Search results for "Bottom"
showing 10 items of 450 documents
The Status of Coastal Benthic Ecosystems in the Mediterranean Sea: Evidence From Ecological Indicators
2020
The Mediterranean Sea is subject to multiple human pressures increasingly threatening its unique biodiversity. Spatially explicit information on the ecological status of marine ecosystems is therefore key to an effective maritime spatial planning and management, and to help the achievement of environmental targets. Here, we summarized scientific data on the ecological status of a selection of marine ecosystems based on a set of ecological indicators in more than 700 sites of the Mediterranean Sea. For Posidonia oceanica seagrass beds, rocky intertidal fringe, and coastal soft bottoms, more than 70% of investigated sites exhibited good to high ecological conditions. In contrast, about two-th…
Ocean acidification as a driver of community simplification via the collapse of higher-order and rise of lower-order consumers
2017
AbstractIncreasing oceanic uptake of CO2 is predicted to drive ecological change as both a resource (i.e. CO2 enrichment on primary producers) and stressor (i.e. lower pH on consumers). We use the natural ecological complexity of a CO2 vent (i.e. a seagrass system) to assess the potential validity of conceptual models developed from laboratory and mesocosm research. Our observations suggest that the stressor-effect of CO2 enrichment combined with its resource-effect drives simplified food web structure of lower trophic diversity and shorter length. The transfer of CO2 enrichment from plants to herbivores through consumption (apparent resource-effect) was not compensated by predation, becaus…
Detection and mapping of Posidonia oceanica dead matte by high-resolution acoustic imaging
2009
A high-resolution echosounder was used to acquire seismo-acoustic records of P. oceanica dead matte patches in the Gulf of Palermo. Seismo-acoustic profiling enabled detection of dead matte structures that are invisible to visual inspection, being hidden by variable layers of sandy sediment. The thickness of the dead matte measured reaches a maximum of 2.2 m. The mean volume of the matte per unit area of seabed surface (MEIx) varies from 0.2 to 2.2 m 3 /m 2 , with an average value of 1.6 m 3 /m 2 and a total volume estimated at 73,000 m 3 . From literature data and from the volume of dead matte calculated in the present work we estimated that total carbon accumulated in the matte is about 2…
Multibeam Sonar System for Detecting Seabed Features
2010
Discriminating between Posidonia oceanica meadows and sand substratum using multibeam sonar
2010
Abstract Di Maida, G., Tomasello, A., Luzzu, F., Scannavino, A., Pirrotta, M., Orestano, C., and Calvo, S. 2011. Discriminating between Posidonia oceanica meadows and sand substratum using multibeam sonar. – ICES Journal of Marine Science, 68: 12–19. High-resolution, multibeam sonar (MBS) (455 kHz) was used to identify two typologies of seabed 8 m deep: Posidonia oceanica meadow and sandy substratum. The results showed that the heterogeneity of the architecture of the P. oceanica canopy and the relatively simple morphology of a sandy substratum can be detected easily by statistical indices such as standard deviation or range-of-beam depth. Based on these indices, an automated classification…
Pinger affects fish catch efficiency and damage to bottom gill nets related to bottlenose dolphins
2009
There is some evidence that the presence of Tursiops truncatus in fishing areas represents a real economic threat to fishermen due the dolphin feeding on the entangled fish, damaging the nets and reducing the fish catch. We have carried out experiments to assess the efficiency of a pinger in decreasing the interaction between the dolphins and fishing nets, in a fishing area off the coast of southern Italy, where Tursiops truncatus is frequently observed to interact with bottom gill nets. Two identical monofilament bottom gill nets (900 m long), one equipped with pingers and the other without, were used to measure the effect of these pingers on the abundance of the catch and net damage. For …
Spatio-temporal composition of discard associated with the deep water rose shrimp fisheries (Parapenaeus longirostris, Lucas 1846) in the south-centr…
2017
Discarding in fisheries is the fraction of the total catch brought on board and returned to the sea dead or alive for legal or economic reasons. The reduction of discard is one of the main objectives of the European Common Fishery Policy. This study aimed to improve the current knowledge of the discard associated with the deep-water rose shrimp (DPS) fisheries in the south-central Mediterranean Sea. We analyzed data collected from January 2009 to December 2013. Multivariate data analysis and generalized additive models (GAMs) were used to assess the spatio-temporal composition of the discard (which represented 36% of the total catch) and factors influencing its distribution. Multiple analys…
Structure and biodiversity of a Maltese maerl bed : new insight into the associated assemblage 24 years after the first investigation
2022
Maerl beds are biogenic benthic habitats distributed worldwide and known to sustain high productivity and biodiversity levels. In the Mediterranean, the number of studies that have been carried out is limited, and little is known on its real distribution, mostly due to the difficulties of exploring such habitats — Due to the high transparency of Mediterranean waters, maerl can be found at depths of over 50 m making mandatory the use of benthic grabs and ROVs. The last published data from Maltese waters were taken two decades ago. In this present study, we provide new insights on this poorly known habitat, in particular regarding the north western bank, designated as a NATURA 2000 protected …
Response of seagrasses and marine biofilms to natural acidification at CO2 vents
Nel corso degli ultimi 200 anni, circa il 30% delle emissioni antropogeniche di CO2 nell’atmosfera sono state assorbite dagli oceani, provocando un abbassamento medio dei livelli di pH oceanici pari a circa 0.1 unità. Questo fenomeno, noto come acidificazione degli oceani, sta determinando conseguenze negative sugli ecosistemi marini e sul loro funzionamento. Le attuali proiezioni climatiche suggeriscono che, in futuro, i cambiamenti climatici continueranno e si intensificheranno se non verranno adottate efficaci misure di mitigazione. Riuscire a valutare la risposta degli ecosistemi marini ai cambiamenti climatici costituisce una vera sfida per la ricerca scientifica, non solo per la diffi…
The Persian Glimpse
2020
The paper presents the results of a residential workshop dedicated to ephemeral architecture and urban renewal. Through theoretical lectures, planning and design exercises and a close relationship with the inhabitants inside the place to regenerate, the work-shop made it clear to the group of students coming from the Politecnico di Milano, the Academy of Fine Arts of Brescia and the University IUAV of Venice that “light” design elements can clearly transform the perception of a place by improving its liveability.