A multidisciplinary study of the Cape Peloro brackish area (Messina, Italy): characterisation of trophic conditions, microbial abundances and activities

In the framework of the VECTOR DIVCOST Project, a 2-year investigation was started in 2006, with the aim of testing the sensibility of microbial parameters to environmental changes and of assessing whether they can provide information about functional changes in the carbon cycle. The investigation was performed in the surface waters of two small brackish ponds (Ganzirri and Faro), located in the Cape Peloro transitional area (Sicily, Italy). The seasonal changes in both the microbial compartment [bacterioplankton, vibrios, exoenzymatic hydrolysis of proteins and polysaccharides, bacterial secondary production (HBP) and community respiration] and the trophic state of suspended matter [total suspended matter (TSM), particulate organic carbon (POC), particulate organic nitrogen (PON), C/N] were analysed in relation to the hydrological characteristics [temperature, salinity, oxygen, fluorescence, NH₄, NO₂, NO₃, PO₄]. Despite marked differences in the nutritional input and the diversification in both carbon budget and trophic level, the two ponds show similar trends in many of the investigated factors, hardly influenced by seasonal variations. Temporally coupled trends were observed for some parameters (enzyme activities, vibrios abundances, respiratory activity), whereas others (POC, PON, heterotrophic bacterial production, bacterioplankton) showed a seasonal shift between the two lakes. The different behaviour found for the some biotic parameters suggests that their response to environmental conditions may be modulated differently between the two lakes, which, despite their spatial proximity and reciprocal connection, do not always show contemporaneous functional processes.     

Flocculation–Sedimentation Combined with Chemical Oxidation Process

Flocculation and sedimentation of particles are essential to many environmental and industrial processes. Solid–liquid separation in olive‐oil mill wastewater treatment by means of Fenton system is the key to work continuously and maintain a constant outlet flow of clarified water at the end of the oxidation process. Natural sedimentation is not capable to eliminate the sludge formed. The efficiency of flocculation operation using different flocculants as QG‐2001, QG‐2002, DQGALFLOC‐130H, and Nalco‐77171 was investigated. The optimum dosage of each flocculant, 150, 2.5, 66, and 6 mg dm^?3, respectively, was determined. The results revealed that the best flocculant was Nalco‐77171, which determined 13.5% v/v final sludge separation and 86.5% v/v final clarified water obtained. Kinetics of sludge removal in the transition zone was adjusted to power law, v/v₀ = Kt^ε, where the exponent, ε, varied in the range 0.141–0.670.     

Glacial to Holocene climate changes in the SE Pacific. The Raraku Lake sedimentary record (Easter Island, 27°S)

Easter Island (SE Pacific, 27°S) provides a unique opportunity to reconstruct past climate changes in the South Pacific region based on terrestrial archives. Although the general climate evolution of the south Pacific since the Last Glacial Maximum (LGM) is coherent with terrestrial records in southern South America and Polynesia, the details of the dynamics of the shifting Westerlies, the South Pacific Convergence Zone and the South Pacific Anticyclone during the glacial–interglacial transition and the Holocene, and the large scale controls on precipitation in tropical and extratropical regions remain elusive. Here we present a high-resolution reconstruction of lake dynamics, watershed processes and paleohydrology for the last 34 000 cal yrs BP based on a sedimentological and geochemical multiproxy study of 8 cores from the Raraku Lake sediments constrained by 22 AMS radiocarbon dates. This multicore strategy has reconstructed the sedimentary architecture of the lake infilling and provided a stratigraphic framework to integrate and correlate previous core and vegetation studies conducted in the lake. High lake levels and clastic input dominated sedimentation in Raraku Lake between 34 and 28 cal kyr BP. Sedimentological and geochemical evidences support previously reported pollen data showing a relatively open forest and a cold and relatively humid climate during the Glacial period. Between 28 and 17.3 cal kyr BP, including the LGM period, colder conditions contributed to a reduction of the tree coverage in the island. The coherent climate patterns in subtropical and mid latitudes of Chile and Eastern Island for the LGM (more humid conditions) suggest stronger influence of the Antarctic circumpolar current and an enhancement of the Westerlies. The end of Glacial Period occurred at 17.3 cal kyr BP and was characterized by a sharp decrease in lake level conducive to the development of major flood events and erosion of littoral sediments. Deglaciation (Termination 1) between 17.3 and 12.5 cal kyr BP was characterized by an increase in lake productivity, a decrease in the terrigenous input and a rapid lake level recovery, inaugurating a period of intermediate lake levels, dominance of organic deposition and algal lamination. The timing and duration of deglaciation events in Easter Island broadly agree with other mid- and low-latitude circum South Pacific terrestrial records. The transition to the Holocene was characterized by lower lake levels. The lake level dropped during the early Holocene (ca 9.5 cal kyr BP) and swamp and shallow lake conditions dominated till mid Holocene, partially favored by the infilling of the lacustrine basin. During the mid- to late-Holocene drought phases led to periods of persistent low water table, subaerial exposure and erosion, generating a sedimentary hiatus in the Raraku sequence, from 4.2 to 0.8 cal kyr BP. The presence of this dry mid Holocene phase, also identified in low Andean latitudes and in Patagonian mid latitudes, suggests that the shift of storm tracks caused by changes in the austral summer insolation or forced by “El Niño-like” dominant conditions have occurred at a regional scale. The palm deforestation of the Easter Island, attributed to the human impact could have started earlier, during the 4.2–0.8 cal kyr BP sedimentary gap. Our paleoclimatic data provides insights about the climate scenarios that could favor the arrival of the Polynesian people to the island. If it occurred at ca AD 800 it coincided with the warmer conditions of the Medieval Climate Anomaly, whereas if it took place at ca AD 1300 it was favored by enhanced westerlies at the onset of the Little Ice Age. Changes in land uses (farming, intensive cattle) during the last century had a large impact in the hydrology and limnology (eutrophication) of the lake.     

The Tertiary： a proposal for its formal definition

The term Tertiary, subdivided into the Paleogene and Neogene, is traditionally used to represent the interval of geological time between the Cretaceous and Quaternary. In the 1990s, however, the Neogene and Paleogene were ratified by the International Union of Geological Sciences as periods/systems of the Cenozoic Era/Erathem, leaving the Tertiary officially undefined. The Tertiary nonetheless remains a formal term that has never been officially eliminated, and its widespread use today implies a long future.     

The geochemical evolution of the Catalan potash subbasin, South Pyrenean foreland basin (Spain)

Over the last decade, our studies in ancient evaporitic basins have been based on a detailed study of a single borehole record. The detailed findings in medium- to large-sized evaporitic basins were shadowed with a relevant question: can interpretations from a representative evaporitic record in a single borehole be extended to the whole evaporitic basin? This paper addresses that question; the results obtained are compared with results from another distant point within the basin. The general methodology not only proves its reliability in interpreting the evolution of evaporitic basins from a single borehole but reveals its capability to obtain detailed palaeoenvironmental interpretations.

The chemical evolution of an Upper Eocene evaporitic sequence from the South Pyrenean foreland basin (Spain) has been investigated along the Súria-19 borehole record. Detailed petrographic and mineralogical study, X-ray microanalysis of frozen primary inclusions trapped in halite (Cryo-SEM-EDS), systematic isotopic analysis (δ³⁴S and δ¹⁸O in sulphates) and computer-based evaporation models have been integrated in a multi-proxy methodology. This study revealed that a variable amount of Ca excess is required throughout different parts of the marine Lower Halite Unit (LHU) for sylvite, instead of K–Mg sulphates, to form. This Ca excess is in turn different from that required for the western sector of the same evaporitic basin (Navarrese subbasin). Quick and variable changes in Ca-rich brines or equivalent dolomitization required are explained as internal processes within the basin rather than secular variations in seawater chemistry.

The general hydrological evolution of the Catalan subbasin is explained as a restricted subbasin with a first marine stage in which continental input (up to 50% of total input) had an important control on the geochemistry of the subbasin. A second stage was determined during potash precipitation, in which the subbasin was cut from any seawater input to end up in its last stage as a purely continental evaporitic basin. Coupling evaporation models and analytical results we have obtained the proportions of recycling and their sources, estimated to change from a 100% (total mass of sulphate) Eocene source to 20% Eocene and 80% Triassic (Keuper) towards the latest stage of potash precipitation. The results obtained have been compared with results from the Navarrese subbasin allowing an integrated interpretation of the hydrological evolution of the whole Upper Eocene South Pyrenean basin. Local geochemical variations within the Upper Eocene south Pyrenean basin are explained by the differences in paleogeographical setting of the Navarrese and Catalan subbasins.     

Sedimentology of Quaternary perched springline and paludal tufas: criteria for recognition, with examples from Guadalajara Province, Spain

Outcrop‐scale geometries and bed relationships of ambient temperature freshwater carbonates are poorly understood because many described tufas have been dismantled by erosion and present only part of a particular depositional model. At the field scale, four end‐member models encompass the tufa continuum: (1) perched springline; (2) paludal; (3) fluvial; and (4) lacustrine tufas. Individual bed types can occur with variable dominance within several of these models, but one or more beds are characteristically dominant only within a single tufa model, so it can be differentiated from relatively isolated outcrop fragments. Two models (perched springline tufas and paludal tufas) are known in outline only in the literature despite being present within the Quaternary deposits of most karstic regions. Perched springline tufas generally form lobate, fan‐shaped mound morphologies on hillslopes and develop from single or multiple spring resurgences. Mature deposits show a subhorizontal top and a steep face on the downflow side. The steep outer zones of tufa mounds may be developed into cascades with moss curtains or can be dominated by shallow rimstone pools according to face angle. Tufa deposits lying downslope of the mounds are usually detrital in nature, especially if some dismantling of the mound has occurred. The relatively thin subhorizontal lobe‐top deposits commonly contain organic‐rich deposits. Paludal tufas develop predominantly in waterlogged valley bottom situations, where line‐sourced waters emerge from valley side and bottom aquifers. Lime mud precipitation predominates in these sites. Mud is deposited as subhorizontal laminites that thin towards the valley axis and downstream of resurgences. Tufa spring‐mounds may form where lesser volumes of water are involved. Individual tussocks (phytoherm cushions) of grasses and rushes are the most diagnostic feature of the model, but sapropels and peats may be intercalated. Diagenesis in both models is rapid. Lithification of individual beds is virtually instantaneous and always occurs before the decay of the associated living vegetation. The resulting highly porous and permeable fabrics remain fresh in Holocene tufas, but aggrading neomorphism and partial spar infill of vegetation moulds is common in older deposits. Dissolution in many perched springline tufas is small scale. Many large cavities are primary, but with later coatings of speleothems. Early removal of organics from paludal tufas is responsible for autobrecciation and differential compaction.     

Distribution and abundance of the Pacific sardine (Sardinops sagax) in the Gulf of California and their relation with the environment

In 1989–90 the small pelagic fishery of the Gulf of California began to show a very marked decline in the catch of its main component, the Pacific sardine (Sardinops sagax). The catch plummeted from 292,000 t in 1988–89 to 7000 t in 1991–92 and 1992–93. This caused a serious economic crisis in the local fishery fleet and industry, and resulted in the loss of 3000 jobs. In 1993–94 the fishery showed signs of recovery as the abundance of the Pacific sardine began to recover. The catch improved to 128,000 t in 1993–94 and further to 215,000 t in 1996–97. In trying to understand this great variability, we proposed the hypothesis that the distribution and the abundance of the Pacific sardine of the Gulf of California is determined by the wind patterns (upwelling) and the sea surface temperature. The results of analyzing data from 25 cruises showed the period of low relative abundance between 1990 and 1993 and one of high abundance between 1993 and 1996. The range of the sardine's distribution expanded as its abundance increased and contracted when abundances were low. The relationship between the abundances of the sardine and environmental variables proved to nonlinear and bell-shaped. The adjusted pattern explained 78.8% of the variability of the sardine abundance. The highest abundance are produced by moderate upwelling (13–18 m³s⁻¹ per 10 m of coastline) and sea surface temperatures of between 19°C and 25°C.     

Detection of underground cavities by combining gravity,magnetic and ground penetrating radar surveys: a case study from the Zaragoza area,NE Spain

A geophysical survey routine is proposed to detect underground cavities and dolines; it is based on the sequential application of magnetic, low-frequency ground penetrating radar (GPR) and microgravity techniques. A case study near Zaragoza (Ebro valley, Spain) demonstrates the applicability of these methods. The strong contrast of magnetic and electromagnetic properties (and to a lesser scale, of density) between the doline filling and the surrounding stratified Tertiary and Quaternary rocks allows the shape of filled cavities to be clearly outlined by these methods.     

Is the analysis of plant community structure better than common species-diversity indices for assessing the effects of livestock grazing on a Mediterranean arid ecosystem?

Grazing in arid Mediterranean ecosystems brings about changes in species diversity, but the best way to measure such changes is unclear. In this study we compared various methods in order to identify indicators that might be useful for the management and conservation of grazed arid Mediterranean ecosystems.Changes in community structure and composition were compared along a previously studied grazing gradient in Cabo de Gata-Nijar Natural Park. Plant diversity was measured by calculating diversity (Shannon information index), evenness (Pielou index) and richness (species number). Rarefaction curves were used to measure plant species richness and the results were compared with traditional richness values. Community structure was measured as the percentage of bare ground and the coverage of overall perennial grasses, Stipa tenacissima L., perennial shrubs and annual plants. Our results showed that the proportion of bare ground, the cover of perennial shrubs and the relative abundance of S. tenacissima are good indicators of grazing effects on vegetation. Overall plant community structure was more sensitive to the grazing gradient than were the diversity indices. Finally, the adequacy of standardized methods for comparing species richness (i.e. rarefaction curves) along a grazing gradient are discussed.