ABSTRACT
The Bagno dell'Acqua lake is characterized by CO2 emissions, alkaline waters (pH = 9) and Eh values which indicate strongly oxidizing conditions. A typical feature of the lake is the presence of actively growing microbialites rich in calcium carbonates and silica precipitates. Mineralogy, petrography and morphology analyses of the microbialites were coupled with the analysis of the microbial community, combining molecular and cultivation approaches. The DNA sequencing revealed distinct patterns of microbial diversity, showing pronounced differences between emerged and submerged microbialite, with the upper layer of emerged samples exhibiting the most distinctive composition, both in terms of prokaryotes and eukaryotes. In particular, the most representative phyla in the microbial community were Proteobacteria, Actinobacteriota, and Bacteroidota, while Cyanobacteria were present only with an average of 5%, with the highest concentration in the submerged intermediate layer (12%). The role of microorganisms in carbonate mineral formation was clearly demonstrated as most of the isolates were able to precipitate calcium carbonate and five of them were characterized at molecular level. Interestingly, when microbial isolates were cultivated only in filtered water, the precipitation of hazenite was observed (up to 85%), opening new prospective in P (phosphate) recovery from P depleted environments.
ABSTRACT
Plastic pollution affects all oceans and sequestration of plastics in sediments is considered its ultimate sink. We report evidence of macroplastic burial retrieved within a sediment core collected at 38 m depth at the mouth of the Mazzarrà River, a torrential river able to carry a large amount of sediment during seasonal flash-floods. Two macroplastic items were found at 68 and 255 cm below the core top (corresponding to the seafloor). Their association with terrestrial vegetal debris and their inclusion in decimetre-thick sandy/silty intervals showing coarsening- and fining-upward trends, suggest that they were deposited by hyperpycnal flows possibly triggered by flood events. These findings testify the potential of sedimentary flows in burying macroplastic at depth below the seafloor, especially in nearshore prodelta environments. Furthermore they raise the quest on the magnitude of macroplastic storage in the subsurface and on the lack of specific devices and strategies for their reckoning.
Subject(s)
Floods , Plastics , Burial , Environmental Monitoring , RiversABSTRACT
Marine litter is an emerging environmental threat affecting all world's oceans including the deep seafloor, where the extent of the phenomenon is still largely unknown. We report the spatial patterns of macro-litter distribution within the Messina Strait's channels (Central Mediterranean), focusing on the transfer mechanisms responsible for its emplacement, a key information to better understand litter distribution. Litter is patchy but pervasive on all surveyed channels, reaching densities up to ~200 items/10 m, the highest reported for the deep sea until now. Litter is often arranged in large accumulations formed by hundreds of land-sourced items, mixed to vegetal and coarse-grained debris, indicating an emplacement from sedimentary gravity flows. Such impressive amount of litter can be explained by the superposition of a very efficient source-to-sink sedimentary transport and a strong urbanization of the coastal area. These findings point out that macro-benthic litter pollution is a major, often overlooked, threat for deep-sea ecosystems. Further explorations are thus required in similar marine settings to fully understand the magnitude of the problem, since they may represent the largest litter hotspots in the deep-sea.
