A current practice of marine aquaculture\ud is to integrate fish with low-trophic-level organisms\ud (e.g. molluscs and/or algae) during farming to\ud minimise effects of cultivation on the surrounding\ud environment and to potentially increase economic\ud income. This hypothesis has been tested in the\ud present article experimentally, by co-cultivating fish\ud and mussels (Mytilus galloprovincialis) in the field.\ud Integrated multi-trophic aquaculture (IMTA) experiments\ud were started in July 2004 by transplanting\ud mussel seed at two depths (-3 and -9 m) within\ud 1,000 m downstream to fish cages and at 1,000 m\ud upstream from cages. Mussels were cultured in nylon\ud net bags for 12 months and the growth recorded\ud biometrically. The outcome of our field experiment\ud corroborated the idea of IMTA effectiveness. In fact,\ud in the study area, the organic matter from fish-farm\ud biodeposition caused changes in the chemical environment\ud (i.e. controls and impacted sites were\ud significantly different for organic matter availability\ud and chlorophyll-a) and this induced changes in\ud growth performance of co-cultivated mussels. Mussels\ud cultivated close to cages, under direct organic\ud emission, reached a higher total length, weight and\ud biomass than mussel cultivated far from farms

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Animals and plants use adhesion to move, to anchor to a substrate, or to disperse seeds and fruits. Some plants developed a root pad as a common strategy to adhere to consolidated substrates. In the marine environment, the seagrass Posidonia oceanica attaches firmly to consolidated substrates via adhesive root hairs, forming a pad structure. We used novel morphological and ultrastructural data to develop a numerical model to study the dynamics of root hair adhesion during contact formation on rough consolidated substrates for this species. Morphological analysis, conducted using Scanning Electron Microscope, highlighted the role of root hair branching in pad formation. Transmission Electron Microscope microscopy allowed us to identify a glue-like substance at the pad/ substrate interface. The numerical model highlighted the role played by the cell wall's elasticity in pad formation and its importance in guaranteeing a firm adhesion. Furthermore, the effectiveness of these mechanisms was assessed at different simulated roughness levels. Increasing knowledge on the adhesion mechanism of seagrass to consolidated substrates could be pivotal in developing advanced seedling-based restoration protocols. The findings of this study could contribute to restoration activities planned to contrast seagrass regression. Transplanting initiatives using seedlings can now better address the search for suitable and low-impact ways to fix germinated plants to the substrate.

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The transition from a planktonic to a benthic life is a critical phase in which sub-adults are particularly exposed to the risk of predation and dispersion into unsuitable habitats, and plays a crucial role in the distribution, structure and dynamics of marine populations. Settlement involves the selection of an adequate substrate that provides shelter and food during early life stages. Percnon gibbesi is an alien brachyuran crab that has invaded the Mediterranean, where it is preferentially associated to boulders covered with shallow algal turf. The mechanisms of substrate selection leading to the settlement of megalopae are still unknown in P. gibbesi, yet their knowledge may shed light on its high invasiveness. We examined the substrate preference and settlement behaviour of 36 megalopae of P. gibbesi using three natural substrates in an experimental mesocosm: gravel, cobbles and flat stones. Video recordings of 30-min trials were used to assess the substrate preference, measure the time to selection and observe the behaviour of the megalopae. Strong preference was given to hard and stable substrates i.e., cobbles and flat stones with interstices where to hide, which are also the most suitable as they provide shelter and food. Direct selection was the dominant behaviour followed by exploration and lastly by hesitation. The megalopae selected quickly the most suitable substrate to settle, likely enhancing their chances of survival. Our findings suggest that rapid settlement on a suitable substrate contributes to the success of the biological invasion of P. gibbesi along the Mediterranean coasts.