ENTE TUTELA PESCA DEL FRIULI VENEZIA GIULIA photo exhibi ti on UNDERWATER LIFE OF THE NORTHERN ADRIATIC “TREZZE” (beachrock outcrops) photo exhibition UNDERWATER LIFE OF THE NORTHERN ADRIATIC “TREZZE” (beachrock outcrops) images by Luigi Paderni at the AQUARIUM OF THE FRESHWATER SPECIES, ARIIS DI RIVIGNANO (Udine, Italy) opening 07 April 2011, h. 16:00 the exhibition will take place from 07.04.2011 to 15.05.2011 Tu We Th Fr 09:00-12:00 & 14:00-17:00 Sa Su & holdays 10:00-13:00 & 15:00-19:00 closed on Mondays i mages by Luigi Paderni free entrance TREZZE & TEGNÙE THE ORIGIN OF NAME The “trezze” (known by this name along the Friulian and the Giulian coasts), and the “tegnùe” (more tipically Venetian), are submersed aggregates consisting of detritus and organogenic matter, or of true rock, characteristic of the Northern Adriatic basin. Both the “trezze” and the “tegnùe” are found over the arm of sea between Trieste and Chioggia (trezze are especially concentrated between Trieste and Lignano), in form of multiple and dispersed spots. Their extension can vary from a few to some thousands of square meters, and elevation from the bottom surface can reach 1-4 meters (Mizzan, 1995; Stefanon, 1966). They represent very special and unique environments (Bellot et al., 1998). Among the flat and homogeneous Northern Adriatic seascape consisting of sandy and muddy bottoms, these hard aggregates are natural reserve areas and natural nurseries for the reproduction and settlement of species which otherwise could not be present in the same zones. Many of these species are also commercially important, such as the European clawed lobster (Scovacricchi 1998 & 1999; Scovacricchi & Burton, 1998), and the black amber. Anchors and fishing nets entangled in the “tegnùe“ or “tenùte” explain the name of these submersed hard aggregates. Trapped nets and anchors in fact cannot be raised onboard because they remain trapped, kept (in Italian they say they are “trattenute” or “tenùte”) by the rocks and the other hard parts of these special marine formations. It is more difficult to find out the etymon of the word “trezze”. Somebody think it derives from the Italian word “trecce” (hair braids) following the romantic idea that the prairies of Posidonia oceanica which were quite abundant in the past appeared like waving braiding aggregates. The “tegnùe” consist of rocky materials which are often classified as beachrocks. Their formation can be associated to zones of percolation of methane gas (CH4) that, producing carbon dioxide (CO2) into the aquatic medium, and in the presence of calcium (Ca), triggered the formation and concreting of carbonates (CaCO3). The process took place in covered sediment layers and the rocks emerged form the sea bottom later on due to erosion of the same sediment (Newton & Stefanon, 1978). The “trezze” more often consist of organogenic materials, and they usually arise from Posidonia meadows, which are mainly extinc nowadays. Over these meadows secondarily developed the coralligenous (calcareous algae, briozoa, serpulids, mollusks, etc ...). SAFEGUARD & VALORISATION The “trezze” and “tegnùe” represent a sort of out-and-out local reefs. Several coastal municipalities, research institutes, associations, divings, local authorities from Chioggia to Venice, Caorle, Cavallino, Lignano Sabbiadoro, Grado and Trieste, have promoted during recent years initiatives to deepen and diffuse the knowledge about these underwater environments. These initiatives focused on the protection of the biological features of these sites (for example their rich biodiversity, the role of nurseries, the ecological worthiness, the importance for fishing), and on their valorisation along the lines carried out for the promotion of surface land typical products or sites. The valorisation of this underwater heritage can produce positive results in terms of scientific and educational results coming from research, awareness, and dissemination activities. Furthermore, other positive outcomes can directly derive from the importance of these sites to professional fishing, their capacity to attract recreational fishermen and pleasure crafts, scuba divers, and more generally the so-called eco-tourists. These sites make simbolically think to a healthy and pulsating Adriatic Sea, and this in turns supports the winning idea of a tourism strictly linked to territory and its peculiarities. Around the “trezze” issue several interests and actors (fishermen, citizens, school, associations, local authorities, research) can collaborate to protect and promote the Adriatic Sea, its bottoms and coasts. These environments support common and shared traditions, values, and the need for integrated policies for the conservation and management of the environment. Photographs by Luigi Paderni ©. Reproduction forbidden. All rights reserved ®. THE NATURE OF SUBSTRATUM The different origin and nature of the two kinds of substrata, as well as the most recent evidences from the geomorphologic research in the Northern Adriatic Sea, make scientists think that the overall distribution arrangement of these marine aggregates is not overlapping the residuals of an ancient coast line which formed in the intertidal zone 3-4 thousand years ago during the alluvional period (Stefanon, 1969 & 1972), as it was hypothesized in the past (A. Stefanon, personal communication). Some rocky aggregates can be also found next to the trezze, and in some cases they could be associated to percolation of freshwaters that emerging in the sea would produce carbonates and trigger the concreting process (A. Stefanon, personal communication). THE PICTURES BY LUIGI PADERNI Within the above described context the images by Luigi Paderni (well-acquainted and much-admired Friulian photographer), better known as “Gigi”, having as subjects the phantasmagoric underwater life of the Lignano’s trezze, help the visitor know, appreciate, and understand an hidden portion of the large environmental and cultural heritage of the Region Friuli Venezia Giulia, a portion which is usually inaccessible to most of the public. ACKNOWLEDGEMENTS & NOTES The Ente Tutela Pesca of Friuli Venezia Giulia kindly thanks the Municipality of Lignano Sabbiadoro and the FotoCineClub-Lignano for providing the photografic material. Texts and graphics have been written and edited for ETP by Tiziano Scovacricchi (CNR ISMAR, Venice, Italy). CITED LITERATURE 1. Bellot, A., Gabriele, M. & Gallotti, D., 1998. Là, in mezzo al mar ... Sub, Anno XV, maggio, pp. 64-67. 2. Mizzan, L., 1995. Le Tegnùe. Substrati solidi naturali del litorale veneziano: potenzialità e prospettive. Azienda Sviluppo Acquacoltura Pesca, Via Forte Marghera 151, 30173 Venezia-Mestre, 46 pp.. 3. Newton, R. & Stefanon, A., 1978. Primi risultati dell'uso simultaneo in Alto Adriatico di side-scan sonar, sub-bottom profiler ed ecografo. Memorie biogeogr. Adriat., Suppl. Vol. 9: 33-66. 4. Scovacricchi, T. & Burton, C.A., 1998. Lobster (Homarus gammarus L.) Research in the Northern Adriatic Sea. The Lobster Newsletter, Vol. 11, July, N 1, p. 11. 5.Scovacricchi, T., 1998. Primi tentativi di rafforzamento degli stock di astice, Homarus gammarus (Linnaeus, 1758), in Alto Adriatico. Biol. Mar. Medit., 5(3): 1455-1464. 6. Scovacricchi, T., 1999. Preliminary studies on stocking depleted populations of the European lobster, Homarus gammarus (L.) (Decapoda, Nephropidae) onto the natural beachrock outcrops in the Northern Adriatic Sea. In: “Stock Enhancement and Sea Ranching”, edited by B.H. Howell, E. Moksness & T. Svåsand, published by Blackwell Science Ltd., Fishing News Books, Oxford, UK, Chapter 27: 393-400. 7. Stefanon, A., 1966. First notes on the discovery of outcrops of beachrocks in the Gulf of Venice. XX Congrès-Assemblée Plenière C.I.E.S.M.M., Rapp. Comm. Int. Mer. Médit., 19(4), pp. 648-649. 8. Stefanon, A., 1969. The role of beachrock in the study of the evolution of the North Adriatic Sea. Memorie di Biogeografia Adriatica, 8: 79-87. 9. Stefanon, A., 1972. Beachrock and paleogeography in the North Adriatic Sea. Rapports et procès-verbaux des réunions C.I.E.S.M.M., 20: 605-608.