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A rapid temperature increase in the 1980-90s has been accompanied by dramatic and unprecedented changes in the biota and communities of the Ligurian Sea. This review uses existing historical series (a few of which have been purposely updated) to assess extent and consequences of such changes. A number of warm-water species, previously absent or occasional in the comparatively cold Ligurian Sea, has recently established thanks to warmer winters. Occurrence among them of invasive alien species is causing concern because of their capacity of outcompeting autochthonous species. Summer heatwaves, on the other hand, caused mass mortalities in marine organisms, some of which found refuge at depth. New marine diseases appeared, as well as other dysfunctions such as the formation of mucilage aggregates that suffocated and entangled benthic organisms. Human pressures have combined with climate change to cause phase shifts (i.e., abrupt variations in species composition and community structure) in different habitats, such as the pelagic environment, seagrass meadows, rocky reefs, and marine caves. These phase shifts implied biotic homogenization, reduction of diversity, and dominance by invasive aliens, and may be detrimental to the resilience of Ligurian Sea ecosystems. Another phase of rapid warming has possibly started in the 2010s and there are clues pointing to a further series of biological changes, but data are too scarce to date for proper assessment. Only well addressed long-term studies will help understanding the future dynamics of Ligurian Sea ecosystems and their possibilities of recovery. [ABSTRACT FROM AUTHOR]

In this paper, we present a map describing the main geomorphological features of the coastal and marine area between the towns of Albenga and Savona (Ligurian Sea, NW Mediterranean) corresponding to a coastal stretch of ∼40 km. To produce this map, we collated data from the literature, orthophotos, perspective photos, multibeam and side scan sonar data, and undertook direct surveys to ground truth data obtained using indirect techniques. We divided the information into nine thematic layers, including bathymetry, natural coastal types, geomorphological elements, seafloor coverage (both geological and biological), coastal and nearshore dynamics, human influence on coastal and marine environments, coastal occupation and protected areas. [ABSTRACT FROM AUTHOR]

Environmental change is commonly considered as a driver for the extinction of rare species. This belief, long established on land, may not apply to marine species. Dramatic environmental change in the shallow marine ecosystems of Kos, an island in the Aegean (east Mediterranean Sea) caused algal reefs to shift to sponge reefs. Among the sponge species that gained supremacy on Kos reefs, the Mediterranean endemicIrcinia retidermatawas previously a rare species. Comparing surveys carried out in 1981 and 2013 by the same method (time-based visual census along random paths by scuba diving), in the same sites, by the same people, showed thatI. retidermataincreased its overall abundance by one order of magnitude, and expanded its occurrence to all the habitats examined. This outcome contradicts the current common belief that rare species in semi-enclosed seas are prone to extinction. Besides being the state preceding final extinction, rarity could represent the source of variation that marine ecosystems need in order to face environmental change. However, for many marine invertebrates, and especially sponges, inferred rarity may simply be the result of insufficient investigation. This study represents an attempt to assess change with time in a rare sponge species’ abundance using visual census by scuba diving. [ABSTRACT FROM AUTHOR]

Habitat mapping plays a key role in the management and conservation of natural systems. In protected areas, where sustainable development is always subordinate to conservation efforts, maps are largely used to represent habitats, development pressures, tourist facilities or legal restrictions such as the zoning of a protected area. Some authors have recently developed a methodology that allows the production of a set of maps for the management of marine protected areas. In this paper, we present the application of this methodology to the case study of the marine protected area ‘Tavolara Punta Coda Cavallo’. [ABSTRACT FROM AUTHOR]

The consequences of date mussel Lithophaga lithophaga harvesting (DMH) on blennioid assemblages was evaluated at Capo Noli-Bergeggi (Savona, north-western Mediterranean Sea) in summer 2005, under the hypothesis that holes bored by L. lithophaga, and left empty by the collection of the bivalve, may represent refuges for these cryptobenthic fishes. Blenniidae and Tripterygiidae were identified to species, and their individuals counted together with the number of empty L. lithophaga holes. The results were compared between ‘impact’ sites affected by the destructive DMH and control sites using two-way ANOVA, and showed that extensive removal of the boring mussels, dramatically increasing the availability of empty holes, favours total number of observed blennioid species and especially Parablennius zvonimiri abundance. [ABSTRACT FROM AUTHOR]

Episodes of coral bleaching and mortality have occurred with increasing frequency over the past two decades, often followed by proliferation of non-constructional organisms leading to a 'phase shift' in reef ecosystems. As the Maldives were severely affected by the 1998 episode, concern raised about the possibility of a phase shift there. The status of Maldivian reefs was surveyed eight years after the mass mortality of 1998; the percentages of biotic and abiotic benthic categories were estimated in both lagoon and ocean reefs. Hard coral cover did not exceed 37%, but no threat was recognized of a phase shift toward the dominance of soft corals, algae or sponges (7% on average). The high percentage of bare coral rock (up to almost 50%) and the local variability of living benthic cover suggest that Maldivian reefs were still in a re-colonization phase. Monitoring of their evolution is in progress. [ABSTRACT FROM AUTHOR]

The endemic Mediterranean seagrass Posidonia oceanica (L.) Delile can colonise either sand or rock, but mostly builds its own substratum through the formation of the so-called matte (a terrace of interlaced rhizomes and roots trapping sediment). We studied two shallow water meadows in the Ligurian Sea (NW Mediterranean) to examine the influence of the substratum nature on three different levels of ecological complexity: individual (the plant), population (the meadow) and community (the leaf epiphytes). Responses to substratum nature showed inconsistency among the three complexity levels in that leaf surface area (plant level) was lower and shoot density (meadow level) was higher on rock, whereas no major differences were found in epiphyte cover and quali-quantitative composition (community level). We argued that responses are integrated through complexity levels up to dampening substratum influence. [ABSTRACT FROM AUTHOR]

The influence of geographical location and depth on the rhizome primary production of Posidonia oceanica was investigated over different spatial scales: large (the whole Ligurian coast), medium (the individual meadows) and small (the sites of each individual meadow). Six Posidonia oceanica meadows, separated by 30 to 60 km from each other, were sampled in summer 2002 along the 300 km of the Ligurian coast (NW Mediterranean). In each meadow, two sites, 100 to 200 m apart, were chosen and in each site 10 orthotrophic shoots were sampled at three depth zones: shallow (1.5-10 m), intermediate (10-15 m), and deep (15-26 m). The annual primary production of the rhizomes was reconstructed through lepidochronology for three previous years (1999, 2000 and 2001). Three-way analysis of variance showed no significant differences in rhizome production at small scale whereas differences at medium scale were significant. These differences were strictly confined at the shallow depths suggesting that local impacts from the coastline are likely to be responsible for the variability in the rhizome primary production among meadows. [ABSTRACT FROM AUTHOR]

Among the various types of human activities, the mechanical damages resulting from uncontrolled pleasure boats anchoring in shallow coastal waters would appear to be responsible for localized regressions of Posidonia oceanica meadows. This paper aims to describe and quantify the impacts of a large anchoring chains system on the structure of the P. oceanica meadow of Prelo cove (Ligurian Sea, NW Mediterranean). In this study, we provide evidence that this chains system had a negative effect on the meadow cover, generating dead ‘matte’ areas within the meadow. Meadow structure mapping, combined with the use of an environmental index (Conservation Index), which is linked to the proportional abundance of dead matte relative to living P. oceanica , underpins significant differences in the cover and in the conservation status of the meadow between areas characterized by the presence of the chains and areas without the chains. We also show that the chains affected the meadow in different ways according to P. oceanica cover. The approach proposed here, based on thematic mapping and a simple environmental index, provides relevant information for management actions on the conservation of Posidonia oceanica meadows. [ABSTRACT FROM AUTHOR]

A quantitative study of sessile macroepibenthos was carried out in Palaeochori Bay (Milos Island, Aegean Sea) using underwater, framed, still photographs. Images of sessile epibenthos were collected from four different rocky shoals at 10–35 m depth: shoal CR, where continuous vent activity was evident, and shoals E, ST and S, without evident vent activity. At each site images were taken from four stations with different slopes. Three replicate photo-samples were collected at each station. Correspondence analysis showed that the distribution of epibenthic communities was mainly related to `normal' environmental gradients such as slope, distance from the shore and depth. No clear, univocal effect of venting was recognized. However, small differences between the vent and non-vent sites were detected under overhangs, where vent effects could be locally amplified due to the entrapment of venting fluids. [ABSTRACT FROM AUTHOR]

Submarine caves with sulphurous springs at Cape Palinuro, Campania, Italy, have a richer fauna than expected from the known oligotrophic nature of the cave habitat. Warm water containing sulphide issues from springs and rises above the cooler ambient sea-water with a sharp thermocline/chemocline between. The warm water then escapes from the caves mixed with cooler sea-water, probably inducing an inflow of ambient sea-water. Bacterial mats, often dominated by large species of attached bacteria resembling Beggiatoa, line the upper parts of the inner caves and act as primary producers, fixing CO2 by means of the autotrophic enzyme ribulosebisphosphate carboxylase. Many of the animals in the innermost parts of the caves live close to the chemocline or just below, where they would experience fall-out of bacterial organic matter, and some carry filamentous bacteria on their tubes and hard parts. Dominant members of the community include sponges, cnidarians, and tubicolous polychaetes. [ABSTRACT FROM PUBLISHER]

The major epibenthic communities on subtidal rocks of Palaeochori Bay and the marine tract on the southern coast of Milos Island (Greece)were described down to 44 m depth. Six sites were investigated by snorkelling and SCUBA diving. Samples, photographs and video images were also taken to integrate information. Three out of the six sites were close to hydrothermal vents, a common feature in the area. In total, nine major epibenthic communities were found, most of which were characterised by a diverse algal growth down to the maximum depth explored. Macrobenthic cover was severely reduced only in the close proximity of vents, a white flocculent bacterial mat covering the rock at the point from which fluid escaped. Large-scale effects of vents on the epibenthic communities were not detected. However, the abundance ofspecies with warm-water affinity was recognisable in both algal and animal dominated communities, which may be related to higher winter temperature in the vent area. Epifaunal communities under overhangs were composed of distinct groups of suspension feeders at vent as compared to non-vent sites: this might indicate differences in trophic conditions. Mounds of the bioconstructional coralline alga Mesophyllum lichenoides were conspicuous only at vent sites, thus suggesting enhanced biodeposition of carbonates due to vent activity. [ABSTRACT FROM AUTHOR]

Mediterranean marine biodiversity has received only a fraction of the attention accorded to its terrestrial counterpart, despite the great cultural and economic importance that the sea has been having for the Mediterranean countries. A rough estimate of more than 8500 species of macroscopic marine organisms should live in the Mediterranean Sea, corresponding to somewhat between 4% and 18% of the world marine species. This is a conspicuous figure if one considers that the Mediterranean Sea is only 0.82% in surface area and 0.32% in volume as compared to the world ocean. The high biodiversity of the Mediterranean Sea may be explained by historical (its tradition of study dates olderthan for almost any other sea), paleogeographic (its tormented geological history through the last 5 my has been determining the occurrence of distinct biogeographic categories), and ecological (its varietyof climatic and hydrologic situations within a single basin has probably no equals in the world) reasons. Present-day Mediterranean biodiversity is undergoing rapid alteration under the combined pressure ofclimate change and human impact, but protection measures, either forspecies or ecosystems, are still scarce. To understand the role and patterns of Mediterranean marine biodiversity, marine ecological research should: first, re-value those scientific areas currently unfashionable with funding agencies (systematics, biogeography and taxonomy); second, start monitoring biodiversity with a long-term approach at a whole Mediterranean scale, possibly through an internationally co-ordinated network of marine protected areas. [ABSTRACT FROM AUTHOR]