Cristina Gambi

Factors shaping biodiversity and functioning of coastal ecosystems in Antarctica are still largely unknown due to the overlap of multiple physical and bio-ecological forcings. Here, we investigated three coastal areas of the Ross Sea (Antarctica) across a coast-offshore transect (25–140 m depth), including an area located in front of the longest-dwelling penguin colony of the Adélie Cove Bay and other two areas, Camp Icarus Bay and Rod Bay, far from the penguin colony. The deposition of the penguin guano determined an extraordinary accumulation of organic matter in coastal sediments (6.9 ± 0.6 mgC g⁻¹), among the highest values reported worldwide so far, which cause apparent detrimental effects on meiofaunal biodiversity, in terms of richness of taxa and nematode species. Meiofaunal abundance showed a wide spatial variability among bays and depths (range: 252 ± 103 to 5961 ± 659 ind. 10 cm⁻²) with lower abundance and biomass at shallow stations. Here, we found a limited food availability possibly associated with the occurrence of the ice-scouring along the coast. Overall, 17 meiofaunal higher taxa were identified and the richness of taxa reached the highest values at 140 m depth in all the three bays investigated. Nematodes were characterized by a high diversity with 100 species identified. A relevant number of exclusive nematode species was observed in each bay and only 16 species were common at all sampling areas. The huge variability of biodiversity among the investigated areas was apparently related to a combination of biological (food availability and trophic interactions) and physical (ice-scouring) factors generating a mosaic of different assemblages. The combination of these factors determined a high turnover (beta) diversity (up to 100% of turnover for meiofaunal rare taxa and 81% for nematode species), which is likely a key driver for the high regional biodiversity observed in the coastal Antarctic sediments.

Nematodes represent >3/5 of the abundance of the world’s metazoans and usually account for nearly 90% of the total benthic fauna, playing a key ecological role in the benthic ecosystem functioning on a global scale. These small metazoans include a relevant number of microscopic predators and, in turn, are the most abundant preys of macro-megafauna and fish juveniles thus playing a key role in marine food webs. Here, using two independent approaches, we test the bioaccumulation in marine nematodes of several heavy metals present in contaminated sediments. We report here that nematodes, despite their short life cycle and small size, bioaccumulate significantly heavy metals. Bioaccumulation increases from deposit feeders and microalgal grazers to predators of microbes and other tiny metazoans. These results suggest that nematodes also contribute to their biomagnification along the food webs and can contribute to increase the transfer of contaminants from the sediments to larger organisms.

The Aeolian Islands (Mediterranean Sea) host a unique hydrothermal system called the “Smoking Land” due to the presence of over 200 volcanic CO₂-vents, resulting in water acidification phenomena and the creation of an acidified benthic environment. Here, we report the results of a study conducted at three sites located at ca. 16, 40, and 80 m of depth, and characterized by CO₂ emissions to assess the effects of acidification on meio- and macrobenthic assemblages. Acidification caused significant changes in both meio- and macrofaunal assemblages, with a clear decrease in terms of abundance and a shift in community composition. A noticeable reduction in biomass was observed only for macrofauna. The most sensitive meiofaunal taxa were kinorhynchs and turbellarians that disappeared at the CO₂ sites, while the abundance of halacarids and ostracods increased, possibly as a result of the larger food availability and the lower predatory pressures by the sensitive meiofaunal and macrofaunal taxa. Sediment acidification also causes the disappearance of more sensitive macrofaunal taxa, such as gastropods, and the increase in tolerant taxa such as oligochaetes. We conclude that the effects of shallow CO₂-vents result in the progressive simplification of community structure and biodiversity loss due to the disappearance of the most sensitive meio- and macrofaunal taxa.

Seagrass meadows play a key role in the provisioning of ecosystem goods and services. These systems are extremely vulnerable to multiple anthropogenic impacts. Therefore, there is an urgent need to develop new techniques to efficiently restore degraded seagrass meadows. Here we tested the efficacy and efficiency of a new technique of seagrass transplant (Cymodocea nodosa) using biodegradable containers. We investigated the effects of this transplant technique in the Adriatic Sea comparing the transplanted seagrass meadows with adjacent donor seagrass meadows and bare sediments used as control. We assessed the recovery rates and the ecological implications of this transplant on key ecosystems functions, including the biomass and detritus provision to local biological communities, and the effects on the biodiversity of the associated benthic fauna. Our results show that this restoration technique was successful, enabling the seagrass survival (approximately 30%) even in high‐energy conditions occurring in winter. The sediments hosting the transplanted seagrasses showed an increase of trophic availability and of rates of organic matter cycling. Despite this, 1 year after the transplant, the abundance and biodiversity of meiofaunal assemblages in the restored seagrasses were still lower than in donor seagrass meadows. These results indicate that the restoration process of seagrass meadows can take a long time, and that a multilevel approach (including the analysis of biodiversity and of the sedimentary processes and biogeochemical cycles) is needed to assess the success of restoration actions in these habitats.

Vegetated marine and freshwater habitats are being increasingly lost around the world. Habitat restoration is a critical step for conserving these valuable habitats, but new approaches are needed to increase restoration success and ensure their survival. We investigated interactions between plants and bivalves through a review and analysis of 491 studies, determined the effects, mechanisms and key environmental variables involved in and driving positive and negative interactions, and produced guidelines for integrating positive interactions into restoration efforts in different habitats. Fifty per cent of all interactions (both correlative and experimental studies) were positive. These were predominant between epifaunal bivalves and plants in all habitats, and between infaunal bivalves and plants in subtidal habitats. Plants primarily promoted bivalve survival and abundance by providing substrate and shelter, while bivalves promoted plant growth and survival by stabilizing and fertilizing the sediment, and reducing water turbidity. The prevalence of positive interactions increased with water temperature in subtidal habitats, but decreased with water temperature in intertidal habitats. The subset of studies conducted in a restoration context also showed mostly positive interactions. Twenty‐five per cent of all interactions were negative, and these were predominant between plants and infaunal bivalves in intertidal habitats, except sulphide‐metabolizing bivalves, which facilitated plant survival. Interactions involving non‐native species were also mostly negative. Synthesis and applications. Promoting facilitative interactions through plant–bivalve co‐restoration can increase restoration success. The prevalence of positive interactions depends on habitat and environmental conditions such as temperature, and was especially important in subtidal habitats (involving both infaunal and epifaunal bivalves) and in intertidal habitats (involving only epifaunal bivalves). Thus sites and species for co‐restoration must be carefully chosen to maximize the chances of success. If done properly, co‐restoration could increase initial survival, persistence and resilience of foundation species, and promote the recovery of associated biodiversity and ecosystem services.

MERCES “Marine Ecosystem Restoration in Changing European Seas” (GA 689518) is the first H2020 European project focused on the ecological restoration of degraded marine habitats and the recovering of their biodiversity and ecosystem services. Specific aims include a) improving existing, and developing new, restoration actions of degraded marine habitats; b) increasing the adaptation of EU degraded marine habitats to global change; c) enhancing marine ecosystem resilience and services; d) conducting cost-benefit analyses for marine restoration measures; e) creating new industrial targets and job opportunities. To achieve these objectives MERCES created a multi-disciplinary consortium (28 Partners from 16 Countries) with skills in marine ecology, restoration, policy, socio-economics, knowledge transfer, dissemination and communication.