Salvatore Mazzola

Unveiling microbial life in new deep‐sea hypersaline Lake Thetis. Part I: Prokaryotes and environmental settings

In September 2008, an expedition of the RV Urania was devoted to exploration of the genomic richness of deep hypersaline anoxic lakes (DHALs) located in the Western part of the Mediterranean Ridge. Approximately 40 nautical miles SE from Urania Lake, the presence of anoxic hypersaline lake, which we named Thetis, was confirmed by swath bathymetry profiling and through immediate sampling casts. The brine surface of the Thetis Lake is located at a depth of 3258 m with a thickness of ≈ 157 m. Brine composition was found to be thalassohaline, saturated by NaCl with a total salinity of 348‰, which is one of highest value reported for DHALs. Similarly to other Mediterranean DHALs, seawater-brine interface of Thetis represents a steep pycno- and chemocline with gradients of salinity, electron donors and acceptors and posseses a remarkable stratification of prokaryotic communities, observed to be more metabolically active in the upper interface where redox gradient was sharper. [(14) C]-bicarbonate fixation analysis revealed that microbial communities are sustained by sulfur-oxidizing chemolithoautotrophic primary producers that thrive within upper interface. Besides microaerophilic autotrophy, heterotrophic sulfate reduction, methanogenesis and anaerobic methane oxidation are likely the predominant processes driving the ecosystem of Thetis Lake.

Trace element concentrations in red swamp crayfish (Procambarus clarkii) and surface sediments in Lake Preola and Gorghi Tondi natural reserve, SW Sicily.

Concentrations of trace elements (Cd, Pb, As, V, Cr, Ni, Cu and Zn) were determined in superficial sediments and in muscle and hepatopancreas tissues of the red swamp crayfish Procambarus clarkii from Lake Preola and Gorghi Tondi Natural Reserve (SW Sicily). In particular, hepatopancreas showed a decidedly higher content of all analysed trace elements with respect to muscles (two- to threefold higher for Cd, Cu, As, Zn and V; four- to fivefold higher for Pb and Cr and seven times higher for Ni). However, no statistically reliable differential accumulation pattern emerged with regard to length and weight for trace elements (except for Cd for which significant positive correlations with length were recorded). Trace element concentrations found in crayfish tissues were in the range considered harmful to human health (except for Cd and Cr). Moreover, the As and Pb concentrations, either in sediment or crayfish tissues, are clearly related to intense agricultural activities, with extensive use of fertilizers and pesticides, that significantly affect the levels of these toxic metals in the study area.