1,721,019 research outputs found
A new ecological index for the status of mesophotic megabenthic assemblages in the mediterranean based on ROV photography and video footage
No full textA new index of ecological status, named Mesophotic Assemblages Ecological Status (MAES) index, was elaborated on the basis of ROV (Remotely Operated Vehicle) photography and video footage in order to assess the status of mesophotic megabenthic assemblages from hard bottom. The index was tested on seven sites located between 50 and 150 m depth in the Ligurian and Tyrrhenian seas (western Mediterranean Sea). The MAES index considers three main parameters: (i) the community structure (number of megabenthic taxa, percent biotic cover in the basal layer, density of erect species); (ii) the condition of the dominant erect species (average height, percent of colonies with epibiosis/necrosis); (iii) the visible human impact (density of marine litter, including lost fishing gears). Two versions of the index have been elaborated, the complete version (MAES) and the quick version (q-MAES), which showed comparable results, therefore suggesting the possibility of fastening assessment times. The sensitivity of the MAES index was correlated with the putative human pressure acting upon the site (semi-quantitatively assessed considering fishing effort and coastal urbanization). A standard working protocol related to the evaluation of the MAES index is here proposed with the intent to create an effective monitoring tool for the assessment of the ecological status of mesophotic assemblages on a large scale, as required by the EU Marine Strategy Framework Directive. MAES index will enhance the comprehension of the dynamics of mesophotic Mediterranean megabenthic assemblages with respect to human pressures and will also provide marine scientists and managers with a valuable tool specifically designed for the conservation of such vulnerable marine ecosystems
Sponges associated with Antarctic stylasterids (Cnidaria, Hydrozoa) from the deep Ross Sea: what’s new?
No full textIn 2017, during the XXXII Antarctic campaign on board R/V Italica, in the context of the PNRA research project GRACEFUL (PNRA16_00069), several deep (670-1022 m) remotely operated vehicle (ROV) explorations in the Ross Sea documented wide areas of thanatocoenosis and scattered living colonies of stylasterids. These aggregations of stylasterids create a secondary substrate defined as a ‘deep marine animal forest’ that supports a high biodiversity of associated sponges. A total of 228 sponges, belonging to 38 species, was recorded attached on Inferiolabiata labiata (Moseley, 1879) fragments. The most abundant species is Iophon radiatum Topsent, 1901, with 47 specimens, followed by Clathrochone cf. clathroclada (Lévi & Lévi, 1982) with 24 specimens and Clathria paucispicula (Burton, 1932) with 17. Ten species are first records from the Ross Sea, one species (Halichondria (Halichondria) cristata Sarà, 1978) represents a first record from Antarctica, and other 9 species are probably new to science.
Very low levels of coral coverage by sponges were found despite the large number of species. On average, we estimated the presence of 2 species per fragment of I. labiata with a maximum of 8 species on a single colony fragment. All the sponge specimens were very small and did not exceed 5 cm2, while 81% of the sponge samples ranged between 0.003 - 0.5 cm2. In fact, these stylasterids represent an available secondary substrate, but being dead, they are prone to be covered by bottom sediments, while filter-feeding epibionts usually prefer living and elevated substrates.
Data from our surveys indicated a rich and diverse sponge fauna associated with stylasterid thanatocoenosis in deep Antarctic waters, in line with the known levels of diversity of this region
Distribution and population structure of deep dwelling red coral in the Northwestern Mediterranean
No full textCommercially harvested since ancient times, the highly valuable red coral
Corallium rubrum (Linnaeus, 1758) is an octocoral endemic to the Mediterranean
Sea and adjacent Eastern Atlantic Ocean, where it occurs on rocky bottoms
over a wide bathymetric range. Current knowledge is restricted to its
shallow populations (15–50 m depth), with comparably little attention given to
the deeper populations (50–200 m) that are nowadays the main target of
exploitation. In this study, red coral distribution and population structure were
assessed in three historically exploited areas (Amalfi, Ischia Island and Elba
Island) in the Tyrrhenian Sea (Western Mediterranean Sea) between 50 and
130 m depth by means of ROV during a cruise carried out in the summer of
2010. Red coral populations showed a maximum patch frequency of
0.20 0.04 SD patchesm
1 and a density ranging between 28 and 204 colonies
m
2, with a fairly continuous bathymetric distribution. The highest red
coral densities in the investigated areas were found on cliffs and boulders
mainly exposed to the east, at the greatest depth, and characterized by medium
percentage sediment cover. The study populations contained a high percentage
(46% on average) of harvestable colonies (>7 mm basal diameter). Moreover,
some colonies with fifth-order branches were also observed, highlighting the
probable older age of some components of these populations. The Ischia population
showed the highest colony occupancy, density and size, suggesting a better
conservation status than the populations at the other study locations. These
results indicate that deep dwelling red coral populations in non-stressed or
less-harvested areas may diverge from the inverse size-density relationship
previously observed in red coral populations with increasing depth
Habitat constraints and self-thinning shape Mediterranean red coral deep population structure: implications for conservation practice
No full textThe Mediterranean red coral, Corallium rubrum, is one of the most precious corals worldwide. Below 50 m depth, C. rubrum populations are generally characterised by large and sparse colonies, whereas shallow populations (above 50 m depth) show high densities of small colonies. We show here instead that populations dwelling between 80 and 170 m depth exhibited a continuous range of population density (from 2 to 75 colonies per 0.25 m2), with less than 1% of variance explained by water depth. An inverse relationship between maximum population density and mean colony height was found, suggesting that self-thinning processes may shape population structure. Moreover, demographically young populations composed of small and dense colonies dominated along rocky vertical walls, whereas mature populations characterised by large and sparsely distributed colonies were found only in horizontal beds not covered by sediment. We hypothesise that, in the long term, shallow protected populations should resemble to present deep populations, with sparsely distributed large colonies. Since the density of red coral colonies can decay as a result of self-thinning mechanisms, we advise that future protection strategies should be based also on a measure of red coral spatial coverage instead of population densit
fishery and conservation of deep red coral banks in the Sicily Channel (Mediterranean Sea)
No full textRecent ROV surveys conducted on the Ragusa bank in the Sicily Channel (Mediterranean Sea) documented illegal and continuous use of the 'ingegno' gear for red coral fishing. Three lost gears were recorded showing different levels of epibiosis thus supporting multi-annual exploitation of the bank. The red coral population of the Ragusa bank showed a typical 'forest-like' configuration with upright, medium-sized colonies similar to those of other commercially exploited deep Mediterranean banks. The direct negative effect of this trawling gear was evident from numerous rocky boulders completely enveloped by lost nets and occasionally turned over. Red coral fragments as well as fragments of 'ingegno' nets were observed in high abundance on the sea floor. This evidence suggests that this gear is highly destructive even on rough sea floors, contrary to the traditional view, which is that it has a more random impact on rough rocky bottoms. The estimated coral uptake of 'ingegno' is 45% of the total coral biomass, while the estimated coral loss, in terms of fragments, is 9%, demonstrating the high impact of this gear. The study highlighted the infringement of the red coral fishing ban by trawling gears as well as a lack of effective policing. The strengthening of controls on landings at nearby harbours, and education programmes for the local maritime communities are among the management actions proposed to protect these surviving red coral populations from the ongoing illegal fishing activity
Marine Robotics for Deep-Sea Specimen Collection: A Systematic Review of Underwater Grippers
No full texthe collection of delicate deep-sea specimens of biological interest with remotely operated vehicle (ROV) industrial grippers and tools is a long and expensive procedure. Industrial grippers were originally designed for heavy manipulation tasks, while sampling specimens requires dexterity and precision. We describe the grippers and tools commonly used in underwater sampling for scientific purposes, systematically review the state of the art of research in underwater gripping technologies, and identify design trends. We discuss the possibility of executing typical manipulations of sampling procedures with commonly used grippers and research prototypes. Our results indicate that commonly used grippers ensure that the basic actions either of gripping or caging are possible, and their functionality is extended by holding proper tools. Moreover, the approach of the research status seems to have changed its focus in recent years: from the demonstration of the validity of a specific technology (actuation, transmission, sensing) for marine applications, to the solution of specific needs of underwater manipulation. Finally, we summarize the environmental and operational requirements that should be considered in the design of an underwater gripper
Sponges associated with stylasterid thanatocoenosis (Cnidaria, Hydrozoa) from the deep Ross Sea (Southern Ocean)
No full textIn the Antarctic seas, where hard substrates are scarce, the presence of secondary bio-substrates formed by calcareous organisms is an essential condition to increase the epibiosis and therefore the diversity of sessile benthic fauna. The aggregations of stylasterid hydrozoa, with their branched carbonate structures, are an example of a secondary habitat defined as a ‘deep marine animal forest’. The three-dimensional habitat made by these corals supports a high biodiversity of associated organisms, usually invertebrates. Recently, deep remotely operated vehicle (ROV) exploration of the Iselin Bank and the Hallett Ridge (Ross Sea, Antarctica) documented wide areas characterised by large thanatocoenosis of stylasterid skeletons lying on flat muddy substrates, with scattered living colonies generally made of few short branches. In our study, sponges associated with 54 dead colonies of two stylasterid species recorded in these areas were investigated. The analysis led to the discovery of a remarkable number of specimens (127) ascribed to 38 sponge species (31 encrusting and 7 massive). Two of these sponges, Asbestopluma (Asbetopluma) sinuosa and Lissodendoryx (Ectyodoryx) inferiolabiatae, are new. In light of the present data, we can assume that, in Antarctica, stylasterid skeletal remains, due to their three-dimensional structure, play an important role in maintaining sponge biodiversity. This is also due to the ability of sponge specie to produce miniaturised specimens able to colonise these peculiar substrata
Submarine canyons along the upper Sardinian slope (Central Western Mediterranean) as repositories for derelict fishing gears
Full text linkBy means of ROV surveys, we assessed the quantity, composition and bathymetric distribution of marine litter in 17 sites along the Sardinian continental margin (Central Western Mediterranean) at depths ranging from 100 to 480m. None of the investigated sites was litter free, but the mean density of litter (0.0175±0.0022itemsm-2) was lower than that reported from other Tyrrhenian regions. The difference in the total litter density among sites was negligible, but the density of derelict fishing gear (DFG) items (most of which ascribable to small scale fishery) in submarine canyons was higher in submarine canyons than in other habitats. Our result suggest that submarine canyons (known to be highly vulnerable ecosystems) act as major repositories of DFGs, and, therefore, we anticipate the need of specific measures aimed at minimizing the loss and abandonment of DFGs in submarine canyons
The “Sardinian Cold-Water Coral Province” in the context of the Mediterranean coral ecosystems
No full textA new cold-water coral (CWC) province has been identified in the Mediterranean Sea in the Capo Spartivento canyon system offshore the southern coast of Sardinia. The ‘Sardinia cold-water coral pro- vince’ is characterized in the Nora canyon by a spectacular coral growth dominated by the branching scleractinian Madrepora oculata at a depth of 380–460 m. The general biohermal frame is strengthened by the common occurrence of the solitary scleractinian Desmophyllum dianthus and the occasional presence of Lophelia pertusa. As documented by Remotely Operated Vehicle survey, this area is a hotspot of megafaunal diversity hosting among other also live specimens of the deep oyster Neopycnodonte zibrowii. The new coral province is located between the central Mediterranean CWC provinces (Bari Canyon, Santa Maria di Leuca, South Malta) and the western and northern ones (Melilla, Catalan- Provençal-Ligurian canyons). As for all the best developed CWC situations in the present Mediterranean Sea, the new Sardinian province is clearly influenced by Levantine Intermediate Water which appears to be a main driver for CWC distribution and viability in this basin
Coral forests diversity in the outer shelf of the south Sardinian continental margin
No full textEcological theory predicts that heterogeneous habitats allow more species to co-exist in a given area, but to date, the knowledge about the relationships between habitat heterogeneity and biodiversity of coral forests in the lower shelf and upper slope along continental margins is rather limited. We investigated biodiversity of coral forests from 8 sites spread over two different geomorphological settings (namely, pinnacles vs. canyons) in the lower shelf along the Sardinian continental margin. Using a combination of multivariate statistical analyses, we show here that differences in the composition of coral assemblages among different geomorphological settings were not statistically significant, whereas significant differences emerged among sites within the same geomorphological setting (i.e. among pinnacles and among canyons). Our results reveal that environmental and bathymetric factors such as sediment coverage, slope of the substrate, terrain ruggedness, bathymetric positioning index and aspect were important drivers of the observed patterns of coral biodiversity in both settings. Spatial variability of coral forests' biodiversity is affected by environmental factors that act at the scale of each geomorphological setting (i.e. within pinnacles and in canyons) rather than by the geomorphological settings themselves (i.e. the widest spatial scale that includes both pinnacles and canyons). This result allows us to suggest that simple categorization of benthic communities according topographically defined habitat is unlikely to be sufficient for addressing conservation purposes
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