PAH levels in sediments from a coastal area heavily subjected to anthropogenic pressure (Asturias, north of Spain)

Physiological responses and adaptive mechanisms of the harmful algal bloom species Heterosigma akashiwo to naphthalene exposure

Polycyclic aromatic hydrocarbons (PAHs), especially naphthalene (Nap), pose a significant threat to coastal ecosystems and may contribute to the occurrence of harmful algal blooms (HABs). However, the response mechanisms of HAB species to PAH pollution remain unclear. This study investigated the physiological and molecular responses of the HAB species Heterosigma akashiwo to varying Nap concentrations. Low concentrations (1-10 μg/L) promoted growth, while high concentrations (20-1000 μg/L) inhibited growth, causing abnormal cell morphology and oxidative stress. Within 96 h, H. akashiwo removed 82.38 % (10 μg/L) and 88.93 % (100 μg/L) of Nap, mainly through biodegradation and intracellular accumulation. Transcriptomic analysis revealed that H. akashiwo employs a multifaceted adaptive strategy to cope with Nap stress. Key mechanisms include the upregulation of calcium signaling, transcription factors (e.g., zinc finger protein C2H2, myeloblastosis transcription factor, basic leucine zipper transcription factor), heat shock proteins (e.g., HSP40), and fatty acid desaturase (FAD), enhancing stress tolerance through detoxification, antioxidant responses, and membrane integrity. Activation of peroxisomal and oxidative phosphorylation genes indicates improved detoxification and energy metabolism. Differential expression of genes in the PI3K-Akt pathway reveals dose-dependent growth responses, with low concentrations promoting proliferation and high concentrations inhibiting growth. These findings offer insights into H. akashiwo's adaptive responses to Nap, aiding ecological risk assessment and bioremediation strategies for PAH pollution in marine environments.

Assessment of polycyclic aromatic hydrocarbon concentrations in the sediments of an estuary heavily affected by heavy industrial activities

The Aviles estuary is one of the most anthropized in Spain due to the significant pressure exerted on it by industry. This study assesses the concentrations, origins, sources, and environmental implications of 16 polycyclic aromatic hydrocarbons (PAHs) as persistent contaminants of the estuary sediments. A total of 79 sediment samples were studied. Results indicate ∑16PAH concentrations ranging from 0.086 to 305.771 μg g-1, with the highest values in the estuary's main channel. High-molecular-weight PAHs (4-6 rings) were predominant, suggesting a pyrogenic origin associated to industrial combustion processes. Lower molecular weight PAHs (2-3 rings) were mainly observed near the estuary mouth. Diagnostic ratio analysis confirmed that PAHs in the estuary predominantly originate from mixed combustion sources, including industrial processes, vehicle emissions, and maritime activities. Spatial distribution maps identified three contamination hotspots: (i) the Albares River, linked with steel industry emissions; (ii) a central estuary site near an aluminium smelter discharge point, connected to PAHs from industrial operations; and (iii) the estuary mouth, where PAHs from industrial wastewater discharges and shipping activities were detected. Cluster analysis further distinguished areas with similar contamination profiles, confirming the influence of industrial and maritime activities. Finally, the risk assessment comparisons with international pollution thresholds revealed that PAH levels in the Avilés Estuary are significantly higher than in other European and global estuarine environments. Over 90 % of samples exceeded both low and median effect range limits, indicating substantial toxicity risks. Moreover, ecological risk quotient classified 92 % of sediment samples as posing a high risk to aquatic life.

Anthropogenic stressors that favour nuisance species. A study from environmental DNA in marine plankton samples

Anthropogenic stressors reduce marine biodiversity. Tolerant species may develop in altered areas where they occupy niches that native species are unable to use. Species of biosecurity concern, like invasive aliens or harmful microalgae, are especially successful in disturbed areas. Here, we employed multiple regression approach to investigate the relationship between the proportion of planktonic stages of invasives and anthropogenic stressors. Planktonic species were inventoried from environmental DNA on water samples from the Bay of Biscay. Key findings were that the proportion of invasives was associated with port and touristic activities that are vectors for biological invaders, and with industrial pollution, likely for their tolerance to disturbed environments. The proportion of toxic algae was correlated with port activity, reinforcing the role of maritime traffic as a vector of harmful microalgae. An increase of nuisance species is expected under the current growth of pollution in the ocean. Promoting awareness of biological invasions among maritime sectors and tourists, and controlling pollution, seem priorities for environmental conservation in this region and elsewhere.

Environmental impact and mobility of thallium and other metal(oid)s in soils and tailings near a decommissioned Zn-Pb mine (Raibl, NE Italian Alps)

The potential impact of decommissioned mining areas on environmental quality is of major concern for local communities, posing a risk to water resources and human health. This study aims to investigate the impact of extraction activities on the surface environment by evaluating the occurrence of metal(oid)s, including potentially toxic elements (PTEs, i.e. As, Cd, Fe, Tl, Zn, Pb) and critical elements (As, Ge), at the Zn-Pb Raibl mining area (northeastern Italy). Elevated concentrations of metal(oid)s are found near mine waste heaps (< 100 mg/kg for Tl, Sb, Cd, Ge; > 1,000 mg/kg for As; > 1% for Pb and > 10% for Zn and Fe), which are made up of flotation tailings and waste rocks scattered around the mining village and stored in the tailings impoundments. Conversely, upstream from the mine, the environment is largely uncontaminated. According to the results, total and leachable metal(oid) concentrations are positively correlated. Tailings (65.1-754 mg/kg of Tl) are identified as the primary source of leachable Tl (11.4-255 mg/kg) and metal(oid)s are generally more mobile in organic-rich soils, suggesting increased metal(oid) mobility with soil ageing due to low soil pH and potential soluble organometallic complexes. Furthermore, the findings suggest that reprocessing of mine tailings could be a potential solution to recover valuable elements together with residue backfilling. Lastly, results from this study highlight how crucial mining site management is to limit PTE dispersion and reducing risks to the environment and public health.

Polycyclic aromatic hydrocarbons in sediments and bivalves along the Moroccan Mediterranean coast: Spatial distribution, sources, and risk assessment

Polycyclic aromatic hydrocarbons (PAHs) are commonly found in the marine environment and can have harmful impacts on marine biodiversity. Therefore, investigation of the occurrence, source and risks of PAHs is of great importance to protect ecosystem and human health. The objectives of this work were to assess the concentrations and distribution of PAHs in marine sediments and in mollusc bivalve (Callista chione) along the Mediterranean coasts of Morocco and finally evaluate the risk to human health caused by exposure to PAHs. Five sediments samples and seventy five C. chione specimens, were collected along the Moroccan Mediterranean coasts. The ∑PAHs levels in sediment varied considerably, varying from 1 to 251 ng/g with an average of 50.38 ng/g, while values for bivalves varied from 1 to 51 ng/g dw with an average concentration of 16.76 ng/g dw. The PAHs profile indicates the dominance of 2 and 3 rings PAHs both in bivalves and sediments. PAH concentrations generally rise as one moves from northeast to northwest part of the studied area, closer to the Strait of Gibraltar. The assessment of PAH isomeric ratios revealed a mixed pyrolytic/petrogenic source. Based on the sediment quality guidelines (SQGs), the risk of PAHs in the sediments was considered to be comparatively low. Similarly, Ecological risk assessment based on risk quotient (RQ) and toxic equivalency factors (TEFs) revealed potentially low ecological risks from PAHs. Exposure to PAHs via bivalve consumption does not cause adverse impacts on the health of consumers following the calculated health risk indices. As the levels of PAHs in biota are not negligible, continuous mentioning marine organisms campaigns should be performed to highlight the distribution and concentration of PAHs and assess the risk for human health from consumption of seafood.

PAHs contamination in ports: Status, sources and risks

Polycyclic aromatic hydrocarbons (PAHs) constitute important organic contaminants that have been degrading coastal ecosystems over the years. Evaluating PAH status in port ecosystems aligns with societal goals of maintaining clean habitats and sustainability. This comprehensive review systematically analyzed 123 articles, exploring the global distribution, sources, and ecological risks linked to PAH contamination in ports, focusing on water, sediment, and biota. The mean concentrations of 16 PAHs in water, sediment, and biota across worldwide ports were 175.63 ± 178.37 ng/L, 1592.65 ± 1836.5 μg/kg, and 268.47 ± 235.84 μg/kg, respectively. In line with PAH emissions and use in Asia, Asian ports had the highest PAH concentrations for water and biota, while African ports had the highest PAH concentrations for sediment. The temporal trend in PAH accumulation in sediments globally suggests stability. However, PAH concentrations in water and biota of global ports exhibit increasing trends, signaling aggravating PAH contamination within port aquatic ecosystems. Some ports exhibited elevated PAH levels, particularly in sediments with 4.5 %, 9.5 %, and 21 % of the ports categorized as very poor, poor, and moderate quality. Some PAH isomers exceeded guidelines, including the carcinogenic Benzo(a)pyrene (BaP). Coal, biomass, and petroleum combustion were major sources for PAHs. The structure of ports significantly influences the concentrations of PAHs. PAH concentrations in sediments of semi-enclosed ports were 3.5 times higher than those in open ports, while PAH concentrations in water and biota of semi-enclosed ports were lower than those in open ports. Finally, risk analyses conducted through Monte Carlo simulation indicated moderate to high risks to aquatic species, with probabilities of 74.8 % in water and 34.4 % in sediments of ports worldwide. This review underscores the imperative to delve deeper into the accumulation of PAHs and similar pollutants in ports for effective management and environmental protection.

Ecotoxicological and health risks associated with sediment-bound polycyclic aromatic hydrocarbons in peri-urban closed and open coastal lagoons

Coastal urbanisation has ramifications for the sustainable development of developing nations. There are often unquantified ecological and health risks associated with urbanisation. Sixteen polycyclic aromatic hydrocarbons (PAHs) were analysed in surface sediment from three peri-urban coastal lagoons in southern Ghana. We found significant spatial variations of sediment PAHs. These variations were attributed to physiography of the lagoons and diverse anthropogenic activities surrounding them. Total PAHs ranged from 20.81 to 24,801.38 μg/kg (dry weight), underscoring a low to very high pollution level. Diagnostic ratios revealed both pyrogenic and petrogenic origins. Over 50 % of individual PAHs were of moderate ecological risk to benthic organisms, and cancer risk to humans was above the World Health Organisation's recommended safety limit (1 × 10-6). These ecological and health risks should be wake-up call for a more integrated urban planning approach to coastal urbanisation as coastal communities largely depend on natural ecosystems for food and livelihood opportunities.