Effects of the installation of offshore pipelines on macrozoobenthic communities (northern and central Adriatic Sea).

Macrozoobenthos living around several pipelines placed at different depths and sediment types in the Western Adriatic Sea was investigated for three years after structures' deployment to detect possible effects due to their installation and presence. Three environmental habitats were considered based on the grain size (silty clay, clayey silt and sand). Samplings were taken within a radius of 100 m from the pipelines and at control sites. Multivariate and univariate analysis showed peculiarities of the three habitats due to the different sediment type, without differences between pipelines and controls inside each group. Silty clay and clayey silt communities appeared quite similar, being mainly represented by opportunistic species typical of the Adriatic coastal area. Benthic populations found at the offshore relict sand were characterized by a higher percentage of sensitive species. Independently of sediment typology, pipelines' installation seems to not affect the benthic populations that appear more influenced by environmental features.

Non-indigenous macrozoobenthic species on hard substrata of selected harbours in the Adriatic Sea.

The intense shipping traffic characterising the Adriatic Sea favours the spread of marine organisms. Yet, a study of 12 Adriatic ports (4 on the western side and 8 on the eastern side of the basin) found that non-indigenous species (NIS) accounted for only 4% of the benthic communities settled on hard substrates. The cirripeds Amphibalanus amphitrite and Balanus trigonus, found in 8 harbours, were the most common invaders followed by Amphibalanus eburneus, the ascidian Styela plicata, and the bivalve Magallana gigas. The highest percentage of NIS was recorded in Venice and Ploce, the harbours with the least rich native communities; the lowest percentage was retrieved in Trieste, Koper, Pula, and Rijeka, the harbours hosting the highest species diversity. In contrast, the ports of Bari and Ancona showed both high NIS percentages and highly diversified communities.

Environmental Impact of Offshore Gas Activities on the Benthic Environment: A Case Study.

Multidisciplinary monitoring of the impact of offshore gas platforms on northern and central Adriatic marine ecosystems has been conducted since 1998. Beginning in 2006, 4-5 year investigations spanning the period before, during, and after rig installation have explored the effects of its construction and presence on macrozoobenthic communities, sediment, water quality, pollutant bioaccumulation, and fish assemblages. In this study, sediment samples collected at increasing distance from an offshore gas platform before, during and after its construction were subjected to chemical analysis and assessment of benthic communities. Ecological indices were calculated to evaluate the ecological status of the area. Ecotoxicological analysis of sediment was performed to establish whether pollutants are transferred to biota. The study applied a before-after control-impact design to assess the effects of rig construction and presence and provide reference data on the possible impacts of any further expansion of the gas extraction industry in the already heavily exploited Adriatic Sea. Only some of the metals investigated (barium, chromium, cadmium, and zinc) showed a different spatial and/or temporal distribution that may be platform-related. In the early phases, the sediment concentrations of polycyclic aromatic hydrocarbons were below the detection limit at all sites; they then became detectable, but without significant spatial differences. The present findings suggest that the environmental effects of offshore gas platforms may be difficult to quantify, interpret, and generalize, because they are influenced by numerous, often local, abiotic, and biotic variables in different and unpredictable ways.

Trophic structure of polychaetes around an offshore gas platform.

The distribution of polychaetes associated with an offshore gas platform built on a muddy-sandy bottom in the northern Adriatic Sea was investigated with emphasis on their feeding structure. Polychaete species were collected at different distances from the rig using a Van Veen grab. Assessment of the polychaete community and trophic groups for impacts related to the presence of the platform demonstrated significantly different abundances at rising distances from the rig. The present findings highlight an effect of the rig on the spatial distribution of polychaete assemblages. Even though the effects of gas platforms on surrounding benthic communities have been investigated in the Adriatic Sea, no studies have addressed the distribution of polychaete trophic groups along a gradient based on distance from the rig.

Spatial pattern and weight of seabed marine litter in the northern and central Adriatic Sea.

The present study analyzes spatial distribution and typology of marine litter on the seabed in the FAO Geographical Sub-Area 17 (northern and central Adriatic Sea). Two surveys were conducted during fall 2011 and 2012 and 67 stations were sampled each year. Litter items were collected using the "rapido" trawl, a modified beam trawl commonly used by the Italian fishermen to catch flat fish and other benthic species. Marine litter in the catches was sorted and classified in 6 major categories (plastic, metal, glass, rubber, wood, other). Plastic litter was further subdivided in 3 sub-categories based on its source: fishing nets, aquaculture nets and other. Plastic was dominant in terms of weight followed by metal and other categories. The highest concentration of litter was found close to the coast likely as a consequence of high coastal urbanization, river inflow and extensive navigation associated with the morphological and hydrological features of the basin.

Offshore platforms: comparison of five benthic indicators for assessing the macrozoobenthic stress levels.

Within the European Water Framework Directive, many studies have been conducted to evaluate the sensitivity/robustness of a variety of indices in relation to natural or anthropogenic disturbance events. However, these indices have rarely been applied to verify the impacts of disturbances in offshore environments, though the Marine Strategy Framework Directive recommends their use for assessing benthic community conditions and functionality. The aim of this paper was to determine which biotic indicator performed the best for detecting the impacts of offshore structures on benthic populations in the Adriatic Sea. The impacts of four rigs were investigated six months after their installation, and the H', AMBI, m-AMBI, BENTIX, and BOPA indices were assessed. Although these five indices delivered some contradictory results because of the differences in their structure and discrepancies in their assignment of species sensitivity, the BENTIX, H' and BOPA indices appear to evaluate stress levels better than the AMBI and m-AMBI indices, which tend to provide results that are slightly overly optimistic.