Several diatom species produce resting stages as part of their life cycle. These resting stages accumulate in the sediments where they can remain for a long time before being re-suspended in the water column and switching to active growth. Until now, the abundance and diversity of viable diatom resting stages have been assessed using the Serial Dilution Culture (SDC) method. In the present study, surface sediment samples from the Gulf of Naples were used to compare results obtained with the SDC method with those provided by HTS metabarcoding based on DNA extracted from the same sediment sample; the marker used was the V4 region of 18S rDNA. HTS metabarcoding showed a marked dominance of polar centric diatoms, among which Chaetoceros species were the most represented, in terms of both sequence and ribotype number. Almost all the most abundant ribotypes identified with metabarcoding matched records of species observed in SDCs. In some cases, however, this marker region could not distinguish between...

This study aims to investigate the effect of two different groups of phenolic compounds (the alkylphenols nonylphenol (NP) and octylphenol (OP), and the chlorophenol pentachlorophenol (PCP)) on constructed wetlands (CWs) performance, including on organic matter, nutrients and contaminants removal efficiency, and on microbial community structure in the plant bed substrate. CWs were assembled at lab scale simulating a vertical flow configuration and irrigated along eight weeks with Ribeira de Joane (an urban stream) water not doped (control) or doped with a mixture of NP and OP or with PCP (at a 100 μg·L⁻¹ concentration each). The presence of the phenolic contaminants did not interfere in the removal of organic matter or nutrients in CWs in the long term. Removals of NP and OP were >99%, whereas PCP removals varied between 87% and 98%, mainly due to biodegradation. Microbial richness, diversity and dominance in CWs substrate were generally not affected by phenolic compounds, with only PCP decreasing diversity. Microbial community structure, however, showed that there was an adaptation of the microbial community to the presence of each contaminant, with several specialist genera being enriched following exposure. The three more abundant specialist genera were Methylotenera and Methylophilus (methylophilaceae family) and Hyphomicrobium (hyphomicrobiaceae family) when the systems were exposed to a mixture of NP and OP. When exposed to PCP, the three more abundant genera were Denitromonas (Rhodocyclaceae family), Xenococcus_PCC_7305 (Xenococcaceae family) and Rhodocyclaceae_uncultured (Rhodocyclaceae family). To increase CWs efficiency in the elimination of phenolic compounds, namely PCP which was not totally removed, strategies to stimulate (namely biostimulation) or increase (namely bioaugmentation) the presence of these bacteria should be explore. This study clearly shows the potential of vertical flow CWs for the removal of phenolic compounds, a still little explored subject, contributing to promote the use of CWs as nature-based solutions to remediate water contaminated with different families of persistent and/or emergent contaminants.

Floating wetland islands (FWI) are considered nature-based solutions with great potential to promote several ecosystem services, such as biodiversity and water quality enhancement through phytoremediation processes. To our knowledge, the present work is the first to scientifically document the in-situ establishment of an FWI in a seawater port marina. The establishment and performance of a cork floating platform with a polyculture (Sarcocornia perennis, Juncus maritimus, Phragmites australis, Halimione portulacoides, Spartina maritima, Limonium vulgare) was evaluated. The diversity of organisms present in the FWI was undertaken based on the macrofauna assessment, taking into consideration marine water characterization, with a focus on hydrocarbons. Microbial communities were assessed based on metabarcoding approach to study 16S rRNA gene from environmental DNA retrieved from biofilm (from the planting media), marine biofouling (from the submerged platform) and surface marina water. S. perennis was the species with the highest survival rate and growth. The structure of the microbial community showed clear differences between those established in the FWI and those in the surrounding water, showing the presence of some bacterial groups that can be relevant for bioremediation processes (e.g., Saprospiraceae family). Concerning the macrofauna analysis, Mytilus sp. was the predominant taxa. To be of relevance, total petroleum hydrocarbons were detected at the marina up to ca. 6 mg/L. This study gives new insights into broadening FWI application to the saline environments of port marinas and to supporting a management strategy to promote several ecosystem services such biodiversity, species habitat, water quality enhancement and added aesthetic value to the marina landscape.