Naslov
Shallow-Water Buried Lophelia-Madrepora Coral Mounds in the Mid-Adriatic

Autori
Taviani, M. ; Angeletti, L. ; Antolini, B. ; Bakran-Petricioli, Tatjana ; Bonamini, E. ; Casati, C. ; Cavallini, G. ; Ceregato, A. ; Devoti, S. ; Diaconov, A. ; Froglia, C. ; Garilli, V. ; Giordano, F. ; Malatesta, D. ; Maselli, V. ; Plazzi, F. ; Raspagliosi, M. ; Rodolfo-Metalpa, R. ; Trevisan, G. ; Zibrowius, H. (ARCO Shipboard Staff)

Izvornik
Knjiga sažetaka, HERMES Final Meeting (Carvoeiro, Portugal, 2-6 March 2009), Abstract Book p. 61.

Vrsta, podvrsta
Ostale vrste radova, ostalo

Godina
2009

Ključne riječi
deep sea

Sažetak
The Hermes oceanographic mission ARCO (AdRiatic COrals: 13-22 December 2008, R/V Urania) was organized by CNR-ISMAR with the goal to identify and map yellow coral (Dendrophyllia cornigera) thickets up to 1 m high at intermediate depths (ca 200 m) in the region of the Middle Adriatic Depression (MAD). Previous AMS-C14 dating of Dendrophyllia corals from this area provided a late Holocene age ; furthermore, some specimens are heavily bioeroded and encrusted by living or recently dead epifauna including polychaetes and Neopycnodonte oysters. This evidence suggests that this yellow coral is still alive in the middle Adriatic at this location. The presence of coral grounds here is well known to fishermen that avoid the area for the potential damage to their nets. During ARCO, the area known to host corals was first mapped in detail and imaged by multiswath bathymetry, chirp and side scan sonars, revealing bottom features that were interpreted as potential coral mounds. A ROV survey however did not image as expected Dendrophyllia coral thickets emerging from the muddy area draping the topographic highs between the major depressions. Instead, bottom sampling (large volume grab, gravity corer etc.) recovered a large amount of dead ‘white corals’. Before our finding, there were only a few sporadic citations of such corals at these Adriatic latitudes, summarized by Zupanovic and Jardas (1989). The ‘white corals’ are mainly the branching scleractinians Lophelia pertusa and Madrepora oculata, with subordinate Dendrophyllia cornigera, and Caryophyllia smithii ; the solitary coral Desmophyllum dianthus is rare. Encalcified Eunice parchment tubes were consistently associated with Lophelia and Madrepora frames. Although extremely well preserved and with alabastrine luster, the white corals were all dead and covered by a thin layer of mud (< 15 cm, Minicore ARCO- and gravity core ARCO-). Corals do not show Fe-Mn oxide patinas, and bioerosion or fouling is limited. Dead individuals of the cemented bivalves Neopycnodonte cochlear and, more rarely Spondylus gussonii, are occasionally found attached to Lophelia colonies. Interestingly, most ‘white corals’ are represented by individuals of unusually large size and thickness. Differently from (part at least of) Dendrophyllia colonies, the Lophelia-Madrepora thickets are possibly extinct in the MAD. They might have belonged to a coral province that established at the end of the last glacial age on topographic highs of the MAD on both sides of the Italo-Croatian midline. At present live Lophelia thriving at shallow depths is found in Norwegian fjords. It is quite remarkable that Lophelia has been found at such shallow depth in the Adriatic. Furthermore, the actual depth of recovery (ca. 200 m) should be considered as the maximum figure since at the presumed time of their life at the end of the Pleistocene, sea level was lower than present and corals possibly settled the area when it was only some 100-120 m deep. A number of Pleistocene shells were also recovered from this site, including infaunal boreal species such as the bivalves Panopea norvegica, Pseudamussium peslutrae and the vagrant gastropod Buccinum humphreysianum together with unusually large axes of the octocoral Funiculina quadrangularis. Essentially, this region of the MAD seems a frozen-in-time latest glacial seascape. On-going U/Th and AMS-C14 dating will reveal the age of these subfossil ‘white corals’. As a working hypothesis, we suggest tentatively that they were lethally impinged by a sudden silting, perhaps in response of a milder climatic pulse resulting in stronger rains and enhanced sediment transport in the Adriatic. A similar situation has been documented elsewhere in the Mediterranean basin but at deeper bathymetries (e.g., Remia and Taviani, 2005). The discovery of this large (supposedly) glacial deep water coral province in the middle Adriatic is highly significant in understanding the general spatio-temporal evolution of deep water corals in the Mediterranean basin and may help in assessing the links among the recently discovered coral provinces of the southern Adriatic and Ionian seas.

Izvorni jezik
Engleski

Znanstvena područja
Biologija

POVEZANOST RADA