Daniela Basso

Deep rhodolith distribution in the Pontian Islands, Italy: a model for the paleoecology of a temperate sea

Abstract Within the bathymetric range (27–98 m) of the soft bottoms investigated off the Pontian Islands, rhodoliths have been classified into three morphological groups: (1) the unattached, monospecific branches, mainly composed of the non-geniculate coralline red algae Phymatolithon calcareum, Lithothamnion corallioides and Lithothamnion valens : (2) the prâlines (sensu stricto), monospecific little nodules with protuberances or short branches and a compact internal structure, normally due to the concentric growth of Lithothamnion minervae or Lithophyllum racemus over a pebble or a skeletal remain; (3) the large, multispecific rhodoliths with a ‘boxwork’ internal structure, due to long periods of growth under calm conditions interrupted by episodes of overturning and/or partial covering by sediments, with evident sedimentary fillings and a first nucleus often difficult to identify. A predictive model of distribution of species and growth forms of corallines and peyssonnelians in the framework of the Mediterranean circalittoral benthic zonation has been developed along two opposite gradients: (1) the frequency of overturning of the rhodoliths and (2) environmental stability of the bottom, conditioned by: sedimentation rate; absolute hydrodynamics of the environment; shape and density of the single rhodolith (depending on its nucleus).

Shallow-water Sporolithon Rhodoliths from North Island (New Zealand)

Abstract Shallow-water Sporolithon rhodoliths from New Zealand are described here on the basis of shape, size, composition, internal structure, and major taphonomic attributes, with the aim of discussing their significance in the framework of current ecological and paleoecological models of rhodolith formation and accumulation. The very shallow water environment (<2 m) of the Whangaparaoa Peninsula undergoes daily tidal currents and seasonal storm conditions. These factors, along with the availability of cobbles and pebbles as suitable substrate, lead to the accumulation of spherical, fruticose, monospecific, nucleated, and internally compact rhodoliths. The observed taphonomic features include apical abrasion, intercalary growth of protuberances after mechanical breakage, and multiple growth stages with distinctive bioerosion (by bivalves, annelids, and cyanobacteria), which are identified by internal abrasion surfaces and dark layers. A review of the pattern of global distribution of the coralline genera comprising very shallow-water rhodoliths (<2 m) identifies five major categories: (A) unattached protuberances, commonly monospecific, made up of one or more genera (Phymatolithon, Lithothamnion, Lithophyllum) in cool to cold waters at middle to high latitudes; (B) rhodoliths composed of dominant Hydrolithon and other mastophoroids (Neogoniolithon or Spongites) with subordinate Lithophyllum in the tropics; (C) unattached protuberances of Neogoniolithon associated with seagrass meadows, from middle latitudes, in warm to warm-temperate waters; (D) mainly fruticose, monospecific, rhodoliths composed of Mesophyllum, Lithothamnion, Hydrolithon, and Neogoniolithon under tidal currents in cool waters in the Southern Hemisphere; and (E) Sporolithon rhodoliths of cool waters in the Southern Hemisphere, which suggest an austral polar emergence of the genus.

First evidence of benthic communities based on chemosynthesis on the Napoli mud volcano (Eastern Mediterranean)

Abstract Some molluscan valves attributed to Myrtea sp. (Lucinidae), Vesicomya sp. and another undetermined Vesicomydae were sampled in 1993 (cruise TTR3/Leg2) and 1994 (cruise UM94) by coring on the top of the Napoli Dome, a mud volcano located on the Mediterranean Ridge, at about 1900 m of water depth. These bivalves belong to an unknown, apparently rich benthic community associated to the sulphides and methane-rich emissions that characterize the Napoli Dome. Outside the Mediterranean, deep-sea Lucinidae and Vesicomyidae are associated with cold-seeps and hydrothermal vents and are known to be sustained by bacterial chemosynthetic activity based on sulphide and/or methane oxidation. The same explanation is given for this newly discovered deep Mediterranean fauna, firstly described here.

Fossil and living corallinaceans related to the mediterranean endemic speciesLithophyllum racemus (Lamarck)Foslie

SummaryNew observations on asexual and sexual thalli of the Mediterranean speciesLithophyllumracemus and description of its variability in a Tyrrhenian population have led to reinterpretation of the features of some fossil and living taxa. The external appearance and the reproductive and vegetative anatomy of the fossil speciesLithophyllum viennotii corresponds to tetrasporangial plants ofL. racemus. The fossil speciesLithophyllum microsporum, whose holotype is redescribed here, represents a sexual stage ofL. racemus, probably the carpogonial/carposporangial plants.Consequently, the stratigraphical distribution ofL. racemus is widened back to the Aquitanian, and the species can thus be considered a Mediterranean paleoendemic. No character was found supporting the distinction ofLithophyllum duckeri fromL. racemus, therefore this species is also considered conspecific withL. racemus.

The taxonomy ofLithothamnium ramosissimum (Gümbel nonReuss)Conti andLithothamnium operculatum (Conti)Conti (Rhodophyta, Corallinaceae)

SummaryAfter revision of the Reuss collection (Piller, 1994),Lithothamnium ramosissimumReuss 1847 is considered to be conspecific withPalaeothamnium archaeotypumConti 1946, which is now a junior synonym. On this basis,L. ramosissimum(Reuss) Piller is also possibly conspecific withL. ramosissimumReusssensuGümbel and consequently, withL. ramosissimum (Gümbel nonReuss) described by Conti. However, the loss of Gümbels original collection prevents a definitive resolution concerning his descriptions. The revision of Contis original collection of the Miocene Leithakalk material and the comparison of the morphology and biometry ofL. ramosissimum (Gümbel nonReuss)Conti and ofPalaeothamnium archaeotypumConti shows that they are not conspecific and must be regarded as separate species, regardless of the status of the genusPalaeothamniumConti.SinceL. ramosissimum (Gümbel nonReuss)Conti shows the same macroscopic and microscopic morphology and biometry asLithothamnion valensFoslie,L. valensFoslie has priority overL. ramosissimum (Gümbel nonReuss)Conti.The morphology and anatomy of the holotype ofLithothamnium operculatum(Conti) Conti from the Tertiary Piedmont Basin and Contis original collection ofL. operculatum from the Miocene Leithakalk have been compared with those of living plants ofPhymatolithon calcareum(Pallas) Adey & McKibbin, and considered to be conspecific. Therefore, the nameP. calcareum has priority.The stratigraphic distribution ofL. valens andP. calcareum is therefore extended back to the Tertiary.

LATE EOCENE PLANKTONIC FORAMINIFERAL RESPONSE TO AN EXTRATERRESTRIAL IMPACT AT MASSIGNANO GSSP (NORTHEASTERN APPENNINES, ITALY)

The 4–8 m segment of the Global Stratotype Section and Point (GSSP) for the Eocene-Oligocene boundary at Massignano contains a well studied and documented impactoclastic layer with anomalous concentrations of extraterrestrial iridium, shocked quartz, Ni-rich spinels, impact spherules, and a prominent 3 He anomaly. This layer, located at 5.65 m and dated at 35.7 ± 0.4 Ma (Late Eocene), appears to be coeval with the Chesapeake Bay or the Popigai impact structure. We have investigated planktonic foraminifers from this interval with the aim of assessing the effects that the impact may have had on the environment and this group of organisms. Interpretation of data suggests that the impact had no abrupt, dramatic effects on planktonic foraminifers. However, since it occurred in a stressed environment characterized by gradual and progressive cooling, it enhanced climatic deterioration and variations in water mass structure. The cooling produced shallowing of the thermocline depth and drastic reduction in abundance of shallow- and warm-water species. The short-term warming episode in the lower part of Zone P16 between 5.8 m and 5.9 m may be due to a short-term-impact-induced greenhouse episode and seems to be global in extent. Finally, the relatively long duration of the environmental perturbation that followed the impact event, which culminated with the Early Oligocene sharp temperature drop, suggests that a feedback mechanism sustained the initial impact-induced changes.

A Mediterranean population of Spongites fruticulosus (Rhodophyta, Corallinales), the type species of Spongites, and the taxonomic status of S. stalactitica and S. racemosa

D. Basso and G. Rodondi. 2006. A Mediterranean population of Spongites fruticulosus (Rhodophyta, Corallinales), the type species of Spongites, and the taxonomic status of S. stalactitica and S. racemosa.Phycologia 45: 403–416. DOI: 10.2216/04-93.1 Tetrasporangial male and female/carposporangial plants of a Mediterranean population of Spongites fruticulosus are described and compared with the type material of S. fruticulosus, Spongites racemosa and Spongites stalactitica. The three species were established by Kützing on the basis of Mediterranean collections. The type material of S. fruticulosus is a rhodolith composed of a tetrasporangial plant possessing uniporate conceptacles, multistratose noncoaxial hypothallium and ovoid epithallial cells, growing on another unidentified sterile coralline with different vegetative characters. Spongites fruticulosus is lectotypified here with the tetrasporangial plant. The original material of S. racemosa represents a male plant of Neogoniolithon, here identified as Neogoniolithon racemosum (Kützing)comb. nov. The type material of S. stalactitica is a rhodolith composed of a mixture of two species belonging to different genera: one, here selected as lectotype of S. stalactitica, is a female plant regarded as conspecific with S. fruticulosus. The second is the tetrasporophyte of a Neogoniolithon species. Detailed morphological-anatomical accounts of the species are presented, and their features are documented and discussed. The comparison between the Mediterranean types and new collections and the Australian population of S. fruticulosus revealed that Mediterranean plants have smaller sexual and asexual conceptacles and lack trichocytes. However, overlap in conceptacle dimensions and the rarity of trichocytes in the Australian specimens do not allow us to separate the Mediterranean and the Indo-Pacific populations into different species at this time.

Pleistocene coralline algal build-ups (coralligène de plateau) and associated bioclastic deposits in the sedimentary cover of Cutro marine terrace (Calabria, southern Italy)

Abstract Carbonate build-ups mainly constructed by encrusting coralline red algae are currently developing on Mediterranean soft bottoms, at depths ranging from 20 m to 160 m. They are usually referred to as ‘coralligène de plateau’. Few fossil examples of these bioconstructions have been described in the literature and their evolution in the context of a stratigraphic cycle has never been modelled in detail. Cutro marine terrace (Calabria, southern Italy) preserves mid-Pleistocene deposits assigned to Marine Isotope Stage (MIS) 7 or MIS 9. Extensive algal build-ups representing the deepest unit of the succession occur in the outer and central portion of the terrace, interpreted as the most distal setting from the palaeo-shoreline. Two studied sections, Vrica and Telegrafo, showed that the solid biogenic framework grew over a basal rhodolithic layer, which was stabilized by the binding activity and overgrowth of non-geniculate Corallinales (calcareous red algae). Therefore, these bioconstructions represent a rare fossil example of coralligène de plateau. At the Telegrafo section, Titanoderma pustulatum has been identified as the major rhodolith component. The build-ups are dominated by T. pustulatum, associated mainly with Mesophyllum spp. and locally with Lithophyllum stictaeforme. Rhodalgal bioclastic deposits are found in lateral contact with the build-ups. The two facies developed together under a hydrodynamic regime where phases of sedimentation from storm-driven currents alternated with phases of calm conditions. They were deposited during a single stratigraphic cycle beginning with the generation of a ravinement surface during the transgressive systems tract (TST) and ending with the burial of the coralligène by well-sorted shoreface bioclastic sands. Optimal and extensive growth of the coralligène took place during the highstand systems tract (HST).

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 km2 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 km2. The 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. This 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. The total coralline cover (living plus dead) in the Cilento area is 13.96 km2, with a total 316800 tons of algal carbonate in the surface 1 cm layer, that correspond to 20430 g m-2. Living maerl is recorded at a depth of 47 m, with a live coralline cover of about 40% over a minimum area of about 1.2 km2. This live maerl has a thickness of about 1 cm and is composed mainly of unattached branches of Lithothamnion corallioides (P.L.Crouan & H.M.Crouan) P.L.Crouan & H.M.Crouan, 1867. The molluscan association of the maerl bed is dominated by characteristic species of the Coastal Detritic Biocoenosis. The production of carbonate by living coralline algae has been calculated as weight of live corallines in 1 cm-thick layer × 100 y-1 × total area-1 and corresponds to 90.8 g m-2 y-1.

The coralline flora of a Miocene maërl: the Croatian “ Litavac”

The fossil coralline flora of the Badenian bioclastic limestone outcropping in Northern Croatia is known by the name “Litavac”, shortened from “Lithothamnium Limestone”. The name was given to indicate that unidentified coralline algae are the major component. In this first contribution to the knowledge of the coralline flora of the Litavac, Lithothamnion valens seems to be the most common species, with an unattached, branched growth-form. Small rhodoliths composed of Phymatolithon calcareum and Mesophyllum roveretoi also occur. The Badenian benthic association is dominated by melobesioid corallines, thus it can be compared with the modern maerl facies of the Atlantic Ocean and Mediterranean Sea. Since L. valens still survives in the present-day Mediterranean, an analogy between the Badenian Litavac and the living L. valens facies of the Mediterranean is suggested.