Vertical distribution of dissolved organic carbon (DOC) in the Western Mediterranean Sea in relation to the hydrological characteristics

Vertical profiles of dissolved organic carbon (DOC) from eight hydrological stations in the Tyrrhenian Sea, Sardinia Channel and Algerian Sea, are reported. DOC exhibits concentrations ranging from 58 to 88 μM in surface water, 43–57 μM in the intermediate layer and 49–63 μM in deep waters. The assessment of the hydrological characteristics allows different water masses in the study area to be identified; moreover, different hydrological processes are observed in the Tyrrhenian and Algerian basins. DOC exhibits different values in the different water masses. The lowest DOC concentrations (43–46 μM) were found in the Tyrrhenian Levantine Intermediate Water (LIW). Correlations between DOC and apparent oxygen utilization (AOU), investigated within each water mass, exhibit different behaviors in the intermediate and deep waters, suggesting the occurrence of different processes of oxygen consumption in the different water masses.     

Mediterranean cities under fire. A critical approach to the wildland–urban interface

Wildfires are widely reviewed as key inputs to Mediterranean ecosystems. However, research is often flawed by major biases. (1) The approach adopted by most planners focusing on forest fires dismisses the human dimension of fire as a component of agricultural production systems. (2) The Wildland–Urban Interface (WUI) concept postulates that cities and wildlands/wildfires are, and should remain, worlds apart, a statement whose truth is increasingly questioned by recent disastrous “urban wildfires”. (3) The Mediterranean Basin as a fire-prone area is all the more fantasized, as it is almost never studied as a whole.The present paper takes a critical view of city–wildland/wildfire interrelationships through a large-scale study of the Mediterranean Basin based on MODIS MCD12Q1 (Land Cover Type) and MCD45A1 (Burned Area Product) data collected between 2001 and 2013. The Mediterranean is an ideal place to investigate, as its human-dominated and urbanized landscapes are known to be extremely vulnerable to fire hazards. Data processing reveals that (wild)fires and cities maintain indissoluble ties, as if both elements could not be considered mutually exclusive on a geographical basis. Urban sprawl, reduced rural autonomies, changes in forest covers, old agricultural practices, and military conflicts provide the framework for an extended mitigation process challenging the WUI concept as a space divider.     

Fire severity and surface rock fragments cause patchy distribution of soil water repellency and infiltration rates after burning

Although fire‐induced soil water repellency (SWR) and its effects on soil hydrology and geomorphology have been studied in detail, very few studies have considered the effect of rock fragments resting on the soil surface or partly embedded in soil. In this research, we have studied the effect of rock fragments on the strength and spatial distribution of fire‐induced SWR at different fire severities. A fire‐affected area was selected for this experiment and classified into different zones according to fire severity (unburned, low, moderate and high) and rock fragment cover (low, <20% and high, >60%). During 7 days after fire, SWR and infiltration rates were assessed in the soil surface covered by individual rock fragments and in the midpoint between two adjacent rock fragments (with maximum spacing of 20 cm). SWR increased with fire severity. Rock fragments resting on the soil surface increased the heterogeneity of the spatial distribution of fire‐induced SWR. SWR increased significantly with rock fragment cover in bare areas under moderate and high fire severity, but quantitatively important changes were only observed under high fire severity. In areas with a low rock fragment cover, water repellency from soil surfaces covered by rock fragments increased relative to bare soil surfaces, with increasing SWR. In areas with a high rock fragment cover, SWR increased significantly from non‐covered to covered soil surfaces only after low‐severity burning. Rock fragment cover did not affect infiltration rates, although it decreased significantly in soil surfaces after high‐severity burning in areas under low and high rock fragment cover. Copyright © 2013 John Wiley & Sons, Ltd.     

Drought assessment in a south Mediterranean transboundary catchment

ABSTRACT

Predicting the impacts of climate change on water resources remains a challenging task and requires a good understanding of the dynamics of the forcing terms in the past. In this study, the variability of precipitation and drought patterns is studied over the Mediterranean catchment of the Medjerda in Tunisia based on an observed rainfall dataset collected at 41 raingauges during the period 1973–2012. The standardized precipitation index and the aridity index were used to characterize drought variability. Multivariate and geostatistical techniques were further employed to identify the spatial variability of annual rainfall. The results show that the Medjerda is marked by a significant spatio-temporal variability of drought, with varying extreme wet and dry events. Four regions with distinct rainfall regimes are identified by utilizing the K-means cluster analysis. A principal component analysis identifies the variables that are responsible for the relationships between precipitation and drought variability.     

Contrasting patterns of precipitation seasonality during the Holocene in the south‐ and north‐central Mediterranean

Pollen‐based quantitative estimates of seasonal precipitation from Lake Pergusa and lake‐level data from Lake Preola in Sicily (southern Italy) allow three successive periods to be distinguished within the Holocene: an early Holocene period before ca. 9800 cal a BP with rather dry climate conditions in winter and summer, a mid‐Holocene period between ca. 9800 and 4500 cal a BP with maximum winter and summer wetness, and a late Holocene period after 4500 cal a BP with declining winter and summer wetness. This evolution observed in the south‐central Mediterranean shows strong similarities to that recognized in the eastern Mediterranean. But, it contrasts with that reconstructed in north‐central Italy, where the mid‐Holocene appears to be characterized by a winter (summer) precipitation maximum (minimum), while the late Holocene coincided with a decrease (increase) in winter (summer) precipitation. Maximum precipitation at ca. 10 000–4500 cal a BP may have resulted from (i) increased local convection in response to a Holocene insolation maximum at 10 000 cal a BP and then (ii) the gradual weakening of the Hadley cell activity, which allowed the winter rainy westerlies to reach the Mediterranean area more frequently. After 4500 cal a BP, changes in precipitation seasonality may reflect non‐linear responses to orbitally driven insolation decrease in addition to seasonal and inter‐hemispheric changes of insolation. Copyright © 2011 John Wiley & Sons, Ltd.     

Marine conservation challenges in an era of economic crisis and geopolitical instability: The case of the Mediterranean Sea

In the Mediterranean Sea, socio-economic drivers may accelerate the process of exclusive economic zone (EEZ) declarations. Despite the challenges, the EEZ declarations may provide important opportunities for leveraging change to national policy towards the development of large-scale conservation of marine ecosystems and biodiversity in this zone. Using the Mediterranean Sea as a case study, we aim to highlight a set of best practices that will maximize the potential for the development of large-scale marine conservation initiatives. These include a range of approaches, such as using surrogates to fill the many biodiversity data gaps in the region, further the development of consistent and open access databases, and the utilization of technological developments to improve monitoring, research and surveillance of less accessible and under-explored marine areas. The integration of Mediterranean-wide and local conservation efforts, the facilitation of transboundary collaboration, and the establishment of regional funds for conservation will further enhance opportunities for marine conservation in this region.     

Occurrence and fate of polycyclic aromatic hydrocarbons in the coastal surface microlayer

Polycyclic aromatic hydrocarbons (PAHs) were measured in the coastal sea surface microlayer (SML), the sub-surface waters (SSW) and the overlying atmosphere in order to investigate the influence of the SML on contaminant enrichment and air-sea exchange. Samples were collected at two contrasting locations of the NW Mediterranean, one urban influenced (off Barcelona, Spain) and another comparatively clean (off Banyuls-sur-Mer, France). Statistical data analysis confirmed the accumulation of PAHs in the SML with respect to the SSW (20.3+/-9.1 vs. 13.1+/-10.0 ng L(-1) in the dissolved phase; 709+/-207 vs. 158+/-111 ng g(-1) in the particulate phase). This accumulation was higher at the contaminated location (Barcelona station) compared with the more pristine one, with PAH enrichments 1.5 and 4.5 times higher for the dissolved and particulate phases, respectively, indicating that the enrichment of PAHs in the SML is dominated by particle transport processes.     

Macroalgal survival in ballast water tanks

Despite a large amount of research into invasive species and their introductions, there have been no studies focused on macroalgal transport in ballast water. To address this, we collected replicate samples of ballast water from 12 ships in two Mediterranean harbours (Naples and Salerno). Filtered samples were kept in culture for a month at Mediterranean mean conditions (18 degrees C, 12:12h LD, 60micromol photons m(-2)s(-1)). Fifteen macroalgal taxa were cultured and differed according to the geographic origin of the ballast water. Most of the cultured algae were widely distributed species (e.g. Ulva spp. and Acinetospora-phase). However, Ulva ohnoi Hiraoka and Shimada, described from Japan, was hitherto unknown in the Mediterranean Sea. We show for the first time that ballast water can be an important vector for the transport of microscopic stages of macroalgae and that this can be a vector for the introduction of alien species.     

Evolution of isotopic compositions in groundwater of the area between the Gulf of Oman and the Arabian Gulf

The stable isotopes of oxygen and hydrogen have been implemented to assess the recharge mechanisms in an area in the UAE bounded to the northwestern part of the Gulf of Oman and the southeastern part of the Arabian Gulf. The conversion of stable isotopes to deuterium excess was utilized as a supportive tool to understand the process of groundwater recharge. The concluding results of this study showed that the origin of moisture is the Mediterranean Sea. The precipitation is the main source of recharge, in which the precipitation having undergone evaporation before recharge occurs. The comparison between regression line for data collected in 1996 and regression line for samples collected in 2006 suggests that the precipitation water which recharged the groundwater, was diluted with groundwater and this dilution is observed from decreasing of the deuterium excess of collected groundwater samples with increasing isotopes of oxygen. The dilution of groundwater with the recharge water suggests modern-day recharge as it is seen from high deuterium excess that exceeded the deuterium excess of LMWL and was close to MMWL.