Global change and marine communities: alien species and climate change

Anthropogenic influences on the biosphere since the advent of the industrial age are increasingly causing global changes. Climatic change and the rising concentration of greenhouse gases in the atmosphere are ranking high in scientific and public agendas, and other components of global change are also frequently addressed, among which are the introductions of non indigenous species (NIS) in biogeographic regions well separated from the donor region, often followed by spectacular invasions. In the marine environment, both climatic change and spread of alien species have been studied extensively; this review is aimed at examining the main responses of ecosystems to climatic change, taking into account the increasing importance of biological invasions. Some general principles on NIS introductions in the marine environment are recalled, such as the importance of propagule pressure and of development stages during the time course of an invasion. Climatic change is known to affect many ecological properties; it interacts also with NIS in many possible ways. Direct (proximate) effects on individuals and populations of altered physical-chemical conditions are distinguished from indirect effects on emergent properties (species distribution, diversity, and production). Climatically driven changes may affect both local dispersal mechanisms, due to the alteration of current patterns, and competitive interactions between NIS and native species, due to the onset of new thermal optima and/or different carbonate chemistry. As well as latitudinal range expansions of species correlated with changing temperature conditions, and effects on species richness and the correlated extinction of native species, some invasions may provoke multiple effects which involve overall ecosystem functioning (material flow between trophic groups, primary production, relative extent of organic material decomposition, extent of benthic-pelagic coupling). Some examples are given, including a special mention of the situation of the Mediterranean Sea, where so many species have been introduced recently, and where some have spread in very large quantities. An increasing effort by marine scientists is required, not only to monitor the state of the environment, but also to help predicting future changes and finding ways to mitigate or manage them.     

Links Between Bottom-Water Anoxia,the Polychaete <Emphasis Type="Italic">Nereis diversicolor</Emphasis>, and the Growth of Green-Algal Mats

Sediment–water incubations were used to study effects of episodic anoxia on filamentous Ulva sp. Treatments included undisturbed sediment with (AnoxSed) and without (NatSed) exposure to 5 days of anoxia, and cores with only the top 0.5 cm of sediment (SurfSed; no macrofauna, restricted pore-water nutrient pool). All three treatments contained Ulva propagules. An Ulva mat developed in the SurfSed, and after the anoxic period in the AnoxSed cores. No growth was observed in the NatSed treatment. In the AnoxSed, Ulva was progressively removed upon reoxygenation through grazing by Nereis. The results suggest that episodic anoxia stimulates the growth of macroalgal mats not only by increasing the availability of nutrients from the sediment, but also by reducing macrofaunal grazing pressure. Infauna (grazing and bioturbation), benthic microalgae (nutrient competition and retention), and pore-water nutrients appear key components in a biogeochemical network with complex feedbacks controlling the growth of green-algal mats in shallow-water systems.     

Relocation effects of dredged marine sediments on mercury geochemistry: Venice lagoon,Italy

Understanding the biogeochemical process of Hg is critical in the overall evaluation of the ecological impacts resulting from the reuse of Hg-contaminated dredged sediment. Sediment banks (V1 and V2) were constructed with freshly dredged sediments from a navigational channel in Venice Lagoon, Italy, with the goal of clarifying potential differences in the biogeochemistry of Hg between the reused dredged sediments and those from surrounding sites (SS1 and S2). Toward this purpose, Hg and monomethylmercury (MMHg) concentrations, and Hg methylation rates (MMRs) in the surface 2.5 cm sediments were monitored, along with ammonium, iron, sulfate and sulfide concentrations in the pore waters of banks and surrounding sites from November 2005 to February 2007. Pore water analyses indicate that the bank sediments are characterized by lower levels of sulfate and iron, and by higher levels of ammonium and sulfide compared to the surrounding sediments. With respect to Hg speciation, the fractions of MMHg in total Hg (%MMHg/Hg) and the MMRs were significantly lower in the bank V1 compared to those in the reference site SS1, whereas the %MMHg/Hg and the MMRs were similar between V2 and S2. A negative correlation is found between the logarithm of the particle-water partition coefficient of Hg and the MMR, indicating that the reduced MMRs in V1 are caused by the limited concentrations of dissolved Hg. Organic matter appears to play a key role in the control of MMR via the control of Hg solubility.     

Compromise not consensus: designing a participatory process for landslide risk mitigation

With the escalating costs of landslides, the challenge for local authorities is to develop institutional arrangements for landslide risk management that are viewed as efficient, feasible and fair by those affected. For this purpose, the participation of stakeholders in the decision-making process is mandated by the European Union as a way of improving its perceived legitimacy and transparency. This paper reports on an analytical-deliberative process for selecting landslide risk mitigation measures in the town of Nocera Inferiore in southern Italy. The process was structured as a series of meetings with a group of selected residents and several parallel activities open to the public. The preparatory work included a literature/media review, semi-structured interviews carried out with key local stakeholders and a survey eliciting residents’ views on landslide risk management. The main point of departure in the design of this process was the explicit elicitation and structuring of multiple worldviews (or perspectives) among the participants with respect to the nature of the problem and its solution. Rather than eliciting preferences using decision analytical methods (e.g. utility theory or multi-criteria evaluation), this process built on a body of research—based on the theory of plural rationality—that has teased out the limited number of contending and socially constructed definitions of problem-and-solution that are able to achieve viability. This framing proved effective in structuring participants’ views and arriving at a compromise recommendation (not, as is often aimed for, a consensus) on measures for reducing landslide risk. Experts played a unique role in this process by providing a range of policy options that corresponded to the different perspectives held by the participants.

     

Recent progress on combining geomorphological and geochronological data with ice sheet modelling,demonstrated using the last British–Irish Ice Sheet

Palaeo-ice sheets are important analogues for understanding contemporary ice sheets, offering a record of ice sheet behaviour that spans millennia. There are two main approaches to reconstructing palaeo-ice sheets. Empirical reconstructions use the available glacial geological and chronological evidence to estimate ice sheet extent and dynamics but lack direct consideration of ice physics. In contrast, numerically modelled simulations implement ice physics, but often lack direct quantitative comparison with empirical evidence. Despite being long identified as a fruitful scientific endeavour, few ice sheet reconstructions attempt to reconcile the empirical and model-based approaches. To achieve this goal, model-data comparison procedures are required. Here, we compare three numerically modelled simulations of the former British–Irish Ice Sheet with the following lines of evidence: (a) position and shape of former margin positions, recorded by moraines; (b) former ice-flow direction and flow-switching, recorded by flowsets of subglacial bedforms; and (c) the timing of ice-free conditions, recorded by geochronological data. These model–data comparisons provide a useful framework for quantifying the degree of fit between numerical model simulations and empirical constraints. Such tools are vital for reconciling numerical modelling and empirical evidence, the combination of which will lead to more robust palaeo-ice sheet reconstructions with greater explicative and ultimately predictive power.     

Marine quality assessment by use of benthic species-abundance distributions: a proposed new protocol within the European Union Water Framework Directive

The aim of this study is to develop a new method for classification of marine benthic quality according to the European Union Water Framework Directive. Tolerance values to environmental disturbance were determined in an objective analysis for benthic species along the Swedish west coast by using 4676 samples from 257 stations. Based on a combination of the species tolerance values, abundance and diversity, a benthic quality index (BQI) was calculated for the assessment of environmental status at a particular station. The qualification of BQI was evaluated in relation to known spatial and temporal gradients of disturbance.     

Spinor: Visible and Infrared Spectro-Polarimetry at the National Solar Observatory

The Spectro-Polarimeter for Infrared and Optical Regions (SPINOR) is a new spectro-polarimeter that will serve as a facility instrument for the Dunn Solar Telescope at the National Solar Observatory. This instrument is capable of achromatic polarimetry over a very broad range of wavelengths, from 430 to 1600 nm, allowing for the simultaneous observation of several visible and infrared spectral regions with full Stokes polarimetry. Another key feature of the design is its flexibility to observe virtually any combination of spectral lines, limited only by practical considerations (e.g., the number of detectors available, space on the optical bench, etc.). Visiting Astronomers, National Solar Observatory, operated by the Association of Universities for Research in Astronomy, Inc. (AURA), under cooperative agreement with the National Science Foundation.     

Stochastic models in the DORIS position time series: estimates for IDS contribution to ITRF2014

This paper focuses on the investigation of the deterministic and stochastic parts of the Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) weekly time series aligned to the newest release of ITRF2014. A set of 90 stations was divided into three groups depending on when the data were collected at an individual station. To reliably describe the DORIS time series, we employed a mathematical model that included the long-term nonlinear signal, linear trend, seasonal oscillations and a stochastic part, all being estimated with maximum likelihood estimation. We proved that the values of the parameters delivered for DORIS data are strictly correlated with the time span of the observations. The quality of the most recent data has significantly improved. Not only did the seasonal amplitudes decrease over the years, but also, and most importantly, the noise level and its type changed significantly. Among several tested models, the power-law process may be chosen as the preferred one for most of the DORIS data. Moreover, the preferred noise model has changed through the years from an autoregressive process to pure power-law noise with few stations characterised by a positive spectral index. For the latest observations, the medians of the velocity errors were equal to 0.3, 0.3 and 0.4 mm/year, respectively, for the North, East and Up components. In the best cases, a velocity uncertainty of DORIS sites of 0.1 mm/year is achievable when the appropriate coloured noise model is taken into consideration.     

The XMM-Newton Bright Serendipitous Survey: First Extragalactic Results

We present here some initial results from the ongoing XMM-Newton bright serendipitous survey. The survey is aimed at selecting and spectroscopically identifying a large and statistically representative sample of bright (f _x ≳ 7× 10⁻¹⁴ c.g.s) serendipitous X-ray sources in the 0.5–4.5 keV energy band (BSS) and a complementary (smaller) sample in the 4.5–7.5 keV energy band (HBSS). The work is partly based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributors directly founded by ESA member states and the USA(NASA) and on observations collected at TNG. The TNG telescope is operated on the island of La Palma by the Centro Galileo Galilei of the INAF in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofísica de Canarias. On behalf of the XMM-Newton Survey Science Center.