Search

Changes in the ocean temperature, seawater acidity, and oxygen level are parts of global change that may indirectly impact the biogeochemical cycles of trace metals in the marine system, particularly for the particulate phase. The different factors influencing the level of particulate trace metals are interesting topics for investigation. Following up on marine research in the estuary and coastal areas, we specifically review the distribution of particulate trace metals. This review aims to provide an overview of the progress of studies on particulate metals in the marine environment and to understand the factors that influence the level of particulate metals. Spatially, the distribution of particulate trace metals decreases towards the sea due to the influence of salinity, while the temporal distribution portrays the unique feature of each location that differences in metal sources and phytoplankton bloom periods might cause. • SPM has the high ability to absorb metals and control their bioavailability. • Salinity is an important factor affecting the particulate metals in marine systems. • The Kd values depend on the nature of the metal, SPM, and geochemical parameters. • Particulate metals change seasonally caused by riverine input or biogenic processes. [ABSTRACT FROM AUTHOR]

• DOC crucial in coastal biogeochemical cycles, but its behavior varies based on sources. • Bulk DOC stable isotope ratio (δ 13C DOC) faces limitations in complex coastal waters. • Issues like narrow separation and reservoir effects in δ 13C DOC addressed by deuterium (δ 2H n). • The result shows δ 2H n and δ 13C DOC agree well in quantifying the terrigenous DOC fraction. • The δ 2H n proves comparable effectivity in quantifying tDOC, offering an alternative in settings where δ 13C DOC is inadequate. Dissolved organic carbon (DOC) is a key component of coastal biogeochemical cycles, but its composition and reactivity depend on the relative contribution of autochthonous aquatic versus allochthonous terrigenous DOC (tDOC). In complex coastal waters, tDOC is commonly quantified using the bulk DOC stable carbon isotope ratio (δ 13C DOC). However, several limitations can hamper the use of δ 13C DOC in marine ecosystems, such as (1) the narrow and often overlapping separation of the autochthonous and allochthonous endmembers, and (2) mineralization of tDOC to dissolved inorganic carbon creates a reservoir effect such that autochthonous DOC can acquire a terrigenous-like δ 13C DOC. The stable isotope ratio of non-exchangeable hydrogen in the DOC (δ 2H n) has emerged as a new tool that can potentially overcome these limitations: (1) δ 2H n has a large separation between aquatic and terrigenous endmembers (>50‰) and (2) it is not subject to reservoir effects caused by tDOC mineralization. Here, we evaluate the potential of δ 2H n obtained from solid phase-extracted dissolved organic matter (SPE-DOM), by comparing it to δ 13C DOC and chromophoric DOM (CDOM) optical properties. We collected samples at a site in Southeast Asia's Sunda Shelf that experiences substantial seasonal variation in tDOC input, driven primarily by the monsoon-induced physical advection of peatland-derived tDOC. Over a 1-year monthly time series, the terrigenous fraction of DOC (f terr) determined using δ 2H n of SPE-DOM and δ 13C DOC of bulk DOC was well correlated (r2 = 0.42), and there was no significant difference in f terr between the two isotope systems. In fact, δ 2H n displayed slightly stronger correlations with salinity and CDOM optical properties compared to δ 13C DOC. Our results indicate that δ 2H n of SPE-DOM is effective for quantifying tDOC across coastal gradients, potentially offering greater sensitivity than δ 13C DOC , and is a viable alternative in settings where δ 13C DOC is inadequate. [ABSTRACT FROM AUTHOR]

Seagrass carbon emission is mainly due to the land-use change; therefore, conservation will be an approach required for carbon offset. A method for estimating carbon offset from conservation activities has been developed. This study aims to evaluate the carbon-offset potential of the seagrass ecosystem by applying this method to five provinces in Indonesia. North Maluku has the widest seagrass area, but only 5% of this is the conserved area. Meanwhile, Jakarta has the highest percentage of its conserved seagrass within the area. Emission reduction at the year 2020 ranged 0.03–1.02 tC/year (with leakage) or 0.05–2.04 tC/year (without leakage). The percentage of emission reduction among the five provinces ranged from 0.75% to 11.3%. About 9.03 tC/year emission from seagrass ecosystems in Jakarta will decrease by up to 8.01 tC/year. Further assessment shows a positive correlation between the percentage of the conserved area and the percentage of emission reduction. • The study aims to evaluate the carbon offset potential of the seagrass ecosystem of five provinces in Indonesia. • Emission reduction (2020) ranged 0.03–1.02 tC/year (with leakage) or 0.05–2.04 tC/year (without leakage). • The study projected 2030 carbon emissions based on the baseline year of 2020. • The percentage of emission reduction among the five provinces ranged from 0.75% to 11.3%. • The projection needs improvement as field data becomes available for the intervening years. [ABSTRACT FROM AUTHOR]

Ongoing global changes such as increasing sea-surface temperatures, decreasing acidity levels, and expanding oxygen-minimum zone may impact on the biogeochemical cycles of trace metals in ocean systems. Each trace metal has unique characteristics and a distinctive distribution pattern controlled by chemical, biological, and physical processes that occur in ocean systems. The correlations of variability drivers in trace metals are interesting topics for investigation. Following up on ocean research in the coastal and estuary area, we specifically review the distribution of trace metals in seawater and suspended and surface sediment. The marginal seas usually feature significant terrestrial inputs accompanied by several active water-mass currents. The purpose of this review is to provide an overview of variability related to trace-metal distribution in coastal and estuary systems and to specifically describe the distribution, profile and drivers that affect trace metals variability. • Trace-metal distributions in ocean systems have been classified into conservative-, nutrient-, and scavenged-type profiles • Several variability drivers of trace metals may be involved in differences of metal distribution in particular ocean systems • The availability of dissolved trace metals is likely to increase in the future due to increasing SST, decreasing pH or decreasing DO • Suspended matter which generally derives from terrestrial input plays a role in determining the fate of trace metals • The study findings improve our understanding of trace-metal characteristics in the marine environment [ABSTRACT FROM AUTHOR]

The effects of Ocean acidification (OA) on the coastal waters of small islands in Indonesia have yet to be extensively studied. This research aims to investigate the process of OA in the coastal waters of small Indonesian islands and examine how land-sea interactions impact carbonate mineral saturation. We collected seawater samples from seven locations on small islands in Indonesia between 2015 and 2021 to analyze the aragonite saturation state. The result shows that most of Indonesia's coastal waters are accompanied by supersaturation of aragonite saturation state (Ωarag>1). Selayar Island's waters had the highest aragonite saturation, averaging 4.96 ± 0.48, while Pari Island's coastal waters had the lowest, averaging 2.49 ± 0.50. Salinity had the greatest effect on Ωarag in all of the sampling sites, ranging from 24.13% to 52.92%, except Aceh Island, where temperature had a greater impact (34.35%) than salinity (26.99%). By the end of this century, Ωarag is predicted to decline based on projections related to climate change. Small island coastal waters are expected to experience a more substantial decline compared to those near the mainland, ranging from 4.71% to 79.58%. The coastal waters of Weh and Selayar Island are probably going to decline the greatest, while the coastal waters of Sorong (mainland) are probably going to decline the least. All seven sampling locations are expected to observe the decrease. This decline will be observed at all seven sampling locations, with Ωarag values ranging from 1.91 to 3.35. • Regional disparities reveal lower Ωarag in Pari, Lombok; higher levels in Selayar, Flores. • Salinity impact ranges 24.13%–52.92%, showing a negative sea surface temperature-Ωarag correlation. • Climate change projections for 2100 predict substantial Ωarag reduction in Indonesian coastal waters. • The susceptibility to ocean acidification suggests coral reefs deteriorate by 2100, except for those in the coastal waters of Selayar Island. [ABSTRACT FROM AUTHOR]