Abstract:
We studied the spatial variability and within-year temporal changes in hydrological features, grain size composition and chemical
characteristics of sediments, as well as macrofaunal assemblages, along a heavily modified inlet in the Gulf of Oristano (western Sardinia,
Italy). The inlet connects the Cabras lagoon to the gulf through a series of convoluted creeks and man-made structures, including a dam
and fish barriers built in the last three decades. Sediments were muddy and mainly composed of the ‘‘non-sortable’’ fraction (i.e., <8 lm
particle size) in all four areas investigated: Lagoon, Creeks, Channel and Seaward. Along the inlet, however, the ratio between the <8 lm
and the 8–64 lm fractions was highest in Creeks and Channel, between the fish barriers and the dam, suggesting impaired hydrodynamics.
Consistently, steep gradients in water salinity, temperature and dissolved oxygen concentrations were found in proximity to the fish
barriers. The whole inlet was characterized by a major organic enrichment of sediments, with up to an annual mean of 33.6% of organic
matter and 11.7% of total organic carbon in Seaward due to the presence of seagrass leaf litter. Acid-volatile sulphide and chromiumreduced
sulphur concentrations were highest throughout the year in Seaward and Lagoon, respectively, with a peak in summer. Consistently,
the whole inlet supported low structured macrofaunal assemblages dominated by few opportunist species, with a relatively lower
diversity in Lagoon throughout the year and the highest abundances in Seaward in summer. We infer that the presence of artificial structures
along the inlet, such as fish barriers and the dam, impair the lagoon-gulf hydrodynamics, sediment exchange and animal recruitment
and colonization. We suggest that the removal of these structures would favour water renewal in the Cabras lagoon, but would also
increase the outflow of organic C-bonding fine particles into the gulf with serious consequences for Posidonia oceanica and Cymodocea
nodosa seagrass meadows. We conclude that all possible consequences of such initiatives should be carefully considered before any action
is taken.
Marine reserves are widely used throughout the world to prevent overfishing and conserve biodiversity, but uncertainties remain about their optimal design. The effects ofmarine reserves are heterogeneous. Despite theoretical findings, empirical studies have previously found no effect of size on the effectiveness of marine reserves in protecting commercial fish stocks. Using 58 datasets from 19 European marine reserves, we show that reserve size and age do matter: Increasing the size of the no-take zone increases the density of commercial fishes within the reserve compared with outside; whereas the size of the buffer zone has the opposite effect. Moreover, positive effects of marine reserve on commercial fish species and species richness are linked to the time elapsed since the establishment of the protection scheme. The reserve size-dependency of the response to protection has strong implications for the spatial management of coastal areas because marine reserves are used for spatial zoning.
The contribution of biogenic sediments produced by the Posidonia oceanica seagrass ecosystem to shore sediment composition was studied in four beaches along the Sinis Peninsula, west Sardinia. The beach sediments showed a variable amount of biogenic carbonate derived from sediments of P.oceanica meadows.
Abstract:
Mapping of benthic assemblages of the coastal zone was realised in the Marine Protected Area of Sinis - Mal di Ventre (Western Sardinia) in order to identify the suitable areas for the anchoring of pleasure boats. Based of the nature of substrata and benthic assemblages different solutions for the management of anchoring were proposed.
Abstract:
Recently completed sedimentological and palaeontological analyses of the Messinian deposits of western Sardinia yielded
dating, palaeoenvironmental and new sequence stratigraphic interpretations.
The Basal Marls and the Capo San Marco Formation are referred to the Messinian. Both formations were deposited in a
ramp setting, whereas the overlaying Sinis Limestone Formation is interpreted as a carbonate platform of wide extent, probably
equivalent to part of the Terminal Carbonate Complex. All these deposits are considered to have formed under normal marine
conditions. The three formations developed during one and a half cycles of progradation –retrogradation.
Compared with other Messinian Mediterranean carbonate platforms, the Sinis Peninsula exhibits several unusual
features:
(1) The notable absence of scleractinian coral reefs is related to dominantly cool seawater in this area.
(2) The Capo San Marco Formation contains widespread microbial –bryozoan –serpulid carbonate buildups, partially
associated with upwelling currents.
(3) The breccias at the top of the Sinis Limestone Formation are regarded as resulting from a major seismic shock
over the whole peninsula
