The perfect microsite: How to maximize Posidonia oceanica seedling settlement success for restoration purposes using ecological knowledge.

The use of sexual propagules to restore seagrass meadows has raised increasing attention in the last years as seed-based strategies avoid impacts on donor beds while preserving genetic diversity in restored populations. However, the availability of suitable microsites for seedling establishment at transplantation locations is crucial in order to achieve positive outcome of restoration actions. In this study we develop ad-hoc holders that act as optimal microsites for Posidonia oceanica seedling establishment. Holders are intended to be transferred in the field for restoration purposes after few months of indoor seedling culture. Seedling ability to self-anchor to rocky substrates via adhesive root hairs was exploited. We tested rocky holders with different designs in order to maximize seedling survival and settlement. The effect of the holder design on seedling anchorage performances was evaluated. Holders were provided with different topographical complexity and substrate slope. Topographical complexity significantly influenced settlement success, as seedlings did not attach to flat holders, while anchorage reached 100% on holders provided with complexity at seed and the root scales. Substrate slope did not affect the percentage of anchored seedlings, conversely it influenced root growth pattern and thus anchorage stability. This study shows how ecological knowledge of species' life history strategies and associated critical traits provides valuable hints to develop alternative approaches to seagrass restoration tailored to the biology of the system under study.

Microplastics impair the feeding performance of a Mediterranean habitat-forming coral.

The impact of plastic debris, and in particular of microplastics (here referred as particles smaller than 5 mm) on aquatic environments has now become a topic of raising concern. Microplastics are particularly abundant in the Mediterranean Sea, potentially exerting substantial pressures on marine organisms at different levels of organization. Ingestion of microplastics has been observed in a large number of marine species. The aim of this work is to test if microplastics produce a feeding impairment in Astroides calycularis, a shallow water, habitat-forming coral endemic to the Mediterranean Sea. Our findings suggest a lack of any avoidance mechanism allowing the polyps to discern between food items and microplastics when occurring simultaneously. Moreover, polyps spend a considerable amount of time on handling microplastic particles. As a consequence, microplastics impair the feeding efficiency in A. calycularis, since polyps may not be fully able to profit from the drifting plankton aggregations. Therefore, we suggest that microplastics can cause a reduction of fitness in A. calycularis, and presumably also in other species characterized by suspension feeding strategy.