Giulio Relini

The Ligurian Sea: present status, problems and perspectives

The Ligurian Sea is a deep basin in the northernmost sector of the western Mediterranean which shows peculiar hydrodynamic and meteo-oceanographic features. The coasts of the Ligurian Sea are among the most urbanised and industrialised along the Italian coastline: the main causes of disturbance being littoral urban development and harbour activities, the building of littoral rail- and highways, and the presence of several polluted discharges. This review, by evaluating the huge scientific output published in the last three decades, describes and discusses the most important geological, hydrological and biological characteristics of the Ligurian Sea. We show that this regional sea has largely been investigated in terms of its geological and structural evolution, as well as in terms of the sedimentation dynamics of the littoral and deep bottoms, with particular attention to the sedimentation balance of the beaches and their erosive processes. We report that the prevalent hydrodynamic and meteo-oceanographic conditions favour a continuous exchange of coastal water masses, and that the seasonal and interannual dynamics of water masses can effects the local climate, with direct and indirect consequences on fish and benthic communities documented in the last decade. We stress that although recent studies offer good knowledge of the distribution of coastal benthic communities, only scant information is available for the whole continental shelf, the submarine canyons and the rocky bathyal bottoms. Our meta-analysis reveals that significant fishing activities are monitored, but also that certain sectors of the biological resource are suffering, and suggests the set up of appropriate management measures. The Ligurian Sea hosts a number of Marine Protected Areas (MPAs) of high relevance, while the institution of the Whale Sanctuary completes the protection policy of the Regione Liguria. Our meta-analysis points out the need for long-term studies, based primarily on the analysis of those areas of the Ligurian Sea that have been little investigated to date. Finally, only properly addressed studies, using experimental approaches and along appropriate spatial and temporal scales, might allow us to understand the functioning of the Ligurian marine ecosystems, evaluate their health conditions and the dynamics of the main variables that affect the distribution of the single species (including species of high economic value) and benthic communities.

History, ecology and trends for artificial reefs of the Ligurian sea, Italy

From 1970 to the present 10 artificial reef sites have been developed in coastal waters of the Ligurian Sea, Italy. They range from Ventimiglia, in the west, to La Spezia, in the east, with the largest and best known reef complex being located in the Gulf of Genoa at Loano and consisting of 2,745 m3, about 5,200 t of material and covering a surface of 350 ha. Design and construction practices have advanced from an initial, unsuccessful effort that used automobile bodies (now banned) to current use of custom-designed concrete modules deployed systematically. Funding for reef construction has come since 1983. The earliest aim of reefs was as a physical barrier to protect habitats against illegal otter trawl fishing. Newer objectives include habitat restoration, enhancement of biodiversity and fishing catch, and research to test materials and designs for physical and ecological performance. Reefs also functions as environmental observation stations, with the invasive species Caulerpa taxifolia (Vahl) C. Agardh, being recorded on the reef at Alassio. For some Artificial Reefs (Ars), benthic organisms and fishes, settlement, biomass and development of community are recorded. In Loano AR, immersed in 1986, more than 150 algae species are recorded, more than 200 benthic animal species and 78 species (87 taxa) of fishes. Fifty-six species (61 taxa) of fishes are recorded by visual census, the others are caught only by trammel net and long line. Trammel catches at Loano are on average about 2.32 kg/100 m net. Comparisons among ARs reveal that age of the reef, location and presence of seagrass meadows are crucial for success. An indication of functional equivalence between ARs and natural rocky reefs is seen if both fish and sessile macrobenthos are compared. After 34 years of investigation a database comprising at least one hundred scientific articles based on research programs of up to 15 years, and other unpublished reports, provides information to guide future planning of reefs. On the basis of acquired experience, some management advice is suggested and the best design for the basic module in the Ligurian sea is described. The role of ARs, providing protection of coastal environment against the illegal otter trawling, nursery, microhabitat and food supply, while increasing biodiversity, biomass of benthos and fishes, and facilities for ecotourism, is outlined.

The macrofouling on offshore platforms at Ravenna

Abstract The fouling which settles on gas platform piles was studied using samples taken in 1993 from the PCWA and ANTARES platforms positioned, at 7 and 10.5 km from the shore respectively and on bottoms at 12 m and 14 m in the Adriatic Sea. For each platform a pile was chosen as representative of the macrofouling found on the whole platform. In March and September 1993 samples were obtained by scraping an area of 600 cm2 from three or four different aspects (North, East, South, West), at the same depth. Samples were taken at depths of 0.5, 5.5 and 12 m on PCWA and 0.5, 7 and 12 m on ANTARES. Photographs and video recordings taken over the whole length of the chosen pile were used for an additional description of the settlement. On both platforms the macrofouling was characterized by a dominance of mussels from sea surface to a depth of about 10 m. Near the bottom the bivalve Crassostrea gigas, barnacles, hydroids and serpulids were more important. The presence of the bryozoan Schizoporella errata (present only at ANTARES) and the zoanthid Epizoanthus arenaceus (present only at PCWA) were the main differences at this depth. The fouling, or mussel weights, of the two platforms were similar for the two seasons, even though the highest values were registered in September on PCWA (1 m) with 1561.3 g/dm2, of which 1553 g/dm2 comprised mussels. A comparison is drawn with a previous fouling experiment (which used one-year panels) carried out in 1975–76.

An offshore buoy as a small artificial island and a fish-aggregating device (FAD) in the Mediterranean

The ODAS Italia 1 oceanographic buoy is moored in the Ligurian Sea, 37 nm from Genoa, along the Genoa-Cape Corse transect (43° 48.90′ N–09° 06.80′ E), over a 1270 m deep sea bottom. The underwater portion of the buoy is 37 m long and 0.60 m in diameter, acting as a small island for colonization of fouling organisms and as a fish-aggregating device (FAD). The role of the buoy in attracting and maintaining fish assemblages was investigated by visual censuses in different seasons at depths of 0–40 m. Fish from seven families, comprising 12 species, of which three are benthic, were recorded with maximum abundance in summer. Fouling was studied from samples collected on the buoy and on immersed panels. The fouling community of the buoy consisted of 34 algae and 100 animal species, including three fish. The settlement processes of the fouling community on the panels, in particular on those exposed for over 70 months at 12 m and 33 m depth, are described based on counts of settled organisms, the covering index of each taxa and biomass assessments. On the panels, 63 species were identified. The fouling biomass, on the panel submerged for 70 months, assessed as wet weight, reached 2.8 kg/m2 at 12 m depth and 4.8 kg/m2 at 33 m depth.Observations of benthic organisms settled directly on the buoy were made between 1988 and 1989 and when the buoy was retrieved and brought back to shore on April 15, 1991 after 52 months at sea. At this time, the fouling community along the full 37 m length of the buoy was sampled, and 91 taxa, including 83 species, were identified. Several of the species present on the buoy are shallow, coastal species, some with a very short larval period. Possible ways of colonization by such species are discussed. Despite seasonal changes, the pelagic fish community was more stable over the period of 11 years of study than the benthic community settled on the buoy (that is still developing).

Coal Ash for Artificial Habitats in Italy

In Italy artificial reefs are generally multipurpose structures (Relini and Orsi- Relini, 1989) placed in near-shore areas to prevent illegal trawling in water shallower than 50 m, so protecting the natural environment and special biocoenosis (such as Posidonia oceanica beds). Such reefs provide attachment surfaces, protection and shelter for eggs and juveniles of commercial species and enhance local fish populations for capture by sport and professional fishermen. Local fishing communities are increasingly requesting deployment of artificial reefs in‘their’areas of operation. This increase in demand implies a need for large quantities of materials for reef construction if requests are to be satisfied.

The Loano Artificial Reef

In the past 40 years the coastal marine environment in the Western Ligurian Riviera has been affected by three major human activities: (1) Illegal fishing, especially otter-trawling, in the shallow (< 50 m) coastal zone where this type of gear is banned. The problem is often compounded by the use of undersize net mesh in the cod end of the trawls. (2) Pollution, mainly sewage discharges into the sea. Such discharges increased considerably in recent decades following an increase in the number of inhabitants in the Italian Riviera and the success of the tourist industry. (3) Siltation caused by badly planned beach replenishment schemes designed to repair sandy shores. These schemes have used fine silty material rather than sand or gravel with the result that the seabed has become muddy and marine flora has been destroyed. Where the result is the decline or disappearance of the seabed-stabilizing Posidonia (seagrass) meadows a chain reaction may be involved in which storms become even more destructive to beaches and so more material has to be discharged to maintain the sandy shore for tourism. The result is that the natural rocky seabed is disappearing while the sandy seabed is becoming abiotic at a macroscopic level. The effect of this situation on small coastal fisheries has already resulted in a significant decrease in quality and quantity of fish caught.

Fish biodiversity in a Caulerpa taxifolia meadow in the Ligurian Sea.

Abstract The fish population of a flat marine area (near Imperia in the Ligurian Sea), depths between 4 and 8 m, colonized by the allochthonous alga Caulerpa taxifolia (Valhl) C. Agardh, was studied during a series of observations from October 1994 to October 1996. Visual censuses and catches using 200 m trammel nets were carried out. Fifty different fish species were observed, Sparidae and Labridae, with 12 and 10 species respectively, were the two most represented families. Maximum Shannon‐Weaver index obtained by censuses was 3.29 and by net catch 3.40. Abundances of Symphodus tinea and Scorpaena porcus seemed to be a characteristic of this community. A comparison with fishing data obtained in a control area without C. taxifolia, but colonized by the phanerogam Cymodocea nodosa, gave an idea of the changes produced in the fish population as a consequence of the spread of the allochthonous alga. A comparison with Mediterranean rocky environments indicated the existence of some shared qualitative charact...

Large-Scale Spatio-Temporal Patterns of Mediterranean Cephalopod Diversity

Species diversity is widely recognized as an important trait of ecosystems’ functioning and resilience. Understanding the causes of diversity patterns and their interaction with the environmental conditions is essential in order to effectively assess and preserve existing diversity. While diversity patterns of most recurrent groups such as fish are commonly studied, other important taxa such as cephalopods have received less attention. In this work we present spatio-temporal trends of cephalopod diversity across the entire Mediterranean Sea during the last 19 years, analysing data from the annual bottom trawl survey MEDITS conducted by 5 different Mediterranean countries using standardized gears and sampling protocols. The influence of local and regional environmental variability in different Mediterranean regions is analysed applying generalized additive models, using species richness and the Shannon Wiener index as diversity descriptors. While the western basin showed a high diversity, our analyses do not support a steady eastward decrease of diversity as proposed in some previous studies. Instead, high Shannon diversity was also found in the Adriatic and Aegean Seas, and high species richness in the eastern Ionian Sea. Overall diversity did not show any consistent trend over the last two decades. Except in the Adriatic Sea, diversity showed a hump-shaped trend with depth in all regions, being highest between 200–400 m depth. Our results indicate that high Chlorophyll a concentrations and warmer temperatures seem to enhance species diversity, and the influence of these parameters is stronger for richness than for Shannon diversity.

Seventeen instars of adult life in female Aristeus antennatus (Crustacea: Decapoda: Aristeidae). A new interpretation of life span and growth

A new interpretation of growth in A. antennatus is proposed on the basis of data recorded over a period of twenty years on the fishing grounds off Portofino. Detailed size-frequency distributions of female A. antennatus, obtained from on board measurements of large numbers per haul or per day of fishing, have been interpreted as formed of about 17 growth instars. Five of these, in the range 38–53 mm CL, were traced in their growth after the apparently fortuitous event of a massive recruitment which took place in 1987. The shift indicated above of five instars occurred in 3 years; a long life span, of about 8–9 years, was then assigned to the female red shrimp. Males were supposed to have an identical life span, with smaller sizes at age. The ‘1987 shrimps’ were and remained for years distinct from the previous ones, in terms of both their size structure and reproductive characteristics. They were similar to southern Mediterranean stock(s) and slowly evolved towards a northern pattern. This fact points to ...

Total and organic mercury concentrations in offshore crustaceans of the Ligurian Sea and their relations to the trophic levels

Abstract Total mercury and organic mercury were measured in five crustaceans representative of an offshore pelagic food web in the Gulf of Genoa, Italy: Meganycthiphanes norvegica, Gennadas elegans, Pasiphaea sivado, Pasiphaea multidentata and Aristeus antennatus . According to their predator-prey relationships, they represent three trophic levels in the Ligurian Sea. The concentrations of total and organic mercury increase with the trophic levels and with the weight of the specimens (except in G. elegans and in females of A. antennatus ). However, at higher trophic levels the specimens are also larger. Only in P. sivado , do levels of inorganic mercury increase significantly ( P = 0.001) with the size of the specimens. The ratio between organic mercury and total mercury did not increase with the trophic level.