Determination and comparison of selected heavy metal concentrations in seawater and sediment samples in the coastal area of Suva, Fiji

Combined toxicity of polyvinyl chloride microplastics and copper to marine jacopever (Sebastes schlegelii)

Marine organisms commonly encounter co-stress resulting from the coexistence of microplastics (MPs) and heavy metals pollution in marine environments. Nevertheless, the combined effects and toxicity mechanisms of MPs and heavy metals on marine organisms remain unclear. This study integrated growth, physiological, morphological, and biochemical markers to assess the individual and combined toxicity of polyvinyl chloride MPs (PVC MPs, 1 × 104 particles/L) and copper (Cu, 200 μg/L) on marine jacopever (Sebastes schlegelii). The results revealed that co-exposure to MPs and Cu had a more detrimental impact on jacopever compared to the single-exposure groups, as evidenced by the enhanced growth inhibition, respiratory stress, and hepatotoxicity. This phenomenon may be attributed to PVC MPs accelerating the accumulation of Cu in jacopever liver. Therefore, peroxidation damage occurred in the co-exposed liver and may result in liver dysfunction. These findings contribute valuable insights into the risks associated with the coexistence of MPs and heavy metal pollution in marine ecosystems.

Enhanced Removal of Ultratrace Levels of Gold from Wastewater Using Sulfur-Rich Covalent Organic Frameworks

In view of the increasing global demand and consumption of gold, there is a growing need and effort to extract gold from alternative sources besides conventional mining, e.g., from water. This drive is mainly due to the potential benefits for the economy and the environment as these sources contain large quantities of the precious metal that can be utilized. Wastewater is one of these valuable sources in which the gold concentration can be in the ppb range. However, the effective selective recovery and recycling of ultratrace amounts of this metal remain a challenge. In this article, we describe the development of a covalent imine-based organic framework with pores containing thioanisole functional groups (TTASDFPs) formed by the condensation of a triazine-based triamine and an aromatic dialdehyde. The sulfur-functionalized pores served as effective chelating agents to bind Au3+ ions, as evidenced by the uptake of more than 99% of the 9 ppm Au3+ solution within 2 min. This is relatively fast kinetics compared with other adsorbents reported for gold adsorption. TTASDFP also showed a high removal capacity of 245 mg·g-1 and a clear selectivity toward gold ions. More importantly, the material can capture gold at concentrations as low as 1 ppb.

Distribution, sources and influencing factors of heavy metals in the Ledong Sea, South China Sea

The Ledong Sea Area is located on the southwest side of Hainan Island. In recent years, with the development of industrialization and urbanization, the problem of heavy metals in marine sediments has gradually become a global problem, and research on this topic is of great significance for nearshore environmental protection and coastal management. This paper analysed the heavy metal content of 97 surface sediments in the Ledong Sea, indicating unpolluted to moderately polluted and low to moderate risk. Cu, Zn, Hg, Pb, Cr, and Cd are highly correlated, with similar origins, and originate from rivers carrying industrial wastewater, domestic sewage, and weathered material from the parent rocks, which are subsequently redistributed under the action of ocean dynamics. The distribution of Hg is mainly influenced by feed and biological metabolites during the farming process. As originates from rivers carrying large amounts of agricultural pesticide and fertilizer residues.

A new approach for the determination of As, Cu, and Pb in seawater samples using manganese oxide octahedral molecular sieve as a sorbent for dispersive solid-phase microextraction

This study introduces a novel method for preconcentrating As, Cu, and Pb from seawater samples using manganese oxide octahedral molecular sieve (OMS-2), as a sorbent, and the analysis by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The OMS-2 nanomaterial was synthesized and characterized using X-ray diffraction and scanning electron microscopy, revealing a crystallite size of 20.9 nm and a typical needle-like morphology of cryptomelane structure. To optimize the ICP-OES operating conditions and the preconcentration process, a central composite design was used. The optimal conditions for ICP-OES analyses were 1200 W and 0.7 L min-1 for the levels of the radio frequency potential (RF) and nebulization gas flow rate, respectively. The optimal conditions for the adsorption process were achieved at a pH of 6.5, 30 mg of OMS-2, and 35 min of stirring time, in the presence of the sample matrix. The enrichment factors obtained were 66, 45, and 21, and a limit of detection of 0.3, 0.1, and 2.1 μg L-1 for As, Cu, and Pb, respectively. The recovery tests ranged from 80 % to 120 %. The method was successfully applied to determine As, Cu, and Pb in seawater samples.

Thiol-Functionalized MIL-100(Fe)/Device for the Removal of Heavy Metals in Water

The preparation of a functional device based on a functionalized MIL-100(Fe) metal-organic framework for the solid-phase extraction of heavy metals is reported. By a simple and easy straightforward grafting procedure, a thiol-functionalized MIL-100(Fe) material (MIL-100(Fe)-SH) with a S/Fe ratio of 0.80 and a surface area of 840 m2 g-1 was obtained. MIL-100(Fe)-SH exhibited a higher Hg(II) extraction (96 ± 5%) than that of MIL-100(Fe) (78 ± 4%) due to the interaction between thiol groups and Hg(II) ions. For practical applications, the obtained MIL-100(Fe)-SH was integrated by a simple method to a 3D printed support based on a matrix of interconnected cubes using poly(vinylidene fluoride) as binder, obtaining a functional device that simultaneously acts as stirrer and sorbent. The developed device showed high efficiency for the removal of Hg(II), good reusability, and excellent performance for the simultaneous preconcentration and further detection and quantification of Hg(II), Pb(II), and As(V) in tap, well, and lake water samples.

Terrestrial inputs and physical processes control the distributions of potentially toxic elements (PTEs) in the seawater of the large-range Beibu Gulf, the northern South China Sea

The potentially toxic elements (PTEs), Cu, Pb, Zn, Cd, Cr, Hg and As in the water from the Beibu Gulf, were investigated to reveal the contaminant characteristics and assess the risks to human health. The results showed that the concentration of PTEs in the Beibu Gulf varies significantly both seasonally and spatially, with higher concentrations in summer and in the northern and southern gulf. Terrestrial inputs and local anthropogenic discharge are responsible for the higher level in the northern gulf, and the transportation of water masses is also an important factor for the higher concentrations in the southern gulf. Ecological risk assessment suggested that Hg is the main ecological risk factor. The health risk assessment revealed that dermal exposure to PTEs in the gulf presents potentially carcinogenic health effects for humans. This study provides new insight into the transport of PTEs over a large area of the Beibu Gulf.

Spatial distribution and risk assessment of heavy metals in the coastal waters of the Gulf of Suez, Red Sea, Egypt

To assess ecological and health risks connected with heavy metal contamination in the Gulf of Suez, Red Sea seawater during winter 2021. The selected heavy metals were detected using the "AAS" Technique. The results presented that; the average metal concentrations ranged between (0.57, 1.47, 0.76, 5.44, 0.95, 18.79, and 1.90 μg/l) for Cd, Pb, Zn, Mn, Fe, Cu, and Ni along the investigated area. Pollution Index for overall Gulf sectors <1, indicating a slightly and moderately affected region. Metal Index for the Gulf is >1, representing the existence of heavy metal pollution, which is alarming in this area. (HPI) Heavy metal pollution index <100 indicates low contamination of heavy metal "and is apposite for consumption. The Gulf's ecological risk index (Eri) mostly fell under the low-ecological risk. The risk health estimation revealed that CDI values for carcinogenic were (10-5 to10-7), (10-6 to10-8), and (10-9 to10-11) for ingestion, dermal, and inhalation, respectively. Ingestion for children is twice as high as the proportions documented for adults. At the same time, THQ values for non-carcinogenic ingestion, dermal, and inhalation were (10-5 to 10-8), (10-4 to 10-5), and (10-10 to 10-12), respectively. Also, the total hazard quotient (THQ ing. + THQ inh.) values were <1 acceptable limit, indicating no non-carcinogenic risk to the residents through dermal adsorption and oral water intake. The ingestion pathway was the main pathway for total risk. In conclusion, the overall hazard risks are lower than the permissible limit of <1 regarding heavy metals.

Contamination, sources and health risks of potentially toxic elements in the coastal multimedia environment of South China

Coastal ecosystems are vulnerable to the accumulation of potentially toxic elements (PTEs), which pose a threat to marine ecosystems and human health. In this study, the concentrations of eight PTEs in a typical area of South China were analysed, and their distributions, seasonal variations, pollution degrees, potential health risks and sources in seawater, sediment and organisms were evaluated. The comprehensive pollution index (CPI), pollution load index (PLI), potential ecological risk index (PERI) and target hazard quotient (THQ) were applied to assess seawater, sediment and organism quality, respectively. The annual mean concentrations of Zn, Hg, Cr and As in the bottom seawater were higher than those in the surface water while those of Pb, Mn and Cu were higher in the surface seawater. The mean content of Hg was higher than the corresponding background value of that in China Shelf Sea sediment. Marine organisms have a high enrichment capacity for Cu, Zn, Cr, Hg, As and Mn in seawater. Based on CPI, the seawater was generally not polluted by PTEs. The PLI and PERI results demonstrated that Hg was the main contamination element in surface sediment. The total target hazard quotient (TTHQ) analysis illustrated that long-term consumption of some fish by children poses a noncarcinogenic health risk, while that risk to adults is negligible. Natural sources, agricultural activity sources, coal burning and industrial emission sources were the main sources of the PTEs in surface sediments according to positive matrix factorization (PMF) model.

Distribution, Multi-Index Assessment, and Sources of Heavy Metals in Surface Sediments of Zhelin Bay, a Typical Mariculture Area in Southern China

The occurrence, multi-index assessment, and sources of heavy metals in surface sediments of Zhelin Bay were investigated. Average heavy metal concentrations (mg/kg) were 81.89 (Cr), 770.76 (Mn), 16.81 (Co), 62.25 (Ni), 96.30 (Cu), 162.04 (Zn), and 73.40 (Pb), with the concentrations of studied seven heavy metals being significantly higher than their corresponding background values. Geo-accumulation index (I_geo) and pollution load index (PLI) were implemented to assess degree of heavy metal contamination. The I_geo and PLI indicated that Cr, Mn, Co, Zn, and Pb were slightly polluted, and Cu and Ni were moderately polluted in the region. Potential ecological risk index (RI) and mean possible effect level (PEL) quotient were conducted to assess ecological risk. The RI and mean PEL quotient demonstrated that surface sediments of Zhelin Bay were slight ecological risks and exhibited a 21% probability of toxicity. Principal component analysis (PCA) combined with the correlation analysis (CA) and hierarchical cluster analysis (HAC) revealed that the heavy metal contamination in Zhelin Bay might originate from three type sources.

Distribution and transport of heavy metals in surface sediments of Chengbei Sea in the Bohai Sea

It is of great significance to study the distribution characteristics and transport of heavy metals in complex sedimentary environments and areas with intensive human activities. This study analyzed sediment size, heavy metal contents (Cu, Zn, Cd, Cr, and Pb), organic carbon content, and sulfide content in surface sediments collected from 27 sites in Chengbei Sea. The main controlling factors of the distribution and transport of heavy metals were discussed from the perspective of sediment dynamics. The concentrations of Cu, Zn, Cd, Cr, and Pb in surface sediments were 7.9-20.5 mg/kg, 33.8-94.6 mg/kg, 0.08-0.26 mg/kg, 6.3-62.3 mg/kg, and 3-13.4 mg/kg, respectively. According to the geoaccumulation index, the study area was not polluted by the heavy metals, except for Cd, which did not pollute only areas with relatively coarse-grained sediments. Combining the results of correlation analysis, tidal residual current analysis, sediment transport trend analysis, and principal component analysis confirmed that Cu, Zn, and Cd originate from natural sources, and their distribution characteristics are mainly controlled by the grain size of surface sediments. Cr and Pb could be attributed to human activities, such as oil exploration, and their distribution characteristics were affected by sediment transport and tidal residual current. Zonation of the sedimentary dynamic environment also provided reference for the relationship between the distribution of heavy metals in surface sediments and sedimentary environments.

Adsorption of heavy metals from the aqueous solution using activated biomass from Ulva flexuosa

The removal of various highly toxic heavy metals from wastewater environment is an important task to improve environment. The biosorption potential of cadmium, cobalt and zinc was evaluated using Ulva flexuosa biomass. The impacts of adsorbent dosage, pH of the medium, contact time, and agitation speed were analyzed. The maximum biosorption potential was reached at pH 4.0, 0.4 g initial biosorbent dosage, contact time 40 min and 30 mg/L initial metal concentration for cadmium, while the other factors were similar to zinc, except 35 min contact time (p < 0.01). The optimum absorption was pH 4, 0.6% adsorbent dosage, after 30 min contact time with the heavy metals and 40 mg/L cobalt concentration. Heavy metal removal efficiency was 94.8 ± 3.3%, 87.5 ± 2.3%, and 90.8 ± 1.4%, for cadmium, cobalt, and zinc, respectively (p < 0.01). The Langmuir constant (R²) was 0.980 for cadmium, 0.838 for cobalt and it was 0.718 for zinc. The present results revealed that the selected acid modified biomass was highly suitable for the adsorption of metal ions such as, Cd²⁺, Co²⁺ and Zn²⁺. The present work revealed the potential application of algal biomass for the removal of various heavy metals from the environment.

Histopathological Analysis of Faunus Ater Ovotestis in Bale and Reuleueng Rivers, Aceh Besar Regency, Aceh Province Indonesia

BACKGROUND: Faunus ater is one of the macrozoobenthos that is often consumed by the community, especially in the Leupung and Lhoknga areas, Aceh Besar District. The presence of Pb and Zn is suspected to be able to damage the body cells of F. ater, especially the ovotestis organ. Ovotestis is an organ in mollusks in general that can produce egg cells and sperm cells simultaneously. AIM: The purpose of this study was to analyze the level of damage to the Ovotestis of F. ater based on the state of the damaged Ovotestis cells. METHODS: The method of this research method is F. ater that samples were taken from Bale and Reuleung River, each river is divided into three stations and at each station, three samples of F. ater are taken. Ovotestical histopathological analysis was carried out at the Histology Laboratory, Faculty of Veterinary Medicine, Syiah Kuala University. Preparation of ovotestis histology preparations using the paraffin method. Previously, F. ater was terminated and carcass surgery was performed. The level of damage to female gametes and male gametes was carried out descriptively by observing gonadal cells undergoing necrosis, hypertrophy, and lysis. Observation of the level of damage to the ovotestis tissue of F. ater was carried out using a cell damage scoring system, namely, the level of damage, the type of damage, and the scoring value. RESULTS: The level of tissue damage to the ovotestis organ of F. ater was at level III with a score of 6. The highest percentage of damage occurred in Krueng Bale, namely, 19.027% for male gonads and 42.687% for female gonads. While the highest percentage of damage to ovotestis organ occurred in Krueng Reuleung 15,489% for male gonads and 40,695% for female gonads. CONCLUSION: The result shows that there was damage to the gonads of F. ater in Krueng Bale and Krueng Reuleung based on the number of fully-formed oocytes/sperm, the number of incompletely formed oocytes/sperm, and the number of damaged oocytes/sperm.

Determination of the Risk on Human Health of Heavy Metals Contained by Ship Source Bilge and Wastewater Discharged to the Sea on the Mediterranean by Monte Carlo Simulation

Discharge of bilge and wastewater from ships into the sea poses a risk to human health due to the heavy metals. In this study, shipborne bilgewater and wastewater carcinogenic and non-carcinogenic human health risks determine by using the measured and literature values of heavy metals copper, iron, vanadium, chromium, manganese, cobalt, nickel, zinc, arsenic, cadmium, and mercury in the shipborne bilgewater and wastewater. The heavy metal contents of seawater were selected from 11 points determined in Antalya Bay, wastewater, and bilge samples taken from two ships. The human health risk was determined using the Monte Carlo Simulation (MCS) method using these measured values and the heavy metal concentrations in the Mediterranean Sea in the literature. The risk of carcinogenicity of heavy metals from wastewater by dermal route, ingestion, and from bilge water by dermal way and ingestion were evaluated. The wastewater is dermal Ni > As > Cr, the wastewater is Ni > Cr > As by ingestion, the dermal Ni > As > Cr in the bilge, and the risk of ingestion is Ni > Cr > As. It has been determined that the non-carcinogenic Cr, Co, Hg, and As values in the wastewater and bilge water are above the acceptable 1 and therefore expose a risk to human health. The human health carcinogenic risk caused by heavy metals generating from the bilge and wastewater is much higher than the standard values determined by the WHO. For the first time in this study, it was determined that bilge water exposes a high risk for both swimmers and ship personnel in the health risk assessment of shipborne wastewater and bilge water.

Lipid profiling differentiates the effect of ambient microenriched copper on a coral as an advanced tool for biomonitoring

Copper can be beneficial or harmful to coral at environmentally relevant levels, making environmental monitoring a challenging. Membrane lipids make the cell a dynamic environment according to the circumstances; thus, the lipid profile should be indicative of an environmental/physiological state. To gain more insight into the copper effect on coral health and be a basis of biomonitoring, glycerophosphocholine profiling of coral exposed to microenriched copper levels was conducted in this study. The copper microenrichments resulted in a diacritical effect of decreasing carbonic anhydrase activity, following a supplementation effect, on coral lipid metabolism. Microdifferences in copper levels are critical to determine the coral metabolic state and were therefore included in this study. In addition, an excellent quantitative model correlating the coral lipid variation with the exposed copper levels or the induced physiological effect was obtained to demonstrate its performance for biomonitoring.

Heavy Metal Distribution in Surface Sediments of the Coastal Pearl Bay, South China Sea

Six heavy metals (As, Cu, Cd, Zn, Cr, and Pb) in surface sediments (0–5 cm) from the twenty selected sites of the coastal Pearl Bay (South China Sea) were analyzed to assess the distribution pattern and potential ecological risk. Overall concentrations (mg/kg, dw) in the sediment samples were: As (10.88 ± 6.50), Cu (24.16 ± 18.63), Cd (0.55 ± 0.78), Zn (48.53 ± 30.06), Cr (35.78 ± 28.66), Pb (31.28 ± 18.50). Results showed that the overall mean values of Cd concentrations exceeded the standard of China Marine Sediment Quality, caused by significantly high levels of Cd contents in five sites (S8, S11, S13, S16, and S17) at the offshore area of Pearl Bay. Generally, the metal concentrations showed a decreasing trend from the offshore area to the inner bay. Various index values such as the geo-accumulation index (Igeo), the ecological risk index (Eri), and the contamination factor (CF) demonstrated that the coastal Pearl Bay was not polluted by the examined metals except for Cd, which might cause contamination and ecological risk in the region. Principal component analysis (PCA) results indicated that Cu, Zn, and Cr might originate from natural sources inland, and Pb and As might come from the gasoline and diesel fuel from engine boats. It is recommended that further research should focus on detecting the acute source and transferring mechanisms of the toxic metal Cd.

Lipid profiling of coral symbiosomes in response to copper-induced carbon limitation: A metabolic effect of algal symbionts on the host immune status

Copper micropollutants are known to constrain coral's assimilation of carbonate, affecting the carbon available to algal symbionts and thus inducing a light stress. However, little is known regarding the physiological relevance of lipid metabolism in coral symbiotic algae in a carbon-limited state. Membrane lipids exhibit multiple physicochemical properties that are collectively responsible for the dynamic structure of cells depending on the physiological demands of the circumstances. To gain insight into lipid metabolism's importance in this regard, glycerophosphocholine (GPC) profiling of symbiosomes in coral (Seriatopora caliendrum) exposed to environmentally relevant copper levels (2.2-7.5 μg/L) for 4 days was performed in this study. Notably, reducing the number of 22:6-processing GPCs and increasing that of lyso-GPCs likely addressed the demands of metabolizing excess light energy, such as affecting the membrane dynamics to promote mitochondrial uncoupling. The decrease in 22:6-processing GPCs additionally protected cellular membranes from elevated oxidative stress, reducing their susceptibility to peroxidation and offsetting oxidized lipid-induced effects on membrane dynamics. The change in plasmanylcholines specifically localized within the symbiosome membrane also met the membrane requirements for responding to oxidative stress conditions. Moreover, increasing the 20:4-possessing plasmanylcholines and lysoplasmanylcholines and reducing the 22:6-possessing plasmanylcholines likely resulted in an imbalance of the immune reaction, influencing the coral-algae symbiosis given the role of such plasmanylcholines in cell signaling. In summary, carbon limitations induced by copper enrichment lead to a shift in the membrane lipid profile of coral symbiosomes, accommodating themselves to light stress conditions while compromising the symbiosis's stability.

Distribution, source and risk assessment of heavy metals in the seawater, sediments, and organisms of the Daya Bay, China

Cu, Pb, Zn, Cd, Cr, Hg and As in seawater, sediment and organisms of the Daya Bay, Guangdong province, China were measured to acquire the comprehensive understanding on distribution, sources and risk assessment of heavy metals (HMs) in the marine ecosystem. The concentrations were relatively ideal, and the Pb was the major pollutant in the seawater and sediment. The contents of HMs were highest in spring; the concentrations near the sewage outlet and shore were noticeable. Submarine pipeline sewage, atmospheric deposition and runoff were the main sources of HMs in coastal waters. Studied HMs were preferentially retained by liquid phase; Cd, Cu and Zn were the most accumulated elements in the organisms from the surrounding environment. Cd in shellfish deserved particular attention, but the health risks including non-carcinogenic and carcinogenic risks of all elements were within acceptable limits. The potential health risks of Pb have been confirmed by molecular docking.

Ecological and human health risk assessment of trace element pollution in sediments and five important commercial fishes of the Oman Sea

The distribution of trace elements in sediments and five commercially important fish species of the Oman Sea were assessed using an atomic absorption spectrometer to determine ecological and human health risk assessment. The ranges of trace elements concentration in sediments were: Cr: 5.42-68.94, Zn: 5.22-18.11, Cu: 1.44-4.87, As: 18.07-79.96, Cd: 0.10-1.27, Ni: 43.0-65.34 and Pb: 8.92-30.53 mg/kg dry weight. Cr, Zn, Cu, Cd and Pb were below the ERL (effects range low) and TEL (threshold effect level) values at all the sampling stations with rarely biological effects. Whereas, As and Ni were higher than ERL and TEL with occasionally biological effects. The patterns of trace elements bioaccumulation in the tissues of all species were: liver> skin> gill> muscle. A significant positive correlation suggests that trace elements accumulation in fish is determined by trace elements in sediments. Estimated Daily Intake (EDI) was significantly lower than the tolerable daily intake (TDI) value. Target Hazard quotient (THQ), total target hazard quotient (TTHQ) and target carcinogenic risk (TR) values indicated no hazard risk from fish consumption. Hence, the consumption of concerned species to people in the Oman Sea is safe.

Effects of Human Activities on the Spatial Distribution, Ecological Risk and Sources of PTEs in Coastal Sediments

Potentially toxic elements (PTEs) have attracted substantial attention because of their widespread sources, long residue time and easy accumulation. PTEs in the surface sediments of inshore waters are strongly affected by human activities because these waters are a zone of interaction between the ocean and land. In the present study, to explore the environmental geochemical behaviour and source of PTEs in the surface sediments of coastal waters, the contents and spatial distributions of copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd), chromium (Cr), mercury (Hg) and arsenic (As) in different regions of Xiamen Bay were investigated. The data were processed by multivariate statistical methods, and the distribution characteristics of PTEs in the surface sediments of Xiamen Bay were analysed. In addition, the pollution load index (PLI), geo-accumulation index (Igeo) and potential ecological index(RI) were used to evaluate the pollution degree and potential risk in the surface sediments of Xiamen Bay, and the positive matrix factorisation (PMF) model was used to analyse the source. The results show that Zn had the highest mean concentration, followed by Pb, Cr, Cu, As, Cd and Hg, among the seven PTEs. The mean contents of Pb, Zn, Cd, Cu and Hg, and especially Hg and Cd, were higher than the corresponding environmental background values. The average PLI value indicated that the Xiamen Bay sediment was moderately contaminated by PTEs. The Igeo results showed that Xiamen Bay was moderately to strongly polluted by Cd and Hg. The proportions of samples with low, medium and strong risk levels were 11.63%, 74.42%, and 13.95% in surface sediments, respectively. PMF models showed that the input of chemical fertilizer and medication, anthropogenic atmospheric components and terrestrial detritus were the main sources of PTEs in the surface sediment of Xiamen Bay.

Assessment of potential variability of cadmium and copper trace metals using hindcast estimates

Trace metals are vital to primary productivity and play an essential role as main components in regulating oceanic biogeochemical cycles. Dissolved and particulate trace metals within the water column may vary due to primary production, temperature, and nutrient changes, factors that may also vary spatially and temporally. Furthermore, assessment of trace metals mainly relies on in situ observation, and so wide-area investigation of trace-metal concentration may be challenging and subject to technical constraints. A specific approach is therefore necessary that combines biogeochemical proxies, satellite data, and trace-metal linear correlation. This study aims to assess the potential spatio-temporal variability of sea surface cadmium (Cd) and copper (Cu) concentrations in Indonesian seas and surrounding areas. The correlations of Cd and Cu concentrations with primary production and nutrient data were used to convert hindcast satellite data into estimates of the metals' concentrations. The potential variability of trace metals can be determined by overlaying both data. Indonesia's Fisheries Management Areas (FMAs) were used for data clustering and analysis. The results show that Cd and Cu trace metals have similar distribution patterns throughout the year. However, dissolved Cu has a more diverse coverage area than dissolved Cd, including within the Halmahera, Seram, and Maluku Seas (FMAs 716 and 717), the Makassar Strait (FMA 717), and the Java-Sumatra upwelling area (FMA 573). Both Cd and Cu concentrations in the Java-Sumatra upwelling region follow the periodic upwelling pattern. Overall, both Cd and Cu show a declining trend in concentration from 2012 to 2019. It is estimated that dissolved Cd concentration declined from 1500-2000 pmol/kg in 2012 to 1000-1500 pmol/kg in 2019 for all locations. Dissolved Cu concentration decreased from 30-35 nmol/kg in 2012 to 25-30 nmol/kg in 2019. Estimated dissolved Cd and Cu follow the linear functions of silicate (SiO₄), nitrate (NO₃), and primary productivity. The fluctuation of anthropogenic activities and global warming are likely to indirectly impact the decline in metal concentrations by affecting nutrients and primary productivity.

Trace metal content in sediment cores and seagrass biomass from a tropical southwest Pacific Island

A unique feature of seagrass among other ecosystem services is to have high phytoremediation potential that is a cost-effective plant-based approach and environmentally friendly solution for metal contamination in coastal areas. The goal of this study was to assess the phytoremediation prospective of seagrass for Cu, Fe, Mn and Zn in Fiji Islands. Heavy metal content was measured in sediments and tissues of the seagrasses Halophila ovalis, Halodule pinifolia and Halodule uninervis to test for local-scale differences. The local study shows that metal concentration in sediment and seagrass tissue was significantly variable, regardless of species and sediment type. Sedimentary concentration of Cu, Fe, Mn and Zn obtained in the present study seemed to be lower than that of previous studies. The results support that H. ovalis is a good bioindicator species since it accumulated up to 5-fold more of these metals compared to the Halodule species.

Deriving Nickel (Ni(II)) and Chromium (Cr(III)) Based Environmentally Safe Olivine Guidelines for Coastal Enhanced Silicate Weathering

Enhanced silicate weathering (ESW) by spreading finely ground silicate rock along the coastal zone to remove atmospheric carbon dioxide (CO₂) is a proposed climate change mitigation technique. The abundant and fast-dissolving mineral olivine has received the most attention for this application. However, olivine contains nickel (Ni) and chromium (Cr), which may pose a risk to marine biota during a gigaton-scale ESW application. Herein we derive a first guideline for coastal olivine dispersal based on existing marine environmental quality standards (EQS) for Ni and Cr. Results show that benthic biota are at the highest risk when olivine and its associated trace metals are mixed in the surface sediment. Specifically, depending on local sedimentary Ni concentrations, 0.059-1.4 kg of olivine m^-2 of seabed could be supplied without posing risks for benthic biota. Accordingly, globally coastal ESW could safely sequester only 0.51-37 Gt of CO₂ in the 21st century. On the basis of current EQS, we conclude that adverse environmental impacts from Ni and Cr release could reduce the applicability of olivine in coastal ESW. Our findings call for more in-depth studies on the potential toxicity of olivine toward benthic marine biota, especially in regard to bioavailability and metal mixture toxicity.

Water resources pollution associated with risks of heavy metals from Vatukoula Goldmine region, Fiji

Although mining is essential for human economic development, is amongst the most polluting anthropogenic sources that influence seriously in water resources. Thus, understanding the presence and concentration of heavy metals in water and sediment in the vicinity of mines is important for the sustainability of the ecosystem. In this work, a multidisciplinary approach was developed to characterize the contamination level, source apportionment, co-existence, and degree of ecological and human health risks of HMs on water resources in the Vatukoula Goldmine region (VGR), Fiji. The outcomes suggested significant contamination by Cd (range: 0.01-0.95 g/L), Pb (range: 0.03-0.53 g/L), and Mn (range: 0.01-3.66 g/L) in water samples surpassed the level set by Fiji and international laws, whereas higher concentration of Cd (range: 2.60-23.16 mg/kg), Pb (range: 28.50-200.90 mg/kg) and Zn (range: 36.50-196.66 mg/kg) were detected in sediment samples. Lead demonstrated a strong significant co-existence network with other metals (e.g., Mn, Ni). Source apportionment recognized four source patterns (Cd, Pb, Ni, and Mn) for water and (Cr, Cd-Pb, Mn, and Zn) for sediment which was further confirmed by principal component analysis. The mine inputs source mainly contributed to Cd (66.07%) for water, while mineral processing mostly contributed to Zn (76.10%) for sediment. High non-carcinogenic (>1) and carcinogenic (>10^-4) health risks, particularly in children, are related to the elevated Cd, Pb and Cr contents from the VGR. Uncertainty analysis demonstrates that the 90th quantile of Cd led to higher carcinogenic risk. Pollution indices disclosed a moderate to extremely contamination status mainly along the Toko dam which poses high ecological risks identified by index calculation. However, sediment quality indicators based on probable effect levels showed that there was a 75% of likelihood that the concentrations of Cd and Pb adjacent to the VGR have a severe toxic impact on aquatic lives.

The tropical Pacific Oceanscape: Current issues, solutions and future possibilities

Marine ecosystems across the world's largest ocean - the Pacific Ocean - are being increasingly affected by stressors such as pollution, overfishing, ocean acidification, coastal development and warming events coupled with rising sea levels and increasing frequency of extreme weather. These anthropogenic-driven stressors, which operate cumulatively at varying spatial and temporal scales, are leading to ongoing and pervasive degradation of many marine ecosystems in the Pacific Island region. The effects of global warming and ocean acidification threaten much of the region and impact on the socio-cultural, environmental, economic and human health components of many Pacific Island nations. Simultaneously, resilience to climate change is being reduced as systems are overburdened by other stressors, such as marine and land-based pollution and unsustainable fishing. Consequently, it is important to understand the vulnerability of this region to future environmental scenarios and determine to what extent management actions can help protect, and rebuild ecosystem resilience and maintain ecosystem service provision. This Special Issue of papers explores many of these pressures through case studies across the Pacific Island region, and the impacts of individual and cumulative pressures on the condition, resilience and survival of ecosystems and the communities that depend on them. The papers represent original work from across the tropical Pacific oceanscape, an area that includes 22 Pacific Island countries and territories plus Hawaii and the Philippines. The 39 papers within provide insights on anthropogenic pressures and habitat responses at local, national, and regional scales. The themes range from coastal water quality and human health, assessment of status and trends for marine habitats (e.g. seagrass and coral reefs), and the interaction of local pressures (pollution, overfishing) with increasing temperatures and climate variability. Studies within the Special Issue highlight how local actions, monitoring, tourism values, management, policy and incentives can encourage adaptation to anthropogenic impacts. Conclusions identify possible solutions to support sustainable and harmonious environment and social systems in the unique Pacific Island oceanscape.

Synergies between local and climate-driven impacts on coral reefs in the Tropical Pacific: A review of issues and adaptation opportunities

Coral reefs in the tropical Pacific region are exposed to a range of anthropogenic local pressures. Climate change is exacerbating local impacts, causing unprecedented declines in coral reef habitats and bringing negative socio-economic consequences to Pacific communities who depend heavily on coral reefs for food, income and livelihoods. Continued increases in greenhouse gas emissions will drive future climate change, which will accelerate coral reef degradation. Traditional systems of resource governance in Pacific island nations provide a foundation to address local pressures and build reef resilience to climate change. Management and adaptation options should build on the regional diversity of governance systems and traditional knowledge to support community-based initiatives and cross-sectoral cooperation to address local pressures and minimize climate change impacts. Such an inclusive approach will offer enhanced opportunities to develop and implement transformative adaptation solutions, particularly in remote and regional areas where centralized management does not extend.

Marine water quality of a densely populated Pacific atoll (Tarawa, Kiribati): Cumulative pressures and resulting impacts on ecosystem and human health

The resilience of coastal ecosystems and communities to poor environmental and health outcomes is threatened by cumulative anthropogenic pressures. In Kiribati, a developing Pacific Island country where human activities are closely connected with the ocean, both people and environment are particularly vulnerable to coastal pollution. We present a survey of environmental and human health water quality parameters around urban South Tarawa, and an overview of their impacts on the semi-enclosed atoll. Tarawa has significant water quality issues and decisions to guide improvements are hindered by a persistent lack of appropriate and sufficient observations. Our snapshot assessment identifies highest risk locations related to chronic focused and diffuse pollution inputs, and where mixing and dilution with ocean water is restricted. We demonstrate the importance of monitoring in the context of rapidly changing pressures. Our recommendations are relevant to other atoll ecosystems where land-based activities and ocean health are tightly interlinked.