Hidden secrets of the Northern Adriatic: “Tegnúe”, peculiar reefs

Abstract

Abstract:Research carried out over the last 40 years has underlined the scientific importance of the rocky outcrops scattered on the Northern Adriatic Sea bed sometimes referred to as "tegnúe". The zoobenthic biocenoses developing over these peculiar geological formations are as extraordinary as they are unique. A study carried out for an entire year in two sampling stations, at different distances from the coast, revealed a very high number of zoobenthic species, including those which have now become rare and are therefore protected in Italian seas. The water turbidity of the northern Adriatic Sea greatly reduces the quantity of light reaching these outcrops, limiting the activity of autotrophic organisms only to sciaphilous genera. Thus, the most represented trophic categories of zoobenthos are suspension, especially filter feeders. Biodiversity values calculated for the communities of these particular reefs are far higher than normally found in the soft seabed in nearby areas, but even higher than in other coralligenous outcrops in other marine ecosystem in the world. The ecological role played by the tegnúe in the Northern Adriatic is extraordinary because as well as being true oases of biodiversity, they are areas naturally protected against bottom trawl-fishing. Thus, they offer shelter and reproduction sites for a number of fish and invertebrate species, including some under stress due to severe fishing pressure.

Gonochorism and planula brooding in the Mediterranean endemic orange coralAstroides calycularis(Scleractinia: Dendrophylliidae). Morphological aspects of gametogenesis and ontogenesis

“…Following a Pleistocene glaciation that lowered seawater temperature in this area, the species disappeared from the Northern Mediterranean Sea (Peres 1967). Currently, A. calycularis is spread in the south-central part of the Western Mediterranean Sea (Zibrowius 1995;Ocañ a et al 2000;AlvarezPérez et al 2005; Figure 1), with some recent records in the north-eastern part of the Adriatic Sea, along the coasts of Croatia (Grubelic et al 2004;Kruzic et al 2005;Bianchi 2007; Figure 1) up to the Gulf of Venice (Casellato et al 2007; Figure 1). The range expansion into the Adriatic Sea is thought to be due to seawater warming and to the Ionian cyclonic stream (Bianchi 2007), with the ascending circulation that seems to have favoured the flow of larvae along the Croatian coasts (Grubelic et al 2004).…”

Methane-Related Carbonate Cementation of Marine Sediments and Related Macroalgal Coralligenous Assemblages in the Northern Adriatic Sea

“…The different number of species recorded at the San Pietro and Bardelli sampling sites (Figure 9.8) may be related to the different distances from the coast (3 and 18 miles, respectively) and depth (16 and 22 m). As suggested by Casellato et al [30], in the Northern Adriatic, the unpredictability of the oceanographical conditions drive the observed variability in benthic communities. These observations are in accordance with [30,31] results on nearby similar outcrops.…”

On the presence of the Mediterranean endemic Microdeutopus sporadhi Myers, 1969 (Crustacea: Amphipoda: Aoridae) in the Gulf of Naples (Italy) with a review on its distribution and ecology

“…gal component plays a minor role in comparison to other coralligenous habitats. These formations, called tegnùe, are a unique environment, a 'true oasis of biodiversity' for the northern Adriatic Sea, compared to the surrounding soft bottoms, and 'act as a trap for the rich content of dissolved and particulate organic matter, and suspended plankton' (Casellato et al, 2007). Among the several species found and not yet listed for Italian seas, M. sporadhi is the only Aoridae present in the few amphipod species (10) identified.…”

“…Among the several species found and not yet listed for Italian seas, M. sporadhi is the only Aoridae present in the few amphipod species (10) identified. No abundance data are available (Casellato et al, 2007;Casellato & Stefanon, 2008).…”