Maerl-bed mapping and carbonate quantification on submerged terraces offshore the Cilento peninsula (Tyrrhenian Sea, Italy)

Abstract

On the continental shelf off the Cilento peninsula (eastern Tyrrhenian Sea) the occurrence of more than 13 km 2 of maerl beds was documented through acoustic surveys. Swath bathymetric data along with a dense grid of chirp-sonar profiles were acquired over more than 180 km 2 . e maerl facies was characterized on the basis of the components analysis of 32 grab samples collected at selected sites. Mapped maerl-beds are predominant on submerged terraces located at variable water depth (wd) between 42 and 52 m. is preferred distribution on submerged terraces is probably associated with relatively vigorous bottom currents generated by local circulation that hinders the deposition of terrigenous sediments. Calcareous red algae result to be the most important producers of carbonates from 40 down to 60 m wd. We calculated the coralline carbonate accumulation from the percentage cover of coralline algae (thin section mapping) × 1 cm-thick layer of sediment × measured coralline density. e total coralline cover (living plus dead) in the Cilento area is 13.96 km 2 , with a total 316 800 tons of algal carbonate in the surface 1 cm layer, that correspond to 20 430 g m -2 . Living maerl is recorded at a depth of 47 m, with a live coralline

Coralligenous and maërl habitats: predictive modelling to identify their spatial distributions across the Mediterranean Sea

“…Coralligenous outcrops would be unlikely to occur in high sedimentary zones without hard substrata, in enclosed estuarine systems, and in sandy areas with low salinities such as river mouths, although some exceptions exist 17 . For maërl beds, flat and coarse grained areas would tend to be suitable habitats, as well as straits with strong bottom currents that reduce sedimenta- tion 23,47 . The present study did not manage to unearth such fineresolution predictor variables in mapped formats that would cover the entire Mediterranean Sea; besides, the spatial resolutions of the variables that were available were coarser than desired.…”

“…These algae can display a branching or a laminar appearance. They sometimes grow as nodules known as rhodoliths that cover all the sea floor, or accumulate within the sand and gravel ripple marks 11,23,50 . Some Authors distinguish between dense accumulations of interlocking rhodoliths within the ripples of muddy and sandy substrates (maërl beds) and rhodoliths dispersed among sediments (rhodolith bottoms).…”

“…They are the result of the building activities of algal and animal constructors, counterbalanced by physical, as well as biological, eroding processes. Because of their extent, biodiversity and production, coralligenous and maërl habitats rank among the most important ecosystems in the Mediterranean Sea [17][18][19][20][21] , and they are considered of great significance both for fisheries 22 and carbon regulation 23,24 .…”

Paleoecology and dynamics of coralline dominated facies during a Pleistocene transgressive–regressive cycle (Capo Colonna marine terrace, Southern Italy)

“…Light and salinity are considered two other environmental factors influencing the distribution of maerl (Littler et al, 1991;Wilson et al, 2004;Steller et al, 2007) with a depth range between 30 and 100 m wd (Bourcier, 1982;Babbini et al, 2006;Sciberras et al, 2009) and an optimum between 40, and 60 m wd (Basso and Brusoni, 2004;Babbini et al, 2006;Savini et al, 2012) for the Mediterranean Sea.…”

“…Calcareous red algae play a primary role as carbonate producers in modern depositional systems of the Mediterranean Sea and are able to develop several algal dominated facies across the continental shelf, characterized by distinct sedimentary attributes (Pérès and Picard, 1964;Carannante et al, 1988;Betzler et al, 1997;Basso, 1998;Ahr, 1997, 2006;Ballesteros, 2006;Canals and Ballesteros, 1997;Barberá et al, 2012;Bracchi and Basso, 2012;Sardá et al, 2005;Savini et al, 2012). Two of the most significant among these facies are rigid build-ups, which can form banks up to 4 m thick and several tens of meters long, the coralligenous, and accumulations of small (few centimeter in size) unattached branches and nodules, praline rhodoliths and maerl.…”