Seagrass meadows are a critical component of estuarine and coastal seascapes, and their structure influence fish assemblages at multiple spatial scales. The patch mosaic model, which defines the seascape as a collection of interacting habitat types, is increasingly adopted to prioritise protected areas and design ecological restoration schemes, hence helping to preserve seagrass meadows and the associated fish assemblages. Despite that, there are few studies investigating the relative contribution of environmental characteristics measured at different spatial scales in determining the distribution of seagrass fish. This study collects fish and environmental observations taken at both site and seascape scales in seagrass meadows in the Venice lagoon (Adriatic Sea, Italy). By means of Generalised Linear Models, it aims to disentangle the relative influence of local water quality and habitat characteristics from that of habitat mosaic properties, investigating the response of whole fish assemblage descriptors, feeding guilds and dominant species. While confirming the primary importance of local habitat quality, the study highlights that also seagrass habitat structure at the seascape scale is relevant for seagrass fish assemblages, influencing total biomass, biomass of macrobenthivorous and hyperbenthivorous/piscivorous species and seagrass specialists such as syngnathids. Conservation of seagrass fish assemblages can therefore be promoted in Mediterranean coastal lagoons by preserving or restoring some features of the habitat mosaic, namely the extension of seagrass patches and their shape complexity, in addition to local water quality and seagrass cover.
Abstract.A fish-based multimetric index was applied to assess the ecological status of fish fauna in both natural and newly restored seagrass meadows in the Venice lagoon (northern Adriatic Sea, Italy), using natural habitats as reference sites. Fish assemblages were then compared, and community attributes of recreated and natural habitats were evaluated. Ecological status resulted higher in natural meadows, and a multivariate analysis showed that an increase in the relative proportion of seagrass specialists at restored sites could represent an indicator of success of seagrass restoration.
Since the 1960s, the Venice Lagoon has suffered a sharp aquatic plant constriction due to eutrophication, pollution, and clam fishing. Those anthropogenic impacts began to decline during the 2010s, and since then the ecological status of the lagoon has improved, but in many choked areas no plant recolonization has been recorded due to the lack of seeds. The project funded by the European Union (LIFE12 NAT/IT/000331-SeResto) allowed to recolonize one of these areas, which is situated in the northern lagoon, by widespread transplantation of small sods and individual rhizomes. In-field activities were supported by fishermen, hunters, and sport associations; the interested surface measured approximately 36.6 km2. In the 35 stations of the chosen area, 24,261 rhizomes were transplanted during the first year, accounting for 693 rhizomes per station. About 37% of them took root in 31 stations forming several patches that joined together to form extensive meadows. Plant rooting was successful where the waters were clear and the trophic status low. But, near the outflows of freshwater rich in nutrients and suspended particulate matter, the action failed. Results demonstrate the effectiveness of small, widespread interventions and the importance of engaging the population in the recovery of the environment, which makes the action economically cheap and replicable in other similar environments.
1. One of the major challenges to ensure effective restoration of estuarine habitats is to establish success criteria to determine whether the goals of restoration are met.2. The aim of this work is to propose and test an approach to identify reference conditions and assess the recovery of nekton (fish, decapods and cephalopods) assemblages at seagrass restoration sites.3. Nekton sampling took place from 2014 to 2017 in the northern Venice lagoon (northern Adriatic Sea, Italy) during spring at eight sites subjected to seagrass (Zostera marina and Zostera noltei) transplantation. In spring 2016, five natural seagrass sites in the same area were additionally sampled, and physico-chemical water parameters and habitat structure were also recorded.
4.A multivariate generalized linear model approach was adopted in order to disentangle the relative effect of water quality and seagrass habitat structure on nekton assemblages of natural habitats. Models were subsequently employed to predict species composition of nekton fauna at each transplantation site, to identify the reference assemblage expected under site-specific abiotic and habitat characteristics. 5. The average distance of the observed assemblage from reference conditions was used to track temporal trajectories of nekton colonization at transplantation sites, and to ultimately evaluate the recovery rate towards restoration goals.6. This study highlights how a predictive approach could serve management purposes in ecological restoration, providing a concise tool to assess the functionality of restored habitats for associated fauna.
Seagrass meadow degradation and loss is one of the major threats to fish biodiversity in coastal marine and lagoon ecosystems in the Mediterranean. Pipefishes and seahorses (family Syngnathidae) are particularly affected by loss of seagrass meadows and other structured habitats, on which they rely for survival and reproduction. Despite their charismatic appearance and peculiar behaviour, their habitat ecology is still poorly understood in Mediterranean coastal waters.
This study focuses on syngnathid assemblage composition and diversity in the shallow waters of the Venice lagoon (Italy), aiming at highlighting habitat preferences and providing insights into the conservation of biodiversity in these ecosystems. Generalized Additive Models were used in order to disentangle the potential effect of habitat typologies and different architectures of seagrass meadows from that of other environmental parameters.
Most abundant taxa and whole syngnathid assemblage indicators were positively associated with seagrass meadows. Only few species, however, were seagrass specialists in shallow waters, and preferred meadows with taller canopies.
Despite that, other structured habitats including short‐leaved seagrass meadows and macroalgal beds were important for some species and overall assemblage diversity.
Managers in Mediterranean coastal lagoons should thus limit human pressures that lead to the depletion of seagrass meadows, with particular attention to long‐ and broad‐leaved species in less confined areas. Nevertheless, syngnathid assemblages would benefit from the preservation and restoration of the overall habitat diversity characterizing shallow waters in coastal lagoon.
Future studies should aim at investigating the potential role of habitats at greater depths in supporting syngnathids.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.