Agenda

Dott. Luca Scapin, DAIS

Abstract: One of the major challenges to ensure effective restoration of estuarine habitats is to establish success criteria, allowing to determine whether the goals of restoration are met. In the northern basin of the Venice lagoon (northern Adriatic Sea, Italy), the LIFE project “SeResto” started in 2014 aiming at restoring seagrass meadows by means of small-scale manual transplantation of sods and rhizomes. The interventions are expected to increase the cover of Zostera marina and Z. noltei in the area, and to subsequently restore the typical features of faunal assemblages associated with seagrass meadows. The aim of this work is to propose a method to identify reference conditions and assess the progress of nekton (fish, decapods and cephalopods) assemblages at seagrass restoration sites. Nekton sampling took place from 2014 to 2017 during spring at eight transplantation sites. In spring 2016, five natural seagrass sites in the same area were additionally sampled, and water physic o-chemical parameters and habitat structure (seagrass floristic composition, percent cover, canopy height, shoot density, leaf area index and epiphytal load) were also recorded. A multivariate approach based on GLMs was adopted, in order to disentangle the relative effect of water quality and seagrass habitat structure on nekton assemblages of natural habitats. Models were then employed to predict species composition of nekton fauna at each transplantation site under target abiotic and habitat conditions, allowing to identify the reference assemblages to evaluate the progress of fauna towards restoration goals. The analysis highlighted that desired restoration outcomes, i.e. presence of Z. marina and greater seagrass cover, are positively linked to presence and density of some pipefishes (Syngnathidae), large gobies (Gobiidae) and some shrimps (Palaemonidae and Hippolytidae) in the nekton assemblage. Sites exhibiting better recovery of habitat structure also supported nekton assembl ages more similar to reference conditions. However, none of the sites showed clear trajectories of progress, suggesting that more than three years are needed for nekton fauna to successfully colonise restored seagrass meadows in coastal lagoons.