• Energy Research

The influence of climate change on the lagoon biota is described

We compared the performance of abundance- and biomass-based M-AMBI in the 13 major Italian lagoons, using a benthic dataset constituted by 208 sampling sites. The relative importance of ecological groups changed when using abundance or biomass, sometimes leading to an improved ecological status classification. Being biomass more ecologically relevant than abundance, the adoption of a biomass-based index may better describe the ecological status of lagoons, where the community is naturally disturbed and dominated by tolerant and opportunist species.

Abstract Changes in macrozoobenthic communities were studied in a shallow eutrophic basin known as the Palude della Rosa in the Venetian lagoon, Italy. The sampling was conducted on a monthly basis from December 1991 to July 1993 at four representative stations. The observed fluctuations of the benthic community structure closely followed the seasonal cycle of the green macroalga Ulva rigida C. Ag., and its overgrowth. Sediment enrichment in organic matter, due to this algal overgrowth, modified the environmental conditions, leading to anoxic crisis over the summer. Significant differences in community composition and diversity were found between those stations that were heavily influenced by Ulva presence and those less influenced. All species were strongly affected by the crisis; so much so that benthic macrofauna almost disappeared. This period was then followed by a recolonization phase of the devoid bottom. Such a recolonization took place over the following winter, following a pattern similar to that found in other studies of organic enrichment elsewhere. The community structural changes were analysed by means of univariate and multivariate techniques.

Non-indigenous ascidians are of particular concern to aquaculture industry and, paradoxically, the activities associated with it represent an important way to translocate these species worldwide. In 2012 a non-indigenous ascidian was found covering the oyster crops in the Ebro Delta (Western Mediterranean). We have identified the ascidian genetically and morphologically as Didemnum vexillum Kott, 2002. This finding indicates that the species is currently expanding its distribution in the Mediterranean Sea, as it has recently been found in the eastern basin (Venice, Adriatic Sea). Introduced populations of D. vexillum are found in temperate and cold waters worldwide, and a successful establishment in the Mediterranean implies a remarkable capacity of adaptability to warm, subtropical conditions. We assessed the life cycle (growth and reproduction) of the ascidian at the studied site. The species has a marked seasonal cycle, with regression in the warmest months and reappearance during winter. In spring D. vexillum reaches its maximum abundance, followed by a peak in reproduction just before regression. This cycle is reversed with respect to the one observed in colder waters, highlighting a plastic biological cycle of this invader and an hitherto unknown ability to establish itself in warm waters. We also analysed the genetic structure of the population of the Ebro Delta and the one established in the Lagoon of Venice using COI sequence data. The low genetic diversity in our samples (three haplotypes) was consistent with what is observed in the introduced populations worldwide. It is likely that the ascidian was introduced with oyster stock from bivalve cultures in the Atlantic French coasts, where the same three haplotypes have been reported. The high boating activity in the Ebro Delta makes further human-mediated transport of the species highly likely, and nearby fishing grounds can be severely affected if invaded. It is urgent to implement measures to prevent the continuous expansion of this ascidian pest in the Mediterranean.

During almost a century of permanence in the Mediterranean, the warm water species Teredo bartschi has adapted to progressively colder climates up to overwintering at water temperatures only a few degrees above zero. A fine-grained analysis of discoveries, synonyms, museum collections and grey literature establishes that this species entered the Mediterranean since at least 1935. Coming from tropical waters through the Suez Canal, the species has undergone to a long period of acclimatization in the Levantine Basin of the Mediterranean and then pushed north at the beginning of this century until it has invaded the Lagoon of Venice. The invasion routes are reconstructed and presented. The lagoon of Venice is a microtidal bar-built estuary located in the northernmost part of the Mediterranean and represents the highest latitude reached by the species on a global scale. Here for over ten years, T. bartschi has now become invasive forming stable and abundant populations. This paper presents some biometrics of hard parts such as pallets and shells as well as the description of siphons, useful for the identification and characterization of the species. The shape of the pallets of the Venetian population differs from the Aqaba's (Giordania) and Mersin's (Turkey) populations. Phenotypic variation are probably due to environmental effects on morphology.

The Doge's Palace of Venice (Italy) has on its canal-side large doorways closed by old wooden doors. Originally, the thresholds were built above high-water level to avoid direct contact with the water and the resulting damage caused by physical and biological agents. As a result of sea-level rise and land subsidence during the last centuries, the doors are now exposed to tides and to attack by marine wood-boring invertebrates such as shipworms and gribbles. As a consequence, the bottom rails of the doors were recently in need of substantial restoration, which took into consideration new materials and techniques. In this framework, an in situ experiment was undertaken to test the resistance of some selected wood species to woodboring organisms. A quick assessment protocol, based on the EN 275 standard, was set up to quantify bioerosion according to wood species and elevation above sea level. Both European and tropical wood species were tested. The former include Scots Pine, as a reference, and Larch, Cypress and Oak as traditional carpentry materials. The latter include Azobe, Okan, and Bilinga. All the European species showed high susceptibility to woodborer attack, whereas no damage was recorded on the tropical woods. The collected shipworms belonged mostly to Lyrodus pedicellatus and Teredo bartschi with some individuals of Teredo navalis. The only species of gribble found was Limnoria tripunctata. New technical solutions were adopted in the restoration aiming to provide a long service life for the replacements and simplifying the maintenance procedures. Experience, results and solutions are presented.