Deep coral forests from the Island of Sardinia

Forests are major ecological structures of the terrestrial environment that enhance biodiversity through different kinds of specialized relations that exist between the vegetal canopy and organisms from all animal reigns. The concept of forest has recently been transplanted in the marine environment; marine forests share all ecological features of terrestrial forests. What is actually peculiar in the marine environment is the shift from the ‘vegetal’ forest in shallow depths (within the photic zone) to the ‘animal’ forest (dwelling in the circalittoral zone) throughout the depth gradient. ‘Animal forest’ concept refers to forests entirely constituted by animals, that substitute to the vegetal canopy in the three dimensional development of the habitat. Benthic suspension feeders are, in fact, the main contributors to the habitat biomass and create important three-dimensional structures that enhance the ecosystem’s overall complexity. Among factors controlling the horizontal distribution of such ecosystems, the geomorphology of the sea bottom is thought to be a key factor in the distribution of deep-sea coral as many coral species require hard substrates, particular light and current conditions. Through the combination of non-invasive techniques such as ROV footage coupled with multi-beam surveys in contrasting geological settings, this thesis aims to test (both at species and community level) if and how distribution and composition of coral forests dwelling in the mesophotic environment (from 50 to 200m depth) could be influenced by contrasting geological settings. Uni- and multivariate as well as multiple regression analyses were used to test for differences in alpha and beta biodiversity in roche du large ecosystems and canyons, which are the most common geological features along continental margins worldwide. Results revealed that, in contrast to what was previously reported in scientific literature, red coral populations are not structured along a bathymetric gradient but other intraspecific, interspecific and environmental interactions may shape the population structure. Investigations on communities emphasized a high variability at mesoscale (10s of km) that overcomes the macroscale (100s of km). In particular, tested environmental variables explain patterns of observed diversity, that is higher within the same geological feature rather than among contrasting geological settings. Finally, a ROV survey conducted over a roche du large ecosystem off Carloforte (SW Sardinia) revealed the presence of a pristine millennial black coral forest of Leiopathes glaberrima. The investigated site is a millennial deep coral oases as well as a nursery area for the spotted catshark Schyliorhinus canicula, which deserves special protection. Our results enhance knowledge on coral forests dwelling in the mesophotic environment and provide useful insights for recasting conservation strategies, both at species and community level

Calcolo del bilancio idrico della regione Sardegna con il modello idrologico SWAT

Una diminuzione del 20% delle precipitazioni nell’ultimo trentennio e perdite del 40% nella rete di distribuzione hanno causato un sensibile abbassamento dei livelli idrici medi nei laghi e negli invasi artificiali della Sardegna, con la conseguenza che negli ultimi anni le municipalità, il comparto agricolo e quello industriale hanno subito le impopolari misure di razionamento. Fino ad oggi, gli enti regionali preposti alla gestione delle acque si sono serviti di modelli a scatola chiusa di tipo black box. Tuttavia da un lato appare incerta l’applicabilità di tali modelli in aree prive di misure e dall’altro tale approccio si dimostra carente nel tenere in conto le trasformazione di uso del territorio e le variazioni climatiche. Questo studio presenta l’applicazione del modello idrologico distribuito e fisicamente basato SWAT per la stima del bilancio idrologico della regione Sardegna. La procedura di caratterizzazione del tipo e della copertura del suolo ha seguito un approccio regionale, utilizzando e valorizzando al massimo le frammentarie informazioni disponibili. Per compensare la mancanza di dati di pioggia a passo giornaliero, necessari al modello idrologico, è stato sviluppato un generatore di tempo basato sull’analisi statistica di dati climatici registrati. In base alla distribuzione spaziale delle grandezze statistiche, le stazioni pluviometriche sono state raggruppate in due gruppi. Lo studio ha prodotto una serie di archivi informatici a scala regionale, creati secondo i formati di input del modello SWAT. L’applicazione del modello ai bacini idrologici della Sardegna ha tenuto conto della qualità dell’informazione descrittiva del territorio come, ad esempio, la risoluzione spaziale delle carte di base, la densità delle reti climatiche e la qualità del dato di pioggia, al fine di garantire la massima verosimiglianza del modello concettuale con le singole realtà in studio. Il sistema informatico è stato progettato ed implementato per supportare studi ed analisi mirati alla pianificazione della gestione della risorsa idrica regionale, all’individuazione di aree soggette a stress idrico e allo studio di fenomeni legati al ciclo dell’acqua, quali il ciclo dei sedimenti e dei nutrienti.A 20% rainfall decrease in the last 30 years, prolonged periods of drought and 40% losses in the distribution pipes have substantially lowered available water reserves in Sardinia, with the result of unpopular rationing measures on municipal, industrial and agricultural uses. Up to now black-box models have been the most commonly used methodologies to estimate the regional water budget. Despite their wide use, these models have shown severe limitations in estimating watershed outlet outputs far from the monitoring stations and in covering climate changes properly. In this study, we present the application of the hydrological distributed SWAT model to evaluate the water budget at the regional scale. The model parameterizations with regards to the land cover and soil type are estimated at the regional scale on the basis of available geographic data. In order to generate weather daily inputs for the SWAT model a weather generator has been developed on the basis of a statistical analysis of the Sardinian climatic data. Through a clusterization procedure the climatic gages have been grouped into two homogeneous groups. The regional databases have been formatted in the SWAT fashion. The resulting model input data along with the watershed and HRU spatial discretization criteria have been carefully checked to ensure global consistency at the overall scale. The informatics system has been developed and designed to support decision related to the management of the water resources, to identify areas under water stress, or to evaluate complementary phenomena related to the water cycle as the sediment and the nutrient fate at the catchment’s scale.29-38Pubblicat

Marine macro-litter mass outweighs biomass in trawl catches along abyssal seafloors of Sardinia channel (Italy)

: This study provides new insights onto spatial and temporal trends of seafloor macro-litter in the abyssal seafloor of Sardinian channel, in central western Mediterranean (Italy). Trawl surveys were conducted at depths between 884 and 1528 m, thus focusing on one of the least investigated marine environments. None of the considered sites was litter free, with plastics being numerically dominant (57% of items), followed by metal (11%) and glass (16%). Recorded densities and weight ranged between 49.9 and 499 items km-2 and 1.4 and 1052 kg km-2. In the most contaminated sites, the weight of the litter collected in nets represented up to nine times the biomass of benthic megafauna, and, overall, in 60% of hauls macro-litter mass outweighed the biomass collected. Moreover, we report that megafauna was observed to be more abundant in sites where macro-litter presence was more severe. More studies are needed to elucidate the nature of this correlation, with biota being more abundant in hotspots of accumulation of seafloor macro-litter

Persistence of pristine deep-sea coral gardens in the Mediterranean Sea (SW Sardinia)

Leiopathes glaberrima is a tall arborescent black coral species structuring important facies of the deep-sea rocky bottoms of the Mediterranean Sea that are severely stifled by fishing activities. At present, however, no morphological in vivo description, ecological characterization, age dating and evaluation of the possible conservation actions have ever been made for any population of this species in the basin. A dense coral population was reported during two Remotely Operated Vehicle (ROV) surveys conducted on a rocky bank off the SW coasts of Sardinia (Western Mediterranean Sea). L. glaberrima forms up to 2 m-tall colonies with a maximal observed basal diameter of nearly 7 cm. The radiocarbon dating carried out on a colony from this site with a 4 cm basal diameter revealed an approximately age of 2000 years. Considering the size-frequency distribution of the colonies in the area it is possible to hypothesize the existence of other millennial specimens occupying a supposedly very stable ecosystem. The persistence of this ecosystem is likely guaranteed by the heterogeneous rocky substrate hosting the black coral population that represents a physical barrier against the mechanical impacts acted on the surrounding muddy areas, heavily exploited as trawling fishing grounds. This favorable condition, together with the existence of a nursery area for catsharks within the coral ramifications and the occurrence of a meadow of the now rare soft bottom alcyonacean Isidella elongata in small surviving muddy inclaves, indicates that this ecosystem have to be considered a pristine Mediterranean deep-sea coral sanctuary that would deserve special protection

Ontogenetic Shifts in Body Morphology of Demersal Sharks’ Species (Order: Squaliformes) Inhabiting the Western-Central Mediterranean Sea, with Implications for Their Bio-Ecological Role

Several elasmobranch species undergo shifts in body proportions during their ontogenetic growth. Such morphological changes could reflect variation in diet, locomotion, or, more broadly, in the species' interactions with their environment. However, to date, only a few studies have been conducted on this topic, and most of them focused on particular body regions. In the present study, the ontogenetic growth of five different demersal shark species was investigated by using both traditional linear morphometry of the entire body and shape analysis of the caudal fin. A total of 449 sharks were analysed: 95 little gulper sharks, 80 longnose spurdogs, 103 kitefin sharks, 124 velvet belly lanternsharks, and 47 angular roughsharks. From each specimen, 36 linear morphometric measurements were taken. While a first canonical analysis of principal coordinates ruled out the possibility of different growth patterns between males and females, the same analysis statistically discriminated between small and large individuals in every species based on their morphology. A Similarity Percentage analysis revealed that the most important measurements in distinguishing these two groups were those related to body lengths, indicating that large individuals are more elongated than small individuals. The shape analysis of caudal fins revealed allometric growth during ontogenetic development, with adult individuals having a wider fin (discriminant analysis, p < 0.05). These findings could be related to changes in predatory skills, supporting the hypothesis of a shift in the ecological role that these sharks play in their environment, thus providing new essential information for their conservation

Long-term sublethal exposure to polyethylene and tire wear particles: Effects on risk-taking behaviour in invasive and native fish

Anthropogenic polymeric particles pollute even the most remote ecosystems and may compromise organisms' behaviour and movement skills. It is expected that invasive species cope better with pollutants than native species (i.e., pollution resistance hypothesis). In this study, invasive gibel carp (Carassius gibelio) and native crucian carp (Carassius carassius) were used as model organisms. Specimens were fed daily with food pellets (1 % body weight) added with 0.1 % polyethylene (PE), tire wear particles (TWPs) and control. Their behavioural parameters were compared before and after 14 and 60 days of exposure. Additionally, we evaluated burst swimming capacity after 60 days of exposure to the treatments. The fishes exposed to the PE and TWPs treatments showed significant trends toward increased boldness scores and, in the PE treatment, higher utilization of the open field, and both behavioural changes are associated with higher risk-taking. Invasive gibel carp had substantially better swimming performance than crucian carp, but the expected trend in relation to the treatments was not found. Fish exposed to sublethal doses of PE and TWPs showed signs of behavioural changes after two months of exposure that may affect risk-taking behaviour, which might impact species interactions with predators

Onboard Scientific Observers Provide a Realistic Picture of Harvesting and Management Priorities for the Precious Red Coral (Corallium rubrum L.)

Mediterranean red coral Corallium rubrum is considered the most precious coral worldwide. Harvesting activities are performed by licensed scuba divers and managed through the recent pan-Mediterranean management plan issued by General Fisheries Commission for the Mediterranean (GFCM) along with measures locally enacted, imposing limits on licenses, harvesting season, minimum depth of dive, and size. The use of Remotely Operated Vehicles (ROVs) is prohibited, with the only exception being for scientific purposes. Despite measures already in force, the implementation of additional management tools has been recently recommended. This article reports results from the first monitoring campaign on C. rubrum harvesting based on ROVs for seabed exploration and Onboard Scientific Observers (OSOs), carried out from 2012 to 2015 along the coast of Sardinia (Mediterranean Sea—Western basin). More than 450 dives were monitored, confirming how ROV's support eases the scouting of exploitable banks, leading to increases in catches. OSOs reported the collection of colonies below the minimum reference size and catches/dive above limits. Onboard observers collected data also on colony diameter, which is crucial for the estimation of population size structure and exploitation status. OSOs proved to be valid tools in providing additional and reliable information on red coral harvesting, thus deserving to be included among mandatory measures for the sustainable exploitation of red coral in the Mediterranean Sea

Microplastics impair extracellular enzymatic activities and organic matter cycling in oligotrophic sandy marine sediments

Microplastics (MPs) are ubiquitous and constantly accumulating in the marine environment, especially sediments. Yet, it is not well clarified if and how their carbon backbone could interact with surrounding sediments, eventually impairing key benthic processes. We assessed the effects of a ‘pulse’ contamination event of MPs on sedimentary organic matter (OM) quantity, quality and extracellular enzymatic activities (EEAs), which are well established descriptors of benthic ecosystem functioning. Marine sediments were exposed for 30 days to environmentally relevant concentrations (∼0.2 % in weight) of naturally weathered particles (size range 70–210 μm) of polyurethane, polyethylene, and a mixture of the most common polymers that are documented to accumulate in marine sediments. Despite the low concentration, contaminated sediments showed significantly different composition of OM, showing a decrease in lipid content and increase in protein. Moreover, we document a significant decrease (over 25 %) in quantity of biopolymeric C already after 15 days of exposure, compared to controls. Contaminated sediments showed lower C degradation rates (up to −40 %) and altered EEAs, with alkaline phosphatase being ∼50 % enhanced and aminopeptidase being reduced over 35 % compared to control treatments. Overall, the effects generated by the mixture of polymers were smaller than those exerted by the same amount of a single polymer. Our results provide insights on how that MPs can significantly alter marine sedimentary biogeochemistry through altered benthic processes, that could cumulatively impair whole benthic trophic webs by enhancing the accumulation and possible longer-term storage of recalcitrant organic C in the seabed

Bio-Ecological Features Update on Eleven Rare Cartilaginous Fish in the Central-Western Mediterranean Sea as a Contribution for Their Conservation

Cartilaginous fish are commonly recognized as key species in marine ecosystems for their fundamental ecological role as top predators. Nevertheless, effective management plans for cartilagi- nous fish are still missing, due to the lack of knowledge on their abundance, distribution or even life-history. In this regard, this paper aims at providing new information on the life-history traits, such as age, maturity, reproductive period, in addition to diet characteristics of eleven rare cartilagi- nous fish inhabiting the Central-Western Mediterranean Sea belonging to the orders Chimaeriformes (Chimaera monstrosa), Hexanchiformes (Heptranchias perlo and Hexanchus griseus), Myliobatiformes (Aetomylaeus bovinus and Myliobatis aquila), Rajiformes (Dipturus nidarosiensis and Leucoraja circu- laris), Squaliformes (Centrophorus uyato, Dalatias licha and Oxynotus centrina) and Torpediniformes (Tetronarce nobiliana), useful for their assessment and for future management actions. Particularly, the present paper provides for the first time the age estimation of D. nidarosienis and L. circularis which were both found capable of becoming older than ten years. In addition, the present study updates the sizes of first maturity of C. uyato and D. licha, which appeared to be capable of reproducing earlier than what was previously hypothesized, representing very valuable information for a better understanding of these rare species populations status and, eventually, their conservation. On the basis of the stomach content analysis, it was possible to identify five different predator groups

On the presence of the Endangered white skate Rostroraja alba in Sardinian waters

The white skate Rostroraja alba is assessed by the International Union for Conservation of Nature as Endangered globally and is now considered rare in the Mediterranean. This species has never been recorded in Sardinian seas (central western Mediterranean), but an empty eggcase was collected on a sandy bottom off the western Sardinia coasts during the MEDiterranean International Trawl Survey (MEDITS) program in 2019. A morphometric and morphological description of the Sardinian eggcase, after a comparison with measurements from other Mediterranean and Atlantic specimens, showed it to be clearly ascribable to Rostroraja alba