Geochemical and Geophysical Monitoring of Hydrocarbon Seepage in the Adriatic Sea

Advancements in Detection and Mitigation Strategies for Petroleum-Derived Contaminants in Aquatic Environments: A Comprehensive Review

The exponential increase in the production and transportation of petroleum-derived products observed in recent years has been driven by the escalating demand for energy, textiles, plastic-based materials, and other goods derived from petroleum. Consequently, there has been a corresponding rise in spills of these petroleum derivatives, particularly in water sources utilized for transportation or, occasionally, illegally utilized for tank cleaning or industrial equipment maintenance. Numerous researchers have proposed highly effective techniques for detecting these products, aiming to facilitate their cleanup or containment and thereby minimize environmental pollution. However, many of these techniques rely on the identification of individual compounds, which presents significant drawbacks, including complexity of handling, subjectivity, lengthy analysis times, infeasibility for in situ analysis, and high costs. In response, there has been a notable surge in the utilization of sensors or generalized profiling techniques serving as sensors to generate characteristic fingerprints of these products, thereby circumventing the aforementioned disadvantages. This review comprehensively examines the evolution of techniques employed for detecting petroleum-derived products in water samples, along with their associated advantages and disadvantages. Furthermore, the review examines current perspectives on methods for the removal and/or containment of these products from water sources, to minimize their environmental impact and the associated health repercussions on living organisms and ecosystems.

Anthropogenic contribution, transport, and accumulation of Polycyclic Aromatic Hydrocarbons in sediments of the continental shelf and slope in the Mediterranean Sea

A multidisciplinary approach, involving geochemical, sedimentological and oceanographic analyses, was employed to examine the distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in a strongly anthropized area of the marginal Adriatic Sea (Mediterranean basin). The investigation into PAH distribution considered the grain size and biogeochemical properties of the sediments, as well as in relation to the main oceanographic processes and river inputs. Both biogeochemical and hydrographical inputs regulated the sedimentation of organic particles, influencing the distribution of PAHs. The results indicated PAH levels in 116 marine surface sediments ranging from 4 to 235 ng g-1 (average 55 ng g-1). The distribution of PAHs in Adriatic Sea surface sediments aligned with a higher clayey sedimentation in the deeper basin areas of the Middle Adriatic Depression.

Potentiometric-Type Gas Sensor Using MgFe2O4 Sensing Electrode for Detection of Hydrocarbon Based on Carbon Number

Hydrocarbon (HC) monitoring is necessary for safe and effective operations in industries such as petroleum and gas. In this study, total hydrocarbons can be detected by using yttria-stabilized zirconia (YSZ)-based potentiometric-type gas sensor using MgFe₂O₄ sensing electrode (SE). The sensor was found to generate a similar response magnitude to those of hydrocarbons that have the same carbon number, irrespective of the type of carbon bond (total hydrocarbon detection). Aside from being capable of detecting total hydrocarbons sensitively and selectively with rapid response time, the sensor using MgFe₂O₄-SE also exhibited a linear relationship between sensor responses and carbon number. In addition to that, the developed sensor showed a logarithmically linear relationship between sensor responses and HC concentration in the range 20-700 ppm. These sensing characteristics were confirmed to be reproducible, and sensor responses toward HC were found to be repeatable and gradually decreased with increasing in O₂ concentration in the range of 3-21 vol %.

Mercury levels in Merluccius merluccius muscle tissue in the central Mediterranean Sea: Seasonal variation and human health risk

In this study we analysed total mercury (THg) levels in European hake (Merluccius merluccius) - an ecologically and commercially important species throughout the Mediterranean - caught in the northern and central Adriatic Sea. To the best of our knowledge, this is the first study evaluating THg levels in hake fillets in relation to ecological (season) and biological (body size, sex, sexual maturity, lipid content) parameters. THg levels in muscle showed no sex-related differences; in contrast, significant season-related differences were found in females, with higher levels in spring-summer compared with autumn-winter. No season-related differences were seen in males. A significant sex effect was found for body size and sexual maturity. Females showed a correlation between THg level and length, THg being significantly higher in mature compared with immature specimens. No significant sex effect was found for muscle lipid content, because a correlation between THg concentration and tissue lipids was found in both sexes. Since the mean THg concentration found in M. merluccius fillets (0.64 ± 0.29 mg kg^-1 dry weight; range, 0.20-1.53) was consistently under the level set by EU regulations, this study demonstrates that European hake caught in the northern and central Adriatic is safe for human consumption.

Assessment of seasonal relationship between polycyclic aromatic hydrocarbon accumulation and expression patterns of oxidative stress-related genes in muscle tissues of red mullet (M. barbatus) from the Northern Adriatic Sea

In this study, we examined the seasonal association between Polycyclic Aromatic Hydrocarbon (PAH) concentrations and mRNA expression profiles of some antioxidant genes (i.e. CAT, GST and SOD), as well as lipid peroxidation (LPO), in muscle of sexually inactive females of red mullet (Mullus barbatus). Fish were captured in a fishery area of the Northern Adriatic Sea during both winter and summer. We found significantly (p < 0.05) higher ∑HMW-PAHs concentrations in muscle of specimens caught during winter than summer. On the basis of sampling season, red mullets exhibited different gene expression profiles of antioxidant enzymes showing lower levels of both CAT and GST in winter than in summer. Accordingly, CAT was found to be negatively associated with ∑PAH concentrations, especially ∑LMW-PAH, in individuals collected during winter. Seasonal-related downregulation of some oxidative stress biomarker expression is suggestive of greater susceptibility of red mullets to PAHs during winter.

Bacterial and archaeal diversity in oil fields and reservoirs and their potential role in hydrocarbon recovery and bioprospecting

Hydrocarbon is a primary source of energy in the current urbanized society. Considering the increasing demand, worldwide oil productions are declining due to maturity of oil fields and because of difficulty in discovering new oil fields to substitute the exploited ones. To meet current and future energy demands, further exploitation of oil resources is highly required. Microorganisms inhabiting in these areas exhibit highly diverse catabolic activities to degrade, transform, or accumulate various hydrocarbons. Enrichment of hydrocarbon-utilizing bacteria in oil basin is caused by continuous long duration and low molecular weight hydrocarbon microseepage which plays a very important role as an indicator for petroleum prospecting. The important microbial metabolic processes in most of the oil reservoir are sulfate reduction, fermentation, acetogenesis, methanogenesis, NO3- reduction, and Fe (III) and Mn (IV) reduction. The microorganisms residing in these sites have critical control on petroleum composition, recovery, and production methods. Physical characteristics of heavy oil are altered by microbial biotransformation and biosurfactant production. Considering oil to be one of the most vital energy resources, it is important to have a comprehensive understanding of petroleum microbiology. This manuscript reviews the recent research work referring to the diversity of bacteria in oil field and reservoir sites and their applications for enhancing oil transformation in the target reservoir and geomicrobial prospecting scope for petroleum exploration.

Occurrence and distribution of microbial pollutants in coastal areas of the Adriatic Sea influenced by river discharge

The transport of a variety of pollutants from agricultural, industrial and urbanised areas makes rivers major contributors to the contamination of coastal marine environments. Too little is known of their role in carrying pathogens to the coast. We used DNA-based metabarcoding data to describe the microbial community composition in seawater and sediment collected in front of the estuary of the Tronto, the Chienti and the Esino, three Italian rivers with different pollution levels that empty into the north-central Adriatic Sea, and to detect and measure within these communities the relative abundance of microbial pollutants, including traditional faecal indicators and alternative faecal and sewage-associated pollutants. We then applied the FORENSIC algorithm to distinguish human from non-human sources of microbial pollution and FAPROTAX to map prokaryotic clades to established metabolic or other ecologically relevant functions. Finally, we searched the dataset for other common pathogenic taxa. Seawater and sediment contained numerous potentially pathogenic bacteria, mainly faecal and sewage-associated. The samples collected in front of the Tronto estuary showed the highest level of contamination, likely sewage-associated. The pathogenic signature showed a weak but positive correlation with some nutrients and strong correlations with some polycyclic aromatic hydrocarbons. This study confirms that rivers transport pathogenic bacteria to the coastal sea and highlights the value of expanding the use of HTS data, source tracking and functional identification tools to detect microbial pollutants and identify their sources with a view to gaining a better understanding of the pathways of sewage-associated discharges to the sea.

Semi-Automated Data Processing and Semi-Supervised Machine Learning for the Detection and Classification of Water-Column Fish Schools and Gas Seeps with a Multibeam Echosounder

Multibeam echosounders are widely used for 3D bathymetric mapping, and increasingly for water column studies. However, they rapidly collect huge volumes of data, which poses a challenge for water column data processing that is often still manual and time-consuming, or affected by low efficiency and high false detection rates if automated. This research describes a comprehensive and reproducible workflow that improves efficiency and reliability of target detection and classification, by calculating metrics for target cross-sections using a commercial software before feeding into a feature-based semi-supervised machine learning framework. The method is tested with data collected from an uncalibrated multibeam echosounder around an offshore gas platform in the Adriatic Sea. It resulted in more-efficient target detection, and, although uncertainties regarding user labelled training data need to be underlined, an accuracy of 98% in target classification was reached by using a final pre-trained stacking ensemble model.

An integrated approach to assess fish spatial pattern around offshore gas platforms: A pilot study in the Adriatic Sea

Research on abundance and composition of fish assemblages surrounding offshore extraction platforms is essential to evaluate their impact as well as to understand relationships between natural and artificial habitats. Also decommissioning practice, which belongs to the lifecycle of these structures, can be encouraged or discouraged if fish school behaviour in the close proximity of the platform is well understood. With thousands of platforms to be decommissioned around the world in coming decades, understanding such dynamic interactions is key to improve spatial management of marine ecosystems. In this context, this study drafts a work plan that can be used to investigate fish presence and abundance, school movement and qualitative species composition around a platform over long time periods. It integrates fishing captures, multibeam echosounder (MBES) investigations, and drop camera shootings to overcome the limitations of the individual methods. Monthly samplings were conducted at a three-leg gas extraction platform placed at ~80 m depth in the central Adriatic Sea, for one year after its installation. MBES completely insonified the studied area, providing data on school shape, volume, surface area and position throughout the water column. Fishing captures were useful for MBES targets' identification by measuring the presence/abundance of nekto-benthic and pelagic species both in the nearby of the structure and in the open sea, while drop camera shootings added evidence of a few species in close proximity to the poles, which were not censused by the other methods. Results underlined the strong attraction exerted by the platform and the significant influence of the explanatory variable distance on the schools' nominal volume.