Plastic Paradox in Blue Carbon Ecosystems.

Plastics are rapidly accumulating in blue carbon ecosystems, i.e., mangrove forests, tidal marshes, and seagrass meadows. Accumulated plastic is diverted from the ocean, but the extent and nature of impacts on blue carbon ecosystem processes, including carbon sequestration, are poorly known. Here, we explore the potential positive and negative consequences of plastic accumulation in blue carbon ecosystems. We highlight the effects of plastic accumulation on organic carbon stocks and sediment biogeochemistry through microbial metabolism. The notion of beneficial plastic accumulation in blue carbon ecosystems is controversial, yet considering the alternative impacts of plastics on oceanic and aboveground environments, this may be the "lesser of evils". Using environmental life cycle impact assessment, we propose a research framework to address the potential positive and negative impacts of plastic accumulation in blue carbon ecosystems. Considering the multifaceted benefits, we prioritize expanding and managing blue carbon ecosystems, which may help with ecosystem conservation, as well as mitigating the negative effects of plastic.

Prioritising plastic pollution research in blue carbon ecosystems: A scientometric overview.

The Blue Carbon Ecosystems (BCEs), comprising mangroves, saltmarshes, and seagrasses, located at the land-ocean interface provide crucial ecosystem services. These ecosystems serve as a natural barrier against the transportation of plastic waste from land to the ocean, effectively intercepting and mitigating plastic pollution in the ocean. To gain insights into the current state of research, and uncover key research gaps related to plastic pollution in BCEs, this study conveyed a comprehensive overview using bibliometric, altmetric, and literature synthesis approaches. The bibliometric analysis revealed a significant increase in publications addressing plastic pollution in BCEs, particularly since 2018. Geographically, Chinese institutions have made substantial contributions to this research field compared to countries and regions with extensive BCEs and established blue carbon science programs. Furthermore, many studies have focused on mangrove ecosystems, while limited attention was given to exploring plastic pollution in saltmarsh, seagrass, and multiple ecosystems simultaneously. Through a systematic analysis, this study identified four major research themes in BCE-plastics research: a) plastic trapping by vegetated coastal ecosystems, b) microbial plastic degradation, c) ingestion of plastic by benthic organisms, and d) effects of plastic on blue carbon biogeochemistry. Upon synthesising the current knowledge in each theme, we employed a perspective lens to outline future research frameworks, specifically emphasising habitat characteristics and blue carbon biogeochemistry. Emphasising the importance of synergistic research between plastic pollution and blue carbon science, we underscore the opportunities to progress our understanding of plastic reservoirs across BCEs and their subsequent effects on blue carbon sequestration and mineralisation. Together, the outcomes of this review have overarching implications for managing plastic pollution and optimising climate mitigation outcomes through the blue carbon strategies.

Deciphering the diversity and distribution of chromophytic phytoplankton in the Bohai Sea and the Yellow Sea via RuBisCO genes (rbcL).

Present study investigated composition and distribution of chromophytic phytoplankton in the Bohai Sea (BS) and the Yellow Sea (YS) by using rbcL genes. Bacillariophyceae, Haptophyceae and Pelagophyceae were the most abundant phytoplankton groups. Distinct phytoplankton communities were observed in the BS and the YS: offshore stations were dominated by bloom forming genera Thalassiosira and Skeletonema, while brown tide-forming species including Chrysochromulina spp. and Aureococcus anophagefferens were commonly found in the nearshore areas. Redundancy analysis showed that phosphate, temperature and silicic acid play key roles in structuring chromophytic phytoplankton, such as phytoplankton at nearshore stations were affected by nutrient runoff from adjacent rivers (Yellow River). Anthropogenic activities in the Bohai Sea and seasonal circulation of ocean currents may also contribute to shaping chromophytic phytoplankton communities. This study provides data support and foundational observations of chromophytic phytoplankton in the BS and the YS, and their responses to environmental gradients and human activities.

Heavy Metal Accumulation and Phytoremediation Potentiality of Some Selected Mangrove Species from the World's Largest Mangrove Forest.

Toxic metal pollution is a global issue, and the use of metal-accumulating plants to clean contaminated ecosystems is one of the most rapidly growing ecologically beneficial and cost-effective technologies. In this study, samples of sediment and three mangrove species (Excoecaria agallocha, Avicennia officinalis, Sonneratia apetala) were collected from the world's largest mangrove forest (along the Northern Bay of Bengal Coast) with the aim of evaluating metal concentrations, contamination degrees, and phytoremediation potentiality of those plants. Overall, the heavy metals concentration in sediment ranged from Cu: 72.41−95.89 mg/kg; Zn: 51.28−71.20 mg/kg; Fe: 22,760−27,470 mg/kg; Mn: 80.37−116.37 mg/kg; Sr: 167.92−221.44 mg/kg. In mangrove plants, the mean concentrations were in the order of E. agallocha > A. officinalis > S. apetala. The mean (± SD) concentration of each metal in the plant tissue (root) was found following the descending order of Fe (737.37 ± 153.06) > Mn (151.13 ± 34.26) > Sr (20.98 ± 6.97) > Cu (16.12 ± 4.34) > Zn (11.3 ± 2.39) mg/kg, whereas, in the leaf part, the mean concentration (mg/kg) of each metal found in the order of Fe (598.75 ± 410.65) > Mn (297.27 ± 148.11) > Sr (21.40 ± 8.71) > Cu (14.25 ± 2.51) > Zn (12.56 ± 2.13). The contamination factor (CF) values for the studied metals were in the descending order of Cu > Sr > Zn > Fe > Mn. The values of Igeo (Geo-accumulation index) and CF showed that the area was unpolluted to moderately polluted by Zn, Fe, Mn, Cu and Sr. Enrichment factor (EF) values in both sampling stations portrayed moderate to minimum enrichment. Phytoremediation potentiality of the species was assessed by bio-concentration factor (BCF) and translocation factor (TF). BCF values showed less accumulation for most of the heavy metals (<1) except Mn which was highly accumulated in all mangrove plants. The translocation factor (TF) values depicted that most of the heavy metals were strongly accumulated in plant tissues (>1). However, the BCF value depicts that Mn was highly bioconcentrated in E. agallocha, but the translocation on leaves tissue were minimum, which reveals that E. agallocha is phytoextractor for Mn, and accumulated in root tissues. All the examined plants can be used as phytoextractors as they have bioconcentration factors <1 and translocation factors >1. However, A. officinalis is clearly more suitable for metal extraction than S. apetala and E. agallocha in terms of hyper-metabolizing capabilities.

Heavy Metals Accumulation in Tissues of Wild and Farmed Barramundi from the Northern Bay of Bengal Coast, and Its Estimated Human Health Risks.

Globally, both natural water bodies and aquaculture systems are being severely contaminated by heavy metals due to rising anthropogenic activities. Fish living in aquatic environments can easily accumulate metals in their bodies, which can then be transferred to consumers and put them at risk. In this study, metal concentrations (Pb, Cd, Cr, As, Mn, Cu, Zn) in different organs (gill, liver, and muscle) of farmed and wild Barramundi (Lates calcarifer) fish from the northern Bay of Bengal were evaluated to quantify and compare contamination levels and related human health risk. Heavy metal concentrations were higher in liver tissues of farmed Barramundi than in wild Barramundi, with the following relative mean values in the liver, gills, and muscle: Zn > Cu > Pb > Mn > Cd > Cr > As; Zn > Cr > Cu > Pb > Mn > Cd > As; Zn > Pb > Cu > Cr > Mn > Cd > As; Zn > Pb > Cu > Cr > Mn > Cd > As; and Zn > Pb > Cu > Cr > Mn > Cd > As, respectively. The differences in heavy metal accumulation observed between farmed and wild fish were probably related to the differences in their environmental conditions and dietary element concentrations. However, ANOVA indicated that the variation of metals in wild and Barramundi was not statically significant. Pb concentrations in the liver tissue of farmed Barramundi exceeded the national and international threshold limits, whereas concentrations of other metals were within the limit. Among the examined organs in both fish species (wild and farmed), muscle had the lowest concentration compared to others, and liver was the target organ for Pb, Cu, and Cd accumulations. Metals such as Zn and Mn exhibited higher concentration in the gills. However, all the studied heavy metals were below the maximum permissible limits of national and international standards, but the mean concentrations of Pb and Cd values in the liver of farmed Barramundi exceeded all international and national guidelines. Based on the contamination factors (CF) and pollution indices (PLI and MPI), the degree of contamination in the fish organs was as follows: gills > liver > muscle. The major accumulation tissues for both farmed and wild fish were found to be the gills (MPI = 0.970) and the liver (MPI = 0.692). Based on the estimated daily intake (EDI), the fish samples examined in this study are safe for human consumption as within the recommended daily allowance (RDA) range established by various authorities. According to the Target Hazard Quotient (THQ) and Carcinogenic Risk (CR) calculations, though the Barramundi fishes depicted no potential hazard to humans, farmed fish posed a higher health risk than wild fish.

Metals Bioaccumulation in 15 Commonly Consumed Fishes from the Lower Meghna River and Adjacent Areas of Bangladesh and Associated Human Health Hazards.

The lower Meghna River, the easternmost part of the Ganges Delta, faces severe anthropogenic perturbations as it receives a huge discharge and industrial effluents. To measure the metal concentrations and human health hazards, edible tissues of 15 commercially important fish species were collected from the local fish markets and the lower Meghna River, Bangladesh. Trace and heavy metals such as Pb, Cr, Cu, Zn, Mn, Fe, Hg, Ni, Ca, Co, Se, Rb, Sr, and As were detected using the Energy Dispersive X-ray Fluorescence (EDXRF) method. The hierarchy of mean metal concentrations obtained was: Fe (162.198 mg/kg) > Zn (113.326 mg/kg) > Ca (87.828 mg/kg) > Sr (75.139 mg/kg) > Cu (36.438 mg/kg) > Se (9.087 mg/kg) > Cr (7.336 mg/kg) > Mn (6.637 mg/kg) > Co (3.474 mg/kg) > Rb (1.912 mg/kg) > Hg (1.657 mg/kg) > Ni (1.467 mg/kg) > Pb (0.521 mg/kg) > As (BDL). Based on the metal concentration obtained, the carnivorous species contained more metals than omnivores and herbivores. Similarly, the euryhaline and benthic feeder fishes had more metals than the stenohalines and demersal fishes. The metal pollution index (MPI) suggested that the highly consumed fish species Tilapia (Oreochromis mossambicus) and Rui (Labeo rohita) accumulated higher metals than other fishes. Both the Targeted Hazard Quotient (THQ) and Hazard Index (HI) values for adult and child consumers were <1, indicating that consumers would not experience the non-carcinogenic health effects. Although children were more susceptible than adults, carcinogenic risk (CR) exposure of Cr for all the consumers was found in the acceptable range (10−6 to 10−4), but the CR exposure of Pb was negligible for all the consumers. The correlation, principal component analysis (PCA), and cluster analysis were conducted to identify the sources of metals identified from the fish tissue. The results indicated that the probable sources of the pollutants were anthropogenic, arising from agricultural activities, electroplating materials, and lubricants used near the study area. However, the present study showed a different metal concentration in the samples at different levels but within the threshold levels non-carcinogenic and carcinogenic health risks; hence, the fishes of the area, in general, are safe for human consumption.

Bioaccumulation and potential human health risks of metals in commercially important fishes and shellfishes from Hangzhou Bay, China.

Hangzhou Bay is facing severe anthropogenic perturbation because of its geographic position. We studied species-specific bioaccumulation of metals in commercially important fishes and shellfishes, and calculated the potential human health hazards through their consumption, which has not been reported earlier from this area. The hierarchy of metal concentration in organisms was in the decreasing order of Zn (10.32 ± 7.13) > Cu (2.40 ± 2.66) > As (0.42 ± 0.26) > Cr (0.11 ± 0.08) > Cd (0.07 ± 0.07) > Pb (0.05 ± 0.02) > Hg (0.012 ± 0.009). Except for Cd and As concentrations in fishes, metal concentrations have not exceeded the national and international guideline values. P. laevis and P. trituberculatus were the most bioaccumulative of the species studied. According to the non-carcinogenic risk assessment, children were more susceptible to metal contamination than adults. The carcinogenic risk (CR) values indicated that children were likely to experience carcinogenic threats for taking cancer-causing agents As and Cd through fish consumption. In terms of organisms, intake of two crab species, P. trituberculatus and E. sinensis, as well as the oyster species P. laevis, could be detrimental to consumers.

Evaluation of ecosystem health and potential human health hazards in the Hangzhou Bay and Qiantang Estuary region through multiple assessment approaches.

Anthropogenic pollution has become a major issue governing ecosystem and human health risks. The Hangzhou Bay and Qiantang Estuary region are facing unusual perturbation due to rapid development along the embayment in recent decades. This study evaluated the organic and inorganic pollutants in water, sediment, and from the muscles of higher trophic organisms (fish, crustacean, shellfish) during four different seasons (in 2018-2019) along the Qiantang Estuary and Hangzhou Bay region to assess the ecosystem health and potential hazard status. Dissolved inorganic phosphate and nitrogen were the major pollutants in this area, which led to severe eutrophication throughout the study period. Eutrophication signals coincided well with the phytoplankton abundance, which revels the control of nutrient enrichment on the spatio-temporal distribution of phytoplankton. Food availability, along with salinity and temperature, drives the zooplankton population distribution. Heavy metals were not the issue of water quality as their concentrations meet the national and international baseline standards. However, in the sediments, Copper (Cu) and Arsenic (As) concentrations were higher than the baseline value. Towards the northwestern part of the Qiantang Estuary, the overall potential risk index of sediment with higher Cadmium (Cd) and Mercury (Hg) depicted delicate condition with moderate risk for the sediment contamination. The As concentration in fishes was close to the baseline standards limit irrespective of low As values within water and sediments. The higher concentrations of Zinc (Zn) and As in shellfish muscles, whereas other metals were within the limit of baseline standard in all the organisms. However, the hazard analysis (Targeted hazard quotient, THQ) values for the seafood consumption to human health indicates the potentially threatening consequences of shellfish and crustacean consumption on human health.