Late Quaternary planktonic foraminiferal biostratrigraphy,Strait of Sicily,Mediterranean Sea

The development of a detailed planktonic foraminiferal biostratigraphy for the Late Quaternary (latest 180,000 years) has allowed the dating and correlation of sediments from the Strait of Sicily. Principal component analysis of the assemblages has extracted a climatic history similar to that based upon oxygen isotopic oscillations. Intercore correlations are supported by tephrochronology and sapropel layer stratigraphy. Identification of Termination IA and IB in several high sedimentation rate cores indicates that the Mediterranean Sea experienced a two-stage warming during the last deglaciation. Cores collected between water depths of 200 and 600 m contain an erosional hiatus near their tops, reflecting an increase in the Levantine Intermediate Water flow sometime since 25,000 years B.P. and as recently as 7000 years B.P., during deposition of the youngest sapropel layer. A distinct and unusual planktonic foraminiferal succession is associated with sapropel layers. This begins in a protosapropel layer immediately beneath a sapropel horizon and continues upwards to the immediately overlying oxidized layer.     

Feeding Habits of Percnon gibbesi (H. Milne Edwards, 1853) in the Sicily Strait

The subtropical grapsid crab Percnon gibbesi (H. Milne Edwards, 1853) is one of the most recent alien decapods found in the Mediterranean, where it was discovered at Linosa (Pelagie Islands, Sicily Strait) in summer 1999. At present, the invasion of this species has been recorded in several other insular localities. We studied the feeding habits of the crab in an attempt to understand its success in the Mediterranean. The morphological characteristics of the chela, the feeding adaptations of the gastric mill and the analysis of stomach contents indicate that P. gibbesi is a strictly herbivorous species, a characteristic not shared with any other large-sized infralittoral Mediterranean crab.     

Anchovy egg and larval distribution in relation to biological and physical oceanography in the Strait of Sicily

The European Anchovy (Engraulis encrasicolus, Linnaeus, 1758) represents one of the most important fishery resources in some areas of the Mediterranean. This short-lived, small pelagic fish is characterized by large interannual fluctuations, probably as a result of environmental variability. As part of the European Project Med 98-070, the main aim of which was the study of the anchovy population in the Strait of Sicily, icthyoplankton surveys were carried out between 1999 and 2001, during the peak spawning season for anchovy. Present work reports the relationship between meso-zooplankton biomass and the abundance of anchovy eggs and larvae in the Strait of Sicily. Data on anchovy egg abundance showed that the main spawning area was located in the north-western region of the study area. The branch of the Atlantic Ionian Stream, running parallel to the southern Sicilian coast, acts as a transport mechanism for anchovy eggs and larvae towards the southernmost end of the island, off Cape Passero. Observed distributions were largely consistent with local hydrographic features, which allow larvae to be retained in areas providing the necessary feeding conditions for recruitment success.     

Mesopelagic Fish Larvae Species in the Strait of Sicily and their Relationships to Main Oceanographic Events

This work investigates the spatial distribution and species composition of mesopelagic fish larvae and their relationship with the main oceanographic events in the area studied. Samples were collected during a hydrographic and ichthyoplanktonic survey carried out in the Strait of Sicily in July 2000. Sorting revealed that 1258 out of the 4098 fish larvae identified belonged to mesopelagic species; Cyclothone braueri(67.6% of the total), Electrona Risso(7.8%) and Myctophum punctatum(7.7%) were the most prevalent species, with 850, 97, and 98 individuals, respectively. The surface density patterns of mesopelagic fish larvae appear to be related to the hydrographic characteristics and structures determined by the surface circulation path.     

Late Quaternary paleoceanography as recorded by benthonic foraminifera in Strait of Sicily sediment sequences

At specific times during the late Quaternary, a widespread low-salinity surface water layer was produced over the eastern Mediterranean which created stagnant conditions and associated deposition of sapropelic muds in the deep basins. The Strait of Sicily has been positioned above the anoxic deeper water masses and is therefore devoid of sapropel deposits. Sediment sequences in the region contain a valuable record of upper bathyal (200–1000 m) benthonic foraminiferal change during times of deep-basin stagnation.Quantitative examiniation of benthonic foraminiferal assemblages in Strait of Sicily Quaternary cores generally reveals changes coeval with sapropels S1, S2, S4, S5, and S6. The benthonic foraminiferal expression is seen as increases in frequency ofGlobobulimina affinis, Globobulimina pseudospinescens, Chilostomella mediterranensis, Bolivina dilatata, and otherBolivina species during intervals corresponding to the episodic abyssal stagnation events. Some cores also display a decrease inCassidulina carinata and an increase inArticulina tubulosa.Similar assemblage changes have been previously documented to be closely associated with the sapropel layers in the deep basins of the eastern Mediterranean (the actual sapropel layers usually do not contain benthonic foraminifera). However, in the Strait of Sicily area, the species exhibit less drastic changes than in the deep eastern basins because of the less severe anoxic conditions. In the deep eastern basins, benthonic foraminifera almost totally disappeared in sapropel layers; at the same time, there was a general reduction in foraminiferal numbers in the shallower Strait area.     

Stability of spatial pattern of fish species diversity in the Strait of Sicily (central Mediterranean)

In this paper, species diversity of demersal fish communities was analysed over an area covering about 45,000 km² of the Italian side of the Strait of Sicily (central Mediterranean). Fish abundance data come from a 10-year series (1994–2003) of experimental bottom trawl surveys carried out within the framework of the international program MEDITS. A simple GIS-based method was proposed to identify areas supporting high or low values of diversity and evaluate their temporal stability. A well-defined spatio-temporal pattern in diversity emerged from the analysis, with some areas of great ecological relevance being identified. Importantly, the greatest diversity within the fish communities was consistently seen at the offshore bank on the western part of the south Sicilian shelf (Adventure Bank). The site also supports high total biomass of demersal resources and shows the presence of species of great concern to fisheries. Results suggest that Adventure Bank represents a priority site for investigating the possibility of innovative management of marine ecosystems and demersal fisheries in offshore zones.     

Eocene carbonate clasts in Oligocene siliciclastic sediments of the Trapani Basin (NW Sicily): depositional and stratigraphic significance

The ‘Monte Bosco clays and quartz sandstones’, cropping out at Baglio Beatrice near Castellammare del Golfo (Sicily, southern Italy) and belonging to the Pre-Panormide domain, contain planktic and nannofossil assemblages indicating the lower Oligocene, whereas reworked larger foraminifers occurring in turbidites are upper Eocene, and limestone clasts scattered throughout the section and occurring in channelized conglomerates are lower Eocene (Cuisian) in age. The autochthonous benthic foraminiferal assemblages in the hemipelagic marly clay background sediment indicate a well-oxygenated sea floor and show a deepening-upward trend through the succession from a middle to lower bathyal zone. Turbidites are graded and the coarser fraction, at the base of the beds, is composed by scattered tests of shallow-water late Eocene foraminifers reworked into the Oligocene matrix dominated by planktic foraminifers. The latter dominate the finer fraction characterized by the occurrence of quartz grains. The analysis of six limestone clasts revealed the occurrence of four microfacies characterizing a shallow-marine moderate-energy environment, a high-energy vegetated shoal, a high-energy middle-ramp, and the outer-ramp. The investigated clasts are all of a similar age, middle Cuisian, according to the microfossils, which include alveolinids, ornatorotaliids, and Cuvillierina vallensis. The interpreted microfacies suggest a distally steepened ramp source area, although there is no outcrop of such a platform in NW Sicily. The ‘Monte Bosco clays and quartz sandstones’ were deposited along a slope periodically affected by turbidity currents and debris flows, which cannibalized cemented and unlithified Eocene shallow-water carbonate facies.     

Altitudinal variation in the late quaternary vegetational history of Northwest Greece

The palaeoecological sites of Gramousti lake and Rezina marsh, northwest Greece, although only 20 kin apart are at contrasting altitudes of 285 m a.s.1. and 1800 m a.s.1. Altitudinal difference between the two sites is shown to have a significant effect upon the postglacial vegetational history of the region. Rezina marsh is the highest and smallest site to be studied thus far in Greece and provides some of the first evidence for the location of cold‐stage temperate tree refugia. Migration of tree populations is shown to play an insignificant part in the vegetational development of the mountain region, demonstrating the importance of other factors (internal and external) in the diversity of the postglacial woodland.     

Shifting patterns of Nothofagus cunninghamii (Hook.) Oerst rainforest in the late quaternary of southeastern Australia: Evidence from pollen

An attempt is made to identify the location and nature of areas in which the cool temperate rainforest tree Nothofagus cunninghamii may have survived the glacial period, using fossil pollen data from sites at different altitudes in the Central Highlands of Victoria, Australia.

At one high altitude site Nothofagus has been recorded consistently through the latter part of the Pleistocence including the height of the last glacial. There was a postglacial expansion at most sites to a maximum extent in the early to middle Holocene, followed by a decline at all sites and elimination from two of the lower altitude sites.

The persistence of Nothofagus pollen through the height of the last glacial in a sheltered high altitude site supports the concept of glacial refugia, and leads to the query as to how Nothofagus survived the glacial under winter temperatures several degrees lower than those supporting the tree today. Evidence from evolutionary history, clinal variation in morphology and physiology along altitudinal or environmental gradients, and recent work on leaf physiognomy and ecophysiology contribute to possible explanations.

Elimination of Nothofagus from lower altitude sites after the middle Holocene raises the possibility of a shifting pattern of distribution, with long term survival dependent on the continued existence of locations suitable for the tree through the range of glacial and interglacial conditions. Fossil pollen data provide support for the occurrence of such locations in mountainous areas in sheltered gullies protected from fire.     

A late quaternary stratigraphy for DSDP Site 480, Gulf of California

The Coscinodiscus nodulifer A. Schmidt size-change stratigraphy is applied to the upper 17 cores (86 m) of DSDP Site 480 and the upper six cores (50 m) of Site 479, both from the Guaymas Basin slope, Gulf of California. This stratigraphy locates Oxygen Isotope Stage 2 (18,000 yrs BP) in Core 4, Section 1, Site 480, and Core 3, Section 2, Site 479, and the Stage boundary (24,000 yrs BP) in Core 5, Sections 1–2, Site 480.     

Life history traits of the striped seabream Lithognathus mormyrus (Pisces,Sparidae) from two coastal fishing grounds in the Strait of Sicily

Striped seabream Lithognathus mormyrus [n = 1269; total lengths (TLs) = 112–350 mm] were investigated in two coastal Sicilian fishing grounds (central Mediterranean Sea). Samples were collected from the two landing harbours, Licata and Selinunte, between October 1999 and September 2000. Seasonal and spatial variations in population structure, age, growth, reproduction and mortality were studied. It was found that seasonal differences in the main modes of length–frequency distributions corresponded well with the seasonal growth. The recruits in Licata grew faster and attained a larger size (by 10–20 mm) at ages up to 2 years than in Selinunte. Growth thereafter was relatively slow, with Selinunte specimens growing at a slightly faster rate. Spawning occurred between June and August. Length at the first maturity was different between females and males in the Selinunte (190–181 mm) and Licata (183–171 mm) fishing grounds. The species displayed protandrous hermaphroditism, and somatic growth practically ceased during the period of sex inversion. Total fishing mortality was considerably higher in Licata (F between 0.53 and 0.63 per year) than in Selinunte (F between 0.22 and 0.29 per year). Therefore it is suggested that the striped seabream population in Licata is more vulnerable to overfishing than that in Selinunte.     

A review of long-distance movements by marine turtles, and the possible role of ocean currents

Sea turtle movements often occur in open‐sea unsheltered areas, and are therefore likely to be influenced by major oceanographic processes. Only recently has work started to examine the possible relationships of these movements with dynamic oceanic features, and consequently a clear picture of such interaction is only available in a few cases. Newborn sea turtles are thought to rely on oceanic currents to reach their pelagic nursery habitats. The actual extent and timing of these developmental migrations are known for only a few populations, but these movements probably last several years and range over thousands of km. Large juveniles that have been tracked during their pelagic stage were found to make long‐distance movements, sometimes swimming against the prevailing currents. Older juveniles of most species leave the pelagic habitat to recruit to neritic developmental habitats. This is a very poorly documented phase of the sea turtle life‐cycle, and the few available indications show that turtles may have to swim actively for enormous distances to counterbalance their previous drift with the current. The course and extent of adult postnesting migrations vary greatly among different turtle species, but two main patterns are evident. Some species, like green, hawksbill and loggerhead turtles, shuttle between the nesting beach and a specific feeding area used for the entire inter‐reproductive period. In these cases, individuals swim, rather than drift, to complete their journeys, with possible advection due to currents sometimes helping them to quickly reach their target, but sometimes providing navigational challenges. Other species such as the olive ridley and the leatherback turtle, leave the coastal nesting areas to reach the pelagic environment where they forage, and perform wandering movements. Major oceanographic processes (such as main currents and eddies) have been recently shown to have a remarkable influence on leatherback movements, making it questionable whether these journeys are to be considered migrations or, rather, prolonged stays in vast feeding areas.     

The occurrence and fission-track ages of late neogene and quaternary volcanic sediments,Siwalik group,Northern Pakistan

Volcanic sediments, now mostly bentonites and bentonitic mudstones, occur throughout the Late Neogene and Quaternary Siwalik Group of northern Pakistan. A number of these deposits have been dated by the fission-track method, utilizing zircon phenocrysts from these deposits, and provide the chronometric constraints upon which a paleomagnetic stratigraphy is developed for the Siwalik Group. Notable in the occurrence of these altered tuff horizons is an apparent mode in their stratigraphic development from approximately 3.0 to 1.5 m.y. B.P. which coincides with the period of activity of the Dacht-e-Nawar volcanic complex of east-central Afghanistan. Fission-track ages of certain tuffs for critical areas of northern Pakistan are reported herein.     

Sulfur distribution in lake sediment profiles as an index of historical depositional patterns

Changes in S concentration in sediment profiles from South Lake (Adirondack region, New York, USA) and Ledge Pond (western Maine, USA) indicated an increased input of S beginning around 1850. This S was probably derived from anthropogenic sources. The S budget for South Lake indicated that sedimentation of seston rich in S (0.9% dry mass) accounts for most of the input of S in sediment. Sulfur in both seston and sediment is primarily organic (57 and 22% ester sulfate, 32 and 52% carbon-bonded S, respectively). The transformation and translocation of organic S constitutes a major pathway of S flux in South Lake.     

Reproductive features of the non-native Siganus luridus (Teleostei, Siganidae) during early colonization at Linosa Island (Sicily Strait, Mediterranean Sea)

In July 2003, the finding of a newly settled population of Siganus luridus at Linosa Island (Sicily Strait, Mediterranean Sea) gave us the unusual opportunity to examine the reproductive condition of a Lessepsian migrant during early phases of colonization. Aspects of gonad morphology, fecundity, atresia and oocyte dynamics were investigated by using 43 pioneer specimens collected in concomitance with their first record in the Pelagie Islands. Ovarian development was consistent with the group‐synchronous type, and testicular organization was of the unrestricted spermatogonial testis type, with cystic spermatogenesis. Both males and females had reached final stages of gonad maturation. The rates of follicular atresia were moderate: out of 17 adult females, 10 individuals did not present atretic oocytes; six exhibited <15.1% of secondary growth phase (SGP) oocytes in α‐atresia, while one female presented 45.7% of SGP in α‐atresia. Fecundity estimates did not diverge from what was observed in a reference population along the Lebanese coast. Absolute fecundity ranged from 115 739 to 740 433 oocytes per female (16.5–24.5 cm L_T). Relative fecundity ranged from 1239 to 3162 oocytes g⁻¹, with a mean of 1885 ± 868 oocytes g⁻¹. Our observations indicated that these early settled siganids are reproductively active at Linosa and suggested the forthcoming of self‐maintaining populations across the central Mediterranean area.     

Testate amoebae in late quaternary sediments of the Cape Mamontov Klyk (Yakutia)

The results of the analysis of Rhizopoda from permafrost sediments of the cryolithozone of northeastern Siberia are presented. Testate amoeba communities (Rhizopoda: Testaceafilosea, Testacealobosea) of the late Pleistocene and Holocene and modern habitats of the Cape Mamontov Klyk (the Laptev Sea coast in the vicinity of the Lena River estuary) have been researched. The paleocommunity structure was examined; assessment of rhizopod diversity in sediments of different (fluvial, alluvial, ice complex, alas, and alluvial-dealluvial) geneses was conducted.     

Examining rates and patterns of nucleotide substitution in plants

Driven by rapid improvements in affordable computing power and by the even faster accumulation of genomic data, the statistical analysis of molecular sequence data has become an active area of interdisciplinary research. Maximum likelihood methods have become mainstream because of their desirable properties and, more importantly, their potential for providing statistically sound solutions in complex data analysis settings. In this chapter, a review of recent literature focusing on rates and patterns of nucleotide substitution rates in the nuclear, chloroplast, and mitochondrial genomes of plants demonstrates the power and flexibility of these new methods. The emerging picture of the nucleotide substitution process in plants is a complex one. Evolutionary rates are seen to be quite variable, both among genes and among plant lineages. However, there are hints, particularly in the chloroplast, that individual factors can have important effects on many genes simultaneously.     

Spatio-temporal distribution of recruits (0 group) of Merluccius merluccius and Phycis blennoides (Pisces, Gadiformes) in the Strait of Sicily (Central Mediterranean)

Aspects of the recruitment of hake (Merluccius merluccius L., 1758) and greater fork beard (Phycis blennoides Brunnich, 1768) in the Strait of Sicily (Central Mediterranean) are presented. Data were collected from 1994 to 1999 during the international bottom trawl survey program MEDITS. In view of the available literature on juvenile growth of these two species in the Mediterranean area, a length-based criterion was adopted to separate fish belonging to the 0 group (recruits). Recruit density indices (R/km²) by haul were calculated based upon the likely variability of recruit growth among years and used to study abundance variability and spatial pattern of recruitment and to identify the main nursery areas. Although there was inter-annual variability, two stable areas for M. merluccius were identified on the eastern side of the Adventure Bank and the Malta Bank at depths ranging between 100 and 200 m. The main nursery areas for P. blennoides were deeper (from 200 to 400 m) and two stable nursery areas were identified on the western and eastern side of the Adventure Bank; other nurseries were found in the easternmost part of the Strait in 1998 and 1999. Recruitments of the two species were significantly correlated, with the strongest recruitment occurring in 1998 and 1999 for each species.