Giorgio Tranchida

Distribution of REEs in box-core sediments offshore an industrial area in SE Sicily, Ionian Sea: evidence of anomalous sedimentary inputs.

The distribution of rare earth elements and yttrium (REEs+Y) has been investigated in box-core sediments recovered from four stations in the Sicilian coastal zone seawards of Augusta, one of the most industrialized and contaminated areas in the Mediterranean region. Shale-like REE patterns and low Y/Ho ratios (close to the chondritic ratio) suggest a dominant terrigenous (geogenic) source for REE. Slight enrichment of LREE over the HREE is interpreted as due to preferential adsorptive transfer of LREE from seawater to sediment particles. Samples from offshore cores exhibit slightly positive Gd and negative Ce anomalies. It is here hypothesized that main drivers of anthropogenic Gd flux towards the offshore are dredged contaminated materials that, recovered from the Augusta Bay, have been repeatedly discharged offshore. Consistent with the redox-chemistry of Ce, these anomalous sedimentary inputs induce a decrease of O(2) concentration in the sediment, which in turn triggers Ce regeneration.

Mediterranean circulation perturbations over the last five centuries: Relevance to past Eastern Mediterranean Transient-type events

The Eastern Mediterranean Transient (EMT) occurred in the Aegean Sea from 1988 to 1995 and is the most significant intermediate-to-deep Mediterranean overturning perturbation reported by instrumental records. The EMT was likely caused by accumulation of high salinity waters in the Levantine and enhanced heat loss in the Aegean Sea, coupled with surface water freshening in the Sicily Channel. It is still unknown whether similar transients occurred in the past and, if so, what their forcing processes were. In this study, sediments from the Sicily Channel document surface water freshening (SCFR) at 1910 ± 12, 1812 ± 18, 1725 ± 25 and 1580 ± 30 CE. A regional ocean hindcast links SCFR to enhanced deep-water production and in turn to strengthened Mediterranean thermohaline circulation. Independent evidence collected in the Aegean Sea supports this reconstruction, showing that enhanced bottom water ventilation in the Eastern Mediterranean was associated with each SCFR event. Comparison between the records and multi-decadal atmospheric circulation patterns and climatic external forcings indicates that Mediterranean circulation destabilisation occurs during positive North Atlantic Oscillation (NAO) and negative Atlantic Multidecadal Oscillation (AMO) phases, reduced solar activity and strong tropical volcanic eruptions. They may have recurrently produced favourable deep-water formation conditions, both increasing salinity and reducing temperature on multi-decadal time scales.

Depredation of striped dolphin on squid fishery and behavioural responses to interactive pinger.

The depredation of dolphins on some artisanal fisheries in the Mediterranean Sea is the major source of economic loss. This study aims to reveal the behavior of striped dolphin during interaction with flying squid fishery equipped with interactive pinger in the Ionian Sea (southern Italy). A four channel acoustics acquisition system was used during fishing hauls to record the clicks and to localize the positions of dolphins through the time delay of arrival method. The preliminary analysis shows that dolphins approached the artificial light, used for attract the squids, diving further on 100 m below the fishing boat. The number and the power of dolphins’ clicks decreased after the signals emitted by the interactive pinger. The distances of dolphins from fishing boat do not seem change significantly before and after pinger emissions. Although the efficiency of DDD pingers to decrease the depredation level was demonstrated in some study, the functioning mechanism is still unknown. Our data could indicate th...

Late Quaternary palaeoenvironmental reconstruction of sediment drift accumulation in the Malta Graben (central Mediterranean Sea)

The Malta Graben is a deep tectonic depression in the Sicily Channel, bounded by NW–SE normal faults and filled by thick Pliocene–Quaternary deposits. A previous analysis of a giant piston core (LC09) from the Malta Graben had revealed a wide range of sedimentary features (carbonate turbidites, bioturbated mud and scours), although the chronostratigraphic constraint of the stacking pattern has remained elusive. After establishing a reliable chronological framework based on seven radiocarbon dates for a shorter core from the Malta Graben (ANSIC03-735), a down-core analysis of planktonic foraminifer and coccolith abundance, stable isotopes and sediment grain size was carried out. Since the last glacial maximum, palaeoenvironmental conditions (surface fertility and deep chlorophyll maximum during the last glacial and the Younger Dryas; warm and oligotrophic water masses, with a deep nutricline and intense winter mixing during the Holocene) as well as selected calcareous plankton taxa trends and peaks seem to be similar to those reported for other central and western Mediterranean sites, possibly in spite of a unique response of these areas to late Quaternary climatic fluctuations. Four distinct layers, each tens of centimetres thick, are barren of foraminifers but not of coccoliths. Morphobathymetric data as well as new high-resolution and high-penetration seismic profiles show that prolonged contouritic activity has persisted on the western side of the Malta Graben. It is thus likely that layers barren of foraminifers are due to the overflow of fine-grained (clayey) material beyond drift channel dikes.

Some consideration about the management and economic aspect on the pinger use for mitigation the depredation phenomena in an MPA Mediterranean area.

This study was carried out in a fishing area off the coast of southern Italy, where Tursiops truncatus is frequently observed to interact with bottom gill nets. The experiments aimed to assess the economic efficiency of the DDD pingers during the interaction between dolphins and monofilament bottom gill nets. A net was equipped with pingers and another without to measure the different biomass catch and costs. The economic effectiveness with an estimate of the costs/benefits was evaluated. We modeled a catch per unit effort (CPUE) both in economic terms as euros per 50 m of net set and in biomass terms as kilograms caught per 50 m of net set with and without pingers. The analysis of the data allowed us to evaluate the advantage of the economic aid provided by the European Fisheries Fund (EFF) for the use of pinger. The CPUE of the net equipped with pingers was statistically higher than the control net. The costs of investment for pingers could fully comeback in 74 days and with the economic assistance of EFF in 34 days of fishing. The use of pingers represents productive and economic benefits, even if their potential impact noise should be considered.