Holocene Vegetation History and Palaeoenvironmental Conditions on the Temperate Atlantic Coast of Argentina,as Inferred from Multi-Proxy Lacustrine Records

Holocene vegetation history and palaeoenvironmental conditions are investigated at the south coast of Buenos Aires Province, Argentina. La Olla 1 and Laguna del Sauce Grande sediment sequences are analysed for pollen, calcareous microfossil (ostracods and foraminifers) and plant macrofossil remains (mainly seeds and charophyte oospores). Supplementary information is provided by sedimentological analysis. Modern surface sample data are used to assist in the interpretation of the fossil records. La Olla 1 sequence covers the period 7890 to 7630 cal. BP. The microfauna recovered is characteristic of a shallow marginal-marine environment such as a coastal lagoon. The microfossils indicate a marine connection between 7850 and 7800 cal. BP. Plant macrofossil remains and pollen analyses indicate an extension of the water body after 7780 cal. BP. The pollen record reveals the development of a halophytic plant community in a coastal environment. The sediment record from Laguna del Sauce Grande comprises the last 3000 years. Microfossils and macrofossil remains indicate that the lake history begins with a temporary brackish-water phase. More stable conditions and higher salinity values occur between 1940 and 900 cal. BP. Periods of water level fluctuations occur after 900 cal. BP, with high water levels between 660 and 270 cal. BP. The uppermost samples of the sequence show similar conditions to present day. Pollen spectra indicate a relatively stable vegetation composition throughout the last 3000 years. Pollen assemblages reflect the present regional grassland vegetation with taxa characteristic of the surrounding dune communities.     

Egg to adult identification of 13 freshwater fishes from Italy: a biochemical-genetic key

The family Cyprinidae comprises most of the freshwater fauna of the North Mediterranean region and it is often numerically dominant. Taxonomy based on morphology is problematic, owing to the high intraspecific variation in phenotypic traits, their overlap between species and environmental plasticity of morphometric and meristic characters. A difficult diagnosis, particularly for young developmental stages, can increase resource mismanagement. Here we report on the occurrence of species-specific allozymic patterns, consistent from eggs to adults. These allowed the construction of a biochemical-genetic key for the identification of all stages of 13 freshwater fishes, mainly cyprinids native to the North Mediterranean region (Alburnus alburnus alborella, Barbus plebejus, Chondrostoma genei, Gobio gobio, Leuciscus cephalus, L. lucumonis, L. souffia, Rutilus rubilio, R. erythrophthalmus, Scardinius erythrophthalmus, Tinca tinca, Pseudorasbora parva and Padogobius martensii).     

Esterification of vertebrate-like steroids in the eastern oyster (Crassostrea virginica)

The esterification of two model vertebrate steroid hormones – estradiol (E2) and dehidroepiandrosterone (DHEA) – was studied in the oyster Crassostrea virginica. The activity of acyl-CoA:steroid acyltransferase was characterized in microsomal fractions isolated from oyster digestive glands. The apparent K_m and V_max values changed with the fatty acid acyl-CoA used (C20:4, C18:2, C18:1, C16:1, C18:0 or C16:0), and were in the range of 9–17 μM, and 35–74 pmol/min/mg protein for E2, and in the range of 45–120 μM, and 30–182 pmol/min/mg protein for DHEA. Kinetic parameters were also assessed in gonadal tissue. The enzyme saturated at similar concentrations, although conjugation rates were lower than in digestive gland. Preliminary data shows that tributyltin (TBT) in the low μM range (1–50) strongly inhibits E2 and DHEA esterification, the esterification of E2 being more sensitive to inhibition than that of DHEA. Overall, results indicate that apolar conjugation occurs in oysters, in both digestive gland and gonads, at a very similar rate to mammals, suggesting that this is a well conserved conjugation pathway during evolution. Esterification, together with other mechanisms, can modulate endogenous steroid levels in C. virginica, and might be a target for endocrine disrupters, such as TBT.     

Three-year investigations into sperm whale-fall ecosystems in Japan

We report the first study of sperm whale‐fall ecosystems, based on mass sinking of whale carcasses at shelf depths in the northwest Pacific. We conducted three observations over a 2‐year period on replicate sperm‐whale carcasses implanted at depths of 219–254 m off the southern part of Japan from July 2003 to August 2005. The study was made possible by a mass stranding of sperm whales in January 2002, and the subsequent sinking of 12 carcasses in the waters off Cape Nomamisaki. Dense aggregations of unique chemosynthesis‐based fauna had formed around the whale carcasses after 18 months (July 2003). The mytilid mussel Adipicola pacifica was the most abundant macrofaunal species and covered most of the exposed bone surfaces. The general composition of the fauna was similar to that of deep‐water reducing habitats, but none of the species appearing in this study has been found at hydrothermal vents, cold seeps or deep‐water whale falls. A new species of lancelet, which was the first record of the subphylum Cephalochordata from reducing environments, a new species of Osedax; a rarely encountered benthic ctenophore, and a rare gastropod species were discovered at this sperm whale‐fall site. Benthic communities were similar across all the carcasses studied, although the body sizes of the whales were very different. The succession of epifaunal communities was relatively rapid and the sulphophilic stage was considerably shorter than that of other known whale falls.     

The contribution of microzooplankton to the diet of mesozooplankton in an upwelling filament off the north west coast of Spain

Incubation experiments were carried out daily during a Lagrangian experiment within an upwelled filament off the Galician coast to determine the importance of microzooplankton in the diet of calanoid copepods. Despite low chlorophyll concentrations the microzooplankton formed the minor component of the diet of the copepod community (7 to 15% of carbon ingested through autotrophic and heterotrophic prey). Ingestion of ciliates was greater than that of heterotrophic dinoflagellates, which reflected a higher abundance of ciliates in the water column. Heterotrophic nanoflagellates appeared also to be consumed by the copepods, although the very small size fraction (2–5μm) was probably not grazed by the larger copepods of Calanus spp. Grazing pressure by the copepods enumerated in the net samples was not sufficient to impact significantly the microzooplankton populations (2 to 51% of daily microzooplankton production was removed). Allometric relationships of grazing on microzooplankton for a range of numerically dominant copepod species are developed from the experimental results. The grazing pressure of the whole copepod community is estimated from these relationships. By considering the total mesozooplankton community we suggest that microzooplankton growth was probably restricted by metazoan grazers.     

GIS-based spatial prediction of debris flows using logistic regression and frequency ratio models for Zêzere River basin and its surrounding area,Northwest Covilhã, Portugal

Landslide susceptibility mapping (LSM) is important for catastrophe management in the mountainous regions. They focus on generating susceptibility maps beginning from landslide inventories and considering the main predisposing parameters. The aim of this study was to assess the susceptibility of the occurrence of debris flows in the Zêzere River basin and its surrounding area using logistic regression (LR) and frequency ratio (FR) models. To achieve this, a landslide inventory map was created using historical information, satellite imagery, and extensive field works. One hundred landslides were mapped, of which 75% were randomly selected as training data, while the remaining 25% were used for validating the models. The landslide influence factors considered for this study were lithology, elevation, slope gradient, slope aspect, plan curvature, profile curvature, normalized difference vegetation index (NDVI), distance to roads, topographic wetness index (TWI), and stream power index (SPI). The relationships between landslide occurrence and these factors were established, and the results were then evaluated and validated. Validation results show that both methods give acceptable results [the area under curve (AUC) of success rates is 83.71 and 76.38 for LR and FR, respectively]. Furthermore, the AUC results for prediction accuracy revealed that LR model has the highest predictive performance (AUC of predicted rate?=?80.26). Hence, it is concluded that the two models showed reasonably good accuracy in predicting the landslide susceptibility in the study area. These two models have the potential to aid planners in development and land-use planning and to offer tools for hazard mitigation measures.     

Analysis of a GPS Network Based on Functional Data Analysis

This paper demonstrates the usefulness of approaching the dynamic study of the precise positioning of a network of permanent global positioning system (GPS) stations through functional data analysis. The displacement data for each GPS station, obtained from observations of the global navigation satellite system, are a discrete sample of the positioning curve. The aim of this paper is to reconstruct the original functions in order to use them as functional data. In the method presented in this paper, the geodetic series are obtained first by processing the GPS data with respect to a reference station. Second, for each station, a cleaning process is applied to eliminate the values considered as outliers, and the missing values are imputed by using a Kalman filter. Finally, the original functions are reconstructed by using smoothing techniques and by evaluating several bases of functions. Moreover, these functions are treated with statistical techniques for functional data. This procedure is applied to the permanent stations of the south of the Iberian peninsula and the north of Africa (SPINA) network. The topocentric series: east, north and up are analysed. In the analysis of the positioning curves, there is observed a synchronized behaviour of the functions in those periods of time with important seismic activity. This behaviour also appears in the analysis of the second principal component of the East and up dimensions. Furthermore, the first two principal components of the East coordinate enable us to make a classification of the stations in the SPINA network. The classification made is consistent with the previous knowledge of the tectonic plates in the studied area.