Indicators of oxidative stress and metabolic capacity are key factors in understanding the fitness of wild populations. In the present study, these factors were evaluated in the pelagic Southern Ocean taxa Antarctic krill (Euphausia superba) and myctophid fish (Electrona antarctica, Gymnoscopelus braueri and G. nicholsi) to establish a baseline record for future studies. Mercury (Hg) concentrations were also analysed to evaluate its potential impacts on species biochemical performance. E. superba had higher metabolic activity than most of the myctophid species, which may explain the comparatively lower energy reserves found in the former. The activity of antioxidant enzymes showed, generally, a lower level in E. superba than in the myctophid species. The lack of any relationship between Hg concentrations and organisms' antioxidant and biotransformation defence mechanisms indicate that levels of Hg accumulated in the studied species were not high enough to affect their biochemical processes adversely.

Assessing oil spill toxicity in real time is challenging due to dynamic field exposures and lack of simple, rapid, and sensitive tests. We investigated the relative sensitivity of two commercially available marine toxicity tests to aromatic hydrocarbons using the target lipid model (TLM). State of the art passive dosing in sealed vials was used to assess the sensitivity of brine shrimp (Artemia franciscana) and rotifer (Brachionus plicatilis). Organisms were exposed to toluene, 1-methylnaphthalene and phenanthrene for 24 h. Toxicity results were analysed using the TLM to estimate the critical target lipid body burden and support comparison to empirical data for 79 other aquatic organisms. Our findings demonstrate the applicability of passive dosing to test small volumes and indicate that the two rapid cyst-based assays are insensitive in detecting hydrocarbon exposures compared to other aquatic species. Our results highlight the limitations of applying these tests for oil pollution monitoring and decision-making.

Increasing the precision of nitrogen (N) fertiliser management in cropping systems is integral to increasing the environmental and economic sustainability of cropping. In a simulation study, we found that natural variability in year-to-year climate had a major effect on optimum N fertiliser rates for sugarcane in the Tully region of north-eastern Australia, where N discharges pose high risks to Great Barrier Reef ecosystems. There were interactions between climate and other factors affecting crop growth that made optimum N rates field-specific. The regional average optimum N fertiliser rate was substantially lower than current industry guidelines. Likewise, simulated N losses to the environment at optimum N fertiliser rates were substantially lower than the simulated losses at current industry fertiliser guidelines. Dissolved N discharged from rivers is related to fertiliser applications. If the reductions in N applications identified in the study occurred in the Tully region, the reduction in dissolved N discharges from rivers in the region would almost meet current water quality improvement targets. Whilst there were many assumptions made in this exploratory study, and there are many steps between the study and a practically implemented dynamic N fertiliser recommendation system, the potential environmental benefits justify field validation and further development of the concepts identified in the study.

PURPOSE OF REVIEW: The use of conventional chemical coagulant in treatment of wastewater is gaining great attention. Drawbacks related to the prolonged effects on human health and environment due to the generation of by-product non-biodegradable sludge are becoming the latest topics. Transition from chemical to natural coagulant can be a good strategy to reduce the aforementioned drawbacks. Therefore, this review aims to provide critical discussions on the use of natural coagulant along with the comparative evaluation over the chemical coagulant. RECENT FINDINGS: Treatment performances by chemical and natural coagulant have been reviewed on various types of wastewater with different success rates. Based on this review, a transition from the use of chemical to natural coagulant is highly suggested as the performance of the natural coagulant is comparable to that of the chemical coagulant and in some cases even better. The comparative advantages and disadvantages also convinced that the natural coagulant stands a great chance to be used as an alternative over the chemical coagulant. Though the current utilization of natural coagulant is encouraging, three main aspects were overlooked by researchers: active coagulant agent, extraction, and optimization due to different wastewater characteristics. Furthermore, delving into these aspects could clarify the uncertainties on the natural coagulant. Hence, it makes this transition a prospect of green technology with sustainable application towards wastewater treatment.

PURPOSE OF REVIEW: This review is intended to address the issues of unsafe disposal of antibiotics from various sources to the environment, its incomplete degradation, the resulting antibiotic resistance properties on microorganisms exposed to these antibiotics as well as some currently available techniques to remove both the antibiotic-resistant bacteria (ARBs) and antibiotic-resistant genes (ARGs) from water and wastewater systems. RECENT FINDINGS: There is a linear correlation between the concentration of antibiotics in wastewater and the emergence of ARBs and the presence of ARGs. Wastewater treatment plant (WWTP) remains as one of the primary sources for ARB and ARG, even though the occurrence of ARBs and ARGs has also been reported in environment with no anthropogenic impact. Conventional removal techniques are available together with newer approaches that promises higher ARBs and ARGs removal efficiencies. Use of bioinformatic tools such as plasmidome is important to ensure sufficient information on ARGs, which may be directly mobilized and transferred to pathogens, can be obtained and analyzed. This review highlights the effects of continuous exposure to ARBs and ARGs present in the environment, notably wastewater, to human health. Various sources of antibiotics, classes of ARBs, and types of ARGs are adequately covered including highlights on recent reports from different countries. Conventional and newer approaches to remove ARBs and ARGs from wastewater were also elaborated to further assist reader’s understanding on the subject matter discussed.

PURPOSE OF REVIEW: Effluent organic matter (EfOM) is a blend of organic matter, microbial constituents, biological metabolites, and synthetic chemicals which is originated mainly due to anthropogenic activities and is a matter of emerging environmental concern. The presence of EfOM poses a major challenge in the wastewater treatment processes. This review is aimed to assess the recent progress in developing innovative green approaches for the biotransformation of EfOM into ecofriendly products which is vital to attain the “zero-waste” paradigm to achieve wastewater reclamation and environmental sustainability under the umbrella of circular bioeconomy. RECENT FINDINGS: Characteristics of EfOM and its impact on wastewater treatment processes have been evaluated. The potential and shortcomings of the traditional, advanced, and biological approaches for the EfOM removal have been described. Recent strategies which are based on the combination of two or more of these technologies (hybrid systems) have been discussed to address the challenges/shortcomings of the standalone technologies and to improve the process efficiency. Microalgae and cyanobacteria-based removal of EfOM along with its subsequent utilization as a soil amender is proposed as a novel trend in the future. Assessment of the previously employed technologies provided an insight into their working mechanisms which have suggested several improvements in the processes. Besides, hybrid systems could be an ecofriendly removal of EfOM via biosorption.

Anthropogenic activities have impacted the coastal region of Brazil. In the Paranaguá estuarine complex (PEC), Cananéia-Iguape estuarine-lagoon complex (CIELC), and Santos-São Vicente estuarine complex (SSVEC), such activities occur across differing scales. In these estuaries, the concentrations of mercury (Hg) and stable nitrogen isotopes (δ¹⁵N) were investigated in sediments and marine organisms including benthic macrofauna, fish and cetaceans. Hg bioconcentration occurred primarily in cetaceans, polychaetes and molluscs, and reflects the impact of anthropogenic activities in the regions studied (PEC and SSVEC > CIELC). Bioaccumulation occurred in most of the studied specimens, but biodilution of Hg was observed in the trophic webs of SSVEC and CIELC. Despite measuring lower Hg levels than in studies carried out in the northern hemisphere, the results highlight potential concerns for public and environmental health in these highly productive coastal regions in the southwestern Atlantic which are important for fishing and various economic activities.

Ascidians are an ideal taxon to study invasion processes: they require anthropogenic introduction vectors for long-distance dispersal, are easy to collect and monitor, and are abundant on artificial substrates. In March 2019 we surveyed 11 harbors around Puerto Rico and recorded 47 ascidian species. Eleven of these were only identified to the genus level or above based on morphological or genetic characterization. The remaining 36 species were classified as: 11 introduced (7 with worldwide distributions), 13 cryptogenic, and 12 native. We report the occurrence of Phallusia cf. philippinensis in the Atlantic for the first time. Ascidian community structure did not differ significantly across geographic locations and distances between marinas, while marina size had a significant effect on species richness and composition. Stakeholder involvement and periodic monitoring efforts are essential to detect the arrival of new species and the spread of already introduced ones to natural habitats.

Mercury (Hg) is a well-known toxicant which enters the marine environment by both natural and anthropogenic sources. Consumption of fish and other seafood that contain methylmercury (MeHg) is a leading source of Hg exposure in humans. Considerable efforts have been made to mitigate the Hg presence and reduce its risks to humans. In this review the acknowledged methods of mitigation are summarized such as regulation and maximum allowable limits, and culinary treatments. In addition, selected industrial level trials are reviewed, and studies on Hg intoxication and the protective effects of the essential trace element, selenium (Se), are discussed. In view of the available literature, Hg reduction in fish and other seafood on a large industrial scale still is largely unsuccessful. Hence, more research and further attempts are necessary in order to better mitigate the Hg problem in fish and other seafood products.

The present study examines historical perspectives of the macrobenthic community in response to different phases of anthropogenic perturbations in Kakinada Bay, a tropical embayment on the east coast of India. Multivariate analysis of the snapshot data (1958–2017) revealed considerable changes in the Bay environment following a breakwater construction across the Bay mouth in 1997. Subsequently, port expansion activities, industrialization, urbanization, and geomorphic alterations in the Godavari delta brought deterrent changes in the Bay. The fluctuations over the years in hydrographical and sediment characteristics increased environmental heterogeneity and caused significant spatio-temporal shifts in the macrobenthic community between 1995-1996 and 2016-2017. The observed variabilities were suggestive of anthropogenic perturbations of the system with future repercussions on Bay ecosystem functioning. Overall, this study provides evidence on the long-term impact of anthropogenic activities on coastal marine communities and stresses the importance of macrobenthos as bioindicators of such changes in tropical systems.