Characteristics of the Mesophotic Megabenthic Assemblages of the Vercelli Seamount (North Tyrrhenian Sea)

The biodiversity of the megabenthic assemblages of the mesophotic zone of a Tyrrhenian seamount (Vercelli Seamount) is described using Remotely Operated Vehicle (ROV) video imaging from 100 m depth to the top of the mount around 61 m depth. This pinnacle hosts a rich coralligenous community characterized by three different assemblages: (i) the top shows a dense covering of the kelp Laminaria rodriguezii; (ii) the southern side biocoenosis is mainly dominated by the octocorals Paramuricea clavata and Eunicella cavolinii; while (iii) the northern side of the seamount assemblage is colonized by active filter-feeding organisms such as sponges (sometimes covering 100% of the surface) with numerous colonies of the ascidian Diazona violacea, and the polychaete Sabella pavonina. This study highlights, also for a Mediterranean seamount, the potential role of an isolated rocky peak penetrating the euphotic zone, to work as an aggregating structure, hosting abundant benthic communities dominated by suspension feeders, whose distribution may vary in accordance to the geomorphology of the area and the different local hydrodynamic conditions

Enzymatic activity and organic substrates on a sandy beach of the Ligurian Sea (NW Mediterranean) influenced by anthropogenic pressure.

Enzymatic activities (leucine aminopeptidase, LA; \u3b2-glucosidase, BG; alkaline phosphatase,AP), their related substrates and the bacterial abundance and biomass were studied over 1 yr in 2 adjacent areas of a sandy beach: one occupied by the structures of a private swimming establishment and undergoing major reconstruction work (impacted area), and the other in a more natural area (reference area). Both areas were oligotrophic, characterised by low organic matter content (with a notable contribution from the autotrophic biomass) and low enzymatic activity values. Bacterial abundance did not show significant changes, either spatially or temporally, suggesting that they quickly overcame anthropogenic forcing and seasonal luctuations under the environmental and trophic conditions. The absence of positive correlations between carbohydrates and enzymatic activities suggested the adverse influence of refractory organic matter. Nevertheless, when the environmental conditions were favourable and bacteria were supported by larger N inputs from the sea, the carbohydrate became a trophic resource, thus suddenly changing the enzyme ratios. A multivariate analysis highlighted the predominance of the seasonal over the anthropogenic influence, suggesting a rapid recovery in the impacted area. Nevertheless, changes were observed for the functional relationships between the parameters, in particular those related to the trophic quality of the organic material (lower in the impacted area) and the enzymatic hydrolysis. The coupling of LA and AP was generally tight in order to overcome the P deficiency and, in the impacted area, to overcome trophic limitations related to the input of inorganic debris and refractory organic materials

Organic matter characterisation and turnover in the sediment and seawater of a tourist harbour

A survey of a Ligurian tourist harbour was carried out during winter 2006 and summer 2007 in order to study the organic matter (OM) turnover through extracellular enzymatic activity. Seawater and sediments were sampled at six stations, three inside the port boundaries, one outside the port and two in an area influenced by the outflow of a minor river (Boate). The seawater showed OM turnover times similar to other oligo-mesotrophic coastal areas, and low concentrations of chlorophyll-a and inorganic nutrients. The sediments, instead, revealed high OM loads and a predominance of proteolysis. A significant reduction of the OM loads was observed in the outside station, indicating that the OM accumulation was due to the structures and activities of the harbour and to the Boate influence. The OM biotic recycling via enzymatic activity was enhanced especially during summer. Although the carbohydrates were probably highly refractory, their turnover was notably faster, due to glycolytic enzymatic activity that was enhanced more than the proteolytic in both the sediment and in the seawater. This suggested that the removal and recycling of OM were potentially efficient, and prevented the shift to eutrophication of the Rapallo harbour area

Urbanised beaches of the Ligurian coastal area (NW Mediterranean): A classification based on organic-matter characteristics and hydrolytic enzymatic activities

The beaches of Liguria have been intensively affected by human activities for over a century, transforming nearly the entire coastline from natural to urbanised and significantly upsetting beach ecological properties. The present study aims to investigate 9 Ligurian beaches characterised by different degree of urbanisation, to test if and to what extent the organic-matter (OM) recycling processes can be linked to the human activity. Swash zone sediment, sampled during the springesummereautumn period, when the anthropogenic influence is at its maximum due to tourism, was analysed for OM features and recycling processes. Multivariate statistical analyses showed that huge amounts of detrital OM accumulated in the more urbanised sites, where the anthropogenic influence was at its peak, deriving from higher inhabitant number and density, from the presence of crowded roads very near to the swash zone and sewage treatment plants. The presence of torrent outlets on the beaches provided further OM accumulation. Lipids, carbohydrates and degraded autotrophic pigments were the OM fractions mainly responsible of the differentiation, and rather constant, high labile phosphorus contents were found in the more urbanised sites. The high activity values of the hydrolytic enzymes indicate the response of the microbial system to the OM accumulation in the urban sites. However, a decoupling of the trends of some enzymatic activities (namely glucosidase and lipase) and their target OM was observed in the highly urbanised conditions

Organic matter recycling in a shallow coastal zone (NW Mediterranean): the influence of local and global climatic forcing and organic matter lability on hydrolytic enzyme activity.

Seawater and sediment were collected on a monthly basis from a shallow (10.5 m depth) coastal site in the Ligurian Sea (NW Mediterranean) from November 1993 to December 1994 to determine the main environmental forces that influenced the biogeochemical processes and to study the relationships between the availability and lability of the organic matter (OM) and hydrolytic enzymatic activity. The current direction throughout the sampling year was influenced by the climatic conditions, which showed significant correlations with NAO index values. The current generally flowed northwards in spring. This could cause significantly lower transparency values than in the summer, when an eastward current probably reduced the allochthonous input of material from the main local watercourse and contributed to turning the conditions from mesotrophic to oligotrophic. Spring and summer were separated by transitional periods more than by the canonical autumn and winter seasons. These transitions were characterised by a reduction in salinity values and by resuspension caused by water-column mixing and a current flowing towards the southwest. The significant inverse correlations of the chlorophyll-a and protein concentrations, bacterial abundance and proteolysis of the bottom seawater and transparency showed the direct influence of resuspension on the organic-matter dynamics. Moreover, OM trophic quality influenced the bacterial parameters and the enzymatic activities. The glycolytic \u3b2 glucosidase and chitinase activities and their bacterial cell-specific hydrolytic rates were higher when substrates such as hydrolysable proteins were available, while they decreased when refractory compounds were abundant. The low leucine aminopeptidase:\u3b2 glucosidase ratio values observed in the water column were presumably related to the potential ease with which microbes obtained protein-derived materials and energy, the protein hydrolysable fraction being estimated at ca. 90%. The significant correlations of protein with the chlorophyll-a concentrations suggested an autotrophic-derived origin, although the higher chlorophyll-a values corresponded to lower hydrolysable protein concentrations and an increase in the autotrophic biomass at the surface was correlated with a reduction in the proteolytic affinity for substrates, suggesting that a recent origin did not necessarily mean higher trophic availability. In the sediment, the lower protein:carbohydrate and chlorophyll-a:phaeopigment ratio values indicated higher OM refractivity than in the seawater, thus increasing the need for greater proteolytic activity, significantly increasing the leucine aminopeptidase:\u3b2 glucosidase ratio values and the bacterial cell-specific proteolytic activity. Although the initial trophic quality of the OM was potentially worse than that of the seawater, the heterotrophic microbial component showed successful adaptations, such as Km values similar to those of seawater, higher cell-specific hydrolytic activities and significantly higher growth rates