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.
The Mediterranean is one of the most overfished seas of the world where mesopredators are severely threatened. The trophic strategies of four pelagic species that inhabit the Adriatic Sea (Scomber spp. and Trachurus spp.) were investigated through an integrated approach of stomach contents and stable isotopes analyses. Our study demonstrated that Scomber colias feeds mainly on strictly pelagic prey, with fish larvae as a secondary prey in the Southern Adriatic Sea, while S. scombrus feeds on prey belonging to higher trophic levels. Smaller specimens of Trachurus mediterraneus have a diet mainly based on pelagic prey, while larger fishes rely on prey such as benthic decapods, showing an ontogenetic shift in the diet of the species. Trachurus trachurus shows a preference for offshore and deeper areas and a diet such as that of its congeneric, but no clear ontogenetic shift was observed. This spatial segregation allows the co-existence of these two species of Trachurus. Scomber colias mainly inhabits southern areas and S. scombrus shows a preference for the northern sectors. This latitudinal gradient avoids the overlap of their trophic niches. Bayesian mixing models confirmed that the trophic niches of these species only partially overlap in the middle of the trophic web.
The common sole, Solea solea, is one the most important commercial species in Europe and, within the Mediterranean, the Adriatic basin is the most crucial area for its production. Although the species is overexploited in the basin, data on its trophic ecology are fragmentary, even though this is one of the most important features within the Ecosystem Approach to Fishery. Here, we analysed temporal variations in the feeding ecology of the species by using an integrated approach of stomach contents and stable isotope analyses coupled with the analysis of some condition indices such as the gonadosomatic and the hepatosomatic indices. Changes in diet and trophic level across the years in adult females were clearly linked to the different energetic requirements facing reproduction. Temporal changes throughout the year were mainly related to changes in food availability. This study confirms the opportunistic behaviour of this benthophagous species and its role as a mesopredator, opening new perspectives for further investigations on the effects of the overexploitation of this important fishery resource on the marine trophic web.
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