To understand the impact of hydrodynamics on pollutant transport in Laizhou Bay, China, we conducted numerical simulations using Mike 21. The model was calibrated with good agreements to field monitoring data at various monitoring stations. The simulation results show a clockwise and an anti-clockwise tidally-induced residual circulation in the western and eastern bay, respectively. Historical COD monitoring data also indicate two rings of high COD concentration in the same regions of the bay. This suggests that the hydrodynamics of tidal and residual currents is the main cause of the ring-shaped high COD concentration field in the bay. Pollutant inputs from inland rivers are also important for the COD distribution, making the near-shore side of the COD ring higher than the offshore side. Regions with higher retention time in the bay are usually associated with higher COD concentrations. This study is useful in understanding the mechanism of pollutant spatial distribution and subsequent pollution control in a sea bay.

This study compares the occurrence and characteristics of microplastics (MPs) and heavy metal contaminants in the water and sediment of three habitats (corals, seagrass-beds and near-shores) of Rameswaram Island, India. The overall mean concentration of MPs varies from 24 ± 9 to 96 ± 57 items/L in water, and from 55 ± 21 to 259 ± 88 items/kg in sediment. The value of abundance is the greatest in the coral reef site CR-1 (96 ± 51 items/L; 259 ± 88 items/kg) followed by the seagrass site SG-2 (94 ± 55 items/L; 203 ± 75 items/kg) and the near-shore site St-15 (95 ± 63 items/L; 193 ± 75 items/kg). PE fiber (<1000 μm) is predominant in water, whereas PP fiber and fragment (between 2000 and 5000 μm) dominate the sediment. The SEM images of MPs reveal features which are characteristic of degradation like surface roughness, cracks, protrusions, and chalking, along with surface precipitates of both chemical and biological origin. EDAX images show the presence of Cr, Fe, Hg, Pb, Cu, As and Cd associated with MP surfaces.

Plastic pollution and ocean change have mostly been assessed separately, missing potential interactions that either enhance or reduce future impacts on ecosystem processes. Here, we used manipulative experiments with outdoor mesocosms to test hypotheses about the interactive effects of plastic pollution, ocean warming and acidification on macrophyte detrital decomposition. These experiments focused on detritus from kelp, Ecklonia radiata, and eelgrass, Zostera muelleri, and included crossed treatments of (i) no, low and high plastic pollution, (ii) current/future ocean temperatures, and (iii) ambient/future ocean partial pressure of carbon dioxide (pCO₂). High levels of plastic pollution significantly reduced the decomposition rate of kelp and eelgrass by approximately 27% and 36% in comparison to controls respectively. Plastic pollution also significantly slowed the nitrogen liberation from seagrass and kelp detritus. Higher seawater temperatures significantly increased the decomposition rate of kelp and eelgrass by 12% and 5% over current conditions, respectively. Higher seawater temperatures were also found to reduce the nitrogen liberation in eelgrass. In contrast, ocean acidification did not significantly influence the rate of macrophyte decomposition or nutrient liberation. Overall, our results show how detrital processes might respond to increasing plastic pollution and ocean temperatures, which has implications for detrital-driven secondary productivity, nutrient dynamics and carbon cycling.

The largest-scale green tides in the world caused by Ulva prolifera have been recurring annually in the Southern Yellow Sea since 2007. In this study, spatio-temporal variations of green tides and nutrients were investigated in the spring and summer of 2017, and the roles of different nutrients in the development of green tides are discussed. The results showed that the development of green tides could be divided into two parts according to the distinct growth phases of green tides: (1) the development area (DA), which was located south of 35°N and characterised by the quick expansion of green tide and high-content nutrient; (2) the accumulation area (AA), which was located north of 35°N and characterised by high U. prolifera coverage area and low-content inorganic nutrients. Through calculation of nutrient reductions, we found that DA provided 96% of nitrogen and 87% of phosphorus for the development of green tides in 2017, and the dominant nutrient species were dissolved inorganic nitrogen and dissolved organic phosphorus. Regarding AA, the dominant nitrogen component was dissolved organic nitrogen. Thus, we conclude that reducing the level of nutrient input in order to alleviate the eutrophication of seawater in the Jiangsu coastal area may be an important measure for reducing the scale of green tides.

The distribution characteristics, correlation, and bioavailability of 14 trace elements in different fishes and corals collected from the coral-reef systems of the Xisha Islands, China were systematic studied for the first time. All detected elements were measured using inductively coupled plasma mass spectrometry after pretreatment by microwave digestion. The fishes had slight differences in element enrichment selectivity and bioavailability with average levels as follows: V, 0.100 mg·kg⁻¹; Cr, 0.683 mg·kg⁻¹; Mn, 1.178 mg·kg⁻¹; Fe, 51.806 mg·kg⁻¹; Co, 0.072 mg·kg⁻¹; Ni, 1.286 mg·kg⁻¹; Cu, 1.428 mg·kg⁻¹; Zn, 10.384 mg·kg⁻¹; As, 6.437 mg·kg⁻¹; Se, 0.830 mg·kg⁻¹; Mo, 0.101 mg·kg⁻¹; Cd, 0.051 mg·kg⁻¹; Pb, 0.308 mg·kg⁻¹; and U, 0.008 mg·kg⁻¹. Trace element contents in corals were higher than those in fishes. The distribution characteristics of trace elements in fishes and corals presented a significant correlation in North Reef and Yongle Atoll, thereby indicating an evident effect on living areas compared with trace elements in fishes from the Spratly Islands. Cluster analysis of fishes and corals based on trace elements showed that they had different selectivities and bioavailabilities to trace elements. The EDI and THQ ratios of Cu, As, Cd, Cr, and Pb demonstrated that fishes were unlikely to experience serious adverse effects, except for As in Chaetodon auriga, Myripristis kuntee, Gnathodentex aureolineatus, and Hemigymnus melapterus in Xisha Islands.

The occurrence and composition of meso (5–25 mm) and microplastics (1–5 mm) in Playa Grande beach (Tenerife, Canary Islands, Spain) was monitored during a complete moon cycle on the different moon phases between 17ᵗʰ June and 16ᵗʰJuly 2019. A total of 10 points were sampled each day finding an average content of mesoplastics of 18 g/m² (0.36 g/L) and of microplastics of 13 g/m² (1277 items/m² or 1.6 g/L). Polypropylene and polyethylene accounted for 19% and 76% of the total, respectively. Tar was also found in the 1–5 mm fraction (2% of the total). Among the particles found, 83% were fragments, 11% pellets, 4% fibres and 2% films. The obtained results revealed that microplastic presence could not be related in this case with the tides but with the orientation and strength/speed of the wind.

PURPOSE OF REVIEW: Different selenium species released into the environment by anthropogenic activities pollute surface and ground water resources and can cause severe damage to the environment and ecosystems due to bio-accumulation. Though several physico-chemical methods are available to treat selenium oxyanion-containing wastewater, biological methods have gained significant importance due to their capability to convert selenium oxyanions to elemental selenium nanoparticles. The purpose of this review is to summarize the literature available on biological removal of selenium oxyanions and their recovery as elemental selenium nanoparticles. RECENT FINDINGS: In recent times, the capability of several bacterial and fungal strains to reduce selenate and selenite to form elemental selenium nanoparticles has been reported. The shape, size and location of these selenium nanoparticles along with the selenium oxyanion removal efficiency depend on the operating parameters. Moreover, bioreactor configurations and operation strategies greatly influence the selenium removal and recovery efficiency. Several conventional bioreactor systems can be used to remove selenate and selenite from wastewater and form selenium nanoparticles. However, the selenium nanoparticles are mostly entrapped in the biomass and require a secondary treatment to recover them. On the other hand, some novel bioreactors, viz. inverse fluidized bed bioreactor, rotating biological contractor, horizontal rotating packed bed bioreactor, moving bed biofilm reactor, and hybrid bioreactor, can possibly recover selenium nanoparticles following bioreduction of selenium oxyanions in a single stage system. Thus, this review will help in finding research gaps in this area and providing solutions for resource recovery from selenium oxyanion-containing wastewater.

The Ganga-Brahmaputra delta is among the largest river systems in terms of sediment discharge and the amount of arsenic present in the groundwater. Any slim possibility of arsenic intrusion in the coastal estuaries on account of active submarine groundwater discharge (SGD) can prove fatal to the biotic population at large. In the present study, a working hypothesis for the probable intrusion of arsenic through SGD has been postulated by re-analyzing the data of river discharge, sediment load, and arsenic concentration in the Bengal delta. Our study puts forward a strong argument for the coastal vulnerabilities of Bay of Bengal as the arsenic flux has reached at 1275 × 10³ kg/year and 865.8 × 10³ kg/year in the suspended and the dissolved form respectively. The enriched arsenic adsorbed on the surface of the Cenozoic sediments (dissolved and suspended) is contributing to the majority of arsenic flux to the Bay of Bengal. Furthermore, the flux resulting due to SGD contributes roughly 1% of the total flux, which if unregulated can prove catastrophic to the primary autotrophs. More so, the existence of flood-like conditions, as well as the region susceptibility to the fast-changing climatic trends, significantly increases the risk for the region in the near future. Therefore, ignoring the contributions of SGD in aiding the arsenic carcinogenicity in the coastal region of Bengal cannot continue for long and the time has come when a strong framework for SGD monitoring should be put in place, especially for regions falling under the purview of arsenic hazard zones.

Sea-level rise and overfishing could enhance the strength of hydrological connectivity and the presence of herbivores, resulting in salt marsh loss through physical stress and trophic cascade effects. Our aim was to estimate the effects of these two stresses on autochthonous producers. Survivorship and biomass of Suaeda salsa (S. salsa) were the lowest in areas with high hydrological connectivity, whereas the highest biomass was observed in the areas with moderate connectivity. The biomass of benthic microalgae was higher under low hydrological connectivity and no herbivores. The interactive effects between hydrological connectivity and herbivores on S. salsa but not on benthic microalgae were observed. Herbivores were somewhat (28%) important for the survival of initial S. salsa seedlings, while hydrological connectivity controlled (50%) the biomass of benthic microalgae. Our study highlights that, the autochthonous producers in coastal salt marshes may disappear due to strong hydrological connectivity and the excessive presence of herbivores.