PURPOSE OF REVIEW: Increasing environmental problems demand mitigation solutions to fulfill sustainability development goals. Microalgae offer possibility of valorizing the CO₂ and wastewater-derived nutrients to produce numerous industrial bioproducts. However, developing self-sustained systems for the complete valorization of algal biomass into valuable biobased products is challenging. Currently, sustainable algal processing faces several challenges including costly cultivation, difficult harvesting, and incomplete biomass valorization. This review assessed the prospects of emerging technologies focusing on the integrated approaches for sustainable algal biorefinery development ensuring the sustainability of environment-water-energy nexus. RECENT FINDINGS: Evaluation of various upstream, midstream, and downstream processing technologies provided insights into the processing issues. In upstream processing, high-rate algal ponds and integrated carbon capture and transformation technologies offer waste valorization into eco-friendly algal production. A brief comparison of harvesting technologies mainly focusing on chemical and biological flocculation has shown that integrating physical and biological harvesting methods are more reliable and efficient. Overview of downstream processing has indicated that biomass processing in a cascading manner offers the complete biomass valorization in a zero-waste paradigm. Assessment of cultivation-to-production technologies highlighted that “zero-waste” algal biorefinery has the potential to become reality by integrating the industry 4.0 and phenomics approaches with eco-friendly cultivation, harvesting, and processing technologies. Hybrid methods based on integrated cascading processing offer complete biomass valorization in a circular bioeconomy paradigm.

Discarded plastic bag is a main component of marine debris, posing potential threats to marine biota. This study was conducted to assess the potential effects of microplastics on juvenile Lates calcarifer. Fish were exposed via diet to two microplastic types from conventional polyethylene (PE) and biodegradable (Bio) plastic bags for 21 days. Antioxidative enzymes activity, intestinal microbiome and proteome were determined. PE and Bio microplastics were found to accumulate in gastrointestinal tracts, and no mortality was observed. Microplastics exposure did not induce significant antioxidant response except for the glutathione reductase (GR) modulation. Intestinal microbiome diversity decreased significantly in PE group based on Simpson index. Both types of microplastics induced proteome modulation by down-regulating proteins associated with immune homeostasis. Bio microplastics maintained higher intestinal microbial diversity and induced more proteins alteration than PE microplastics. This study provides toxicological insights into the impacts of conventional and biodegradable microplastics on juvenile L. calcarifer.

This study collected 100–1000 L of surface water from 70 to 74 sites in the Inner Gulf of Thailand in both dry and wet seasons to investigate the relationship between the spatiotemporal distribution of microplastics and environmental variables. The quantity of microplastics in the wet season (34.59 ± 46.02 pieces/L) was significantly higher than the dry season (8.70 ± 15.34 pieces/L). Spatial distribution revealed an abundance of microplastics in river estuaries and seasonal current circulations. Polymeric characterization results showed that the plastic samples primarily consisted of polypropylene and polyethylene. New functional groups, including carbonyl, hydroxyl, and vinyl groups, were found in the chemical structures of the microplastic samples. The amount of freshwater runoff and the negative relationship with salinity confirmed that the river is the key factor in the transportation of microplastics to the coastal sea.

Concentrations of 13 phase-partitioned polycyclic aromatic hydrocarbons (PAHs) in seawater were monitored monthly off Oki Island, Japan, during 2015–2019 to elucidate seasonal variations, main source, and transport pathways of PAHs in the southwestern Sea of Japan. Total PAH (dissolved plus particulate) concentrations in surface seawater at 36°09.0′N, 133°17.3′E (site OK) were in the range 0.49–9.36 ng L⁻¹ (mean 2.77, SD 2.05 ng L⁻¹) with higher levels in summer–autumn, an order of magnitude lower than those in the East China Sea during 2005 and 2009–2011 and about one-third of those recorded in the Sea of Japan in 2008 and 2010. The main sources of dissolved and particulate PAHs were combustion products. Increasing dissolved PAH levels during July–October indicate that the area around southern Oki Island is impacted by PAH-rich summer continental-shelf water transported by the Tsushima Warm Current flowing from the East China Sea.

Proliferation of microplastics in rivers, lakes, estuaries, coastal waters and oceans is a major global challenge and threat to the environment, livelihoods and human health. Reliable predictive tools can play an essential role in developing an improved understanding of microplastics behaviour, exposure and risk in water bodies, and facilitate identification of sources and accumulation hot spots, thereby enabling informed decision-making for targeted prevention and clean-up activities. This study presents a new numerical framework (CaMPSim-3D) for predicting microplastics fate and transport in different aquatic settings, which consists of a Lagrangian, three-dimensional (3D) particle-tracking model (PTM) coupled with an Eulerian-based hydrodynamic modeling system (TELEMAC). The 3D PTM has several innovative features that enable accurate simulation and efficient coupling with TELEMAC, which utilizes an unstructured computational mesh. The PTM is capable of considering spatio-temporally varying diffusivity, and uses an innovative algorithm to locate particles within the Eulerian mesh. Model accuracy associated with different advection schemes was verified by comparing numerical predictions to known analytical solutions for several test cases. The implications of choosing different advection schemes for modeling microplastics transport was then investigated by applying the PTM to simulate particle transport in the lower Saint John River Estuary in eastern Canada. The sensitivity of the PTM predictions to the advection scheme was investigated using six numerical schemes with different levels of complexity. Predicted particle distributions and residence times based on the fourth-order Runge–Kutta (RK4) scheme differed significantly (residence times by up to 100 %) from those computed using the traditional first-order (Euler) method. The Third Order Total Variation Diminishing (TVD3) Runge-Kutta method was found to be optimal, providing the closest results to RK4 with approximately 27 % lower computational cost.

Particulate matter (PM₂.₅) generated in large cities creates new problems in marine ecosystems and may adversely affect its inhabitants. However, the mechanisms underlying the same remain unclear; hence, we investigated the effects of PM₂.₅ on life history traits (e.g., mortality, development, and fecundity), cellular reactive oxygen species (ROS) levels, antioxidant enzyme (e.g., glutathione peroxidase [GPx], superoxide dismutase [SOD], and catalase [CAT]) activities, and the transcript levels of detoxification-related genes (cytochrome P450s [CYPs]) and antioxidant (glutathione S-transferases [GSTs]) in the copepod Tigriopus japonicus. Among the life history traits, developmental time was the only trait to significantly deviate (P < 0.05) in response to PM₂.₅ (compared to that in the controls). Significant changes in ROS levels and antioxidant enzymatic activities (P < 0.05) in response to PM₂.₅, suggested that PM₂.₅ can induce oxidative stress, leading to adverse effects on the T. japonicus life history. In addition, PM₂.₅ induced a differential regulation of various CYP and GST genes, particularly CYP307E1, GST-kappa, and GST-sigma were significantly upregulated (P < 0.05), suggesting that these genes likely play crucial roles in detoxification mechanisms and could be useful as reliable biomarkers for PM₂.₅ toxicity. Overall, the results of this study provide new insights into the potential toxicity of PM₂.₅.

Maritime traffic is increasing globally, with a four-fold increase in commercial vessel movements between 1992 and 2012. Vessels contribute to noise and air pollution, provide pathways for non-native species, and collide with marine wildlife. While knowledge of shipping trends and potential environmental impacts exists at both local and global levels, key information on vessel density for regional-scale management is lacking. This study presents the first in-depth spatio-temporal analysis of shipping in the north-east Atlantic region, over three years in a five-year period. Densities increased by 34%, including in 73% of Marine Protected Areas. Western Scotland and the Bay of Biscay experienced the largest increases in vessel density, predominantly from small and slow vessels. Given well-documented impacts that shipping can have on the marine environment, it is crucial that this situation continues to be monitored – particularly in areas designated to protect vulnerable species and ecosystems which may already be under pressure.

Distribution of five heavy metals (Cd, Cr, Cu, Pb, and Zn) in molluscan and echinoderm species collected from Kerala and Gulf of Mannar in Southern India is presented. Atomic absorption spectrometry was used to determine metal concentrations. Concentrations of metals showed a descending order of Zn > Cu > Pb > Cd > Cr. Zn and Cu might have originated from both natural and man-made sources. However, Cd, Cr, and Pb could have strong anthropogenic influences such as harbour activities and untreated industrial and agricultural runoff. Bioaccumulation factor (BAF) value of Cd in two edible bivalves from Munambam is slightly greater than one. Regular consumption of Cd-loaded shellfish can cause serious health hazards and concerns to humans. BAF results showed that Zn, Cu, Pb, and Cd were more bioaccumulated and beyond the threshold limits in certain species. It is evident that consumption of shellfish from the Kerala coastal waters may have adverse health impacts to the consumers.

Organic pollutants are ubiquitous in estuarine areas, nonetheless, the transport mechanisms of herbicides in such areas are limited. Atrazine and acetochlor were analyzed in suspended particle matter (SPM), surface sediment, and surface water from the Yellow River estuary and the surrounding rivers and sea. Among these rivers, the Yellow River contributes the most herbicide flux to the sea annually. The herbicide concentrations in water and sediment decreased from the estuarine areas to the deep sea. The fugacity fraction values of atrazine exceeded 0.5 in the Yellow River estuary, which supported that the herbicides in sediment desorbed at the estuarine areas. The herbicide in the SPM showed high concentration in the outer sea and increased as a power function with decreasing SPM content. The increasing partition capacity indicated that the herbicides tended to sink into sediment, increasing the ecological risk posed by herbicides. The ecological risk of acetochlor deserves continuous attention.

Collected sediment samples from the cage fish farm were measured to determine carbon and nitrogen stable isotope compositions and to understand the influence of the aquaculture waste on the sediment. The average δ¹³C of the sediment organic matter was −27.2 ‰ and −26.5 ‰, and the average δ¹⁵N value was 5.6 ‰ and 6.2 ‰ in October 2017 and November 2018, respectively. A linear mixing model was used to calculate the contribution ratios of the aquaculture waste in sediment organic matter. The contribution ratio of fish feces was 53.9 % and 25.5 %, and the contribution ratio of waste feed was 18.4 % and 52.6 % in October 2017 and November 2018, respectively. The sediment in the “cage fish area” was characterized by high waste feed ratio in sediment organic matter. The sediment organic matter was affected by the aquaculture waste even at sites 1500 m away from the cage fish farm.