Population connectivity of an overexploited coastal fish,Argyrosomus coronus (Sciaenidae), in an ocean-warming hotspot

The West Coast dusky kob Argyrosomus coronus is a commercially exploited fish with a distribution confined to the Angola–Benguela Frontal Zone (ABFZ) of the southeastern Atlantic Ocean. A previous study revealed that during a recent period of local warming the species extended its distribution into Namibian waters, where it hybridised with the resident and congeneric Argyrosomus inodorus. Environmental changes are a major threat to marine biodiversity and when combined with overfishing have the potential to accelerate the decline of species. However, little is known regarding the evolutionary history and population structure of A. coronus across the ABFZ. We investigated genetic diversity, population structure and historical demographic changes using mtDNA control region sequences and genotypes at six nuclear microsatellite loci, from 180 individuals. A single, genetically homogeneous population was indicated across the distributional range of A. coronus (φ_ST = 0.041, F_ST = 0.000, D = 0.000; p > 0.05). These findings imply that the oceanographic features within the ABFZ do not appear to significantly influence population connectivity in A. coronus, which simplifies management of the species. However, reconstruction of the demographic history points to a close link between the evolutionary history of A. coronus and the environmental characteristics of the ABFZ. This outcome suggests the species’ vulnerability to the rapid environmental changes being observed across this region, and highlights a pressing need for transboundary management to mitigate the impacts of climate change in this global hotspot of seawater temperature changes.     

Oxidation and metal-insertion in molybdenite surfaces: evaluation of charge-transfer mechanisms and dynamics

Molybdenum disulfide (MoS₂), a layered transition-metal dichalcogenide, has been of special importance to the research community of geochemistry, materials and environmental chemistry, and geotechnical engineering. Understanding the oxidation behavior and charge-transfer mechanisms in MoS₂ is important to gain better insight into the degradation of this mineral in the environment. In addition, understanding the insertion of metals into molybdenite and evaluation of charge-transfer mechanism and dynamics is important to utilize these minerals in technological applications. Furthermore, a detailed investigation of thermal oxidation behavior and metal-insertion will provide a basis to further explore and model the mechanism of adsorption of metal ions onto geomedia.     

Stone mobility and longshore transport at reshaping breakwaters

Physical model tests have been performed in two different wave flumes to analyse the threshold of stone movement and quantify the frequency and length of displacements due to head-on wave attacks at a reshaping breakwater. Data on stone movements were obtained from the observation of cumulative displacements at the end of each wave attack and from video records during the attack. Threshold conditions, frequency of movement and displacement length are expressed as function of a suitably modified stability number.A simple model is defined relating longshore transport due to oblique wave attack to stone mobility. The transport model is based on the assumption that movement statistics is affected by obliquity only through the appropriate mobility index and that stones move during up- and down-rush in the direction of incident and reflected waves. Without any calibration, results compare favourably with experimental data available in literature in the range of low mobility conditions where movement statistics was observed. A calibration is provided in order to obtain an accurate transport formula valid in a wide mobility range i.e. for reshaping breakwaters and up to gravel beaches.     

Seasonal variations of exposure biomarkers, oxidative stress responses and cell damage in the clams, Tapes philippinarum, and mussels, Mytilus galloprovincialis, from Adriatic sea

This work investigated the natural variability of several biomarkers in Tapes philippinarum and Mytilus galloprovincialis, sampled from Northern Adriatic where these organisms are important sentinel species for future environmental impact assessment. Levels of metallothioneins, peroxisomal enzymes and acetylcholinesterase, showed a significant seasonality and marked differences between clams and mussels. Among antioxidant enzymes, catalase and GST decreased during the warmer period, the latter enzyme activity resulting particularly high in clams. The total oxyradical scavenging capacity toward peroxyl radicals decreased in mussels from winter to summer, indicating a prooxidant challenge due to higher seawater temperature and intensity of light irradiance. Lysosomal membrane stability did not exhibit significant seasonal variations, while some variations were observed for DNA damages. Overall results indicated a significant influence of seasonal variability on several biomarkers and species-specific differences which should be considered to discriminate the appearance of anthropogenic disturbance.     

Wave overtopping and piling-up at permeable low crested structures

The paper aims at providing a simple model for evaluating piling-up, overtopping, filtration and rip currents for low crested structures. The model is essentially based on mass and momentum balance and on resistance laws that relate piling-up and mass fluxes. A procedure is suggested and validated against 2D and 3D experimental data. This procedure is innovative with respect to existing formulations since it applies both to emerged and submerged structures and it simultaneously accounts for structure permeability, return flow through gaps and dissipative effects.     

An ecotoxicological protocol with caged mussels, Mytilus galloprovincialis, for monitoring the impact of an offshore platform in the Adriatic Sea

An ecotoxicological protocol with caged mussels, Mytilus galloprovincialis, was developed to evaluate the potential impact of an offshore gas platform in the central Adriatic Sea. Reference organisms were collected on a seasonal basis from an unpolluted site and transplanted for four weeks in both the sampling area and to the investigated platform. Chemical analyses of trace metals in mussel tissues were integrated with a multi-biomarker approach for the early detection of biological responses at several cellular targets. Induction of metallothioneins, peroxisomal proliferation and activity of acetylcholinesterase were measured as markers for specific classes of chemicals. Special attention was given to oxyradical metabolism and appearance of oxidative-mediated toxicity to reveal a more general onset of cellular disturbance. In addition to individual antioxidants (superoxide dismutase, catalase, glutathione S-transferases, glutathione reductase, Se-dependent and Se-independent glutathione peroxidases, and levels of total glutathione), the total oxyradical scavenging capacity (TOSC) allowed a quantification of the overall capability to neutralize specific forms of intracellular reactive oxygen species (ROS; i.e. peroxyl and hydroxyl radicals). Cellular damages were evaluated as lysosomal destabilization (membrane stability, accumulation of lipofuscin and neutral lipids), lipid peroxidation products (malondialdehyde) and DNA integrity (strand breaks and micronuclei); the air survival test was finally applied to evaluate the overall physiological condition of mussels. Concentration of trace metals (As, Ba, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Zn) revealed only limited variations in transplanted mussels during various experimental periods and such changes appeared partly related to natural fluctuations. Among biological responses, variations of antioxidants and lysosomal stability were confirmed as sensitive early warning signals for biological disturbance of both natural and anthropogenic origin. The presented protocol with caged mussels allowed marked biological effects caused by the investigated platform to be excluded, and represented a useful approach that is easy to extend for monitoring the impact of offshore activities in the Adriatic sea.     

Stream habitat provided by large wood at risk under drainage law

Watershed management efforts in agriculturally dominated landscapes of North America face nearly two centuries of laws and policies that encouraged habitat destruction. Although streams and wetlands in these landscapes are actively being restored using designs that incorporate science and engineering, watershed drainage laws can constrain action or impact passively restored or naturalized habitat. In general, drainage laws require removal of any riparian vegetation or wood deemed to obstruct flow in streams regulated as drains. We use a case study from Indiana (USA) to introduce the shortcomings of drainage laws for allowing large wood, which is an important habitat feature, to remain in stream ecosystems. Removals of large wood from monitored stream reaches in a regulated drain were associated with subsequent declines in fish biomass. Such legal activities represent an important environmental management problem that exists under drainage laws which apply to streams over a widespread geographic region of North America. Recent litigation in Wisconsin (USA) suggests that if state legislatures fail to update these antiquated laws, the courts may act in favour of science-based management of drains. The statutes and regulations that govern agricultural drainage warrant careful consideration if streams within drainage districts are to be managed to improve ecological function. © 2020 John Wiley & Sons, Ltd.