Organic enrichment can increase the impact of microplastics on meiofaunal assemblages in tropical beach systems.

The cumulative impact of microplastic and organic enrichment is still largely unknown. Here, we investigated the microplastic contamination, the organic enrichment and their effects on meiofaunal distribution and diversity in two islands of the Maldivian archipelago: one more pristine, and another strongly anthropized. Field studies were coupled with manipulative experiments in which microplastic polymers were added to sediments from the non-anthropized island (i.e., without organic enrichment) to assess the relative effect of microplastic pollution on meiofauna assemblages. Our results reveal that the impact of microplastic contamination on meiofaunal abundance and taxa richness was more significant in the anthropized island, which was also characterized by a significant organic enrichment. Meiofauna exposed experimentally to microplastic contamination showed: i) the increased abundance of opportunistic nematodes and copepods and ii) a shift in the trophic structure, increasing relevance in epistrate-feeder nematodes. Based on all these results, we argue that the coexistence of chronic organic enrichment and microplastics can significantly increase the ecological impacts on meiofaunal assemblages. Since microplastic pollution in the oceans is predicted to increase in the next decades, its negative effects on benthic biodiversity and functioning of tropical ecosystems are expected to worsen especially when coupled with human-induced eutrophication. Urgent actions and management plans are needed to avoid the cumulative impact of microplastic and organic enrichment.

Multiple declines and recoveries of Adriatic seagrass meadows over forty years of investigation.

This paper investigated the long-term changes (from 1973 to 2013) of the seagrass meadows of Zostera marina, Zostera noltei and Cymodocea nodosa in the Adriatic Sea subjected to multiple pressures. We examined the changes of the meadows by means of field data collection, observations and analysis of aerial photography to identify the most important drivers of habitat loss. The major decline of seagrass extension observed from 1973 to 1989, was primarily driven by urban development, and by the increase of the blue tourism. From 1989 to 2007 seagrass habitats progressively recovered due to the decrease of urbanization, but from 2007 to 2013 a further significant loss of seagrass meadows was apparently driven by thermal anomalies coupled with an increasing anthropogenic pressure. Our long-term analysis provides evidence that the rates of seagrass loss are faster than the recovery rates (i.e., -4.5 loss rate vs +2.5% recovery rate per year).

Impact of inorganic UV filters contained in sunscreen products on tropical stony corals (Acropora spp.).

Most coral reefs worldwide are threatened by natural and anthropogenic impacts. Among them, the release in seawater of sunscreen products commonly used by tourists to protect their skin against the harmful effects of UV radiations, can affect tropical corals causing extensive and rapid bleaching. The use of inorganic (mineral) filters, such as zinc and titanium dioxide (ZnO and TiO2) is increasing due to their broad UV protection spectrum and their limited penetration into the skin. In the present study, we evaluated through laboratory experiments, the impact on the corals Acropora spp. of uncoated ZnO nanoparticles and two modified forms of TiO2 (Eusolex®T2000 and Optisol™), largely utilized in commercial sunscreens together with organic filters. Our results demonstrate that uncoated ZnO induces a severe and fast coral bleaching due to the alteration of the symbiosis between coral and zooxanthellae. ZnO also directly affects symbiotic dinoflagellates and stimulates microbial enrichment in the seawater surrounding the corals. Conversely, Eusolex® T2000 and Optisol™ caused minimal alterations in the symbiotic interactions and did not cause bleaching, resulting more eco-compatible than ZnO. Due to the vulnerability of coral reefs to anthropogenic impacts and global change, our findings underline the need to accurately evaluate the effect of commercial filters on stony corals to minimize or avoid this additional source of impact to the life and resilience ability of coral reefs.

Thirty year ecosystem trajectories in a submerged marine cave under changing pressure regime.

Marine caves are unique and vulnerable habitats exhibiting high biodiversity and heterogeneity, but threatened by multiple global and local disturbances. Marine caves, although widely distributed along the Mediterranean coast, suffer for the lack of quantitative data on their structure and function, which hinder their conservation status assessment. Thanks to the availability of a nearly 30-year-long series of data (1986-2013), we evaluated ecosystem change in the Bergeggi marine cave (Ligurian Sea, NW Mediterranean), a cave with a complex shape and high habitat heterogeneity. Non-taxonomic descriptors were adopted, namely growth forms (GF) and trophic guilds (TG), which are informative about ecosystem structure and functioning, respectively. The cave experienced a general trend of change during the last three decades, mainly due to the decline in the cover of sessile organisms (especially 3-dimensional forms) matched by an increase of turf and sediment, thus causing the structural and functional homogenization of the cave community. While change before 2004 had been attributed to climatic factors (especially to the summer heat waves of 1999 and 2003), the most important rate of change was observed between 2009 and 2013, coinciding with recent major beach nourishments and the extension of the neighbouring Vado Ligure harbour, thus providing evidences on the importance of local disturbances deriving from coastal interventions. Monitoring the status of cave ecosystems is urgently needed, and the use of effective indicators, such as the specific traits here adopted (morphology and feeding strategy), could provide effective tools to assist marine cave conservation.

Limited impact of beach nourishment on macrofaunal recruitment/settlement in a site of community interest in coastal area of the Adriatic Sea (Mediterranean Sea).

Beach nourishment is a widely utilized solution to counteract the erosion of shorelines, and there is an active discussion on its possible consequences on coastal marine assemblages. We investigated the impact caused by a small-scale beach nourishment carried out in the Western Adriatic Sea on macrofaunal recruitment and post-settlement events. Artificial substrates were deployed in proximity of nourished and non-manipulated beaches and turbidity and sedimentation rates were measured. Our results indicate that sedimentation rates in the impacted site showed a different temporal change compared to the control sites, suggesting potential modifications due to the beach nourishment. The impact site was characterized by subtle changes in terms of polychaete abundance and community structure when compared to controls, possibly due to beach nourishment, although the role of other factors cannot be ruled out. We conclude that small-scale beach nourishments appear to be an eco-sustainable approach to contrast coastal erosion.

Impact of a harbour construction on the benthic community of two shallow marine caves.

Marine caves are unique and vulnerable habitats, threatened by multiple global and local disturbances. Whilst the effects of climate change on marine caves have already been investigated, no information exists about the effects of local human impacts, such as coastal development, on these habitats. This study investigated the impact of the construction of a touristic harbour on two shallow underwater marine caves in the Ligurian Sea (NW Mediterranean). As a standard methodology for monitoring marine caves does not exist yet, changes over time on the benthic community were assessed adopting two different non-taxonomic descriptors: trophic guilds and growth forms. Harbour construction caused an increase of sediment load within the caves, with a consequent decline of filter feeder organisms. Abundance of small organisms, such as encrusting and flattened sponges, was greatly reduced in comparison to organisms with larger and erect growth forms, such as domed mounds and pedunculated sponges. Our study indicated that growth forms and trophic guilds are effective descriptors for evaluating changes over time in marine caves, and could be easily standardised and applied in monitoring plans. In addition, as the harbour construction impacted differently according to the cave topography, the use of a systematic sampling in different zones of an underwater cave is recommended.