The green–blue swing: plasticity of plankton food‐webs in response to coastal oceanographic dynamics

The internal organization of plankton communities plays a key role in biogeochemical cycles and in the functioning of aquatic ecosystems. In this study, the structure of a marine plankton community (including both unicellular and multicellular organisms) was inferred by applying an ecological network approach to species abundances observed weekly at the long‐term ecological research station MareChiara (LTER‐MC) in the Gulf of Naples (Tyrrhenian Sea, Mediterranean Sea) in the summers of 2002–2009. Two distinct conditions, characterized by different combination of salinity and chlorophyll values, alternated at the site: one influenced by coastal waters, herein named ‘green’, and the other reflecting more offshore conditions, named ‘blue’. The green and blue ‘phases’ showed different keystone biological elements: namely, large diatoms and small‐sized flagellates, respectively. Several correlations amongst species belonging to different trophic groups were found in both phases (connectance ~0.30). In the green phase, several links between phytoplankton and mesozooplankton and within the latter were detected, suggesting matter flow from microbes up to carnivorous zooplankton. A microbial‐loop‐like sub‐web, including mixo‐ and heterotrophic dinoflagellates and ciliates, was present in the green phase, but it was relatively more important in the blue phase. The latter observation suggests a more intense cycling of matter at the microbial trophic level in the blue phase. These results show that different modes of ecological organization can emerge from relatively small changes in the composition of aquatic communities coping with environmental variability. This highlights a significant plasticity in the internal structure of plankton webs, which should be taken into account in predictions of the potential effects of climatic oscillations on aquatic ecosystems and biogeochemical cycles therein.     

Influence of the hydrothermal vents on the distribution of benthic foraminifera from the Guaymas Basin,Mexico

The distribution and composition of four benthic foraminifera assemblages from the Guaymas Basin are depicted through Q- and R-mode Factor Analysis. One of these assemblages is distributed near hydrothermal vents,* another developed away from the influence of the vents, and the other two assemblages are found in the subbottom sediments.Biostratigraphic analysis of five cores collected within the hydrothermal region suggest that the foraminiferal remains have been affected by aselective dissolution process. Only small species, such asBulimina spinosa andBolivina sp 2, have been preserved in the subbottom sediments which have been influenced by the hydrothermal activity.     

A method for na-tech risk assessment as supporting tool for land use planning mitigation strategies

Hazardous industrial sites have always represented a threat for the community often provoking major accidents overcoming the boundaries of the plants and affecting the surrounding urban areas. If the industrial sites are located in natural hazard-prone areas, technological accidents may be triggered by natural events, generating so-called na-tech events which may modify and increase the impact and the overall damage in the areas around them. Nevertheless, natural and technological hazards are still treated as two separate issues, and up to now the methods for na-tech risk assessment have been developed mainly for specific natural hazards, generally restricted to some plant typologies and to the area of the plant itself. Based on a review of the current na-tech literature, this article illustrates a risk assessment method as a supporting tool for land use planning strategies aimed at reducing na-tech risk in urban areas. More specifically, a multi attribute decision-making method, combined with fuzzy techniques, has been developed. The method allows planners to take into account, according to different territorial units, all the individual na-tech risk factors, measured through both quantitative and qualitative parameters, while providing them with a na-tech risk index, useful to rank the territorial units and to single out the priority intervention areas. The method is designed to process information generally available about hazardous plants (safety reports), natural hazards (hazard maps) and features of urban systems mainly influencing their exposure and vulnerability to na-tech events (common statistical territorial data). Furthermore, the method implemented into a GIS framework should easily provide planners with comparable maps to figure out the hazard factors and the main territorial features influencing the exposure and vulnerability of urban systems to na-tech events. The method has been tested on a middle-sized Municipality in the Campania Region, identified as 2nd class seismic zone, according to the Ordinance 3274/2003, in which a LPG storage plant, classified as a plant with major accident potential by the Seveso II Directive (art. 9), is located just within the city core.     

Efficiency of calcein tagging on juveniles of the sea urchins Diadema africanum and Paracentrotus lividus

We evaluated the effectiveness of chemical tagging with the fluorescent marker calcein for two key species of herbivorous sea urchins, Diadema africanum and Paracentrotus lividus, to facilitate medium‐ and long‐term ecological experiments. In total, 98 juveniles of D. africanum and 98 P. lividus were tagged with this fluorescent marker, with 12 combinations of different tagging techniques (chemical bath or injection), concentrations of calcein (2, 10 and 20 mg · l^?1), and soaking times (2, 4 and 24 h). Respective control treatments were conducted by means of seawater injection and bathing. The success of tagging was assessed after a month of feeding individuals ad libitum with the algae Dictyota sp. Sea urchins were dissected and their Aristotle's lanterns cleaned with 10% sodium hypochlorite to examine these structures under UV light using a binocular microscope. Each species was evaluated in terms of survival, percentage of tagged individuals and intensity of the resulting tag. The results showed that the method of soaking individuals of both species for 24 h in concentrations of calcein of 10 and 20 mg · l^?1 gave the highest percentage survival (100%) and the resulting tags were clearly visible.     

Use of geoprocessing in the study of land degradation in urban environments: the case of the city of São Carlos,state of São Paulo,Brazil

This paper presents a methodology for the geological engineering survey of land degradation in urban environments using both remote sensing and geoprocessing tools. The area under study was the city of São Carlos, state of São Paulo, Brazil (urban and expansion area). The data presented here were obtained from earlier studies, photointerpretation and geological engineering mapping. The Envi 4.1 software package was used to prepare the digital orthophotos that served as a reference base for the information. Orthorectification of the Ikonos image (PSM, 1 m) was done and compared with other orthophotos from studies of environmental degradation in urban areas. The evolution of land degradation processes was analyzed based on the photointerpretation of aerial photographs taken on different dates and using Ikonos image. This study allowed to conclude that most of the degradation occurring in the city has been caused by unplanned land occupation, in disregard of environmental conditions, resulting in environmental degradation and thus impacting the quality of life of the urban population.     

Diagenetic evolution of lower Jurassic platform carbonates flanking the Tazoult salt wall (Central High Atlas,Morocco)

Platform carbonates diagenesis in salt basins could be complex due to potential alterations of fluids related and non-related to diapirism. This paper presents the diagenetic history of the Hettangian to Pliensbachian platform carbonates from the Tazoult salt wall area (central High Atlas, Morocco). Low structural relief and outcrop conditions allowed to define the entire diagenetic evolution occurred in the High Atlas diapiric basins since early stages of the diapiric activity up to their tectonic inversion. Precipitation of dolomite and calcite from both warmed marine-derived and meteoric fluids characterised diagenetic stages during Pliensbachian, when the carbonate platforms were exposed and karstified. Burial diagenesis occurred from Toarcian to Middle Jurassic, due to changes of salt-induced dynamic related to increase in siliciclastic input, fast diapir rise and rapid burial of Pliensbachian platforms. During this stage, the diapir acted as a physical barrier for fluid circulation between the core and the flanking sediments. In the carbonates and breccias flanking the structures, dolomite and calcite precipitated from basinal brines, whereas carbonate slivers located in the core of the structure, were affected by the circulation of Mn-rich fluids. The final diagenetic event is characterised by the income of meteoric fluids into the system during uplift caused by Alpine orogeny. These results highlight the relevant influence of diapirism on the diagenetic modifications in salt-related basins in terms of diagenetic events and involved fluids.     

Astronomical tuning of the Tortonian 87Sr/86Sr curve in the Mediterranean basin

ABSTRACT This work presents a detailed ⁸⁷Sr/⁸⁶Sr isotope curve for the interval 7.5–9.7 Ma obtained by a high-resolution analysis (sampling spacing of about 40 kyr) of an astronomically calibrated land-based sedimentary sequence exposed in the central Mediterranean area (Gibliscemi section, southern Sicily). The main aim is to verify a synchronous response of the Mediterranean seawater Sr isotope record to the oceanic forcing on the basis of multiple comparisons of the Gibliscemi record with published coeval ⁸⁷Sr/⁸⁶Sr curves. A good correlation with the ⁸⁷Sr/⁸⁶Sr data from the ODP site 926 (equatorial Atlantic ocean), considered to be the Sr chemostratigraphic reference section for the Late Miocene, and from the Pacific DSDP site 590B was registered. Conversely, the comparison of the Gibliscemi Sr isotope data with ⁸⁷Sr/⁸⁶Sr ratios from the coeval segment of the land-based Sardella section (eastern Mediterranean) shows important differences highlighting a local control on the seawater Sr isotope changes in semi-isolated subbasins within the Late Miocene Mediterranean.     

Stratigraphic framework of the thrust geometry and structural inversion in the southeastern Pyrenees : La Garrotxa area

Abstract

The structure of la Garrotxa area within the Cadi unit (south-eastern Pyrenees) consists of a set of duplexes at different scales which repeat the different carbonatic litho-units of the Lower and Middle Eocene. These duplexes are folded by antiformal stacks structures with basement rocks in their cores. The north boundary of these antiformal stacks represents an inversion of pre-existent extensional faults which formed half-graben geometries. The basement rocks involved in the structure represent short-cuts formed in the footwall of the extensional faults. All thrusts of La Garrotxa area branch with the upper Garrotxa thrust. The more complex structure of La Garrotxa area than the adjacent areas within the Cadí unit, is due to the initial complex synsedimentary geometry of the sedimentary pile.

The Cadi unit overlies the Serrat unit with a hangingwall ramp geometry. This unit was deduced from the Serrat-1 well, drilled in 1987. The Serrat unit is made up of a Middle Eocene evaporitic sequence, with alternating shales and anhydrites and a 100 meters thick salt layer close to the top. The total thickness of this evaporitic Beuda sequence is 1 000 meters. The Beuda sequence clearly controlled the thrust geometry of the younger thrusts.