Articles

A quality-controlled, 10-year (2015–2025) biogeochemical dataset was published for the Saigon-Dong Nai River-estuary continuum in Ho Chi Minh City, Vietnam, addressing a critical observational gap in tropical Southeast Asia. The observing program couples a biweekly time series at four fixed stations with seasonal longitudinal transects across 27 sites, encompassing over 19,800 observations of physical parameters, nutrients, organic carbon, and chlorophyll-a.

Mangrove sediments are widely recognized as an important component of long-term carbon storage in coastal ecosystems. However, the structure, evolution, and thematic organization of the scientific literature addressing mangrove sediment carbon have not yet been clearly characterized at the global scale. This study addresses this gap by providing a scientometric analysis of the literature on mangrove sediments as carbon sinks.

The proximate controls on phytoplankton blooms and carbon dynamics were investigated in the eutrophic, wastewater-impacted Saigon River Estuary (Ho Chi Minh City, Vietnam) using a transient 1D reactive-transport model (C-GEM) evaluated against 24 months of monitoring data.

DOM quantity and quality were investigated in semi-arid mangroves with no external organic matter input, developing along an intertidal gradient: a salt-flat, an Avicennia marina stand, and a Rhizophora stylosa stand. Soil and porewater samples were collected during both wet and dry seasons, and analysed for physicochemical parameters, total and dissolved organic carbon (TOC, DOC), chromophoric and fluorescent dissolved organic matter (CDOM, FDOM), and mineralogical composition.

• Dissolved organic carbon content is higher in deeper soil layers.
• The deep dissolved organic matter is older and more humified than at the surface.
• The vertical gradients studied are amplified during neap tides.
• Cr and Mn follow the dissolved organic carbon vertical gradient.
• Ni and Mo follow an opposite vertical gradient to dissolved organic carbon.

Estuaries exchange greenhouse gases with the atmosphere and can either potentially warm or cool the climate. Most studies focus on CO2, but other gases such as CH4 and N2O can also be important. In several tropical deltas, mixing between river water and sea water can lower CO2 levels, leading these systems to act as CO2 sinks even without biological uptake. Here, we measured air‐water CH4 and N2O fluxes in a tropical estuarine delta in Brazil and combined these data with CO2 flux measurements collected at the same time and locations.

TROPECOS scientists involved in WP3 reveal that the composition of dissolved organic matter (DOM) in mangrove soils is strongly influenced by mangrove species and their biological traits, including mycorrhizal associations.

This is crucial because DOM plays a key role in carbon cycling and nutrient export from mangroves. These findings highlight that understanding species-specific DOM dynamics is essential to better assess carbon fluxes and the functioning of atoll mangrove ecosystems.

TROPECOS Scientists involved in WP2  show that the nature of mangrove soil carbon varies significantly depending on the coastal landscape where mangroves grow. These findings challenge the "one-size-fits-all" approach to mangrove conservation and restoration for blue C, with major implications for climate policy and mangrove restoration projects.