Current studies use indices and chemometric approaches to assess the health quality of estuarine systems to support estuarine management. This study aims to use a multivariate approach and a set of indices to evaluate sediment health quality. Levels of Al, As, Cd, Cr, Cu, Fe, Ni, Pb, Sc, V, and Zn were quantified by ICP-OES, and nine indices were applied and evaluated individually. Most of the indices presented high values of Cu, Pb, and Zn, and the aggregative indices differed from each other in magnitude; however, the spatial distribution demonstrated the same trends. From PCA results, it was possible to differentiate lithogenic from the anthropogenic contribution, especially by Cu, Pb, and Zn. Thus, the integration of geochemical approaches and chemometric tools supported the interpretation of elemental contribution in terms of sources and pathway of heavy metals, which was similar to the results of other studies conducted in the area.

Haizhou Bay National Ocean Park is the first national ocean park in China. Consequently, the investigation of the spatial distribution characteristics, source apportionment, and ecological risks associated with heavy metals in this area is of great significance. Twelve sediment samples were collected in October 2016, and the geoaccumulation index (Igeo) method and the potential ecological risk index (PERI) method were used to assess the ecological risk. The results showed that the concentrations of the heavy metals (except Cr and Cu) in the surface sediments of the study area met the primary standard of marine sediment quality (GB18668-2002). The spatial distribution pattern of heavy metals in the surface sediments of Haizhou Bay National Ocean Park featured high concentrations in the southwestern region and low concentrations in the northeastern region, with a gradual decrease with increasing distance offshore, indicating that anthropogenic activities were the main source of heavy metal pollution. The evaluation results of the Igeo and PERI methods showed that Cd was the element posing the greatest ecological risk and that the ecological risk level in Haizhou Bay National Ocean Park corresponded to moderately contaminated. These findings indicate that effective management strategies should be developed to protect the marine environmental quality.

Native generalist grazers can control the populations of non-indigenous invasive algae (NIIA). Here, it was found that the simultaneous consumption of two co-occurring NIIA, Caulerpa cylindracea and C. taxifolia var. distichophylla, hinders the grazing ability of the main Mediterranean herbivorous, the native sea urchin Paracentrotus lividus. The ingestion of any of the two NIIA alone did not produce any difference in sea urchin righting time with respect to usual algal diet. In contrast, the simultaneous consumption of both NIIA, which grow intermingled in nature and are consumed by P. lividus, retarded its righting behavior. Such result reveals substantial physiological stress in the sea urchin, which resulted in reduced motility and coordination. The reported findings reveal the potential of NIIA co-occurrence to escape the supposed control exerted by the main native generalist grazer in Mediterranean sublittoral communities, which in turn can be locked in an “invaded” state.

In 2020, the global cap of maximum allowable sulphur content in marine fuel will be reduced from the current 3.5% to 0.5%. Another way to reduce the sulphur emissions is to install a seawater scrubber that cleans exhausts but instead release acidic water containing nutrients and contaminants back to the marine environment. In the current study, scrubber washwater was tested on a Baltic Sea microplankton community. A significant increase in chlorophyll a, particulate organic phosphorus (POP), carbon (POC) and nitrogen (PON) were observed when the community was exposed to 10% scrubber washwater for 13 days as compared to the control. A laboratory experiment with the filamentous cyanobacteria Nodularia spumigena and the chain-forming diatom Melosira cf. arctica showed negative responses in photosynthetic activity (EC10 = 8.6% for N. spumigena) and increased primary productivity (EC10 = 5.5% for M. cf. arctica), implying species-specific responses to scrubber washwater discharge.

The origins of sediment organic matter (SOM) and their contributions were studied in three contrasting wetlands (mudflat, estuarine and mangrove) of Daya Bay, South China Sea. Lower sediment δ13C but higher δ15N values were observed in coastal wetland than in offshore water of the bay. Greater terrigenous organic matter (TOM) contribution to SOM was observed in lower tidal area in mudflat and estuarine wetland. Higher concentrations of total organic carbon and total nitrogen in the three wetlands, as well as lower sediment δ13C, were found in the wet season. Extremely lower sediment δ15N with higher seawater ammonia were observed in estuarine wetland than in mudflat and mangrove, which was caused by the input of 15N-depleted ammonia from petrochemical industrial wastewater. Mangrove contributed substantially to SOM, with a larger contribution in mangrove area than in non-mangrove area. The mean contribution of TOM to SOM was lower in mangrove than in mudflat.

Ocean acidification is known to affect primary producers differentially in terms of species and environmental conditions, with controversial results obtained under different experimental setups. In this work we examined the physiological performances of the coccolithophore Gephyrocapsa oceanica that had been acclimated to 1000 μatm CO₂ for ~400 generations, and then exposed to multiple drivers, light intensity, light fluctuating frequency, temperature and UV radiation. Here, we show that increasing light intensity resulted in higher non-photochemical quenching and the effective absorption cross-section of PSII. The effective photochemical efficiency (Fv′/Fm′) decreased with increased levels of light, which was counterbalanced by fluctuating light regimes. The greenhouse condition acts synergistically with decreasing fluctuating light frequency to increase the Fv′/Fm′ and photosynthetic carbon fixation rate. Our data suggest that the coccolithophorid would be more stressed with increased exposures to solar UV irradiances, though its photosynthetic carbon fixation could be enhanced under the greenhouse condition.

We present a study of small microplastic particles (S-MPPs) in the sediments of mangrove ecosystem of Khor-e- Khoran, a Ramsar site in Iran. The spatial distribution of S-MPPs (<1 mm) in mangrove surface sediments were investigated, which provided new insights into the detection and composition of S-MPPs in the study area. S-MPPs were extracted via the air-induced overflow (AIO) extraction procedure, and then they were counted and categorized according to the particle shape, color and size. The mean number of S-MPPs at the five sampling sites ranged from 19.5 to 34.5 particles per kg dry sediment in Bandar Gelkan and Bandar Lengeh, respectively. In general, microfibres followed by fragments were the most common type of S-MPPs isolated in each site (>56% and ~35%, respectively). Sewage discharge is probably the main source of extracted fibres in almost all the sites. The observed S-MPPs were classified into two size groups (10–300 μm and 300–1000 μm). The majority of S-MPPs fell into the smallest size group which accounted for 70–97% of the total S-MPPs. Fourier transform infrared (FTIR) analysis of some subsamples showed that polyethylene (PE) was the most common recovered polymer. Some non-plastic particles were also isolated from plastic-like particles of suspected S-MPPs in the mangrove sediments using a Scanning Electron Microscope (FE-SEM). This study provided the first evidence of S-MPPs contamination in the mangroves of the Iranian coast of the Persian Gulf. Long-term studies are required to understand, monitor and prevent further microplastics pollution in the region.

The temporal and spatial distributions of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved silicate (DSi), and their long-term changes were investigated in Bohai Bay (BHB) in spring, summer, and autumn (2013–2014). The high DIN values were consistently distributed in the western inshore waters, mainly determined by terrestrial factors, e.g., riverine input, while DIP and DSi were mostly distributed in the southern coastal waters, the central BHB, or near the sea port Caofeidian in northern BHB, largely related to non-terrestrial factors, e.g., sediment release. Based on the nutrient distribution, BHB could be partitioned into western and eastern parts, with −15 m depth as the separation. The long-term variations of nutrients since 2000 showed an increase in DIN and decreases in DIP and DSi. Relatively slow changes in DIN and DIP and a rapid decrease in DSi were exhibited in summer, which was associated with precipitation and sediment release.

Biodegradation is important for the fate of oil spilled in marine environments, yet parameterization of biodegradation varies across oil spill models, which usually apply constant first-order decay rates to multiple pseudo-components describing an oil. To understand the influence of model parameterization on the fate of subsurface oil droplets, we reviewed existing algorithms and rates and conducted a model sensitivity study. Droplets were simulated from a blowout at 2000 m depth and were either treated with sub-surface dispersant injection (2% dispersant to oil ratio) or untreated. The most important factor affecting oil fate was the size of the droplets, with biodegradation contributing substantially to the fate of droplets ≤0.5 mm. Oil types, which were similar, had limited influence on simulated oil fate. Model results suggest that knowledge of droplet sizes and improved estimation of pseudo-component biodegradation rates and lag times would enhance prediction of the fate and transport of subsurface oil.

The objective was to compare the different effects of essential element Cu and non-essential element Hg on antioxidant and inflammatory responses in the liver of large yellow croaker Larimichthys crocea. Fish were exposed to Cu stresses (72 and 288 μg L−1) and Hg stresses (14 and 56 μg L−1) for 96 h. High-dose Cu increased metallothioneins (MTs) levels and immune defenses in response to elevated reactive oxygen species (ROS), but low-dose Cu had no effect on ROS. High-dose Hg reduced antioxidant and inflammatory responses, which contributed to the increment of ROS. MTs may be a suitable biomarker to assess Cu contamination, but no relationship was observed between MTs levels and Hg content. Furthermore, NFE2-related nuclear factor 2 (Nrf2) and nuclear transcription factor κB (NF-κB) were positively related to their respective target genes in the Cu-exposed groups. In conclusion, Cu and Hg induced some differences in antioxidant and inflammatory responses, which providing some novel insights into toxicological effects of Cu and Hg stresses.