Mineralogical and hydrogeological study of "pouhons" in the lower Palaeozoic formations of the Stavelot-Venn Massif, Belgium

Numerous naturally CO2-rich mineral water springs, locally called pouhons, occur in the Stavelot-Venn Massif. These water springs show a particular composition with a high content of iron, manganese and lithium, and are characterised by a red-orange colour resulting from iron hydroxide precipitation near the land surface. Radon measurements have shown that these ferruginous deposits are weakly radioactive. The Upper Cambrian black shales of the La Gleize Formation are also known to display radioactive anomalies. These rocks show enrichment in HFSE (Pb, U, Y, Ce, Zr, Ti, Nb) and are depleted in transition metals (Co, Ni, Cu, Zn). Specific minerals such as florencite-(Ce), monazite-(Ce), xenotime-(Y) and zircon have been identified and are probably at the origin of the radioactive anomalies. Uranium was gradually leached from these minerals, transported in solution, and finally concentrated in ferruginous muds. These muds are mainly composed of goethite (most often amorphous), residual quartz and calcite in some samples. The most probable hypothesis is that uranium is adsorbed in small concentrations on the goethite surface. On the other hand, the Ottré Formation (Ordovician) appears to be the main source of lithium, iron and manganese. Pouhon waters have therefore probably leached rocks of various mineralogy and chemical composition during their sub-surface circulation.

Seasonal and interannual variability in the density of the postlarvae of Litopenaeus setiferus and Farfantepenaeus duorarum in Términos Lagoon, Gulf of Mexico

White shrimps, Litopenaeus setiferus (Linnaeus, 1767) and pink shrimps, Farfantepenaeus duorarum (Burkenroad, 1939) are two pivotal species in the southern Gulf of Mexico, due to their ecological and economic importance. In this study we present observational evidence of the seasonal and interannual variability of both species in the Términos Lagoon (southern Gulf of Mexico). The results suggest that the hydrography of the water column and the surface circulation exert a strong influence on the density of both species. The results presented here contribute to a better understanding of the dynamics of both species and highlight the need to combine different methodologies to achieve a better interpretation of this system.

Connectivity Analysis Applied to Mesoscale Eddies in the Western Mediterranean Basin

The Western Mediterranean basin (WMED) is characterized by the presence of energetic and dynamic mesoscale cyclonic and anticyclonic eddies. They mainly originate along the Algerian and the Northern currents and have a large influence on the basin circulation. Eddies can last for months, with longer lifetimes associated with the anticyclones, which can move far from their areas of origin. As they partially isolate and transfer water masses, they also have an impact on water properties (physical, chemical and biological), pollutant’s dispersion and transport of eggs, larvae and planktonic organisms. In this study, a connectivity analysis method is applied to the anticyclonic eddies (AEs) identified by an automated hybrid detection and tracking algorithm south of 42° N in the WMED. The same methodology is also applied to the trajectories of Lagrangian surface drifters available in the study area. The purpose is to highlight the connections between different areas of the basin linked to eddy activities in addition to the connectivity due to the mean surface circulation. Drifter data analysis showed that all the WMED sub-basins are strongly interconnected, with the mean surface circulation allowing a shortcut connection among many areas of the basin. The connectivity analysis of the AEs tracks shows that although AEs are ubiquitous in the WMED, their connectivity is limited to well-defined regions, depending on their origin location. Three main regions: the south-western, the south-eastern and the northern parts of the basin are characterized by AEs recirculation, with sporadic export of eddies to the other WMED zones.

Distribution Patterns of Floating Microplastics in Open and Coastal Waters of the Eastern Mediterranean Sea (Ionian, Aegean, and Levantine Seas)

Microplastic pollution is a pervasive anthropogenic phenomenon at the ocean surface. Numerous studies have been performed worldwide; nevertheless, the distribution patterns, morphological properties, and sources of origin in the Eastern Mediterranean Sea are still poorly explored. The purpose of this study is to investigate the distribution patterns of surface floating microplastics (MPs) in the Ionian, Aegean, and Levantine Seas in relation to their sources and sea surface circulation. In total, eighty-four samples were collected using manta nets from 2014 to 2020, covering open waters, coastal waters, and enclosed gulfs (Corfu and Saronikos). MPs concentration measurements revealed high variability ranging from 0.012 to 1.62 items m–2 and did not present maximum concentrations close to MPs hotspot areas. The presence of sea surface slicks, as recorded visually during our samplings, seems to play a key role on the distribution pattern of MPs, and highest concentrations were recorded in samples affected by these formations. The dominant MPs shape type identified were fragments (50–60%), whilst filaments (1–23%), films (3–26%), and foams (0–34%) varied among the studied areas. The majority of MPs in open waters had sizes ≤2 mm peaking between 0.6 and 1.4 mm. Spectroscopic analysis of MPs revealed the presence of 11 polymer types in both open sea and gulfs; the most abundant type was polyethylene (PE), followed by polypropylene (PP), and polystyrene (PS). The relative abundance of polymer types was more diverse in Saronikos Gulf, compared to the open sea due to the proximity to major urban and industrial sources. Our findings suggest that the vicinity to coastal population centers determined the properties, size and polymer types of MPs and highlight that MPs concentrations are affected significantly by local oceanographic conditions, such as surface slicks.