Ligurian Sea (ligurian + sea)

Distribution by Scientific Domains

Selected Abstracts

Identification of Atlantic bluefin tuna (Thunnus thynnus) stocks from putative nurseries using otolith chemistry

Jay R. Rooker
Abstract Chemical signatures in the otoliths of teleost fishes represent natural tags that may reflect differences in the chemical and physical characteristics of an individuals' environment. Otolith chemistry of Atlantic bluefin tuna (Thunnus thynnus) was quantified to assess the feasibility of using these natural tags to discriminate juveniles (age 0 and age 1) from putative nurseries. A suite of six elements (Li, Mg, Ca, Mn, Sr and Ba) was measured in whole otoliths using solution-based inductively coupled plasma mass spectrometry. Otolith chemistry of age-1 T. thynnus collected from the two primary nurseries in the Mediterranean Sea and western Atlantic Ocean differed significantly, with a cross-validated classification accuracy of 85%. Spatial and temporal variation in otolith chemistry was evaluated for age-0 T. thynnus collected from three nurseries within the Mediterranean Sea: Alboran Sea (Spain), Ligurian Sea (northern Italy), and Tyrrhenian Sea (southern Italy). Distinct differences in otolith chemistry were detected among Mediterranean nurseries and classification accuracies ranged from 62 to 80%. Interannual trends in otolith chemistry were observed between year classes of age-0 T. thynnus in the Alboran Sea; however, no differences were detected between year classes in the Tyrrhenian Sea. Age-0 and age-1 T. thynnus collected from the same region (Ligurian Sea) were also compared and distinct differences in otolith chemistry were observed, indicating ontogenetic shifts in habitat or elemental discrimination. Findings suggest that otolith chemistry of juvenile T. thynnus from different nurseries are distinct and chemical signatures show some degree of temporal persistence, indicating the technique has considerable potential for use in future assessments of population connectivity and stock structure of T. thynnus. [source]

Analyses of the stress field in southeastern France from earthquake focal mechanisms

Emmanuel Baroux
Summary Owing to the apparent deformation field heterogeneity, the stress regimes around the Provence block, from the fronts of the Massif Central and Alpine range up to the Ligurian Sea, have not been well defined. To improve the understanding of the SE France stress field, we determine new earthquake focal mechanisms and compute the present-day stress states by inversion of the 89 available focal mechanisms around the Provence domain, including 17 new ones calculated in the current study. This study provides evidence of six distinct deformation domains around the Provence block, with different tectonic regimes. On a regional scale, we identify three zones characterized by significantly different stress regimes: a western one affected by an extensional stress (normal faulting) regime; a southeastern one characterized by a compressional stress (reverse to strike-slip faulting) regime with NNW- to WNW-trending ,1; and a northeastern one, namely the Digne nappe front, marked by a NE-trending compression. Note that the Digne nappe back domain is controlled by an extensional regime that is deforming the western Alpine core. This extensional regime could be a response to buoyancy forces related to the Alpine high topography. The stress regimes in the southeast of the Argentera Massif and around the Durance fault are consistent with a coherent NNW-trending ,1, implying a left-lateral component of the active reverse oblique slip of the Moyenne Durance Fault. In the Rhone Valley, an E-trending extension characterizes the tectonic regime, implying a normal component of the present-day N,^mes fault displacement. This study provides evidence for short-scale variation of the stress states, which arises from abrupt changes in the boundary force influences on upper crustal fragments (blocks). These spatial stress changes around the Provence block result from the coeval influence of forces applied at both its extremities, namely in the northeast the Alpine front push, and in the southeast the northward African plate drift. In addition to these boundary forces, the mantle plume under the Massif Central influences the western block boundary. [source]

Climate control on the long-term anomalous changes of zooplankton communities in the Northwestern Mediterranean

Abstract In marine ecosystems, pelagic copepods, chaetognaths and jellyfish play a key role in matter and energy flow. While copepods support most food webs and the biological pump of carbon into the deep ocean, chaetognaths and jellyfish may affect the strength of the top-down control upon plankton communities. In this study, we show that the main events in the long-term variability of these functional groups in the Northwestern Mediterranean were tightly linked to changes of climate forcing of the North Atlantic sector. Large-scale climate forcing has altered the pelagic food-web dynamics through changes in biological interactions, competition and predation, leading to substantial changes manifested as bursts or collapses in zooplankton populations, and consequently to a major change ca. 1987. These events become more frequent in the 1980s and the early 1990s in the studied zooplankton functional groups suggesting a shift in the functioning of the pelagic ecosystem. The environmental modifications and the results reported here are therefore, indicators of a regime change pointing to a more regeneration-dominated system in the study area. We suggest a chain of mechanisms, whereby climate variation has modified the long-term dynamics of pelagic copepods, chaetognaths and jellyfish in the Ligurian Sea. [source]

A Multidisciplinary Approach to Describe Protists: Redescriptions of Novistrombidium testaceum Anigstein 1914 and Strombidium inclinatumMontagnes, Taylor, and Lynn 1990 (Ciliophora, Oligotrichia)

ABSTRACT. We combined behavioral, morphological (live, stained, scanning and transmission electron-microscope), and molecular data to redescribe two common, intertidal oligotrich ciliates, Novistrombidium testaceum and Strombidium inclinatum. Both species were collected from a rocky shore near Leghorn, Ligurian Sea. A literature review revealed four morphotypes of Novistrombidium testaceum that differ in subtle ways, including oral morphology. These differences may be diagnostic, but we do not consider them sufficient to distinguish different taxa. Although other studies have synonymised Strombidium inclinatum and S. sulcatum, based on oral structures, size, and nuclear structure, there are morphological distinctions between them. In particular, the present study supports a lack of anterior protuberance in both live and preserved S. inclinatum, while S. sulcatum possesses a protuberance. The 18S rDNA molecular data, in accordance with morphological and ultrastructural observations, indicate that the Strombidiida (Oligotrichia) constitute a well-supported clade. The separation of the genera within this clade, even between Novistrombidium and Strombidium, remains unresolved, and the analysis of more species is required. Finally, we recommend that when possible, ecologists, morphological taxon-omists, and molecular biologists combine their expertise to provide comprehensive taxonomic descriptions. [source]

The Pelagos Sanctuary for Mediterranean marine mammals

Giuseppe Notarbartolo-di-Sciara
Abstract 1.In February 2002, France, Italy and Monaco agreed to establish an international sanctuary for Mediterranean marine mammals. The resulting Pelagos Sanctuary encompasses over 87500 km2 of the north-western Mediterranean Sea, extending between south-eastern France, Monaco, north-western Italy and northern Sardinia, and surrounding Corsica and the Tuscan Archipelago. 2.The Pelagos Sanctuary illustrates how the tenets of Marine Protected Area (MPA) design can be reconciled with the dynamic nature of oceanic systems, because its spatial scale was defined by oceanographic and ecological considerations, specifically the location of the Ligurian permanent frontal system. 3.By expanding protective measures beyond national waters, the Pelagos Sanctuary also sets a precedent for the implementation of pelagic protected areas in the high seas. The Pelagos Sanctuary will contribute to the conservation of the Mediterranean Sea at two scales: (i) locally, by protecting important cetacean foraging and breeding grounds in the Ligurian Sea, and by providing ,umbrella' protection to other marine predators in this area; and (ii) regionally, by empowering other conservation measures, such as the Specially Protected Areas Protocol of the Barcelona Convention and the wider goals of the Agreement on the Conservation of Cetaceans of the Black and Mediterranean Seas (ACCOBAMS). 4.However, because few cetacean species are resident within the Sanctuary, their effective long-term conservation will require large-scale management and coordinated monitoring throughout the Mediterranean basin. Copyright 2007 John Wiley & Sons, Ltd. [source]

A new synthetic index and a protocol for monitoring the status of Posidonia oceanica meadows: a case study at Sanremo (Ligurian Sea, NW Mediterranean)

Monica Montefalcone
Abstract 1.The status of a Posidonia oceanica meadow in front of the town of Sanremo, Italy, was studied through a combined use of benthic mapping and synthetic indices. 2.Mapping was accomplished by integrating side scan sonar imagery and data collected by scuba diving along transects placed perpendicularly to the coastline. A thematic map (scale 1:5000) was produced. Extent of the meadow, occurrence of dead matte areas, and morphology of the lower limit (with new definition) are all described. 3.Two synthetic environmental indices were applied to transect data in order to quantify the status of the meadow: the Conservation Index and the Substitution Index. The former is related to the proportion of dead matte; the latter is a novel index measuring the amount of replacement of the ,constructional' seagrass P. oceanica by the ,non-constructional' seagrass Cymodocea nodosa. The potential of a ,phase shift' in Ligurian Sea seagrass meadows is discussed. 4.The approach here proposed, based on detailed mapping plus synthetic indices, may provide immediate information to evaluate the state of Mediterranean Posidonia oceanica for monitoring and management. Copyright 2006 John Wiley & Sons, Ltd. [source]

Origins of the reversed flow over the windward Alpine foothills during MAP IOP3 and IOP8

N. Asencio
Abstract The synoptic-scale situations during the two Intensive Observing Periods (IOPs) of the Mesoscale Alpine Programme (MAP) characterized by persisting precipitation and down-valley flow as observed by the Doppler on the wheel radar (DOW) over the two Alpine valleys (Toce and Ticino) were investigated. The first period (IOP3, 24,27 September 1999) was characterized by a south-westerly flow and convective precipitation, whereas the second period (IOP8, 20,21 October 1999) by a down-valley flow and stratiform precipitation. During IOP3, the down-valley northerly flow over the north-western part of the Po valley was confined within a thin layer of 200,300 m depth. During IOP8, the northerly flow extended from the Alps foothills to the Ligurian sea in a deep layer of 1,2 km height. The Meso-NH numerical model with a 2.5 km horizontal mesh grid reproduced the characteristics of both cases from the valley scale to the meso-, scale. Sensitivity experiments were, furthermore, performed in order to highlight the relationships between wet or dry drainage flow channelled by the Alpine orography, mesoscale upstream flow blocked by the Alps, and a regional cold pool at the foothills inside the Po valley. During IOP8, the diabatic processes were dominant at local scales in confirmation of Steiner results based on the DOW observations and they were significant at regional scales upstream of the Alps by maintaining a cold pool over the Po valley. The IOP3 low-level flow reversal occurred as the flow began to cross over the Alps instead of turning around. A downslope flow is associated with the blocked-regime period upstream of the Alps. Copyright 2006 Royal Meteorological Society [source]