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The Messinian Salinity Crisis (MSC) created a substantial negative impact on the Mediterranean marine fauna and flora because hypersaline conditions were established in many marginal basins. At the northern margin of the Tertiary Piedmont Basin, Northern Italy, the Messinian successions exposed at Banengo and Moncalvo recorded the transition into and through the MSC with well-preserved nanno-, micro- and macrofossils. Siliceous sponge spicules present in these pre-MSC sediments reflect the sponge population in this area with twenty different morphological types of spicule identified, twelve of them attributable to sponge genera of the modern Mediterranean sponge fauna. The most common genera were Stelletta, Geodia and Dercitus, with fewer records of Tethya, Chondrilla, Alectona and Samus. Only two types of spicule belong to species not currently present in the Mediterranean sponge fauna and are putatively attributed to the tropical species Stelletta purpurea and Diplastrella megastellata. The sponge assemblage thriving before the onset of the MSC provided new information on the sponge diversity and palaeoenvironment of this northern sector of the palaeo-Mediterranean basin over this crucial period. These data, integrated with information derived from the associated fossils (nannofossils, benthic and planktic foraminifers, and bryozoans), indicate that the considered sites were coastal localities, with sediments rich in an organic matter likely derived from phytoplankton blooms. At both sites, the presence of patchy rocky substrates on the seafloor is testified by a diversified group of sponges typical of hard substrata. These rocks were, very likely, carbonate as suggested by the presence of spicules of typical boring sponges. In the studied sites, common epiphytic foraminifers and bryozoan segments indicate the presence of Posidonia seagrass or algal meadows. [ABSTRACT FROM AUTHOR]

The Mediterranean red coral, Corallium rubrum (L.), has been a valuable economic resource for more than 2000 years. The Sicily Channel and surrounding areas are one of the most famous red coral fishing grounds of the whole region, hosting the deepest ever found living colonies and large sub-fossil red coral deposits; the so-called Sciacca banks are a unique location in the whole Mediterranean Sea. In this paper, a morphometric description of this sub-fossil population is presented for the first time from studies of colonies in the collection of several coral factories from Torre del Greco (Naples), with radiocarbon age estimations and growth rate evaluations. From the results of this study, after several thousand years Sciacca red coral colonies maintained the organic matrix structure with evident annual discontinuities, allowing estimations of the annual growth rate (about 0.3 mm/year) and the average population age (about 33.5 years). These resulting data are similar to the values determined for deep-dwelling living red coral populations. The radiocarbon dating evidenced a range of ages, from 8300 to 40 years before 1950 CE, mostly falling between 2700 and 3900 YBP, suggesting that colonies accumulated over a wide span of time. In view of the tectonically active nature of the area, several catastrophic events affected these ancient populations, maintaining them in a persistent state of early-stage, structurally similar to the those in current over-exploited areas. [ABSTRACT FROM AUTHOR]

The most important structural changes of the marine communities of the Ligurian Sea (Mediterranean Sea) are described and discussed, stemming from scientific contributions published in the last decades. The main causes of disturbance and stress along the coastline were, since long time ago: huge urban, touristic and industrial developments, harbour activities, building of littoral rail- and motorways, beach replenishments, presence of several polluted drainages, impact of fishery activities. Nevertheless, the EQR-CARLIT index recently evidenced a moderate seawater quality and ecological status, indicating a slow, but progressive improvement of the littoral environment. But, in a changing climate, thermal stress anomalies in 1999, 2003 and 2006 determined major changes in the structure of benthic and fish communities. In addition, the plankton showed significant changes, especially in terms of primary production, while the disappearance of some species and the arrival of others, even of commercial interest, were recorded. Starting from the late 1980s, some thermophilous and/or Lessepsian species reached the Ligurian Sea, often determining processes of “meridionalization” and “tropicalization” of the basin. In a relatively short time span, i.e., 30-40 years, the structural complexity of Ligurian marine communities changed dramatically as never observed before in historical times. [ABSTRACT FROM AUTHOR]

Although echinoderms constitute some of the most conspicuous taxa of the Antarctic benthic communities, the echinoderm fauna of Terra Nova has not been described yet. The present study provides the first species list of echinoids, ophiuroids and asteroids from Terra Nova Bay (30-500 m depth) and describes the depth distribution of these species. Preliminary observations of the summer reproductive condition of some of the species are also included. [ABSTRACT FROM AUTHOR]

Annual growth rates of Antarctic marine organisms are low compared to their relatives from warmer waters. Previous studies hypothesise that high food availability during austral spring–summer may enable Antarctic invertebrates to attain comparatively high short-term growth rates despite the low temperature. Neither a temperature-growth experiment with juvenile Adamussium colbecki (Smith 1902) nor the comparison of A. colbecki summer growth rates with an empirical scallop specific growth-to-temperature relationship could confirm this hypothesis. Hence, summer growth rates of young, immature A. colbecki are strongly affected by temperature, i.e. no “uncoupling” from temperature. [ABSTRACT FROM AUTHOR]

Adamussium colbecki is one of the most well-studied Antarctic molluscs. However, information on its growth rate is currently based on estimates from mark and recapture experiments and from growth-ring analyses. This paper provides the first estimates of the growth pattern of this scallop throughout a year, for individuals maintained under both natural field and laboratory conditions. Results show size-related differences in growth rate, both in the field and in aquaria, with scallops in Terra Nova Bay growing faster than those kept in aquaria. Growth performances were lower than those reported in the literature. [ABSTRACT FROM AUTHOR]

Soft-bottom zoobenthic communities at Terra Nova Bay down to 100 m depth are mainly characterised by the presence of three species, generally occurring together and reaching high values of density: the scallop Adamussium colbecki (Smith 1902), the echinoid Sterechinus neumayeri (Meissner 1900) and the asteroid Odontaster validus Koehler 1911. These three species have a planktotrophic larval behaviour, but differ in terms of extent of gametogenic cycle and in feeding behaviour. The aim of this work is to give a first account of their reproductive conditions at Terra Nova Bay, comparing two following summer seasons, characterised by quite different ice-coverage and, consequently, food availability in the water column. The comparative analysis of the data evidences strong inter-annual differences in the scallop, a suspension-feeding species. In contrast, no significant changes were found in the two echinoderms, suggesting that a 2-year oogenic cycle, coupled with the opportunistic feeding behaviour, allow successful management of inter-annual shortcomings in food supply. On a latitudinal perspective, the comparison between data from McMurdo Sound and Terra Nova Bay shows small (for the echinoderms) or greater (for the scallop) geographical shifts in spawning occurrence. [ABSTRACT FROM AUTHOR]

An experiment and field study were carried out in order to investigate the epibiotic relationship between the hydroid Hydractinia angusta Hartlaub, 1904 and its host, the Antarctic scallop Adamussium colbecki (Smith, 1902), as well as the effect of H. angusta on the recruitment of scallop larvae, since both use the shells of adult A. colbecki as substratum. Four kinds of substrata, with and without epibionts, were exposed to the natural environment at 33 m depth. After 1 year, the analysis of substrata showed that: (1) the hydroid makes use of two substrate colonization strategies, depending on the presence/absence of other epibionts; (2) the settlement of A. colbecki larvae is strongly affected by substrate characteristics and by the presence of the hydroid. Hydroid colonies limit scallop recruitment on the upper valve of adults, where spats usually live for at least 3–5 years attached by means of byssus threads. In this way, the hydroid can affect A. colbecki life history in two ways: by defending, as is usually believed, adults from predators, as well as by limiting the recruitment of its own host. [ABSTRACT FROM AUTHOR]

Along the Victoria Land Coast, the population structure of the Antarctic scallop (Adamussium colbecki) was studied in McMurdo Sound (New Harbor), Terra Nova Bay, and Wood Bay, on a latitudinal span of 3 degrees. At a large spatial scale, most relevant differences between the scallop populations are linked to their depth distributions. The McMurdo and Wood Bay populations show a shallower bathymetric distribution with maximum abundance between 5 and 15 m depth. In contrast, inside Terra Nova Bay, at sites with similar near-shore bathymetric profiles, the maximum biomass is found between 40 and 70 m. This difference can be related to the different ice-cover persistency characterising these two areas, being less at Terra Nova Bay than in the other localities. Differences arise also in the reproductive period: at McMurdo, it seems to occur early in the austral spring, while at Terra Nova Bay, mature females are observed at the beginning of February. Also at a small scale, in sites only a few miles from each other, the population structures inside Terra Nova Bay and Wood Bay vary in terms of abundance and size frequency distribution, suggesting various environmental and biological constraints. Among environmental factors, bottom features (slope, sediment grain size, organic content) and water-column food supply during the summer months may be considered. In addition, as Adamussium is preyed upon by starfishes and fishes, its abundance and population structure may be affected by predators and their abundance. [ABSTRACT FROM AUTHOR]

Sponges often host large amounts of symbionts, mainly represented by cyanobacteria and dinoflagellates. Recent findings show a widespread presence of symbiotic diatoms living inside antarctic demosponges. In this paper, the invasion by large populations of the diatom Melosira sp. into specimens of the hexactinellid sponge Scolymastra joubini is reported. SEM analyses support the hypothesis that the embedded living diatoms have a negative impact on sponge tissues, leading to degenerative processes. [ABSTRACT FROM AUTHOR]

The aim of this work is to improve the knowledge of the mollusc fauna of Terra Nova Bay (Ross Sea), on the basis of more than 100 stations sampled from 25 to 1100 m depth, during Italian Antarctic Expeditions (austral summers 1987/1988, 1989/1990, 1993/1994, 1994/1995, 1995/1996 and 1997/1998). In shallow waters, gastropod fauna is represented by 31 species, among which Neobuccinum eatoni, Onoba gelida, Powellisetia deserta, Philine cf. apertissima and Austrodoris kerguelenensis are the most abundant, while among bivalves (25 species) the commonest species are Adamussium colbecki, Yoldia eightsi, Laternula elliptica and “Montacuta”nimrodiana. At present, most of the Antarctic mollusc species are known as having circumantarctic distribution and are considered eurybathic. Moreover, in general, only scarce data are available on their substrate preferences, because of their occurrence in scattered sampling stations with different sediment features. In the present study carried out at Terra Nova Bay, based on a relatively high number of stations, a clear zonation of mollusc assemblages is shown, according to depth and sediment features. While gastropods characterise the superficial algal belts dominated by the red algae Iridaea cordata and Phyllophora antarctica, bivalve distribution is wider. Adamussium colbecki is the dominant species in the upper 100 m, both on soft and hard bottoms, if the slope is suitable (density up to 40–60 ind./m2). On coarse sands, this species is frequently accompanied by L. elliptica (density <20 ind./m2), while Y. eightsi characterises organic- enriched bottoms (density 70–80 ind./m2). Below 200 m depth Adacnarca nitens, Limatula hodgsoni, “Montacuta”nimrodiana and Mysella gibbosa are commonly found on relatively coarse sediments, while Thyasira dearborni and Yoldiella ecaudata prefer muddy bottoms. In order to identify bivalve assemblages, multivariate analyses were applied to stations grouped into depth ranges, sediment features and location. While shallow bathymetric ranges (25–200 m) are clearly defined, deeper clusters of stations are more influenced by the high degree of eurybathy of most of the species and by the scattered distribution of the sediment particle sizes. [ABSTRACT FROM AUTHOR]

Water samples and particulate materials settling under the pack ice were collected in an ice-covered area near the Terra Nova Bay Italian Station during late summer 1995, in order to study short-term changes in the biochemical composition of particulate organic matter. At the end of the study period the phytoplankton biomass increase (up to >3.0 μg chlorophyll-a l−1) was probably related to the intrusion under the pack ice of chlorophylls-enriched surface waters coming from the near ice-free area. Such increase was associated also with a notable increase in particulate organic matter concentrations, as well as in particulate organic matter vertical fluxes (up to >100 mg C m−2 day−1). Proteins were the most abundant biochemical class of particulate organic matter (on average about 49%), followed by lipids (29%) and carbohydrates (22%). By contrast, organic matter collected in the sediment trap was characterized by the dominance of lipids (about 55% of the total biopolymeric carbon flux) over carbohydrates (28%) and proteins (17%). The hydrolizable particulate biopolymeric carbon accounted for about 23% of total biopolymeric carbon. This value was about one-half of that found in ice-free waters, suggesting that the suspended particulate organic material under the pack ice was less digestible than in ice-free waters or was already partially digested. Despite this, and the decay of labile organic compounds in the sediment trap during the deployment, material settling towards the sea bottom under the pack ice in Terra Nova Bay, owing to its high lipid content, might represent an important high-quality food source for benthic consumers. Finally, assuming as possible the intrusion under sea ice of primary organic matter-enriched waters, we hypothesize the occurrence of a “fertilization” effect deriving from ice-melting areas towards under-ice waters, supplying the latter with an additional rate of primary organic matter. [ABSTRACT FROM AUTHOR]

To date, marine boring organisms are not known for the whole Antarctic region, probably because of the scarcity of calcareous substrata. In Terra Nova Bay (Ross Sea), the study of some populations of the scallop Adamussium colbecki allowed us to record a bioerosive activity on carbonates due to a chlorophyte, belonging to the genus Phaeophyla. The same kind of infestation was also observed on the thick shells of the gastropod Neobuccinum eatoni. The algae actively bore the light-exposed portions of the shells showing, in A. colbecki, an infestation that is strongly size dependent; the ageing of the periostracum is among the most probable causes. The pattern of infestation is not homogeneous in different populations, probably in relation to irradiance intensity; depth, sedimentation rates and ice cover negatively affect the growth and distribution of Phaeophyla sp. [ABSTRACT FROM AUTHOR]

The demosponge siliceous spicules, entrapped in the Mediterranean coralligenous bioherms, are a good tool for reconstructing the sponge ancient communities across time, also allowing a comparison with the current biodiversity. The aim of this paper has been the description of the ancient sponge assemblages of the coralligenous bioherms grown up in the Tavolara-Capo Coda Cavallo Marine Protected Area (northeastern Sardinia, Tyrrhenian Sea) between 5800 and 3700 YBP and its comparison with the living sponge community. On the base of radiocarbon age determinations, it was possible to estimate that these bioherms cover a span of time ranging from the Holocene Climatic Optimum until the Bronze Age Crisis. Their growth rates, 0.21–0.24 mm year−1, were of the same order of estimations conducted around the Mediterranean. The Tavolara ancient sponge diversity was compared with those found in ancient accretions from Ligurian Sea and Ionian Sea. Our results supported the already-described general trend, supporting the hypothesis that the genus richness in the coralligenous bioherms was driven by climatic vicissitudes. Nevertheless, our data strongly indicated that the sponge diversity is also related to the conditions of the coralligenous structures: in the accretions characterized by an active growth of coralline algae the number of sponge genera is similar to those recorded in the ancient assemblages while in coralligenous where the accretion is stopped the number of sponge genera strongly decreases probably due to the competition with frondose macroalgae. [ABSTRACT FROM AUTHOR]