stratification, elevated river discharge, and phytoplankton decay. The model further identified five progressive stages of hypoxia development in the UGoT: reduced extent (November–May), onset (June), quasi-stable (July–August), expansion (September), and redistribution (October). Unusual DO profiles, characterized by minimum concentrations at mid-depth rather than near the bottom, were also observed. Model simulations indicated that these atypical profiles resulted from the intrusion of cold offshore bottom water into the study area. Nearshore DO dynamics were found to be significantly modulated by offshore circulation, stratification, water quality conditions, and tidal forcing. Scenario simulations further demonstrated that riverine nutrient loading is the primary driver controlling the hypoxia budget, whereas reaeration and tidal mixing also contribute substantially. Overall, the results underscore the critical interplay between physical and biochemical processes in shaping DO dynamics and hypoxia development in the UGoT and its eastern coast. These findings highlight the need for continuous autonomous monitoring and targeted riverine nutrient management to mitigate hypoxia in the eastern UGoT, serving as a representative example of shallow coastal systems near river mouths.

• Publication year

  2026

• Venue

  Frontiers in Marine Science

• Publication date

  2026-01-06

• Fields of study

  Not labeled

• Identifiers
  DOI 10.3389/fmars.2025.1708069
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar

• No claims are published for this paper.

• No concepts are published for this paper.

• Spatiotemporal variations in socioeconomic and hydrological factors impacting water quality in Thailand's major rivers

  2025cited by this paper
• Saltwater intrusion in Chao Phraya Estuary: A long, narrow and meandering partially mixed estuary influenced by water regulation and abstraction

  2024cited by this paper
• Monsoon-Driven Dispersal of River-Sourced Floating Marine Debris in Tropical Semi-Enclosed Waters: A Case Study in the Gulf of Thailand

  2024cited by this paper
• Long-term developments in seasonal hypoxia and response to climate change: A three-decade modeling study in the Ariake Sea, Japan.

  2024cited by this paper
• Persistent eutrophication and hypoxia in the coastal ocean

  2023cited by this paper
• Hypoxia in the Upper Gulf of Thailand: Hydrographic observations and modeling

  2021cited by this paper
• Eutrophication and hypoxia in the upper Gulf of Thailand

  2021influential reference
• Thermohaline conditions and circulation in the gulf of Thailand during the northeast monsoon

  2021cited by this paper
• Transport and dilution of fluvial antibiotic in the Upper Gulf of Thailand.

  2021cited by this paper
• The ERA5 global reanalysis

  2020cited by this paper
• Hydro-environmental processes governing the formation of hypoxic parcels in an inverse estuarine water body: Model validation and discussion.

  2019cited by this paper
• Numerical Modeling of Long-Term Biogeochemical Processes and Its Application to Sedimentary Bed Formation in Tokyo Bay

  2018cited by this paper
• The modification of water column conditions in the Gulf of Thailand by the influences of the South China Sea and monsoonal winds

  2016cited by this paper
• On the dynamics of low latitude, wide and shallow coastal system: numerical simulations of the Upper Gulf of Thailand

  2014cited by this paper
• GloFAS – global ensemble streamflow forecasting and flood early warning

  2012cited by this paper
• Dissolved Oxygen Dispersion Model Within Green Mussel Farming Area in Sri Racha Bay, Chonburi Province, Thailand

  2012cited by this paper
• Hypoxia Is Increasing in the Coastal Zone of the Baltic Sea

  2011cited by this paper
• Eco-hydrodynamic modelling of primary production in coastal waters and lakes using BLOOM

  2009cited by this paper
• Spreading Dead Zones and Consequences for Marine Ecosystems

  2008cited by this paper
• Thresholds of hypoxia for marine biodiversity

  2008cited by this paper
• Surface chlorophyll-a dynamics in the upper Gulf of Thailand revealed by a coupled hydrodynamic-ecosystem model

  2008cited by this paper
• Groundwater-derived nutrient inputs to the Upper Gulf of Thailand

  2007cited by this paper
• Influence of local wind field on seasonal circulations in the upper Gulf of Thailand

  2006cited by this paper
• Seasonal Variations in Inorganic Nutrient Budgets of the Bangpakong Estuary, Thailand

  2002cited by this paper
• Inflow of oceanic water into Tokyo Bay and generation of a subsurface hypoxic water mass

  2002cited by this paper
• Seasonal Variation of Stratification in the Gulf of Thailand

  2001cited by this paper
• Overview of hypoxia around the world.

  2001cited by this paper
• Dissection of the GHER turbulence closure scheme

  1999influential reference
• On the performance of a mixed‐layer model based on the κ‐ε turbulence closure

  1995influential reference

• No citing papers are available for this paper.