Agostina Vertino

Mapping Cold-Water Coral Habitats at Different Scales within the Northern Ionian Sea (Central Mediterranean): An Assessment of Coral Coverage and Associated Vulnerability

In this study, we mapped the distribution of Cold-Water Coral (CWC) habitats on the northern Ionian Margin (Mediterranean Sea), with an emphasis on assessing coral coverage at various spatial scales over an area of 2,000 km2 between 120 and 1,400 m of water depth. Our work made use of a set of data obtained from ship-based research surveys. Multi-scale seafloor mapping data, video inspections, and previous results from sediment samples were integrated and analyzed using Geographic Information System (GIS)-based tools. Results obtained from the application of spatial and textural analytical techniques to acoustic meso-scale maps (i.e. a Digital Terrain Model (DTM) of the seafloor at a 40 m grid cell size and associated terrain parameters) and large-scale maps (i.e. Side-Scan Sonar (SSS) mosaics of 1 m in resolution ground-truthed using underwater video observations) were integrated and revealed that, at the meso-scale level, the main morphological pattern (i.e. the aggregation of mound-like features) associated with CWC habitat occurrences was widespread over a total area of 600 km2. Single coral mounds were isolated from the DTM and represented the geomorphic proxies used to model coral distributions within the investigated area. Coral mounds spanned a total area of 68 km2 where different coral facies (characterized using video analyses and mapped on SSS mosaics) represent the dominant macro-habitat. We also mapped and classified anthropogenic threats that were identifiable within the examined videos, and, here, discuss their relationship to the mapped distribution of coral habitats and mounds. The combined results (from multi-scale habitat mapping and observations of the distribution of anthropogenic threats) provide the first quantitative assessment of CWC coverage for a Mediterranean province and document the relevant role of seafloor geomorphology in influencing habitat vulnerability to different types of human pressures.

Enhanced biodiversity in the deep: Early Pleistocene coral communities from southern Italy

The Early Pleistocene fault plane of Furnari, that outcrops in northeastern Sicily (southern Italy), provided a primary hard substrate for the settling and growth of large coral colonies. Even though the corals did not form frameworks, they influenced the composition and distribution of the benthic communities. Corals and associated fauna produced organogenic debris, which was deposited along the fault scarp, within its fractures or at its base.

Mediterranean Corals Through Time: From Miocene to Present

Stony corals, especially scleractinians, are a recurrent component of the benthic fauna of the Mediterranean basin and its Mesozoic-to-Cenozoic precursors. Both morphological and geochemical features of coral skeletons place these organisms among the most important natural paleoarchives of the Mediterranean geological history. The present day low diversity of the Mediterranean scleractinian fauna (25 genera and only 33 species) strikingly contrasts with its high diversity in the Early-Middle Miocene (over 80 genera and hundreds of species). The decline in coral richness has occurred since the late Middle Miocene onwards. This impoverishment trend was not linear, but abrupt in shallow-water environments during and immediately after the Late Miocene and more gradual since the Pliocene onwards. At the end of the Miocene, the Mediterranean coral fauna underwent a drastic modification that led to the disappearance of almost all zooxanthellate corals and the well-established shallow-water coral-reef province. However, the generic diversity of azooxanthellate and deep-water corals did not undergo significant modifications, that were instead much stronger at the end of the Pliocene and of the Pleistocene. Indeed, before the Calabrian stage, all remnant Indo-Pacific-like azooxanthellate genera disappeared and a clear NE Atlantic affinity was established, whereas at the Pleistocene – Holocene boundary, there was a clear reduction in psychrospheric deep-water taxa. The causes that led to the impoverishment of the Mediterranean coral fauna diversity are complex and not all fully understood. However, there is a clear link between the coral diversity decrease, the gradual northward shift outside the tropical belt of the Mediterranean region, and the major climate modifications on a global scale during the last 20 million years.

Microfossils, a Key to Unravel Cold-Water Carbonate Mound Evolution through Time: Evidence from the Eastern Alboran Sea

Cold-water coral (CWC) ecosystems occur worldwide and play a major role in the oceans carbonate budget and atmospheric CO2 balance since the Danian (~65 m.y. ago). However their temporal and spatial evolution against climatic and oceanographic variability is still unclear. For the first time, we combine the main macrofaunal components of a sediment core from a CWC mound of the Melilla Mounds Field in the Eastern Alboran Sea with the associated microfauna and we highlight the importance of foraminifera and ostracods as indicators of CWC mound evolution in the paleorecord. Abundances of macrofauna along the core reveal alternating periods dominated by distinct CWC taxa (mostly Lophelia pertusa, Madrepora oculata) that correspond to major shifts in foraminiferal and ostracod assemblages. The period dominated by M. oculata coincides with a period characterized by increased export of refractory organic matter to the seafloor and rather unstable oceanographic conditions at the benthic boundary layer with periodically decreased water energy and oxygenation, variable bottom water temperature/density and increased sediment flow. The microfaunal and geochemical data strongly suggest that M. oculata and in particular Dendrophylliidae show a higher tolerance to environmental changes than L. pertusa. Finally, we show evidence for sustained CWC growth during the Alleröd-Younger-Dryas in the Eastern Alboran Sea and that this period corresponds to stable benthic conditions with cold/dense and well oxygenated bottom waters, high fluxes of labile organic matter and relatively strong bottom currents

Submarine Slide Topography and the Distribution of Vulnerable Marine Ecosystems: A Case Study in the Ionian Sea (Eastern Mediterranean)

In this work, we sought to document how submarine mass-movements influence the submarine landscape and associated habitat distributions on the upper portion of the northern Ionian Margin (eastern Mediterranean Sea) between 200 m to greater than 1,000 m in water depth (w.d.). In this area, mass-wasting processes have created unique morphological forms that, in turn, have generated high diversity for edaphic and hydrogeologic conditions; and these areas are marked by the patchy occurrence of varying natural benthic habitats. Surficial or sub-surficial Mass-Transport Deposits (MTDs) were documented by seismic and high-resolution morpho-bathymetric data and displayed dense aggregation for detached blocks spread over 1,200 km2 between 400 and 1,000 m in w.d.. Living Cold-Water Coral (CWC) communities populate the blocky region and form coral topped mounds. These habitats are important Vulnerable Marine Ecosystems (VMEs) that are exposed to human pressure in the deep sea. Through production of a detailed geomorphological map and an examination of published data on the extent and distribution of CWC communities in the area, we sought to document how comprehensive research into submarine slide topography should also take into account the peculiar characteristics of their biotopes.

QUATERNARY BUILD-UPS AND RHODALGAL CARBONATES ALONG THE ADRIATIC AND IONIAN COASTS OF THE ITALIAN PENINSULA: A REVIEW

In the Mediterranean, build-ups (created by coralline algae, Cladocora caespitosa , deep-water corals, vermetids, polychaetes and bacteria) and rhodolith beds are important hot-spots of biodiversity. Being severely threatened by anthropogenic impact and climate change, they have been included in international directives on environmental protection. This work wants to support the ongoing research on modern bioconstructions by providing further data on the long-term effects of environmental factors on these habitats. Our results are based on the analysis of the existing literature on the outcropping Quaternary successions of the Adriatic and Ionian coasts of peninsular Italy. The existing reports of build-ups and rhodalgal carbonates have been summarized in an homogeneous data-set and then studied to highlight distribution patterns in space and time. The analyses consistently outlined the importance of sedimentation rate in controlling the general distribution of build-ups and rhodalgal carbonates. The majority of the reports is concentrated south of the Gargano, where the sediment-load of the rivers is small. The majority of the reports is related to coralline algae, suggesting that they were the main carbonate producers during the period. C. caespitosa general distribution is mainly controlled by temperature, with most of the occurrences dating back to the warm periods of the late Ionian and of the Tarantian. Large build-ups of Cladocora are restricted to embayments and gulfs well-protected against storm waves. The distribution of the outcrops of deep-water corals is biased by the geological setting. A remarkable uplift is necessary to bring these corals from their original deep-water setting to elevated areas onshore. Consequently, most of the outcrops are in Southern Calabria which is characterized by a strong Quaternary uplift. Chemosynthetic build-ups, intertidal bioconstructions (made by vermetids, polychaetes or coralline algae), as well as stromatolites, are rare in the study area.

New paleoenvironmental insights on the Miocene condensed phosphatic layer of Salento (southern Italy) unlocked by the coral-mollusc fossil archive

From the Late Oligocene to the Late Miocene, the central Mediterranean area was characterized by the extensive deposition of phosphate-rich sediments. They are usually represented by 10 to 20-cm-thick hardgrounds made of phosphatic and glauconitic sediments containing a rich macrofossil association. This study represents the first thorough investigation of the biotic assemblage of Mediterranean phosphorites aimed at collecting new information on the environmental factors controlling their deposition. The Serravallian/Tortonian phosphatic deposits of the Salento Peninsula (“Aturia level”) have been selected for the abundance of fossil remains and special attention is given to the coral–mollusc association. Two different facies have been recognized: a basal coral rudstone that includes most of the macrofossils, superimposed by a detrital rudstone made of thin layers mainly composed of phosphatic fragments. These two facies are separated by a phosphatic crust several millimeters in thickness. The coral assemblage contains at least 17 azooxanthellate taxa belonging to four families, while the molluscs are represented by a rich gastropod fauna (26 species), associated with bivalves (18 species) and cephalopods (two species). Four distinct depositional phases have been recognized, with the coral rudstone representing the key-facies to reconstruct the onset of the “Aturia level” and the original environment of its fossil content. The composition of the coral–mollusc association has been reliably compared with present-day analog taxa, suggesting the occurrence of a heterogeneous seafloor formed by rocky substrates and accumulations of soft sediment, at around 100–350-m water depth, and under the influence of moderate-to-strong bottom currents rich in nutrients and resuspended organic matter.