Sandy beach ecosystems: key features, sampling issues, management challenges and climate change impacts

Escalating pressures caused by the combined effects of population growth, demographic shifts, economic development and global climate change pose unprecedented threats to sandy beach ecosystems worldwide. Conservation of beaches as functional ecosystems and protection of their unique biodiversity requires management interventions that not only mitigate threats to physical properties of sandy shores, but also include ecological dimensions. Yet, beach management remains overwhelmingly focused on engineering interventions. Here we summarise the key outcomes of several workshops, held during the 2006 Sandy Beach Ecology Symposium in Vigo, Spain, that addressed issues of climate change, beach management and sampling methodology. Because efficient communication between managers and ecologists is critical, we summarise the salient features of sandy beaches as functional ecosystems in 50 'key statements'; these provide a succinct synopsis of the main structural and functional characteristics of these highly dynamic systems. Key outcomes of the workshops include a set of recommendations on designs and methods for sampling the benthic infaunal communities of beaches, the identification of the main ecological effects caused by direct and indirect human interventions, the predicted consequence of climate change for beach ecosystems, and priority areas for future research.     

Succession of macrofauna on macroalgal wrack of an exposed sandy beach: effects of patch size and site

In this study, we used experimental manipulation of algal wrack to test hypotheses about influences on macrofaunal assemblages inhabiting the upper shore level of different sites along an exposed sandy beach. First, we hypothesized that decomposition of algal wrack depends on wrack patch size and site. With respect to macrofauna, we tested the hypotheses that (1) abundance of colonising individuals and species vary with wrack patch size, (2) succession (i.e. sequence of colonisation and species replacement) depends on time, and (3) as a result, macrofaunal assemblages associated with wrack patches vary with the patch size and time. We also predicted that responses could be different across sites because of their slightly different environmental conditions. The decomposition of wrack patches was similar in all sites and was dependent on wrack patch size. It was strongly influenced by time-specific environmental and/or biological factors. The pattern of colonisation, i.e. total number of species and individuals, varied among wrack patch sizes. Small patches had fewer species and individuals than medium and large patches. Nevertheless, pattern of colonisation varied among species, across sites and through time. Colonisation of wrack patches was rapid (i.e. within 3 days) for most species. There was some evidence to support the hypothesis that macrofaunal assemblages change in response to patch size and time.     

An investigation of cathodoluminescence in albite from the A-type Georgeville granite,Nova Scotia

Cathodoluminescence (CL) reveals red and blue colors within single, non-turbid albite (Ab_98–99) grains from the Georgeville granite, Nova Scotia. A 720 nm X-ray excited optical luminescence (XEOL) peak characterizes red CL regions, while a 280 nm XEOL feature dominates blue CL regions. Synchrotron X-ray fluorescence results indicate that red CL and the 720 nm XEOL peak intensities relate to total Fe concentrations. The relationship between red CL and Fe content is confirmed by electron microprobe (EMPA) and laser ablation-inductively coupled mass spectrometry (LA-ICP-MS). The XEOL technique is used to exclude the Fe K-edge as the cause of red CL. X-ray absorption spectroscopy results indicate that Fe in both the red and blue CL regions is Fe³⁺, and that red CL activation may relate to the Si–Al order of the feldspar and to the distribution of Fe on tetrahedral sites. The CL textures, combined with EMPA and LA-ICPMS analyses, indicate that blue CL albite (Ab₉₈) regions contain higher concentrations of Ca, Ti, Pb and rare earth elements, and were replaced, in part, by a more Fe-rich, trace element depleted albite (Ab₉₉) which displays red CL. Complex diffraction contrasts and amorphous deposits identified in transmission electron microscope images suggest that aqueous fluids have reacted with both red and blue CL regions. Fluid inclusion homogenization temperatures of up to 430 °C provide a lower estimate of the fluid temperature.     

Fluvial architecture as a response to two-layer lithospheric subsidence during the Permian and Triassic in the Iberian Basin,eastern Spain

The stratigraphy of a sedimentary basin is mainly the result of the long-term response of a depositional surface to prolonged subsidence. However, the real nature of interrelations between fluvial architecture and subsidence is still unknown. Herein, we present new data on these relationships by combining the results of detailed sedimentological field work with data acquired through automated forward modelling and backstripping for the alluvial Permian and Triassic sediments of the SE Iberian Ranges. Using this methodology, we determined tectonic subsidence of the basin by means of backstripping analysis and crust and lithospheric mantle stretching factors (δ and β, respectively) using forward modelling technique. Results indicated that a configuration of two individual and independent layers during lithospheric subsidence for each tectonic phase fit better for this time of the studied basin evolution than the assumption of subsidence due to a single layer spanning the whole lithosphere.For this study, we simplified fluvial geometries as two main types: isolated (I) and amalgamated (A), with subtypes in each case. Different order bounding surfaces (b.s.) were distinguished in the field, although we only selected those affecting the whole basin under study. These included those b.s. of clear tectonic origin, ranging from individual basin boundary-fault pulses produced over periods of approximately 1 My to those arising from major tectonic events, such as the beginning of extension in the basin, causing major changes in basin geometry over periods of 3–5 My.The comparison of δ and β values and fluvial geometries for each identified tectonic phase in the basin evolution, revealed some possible relationship between subsidence and fluvial geometry: Sections showing the most varied fluvial architectural geometries, including ribbon and nested forms, were related to higher β and δ stretching factors values indicating tectonic phases of greater stretching and subsidence. When both stretching factors were similar and close to 1, fluvial geometry was basically reduced to amalgamated geometry type. Wider ranging of fluvial geometries was associated with stages of basin development in which crust and upper mantle activities differed, that is, showing larger differences of β and δ stretching factors values. The related slope changes are proposed as the main surface control of fluvial styles.Combination of subsidence with other possible controlling factors such as avulsion rate, climate or budget of sediments, gives rise to the definitive alluvial architecture of a basin.     

Long-term water monitoring in two Mediterranean lagoons as an indicator of land-use changes and intense precipitation events (Adra,Southeastern Spain)

During recent historical times the Adra river delta, a detrital coastal aquifer of nearly 32 km² located in a semi-arid, mountainous area of SE Spain, has undergone different changes caused by human activity. Within this context, both the river dynamics in the plain and the geomorphology of the coastline have at various times resulted in the formation of small lagoons. At present only two small (<0.5 km²) lagoons exist, at the eastern edge of the aquifer, which, although closely surrounded by commercial market-garden greenhouses, are protected under international agreements. During the last 30 years of the twentieth century traditional agricultural irrigation techniques have undergone significant changes to improve their efficiency. Surface-water resources in the Adra river basin are regulated via the Beninar reservoir. In addition, the use of groundwater is increasing progressively. Both these factors affect the recharge of the coastal aquifer. To monitor these changes measurements of electrical conductivity and water level fluctuations have been recorded in these lagoons for the last 35 years (1975–2010). A comparison of the hydrochemical characteristics of the water in the lagoons and of the surrounding groundwater from 2003 to 2010 shows marked differences induced by the different hydrological dynamics in each lagoon, as well as by the hydrogeological impact of changes in land use in the delta. The increase in water demand is a consequence of the extension of irrigated areas from the fluvio-deltaic plain to its slopes, originally occupied by unirrigated crops. A reduction in irrigation return-flow is linked to the use of new irrigation techniques. These modifications affect both the recharge regime of the aquifer and its water quality. Moreover, extreme precipitation events, which are characteristic of Mediterranean semi-arid environments, can affect the lagoons’ hydrological dynamics to a considerable extent. One such example is the unusually rainy period from January to March 2010 (>600 mm). This event, along with other effects, has dramatically lowered the salinity of the water in both lagoons. This case study reveals the extreme vulnerability of deltaic environments and also how lagoons can reflect anthropogenic changes over the whole river basin.     

Properties of Magnetic Tongues over a Solar Cycle

The photospheric spatial distribution of the main magnetic polarities of bipolar active regions (ARs) present during their emergence deformations are known as magnetic tongues. They are attributed to the presence of twist in the toroidal magnetic-flux tubes that form the ARs. The aim of this article is to study the twist of newly emerged ARs from the evolution of magnetic tongues observed in photospheric line-of-sight magnetograms. We apply the procedure described by Poisson et al. (Solar Phys. 290, 727, 2015a) to ARs observed over the full Solar Cycle 23 and the beginning of Cycle 24. Our results show that the hemispherical rule obtained using the tongues as a proxy of the twist has a weak sign dominance (53 % in the southern hemisphere and 58 % in the northern hemisphere). By defining the variation of the tongue angle, we characterize the strength of the magnetic tongues during different phases of the AR emergence. We find that there is a tendency of the tongues to be stronger during the beginning of the emergence and to become weaker as the AR reaches its maximum magnetic flux. We compare this evolution with the emergence of a toroidal flux-rope model with non-uniform twist. The variety of evolution of the tongues in the analyzed ARs can only be reproduced when using a broad range of twist profiles, in particular having a large variety of twist gradients in the direction vertical to the photosphere. Although the analytical model used is a special case, selected to minimize the complexity of the problem, the results obtained set new observational constraints to theoretical models of flux-rope emergence that form bipolar ARs.     

Feedback Mechanisms Between Cyanobacterial Blooms,Transient Hypoxia,and Benthic Phosphorus Regeneration in Shallow Coastal Environments

We investigated the dissolved oxygen metabolism of the Curonian Lagoon (Baltic Sea) to assess the relative contributions of pelagic and benthic processes to the development of transient hypoxic conditions in shallow water habitats. Metabolism measurements along with the remote sensing-derived estimates of spatial variability in chlorophyll a were used to evaluate the risk of hypoxia at the whole lagoon level. Our data demonstrate that cyanobacterial blooms strongly inhibit light penetration, resulting in net heterotrophic conditions in which pelagic oxygen demand exceeds benthic oxygen demand by an order of magnitude. The combination of bloom conditions and reduced vertical mixing during calm periods resulted in oxygen depletion of bottom waters and greater sediment nutrient release. The peak of reactive P regeneration (nearly 30 μmol m^?2 h^?1) coincided with oxygen depletion in the water column, and resulted in a marked drop of the inorganic N:P ratio (from >40 to <5, as molar). Our results suggest a strong link between cyanobacterial blooms, pelagic respiration, hypoxia, and P regeneration, which acts as a feedback in sustaining algal blooms through internal nutrient cycling. Meteorological data and satellite-derived maps of chlorophyll a were used to show that nearly 70 % of the lagoon surface (approximately 1,000 km²) is prone to transient hypoxia development when blooms coincide with low wind speed conditions.     

PIANCALDOLI METEORITE: CHEMISTRY,MINERALOGY AND PETROLOGY

The fall occurred near Piancaldoli, Florence, Italy, at 19.14 U.T. on the 10th August 1968. The fireball broke up in the atmosphere producing a cloud like a balloon. The trajectory and the terminal point were calculated, leading to the recovery of three small meteoritic fragments, found on the roof of a house. Chemical analysis gave the following results: SiO₂ 40.80; TiO₂ 0.15; Al₂O₃ 2. 70; Cr₂O₃ 0.47; FeO 17.20; MnO 0.07; MgO 25.18; CaO 1.95; Na₂O 0.64; K₂O 0.07; P₂O₅ 0.20; NiS 0.93; FeS 6.24; Fe° 2.40; Ni° 0.40; Co 0.05; sum 99.45. In the lithic portion of the meteorite the following minerals were found: both clino and orthopyroxenes (En = 76 to 98%), olivines (Fo = 66 to 98%), troilite, pyrrhotite, pentlandite, kamacite, ilmenite, apatite, merillite, schreibersite, chromite and Henderson phase. From all the mineralogical and petrological data, we conclude that the Piancaldoli meteorite is an “unequilibrated ordinary chondrite,” LL3. The microbrecciated structure of the rock and some shock features were observed, while the rock as a whole is unshocked, suggesting that these features were caused by impact events which took place during the accretion of the parent body.     

Magnetic anomalies in the Eastern Caribbean

Despite the many different studies on the origin and evolution of the Caribbean Plate, no proposal has been widely accepted so far. A key element within this field of research is the characterization of the plate subsurface oceanic crust, as it would clarify the conditions in which it originated, the geological period when it formed and its possible geographical location at this first evolution stage. Based on partial results of this research work, we can say that the conclusions of previous studies are valid to a great extent, namely the NE–SW orientation of the striped magnetic anomalies in the Venezuelan Basin’s western section and the existence of W–E preferentially oriented stripes parallel to the Leeward Antilles. The magnetic response of the triangular section in the southeast of the Venezuelan Basin represents cretaceous magnetic quiet zone (CMQZ) and therefore shows a considerable attenuation of the stripe pattern, indicating that the whole East Caribbean subsurface features oceanic crustal material. As for the period recorded by the Caribbean magnetic stripes, we propose the interval between chrons M23 and M0, and part of CMQZ. The wavelengths of the identified anomalies suggest that the ridge associated with the formation of Caribbean ocean floor was slow-spreading when compared to average currently active ridges.