Geomorphological and ecological features of blowouts in a western Mediterranean coastal dune complex: a case study of the Es Comú de Muro beach-dune system on the island of Mallorca, Spain

Many of the coastal dune systems along western Mediterranean shores are in an advanced state of fragmentation and show distinct signs of erosion, largely because of blowout development along the dune front. The Es Comú de Muro beach-dune system on the island of Mallorca (Spain) is a good example of this. In order to better understand and quantify the current situation, 58 blowouts along a ca. 1.5-km-long dune front were investigated. In each case, a number of morphometric and ecological variables were analyzed as a basis for comparison and classification, in particular blowout dimensions and orientation, inner morphometry and topography, morphological types, the role of vegetation in defining the state of the foremost dune line, and the link between vegetation and blowout typology. In comparison with a recent preliminary investigation, the results of the present study provide a more comprehensive picture of the advanced state of fragmentation along the dune front. The blowouts are not evenly distributed, highest densities occurring along the southernmost part of the beach, lowest densities along the northern part. The blowouts were subdivided into two categories on the basis of their shape and general structure, trough blowouts being the most prevalent, followed by mixed trough-saucer shapes. Distinctly saucer-shaped blowouts could not be distinguished. In addition, the blowouts were subdivided into two morphological categories, i.e. simple and branched. It was also possible to link the morphological state of the dune front to certain ecological parameters, in particular vegetation which, in the present case, comprised herbaceous and woody plants. Cluster analyses of species associations (Bray-Curtis similarity indices) were carried out on the basis of the presence/absence of each species. It is shown that, on account of presence counts and the degree of similarity of species associations, some species play a more important role in stabilizing the mobile dune sands than others, a foremost candidate being Ammophila arenaria. It is concluded that active support for such plants should form part of any management strategy aiming to reduce and reverse coastal dune fragmentation processes.     

Biliary fluorescent aromatic compounds (FACs) measured by fixed wavelength fluorescence (FF) in several marine fish species from the NW Mediterranean

The fixed wavelength fluoresce (FF) method was used to estimate the levels of fluorescent aromatic compounds (FACs) in the bile of fourteen fish species of commercial and/or ecological interest. Sampling was carried out in the NW Mediterranean at depths ranging from 50 to 1000 m during four seasonal cruises. During the summer sampling period, some species were also collected from another site (Vilanova fishing grounds) for comparison. Baseline levels of the polycyclic aromatic hydrocarbons (PAHs) naphthalene, phenanthrene, pyrene and benzo[a]pyrene were measured. Some seasonality was observed, with reduced FF levels in summer and no differences among sites, consistent with sediment PAH levels. We discuss our results in relation to fish phylogeny, season, depth, diet, trophic level and swimming capacity. Overall FF levels indicated differences among species; the suprabenthic feeders from shallow and deep communities, and Mullus barbatus in particular, displayed elevated FF values and are potential candidates for additional monitoring studies.     

Photosynthetic pigment changes and adaptations in biofilms in response to flow intermittency

Among the environmental factors affecting benthic algae and cyanobacteria in streams, the one often producing the largest effects is flow intermittency. This study aimed to characterize the responses of algal assemblages to flow intermittency in a Mediterranean intermittent stream during the drying, non-flow (112 days), and rewetting phases. Algae growing in the epilithic, epipsammic and hyporheic streambed compartments were analyzed for pigment composition, and for the existence of structural changes in cells. Chlorophyll-a concentrations decreased between 60 to 90 % during the non-flow phase, indicating low resistance of algal assemblages to desiccation. In contrast, fast recoveries of Chlorophyll-a when flow resumed indicated high resilience. Pigment composition revealed that the epilithic algal assemblage was considerably different than the epipsammic and hyporheic ones. These differences were mainly attributed to the physical conditions prevailing on each streambed compartment that allowed the growth of different algal assemblages. During the non-flow phase, the synthesis of protective carotenoids (i.e. echinenone and scytonemin) and the occurrence of cell resistance structures (i.e. enlarged membrane thickness and resistant spores) enhanced resistance of the epilithic biofilm. The resistance observed in the epilithic biofilm might also be related to the tightly adhered growth-form of algae on this substratum. Main results suggest that algal assemblages in the epilithic compartment, which were the most exposed to desiccation, were structurally and functionally better adapted to flow interruption than those colonizing other streambed compartments, and that this compartment plays a crucial role in maintaining ecosystem functions under varying flow periods.     

Life history of the deep-sea cephalopod family Histioteuthidae in the western Mediterranean

The life cycle of the two species of the deep-sea family Histioteuthidae inhabiting the Mediterranean Sea (Histioteuthis reversa and Histioteuthis bonnellii) was studied from monthly samples taken throughout the year during daytime hours by bottom trawl gears. A small sample of individuals found floating dead on the sea surface was also analyzed. Both species were caught exclusively on the upper slope at depths greater than 300 m. Their frequency of occurrence increased with depth and showed two different peaks, at 500–600 m and 600–700 m depth in H. bonnellii and H. reversa, respectively, which might indicate spatial segregation. Maturity stages were assigned using macroscopic determination and confirmed with histological analyses. Although mature males were caught all year round, no mature females were found, which suggests that their sexual maturation in the western Mediterranean takes place deeper than the maximum depth sampled (800 m). In fact, the increase in mean squid size with increasing depth in H. reversa indicates an ontogenetic migration to deeper waters. The individuals of both species found floating dead on the sea surface were spent females which had a relatively large cluster of small atresic eggs and a small number of remaining mature eggs scattered in the ovary and mantle cavity. The sizes of these females were clearly larger than the largest individuals caught with bottom trawls. A total of 12 and 7 different types of prey, belonging to three major taxonomic groups (crustaceans, osteichthyes and cephalopods), were identified in the stomach contents of H. reversa and H. bonnellii, respectively. In both species fishes were by far the main prey followed by crustaceans, whereas cephalopods were found only occasionally. The preys identified, mainly myctophids and natantian crustaceans, indicate that both histioteuthids base their diet on pelagic nictemeral migrators.     

Influence of transient storage on stream nutrient uptake based on substrata manipulation

Quantification of the transient storage zone (A_s) has become critical in stream biogeochemical studies addressed to examine factors controlling nutrient uptake. It is expected that higher A_s may enhance the interaction between nutrients and biota and thus, increase nutrient uptake. However, results from the literature are controversial. We hypothesized that besides of the size of A_s, the intrinsic physical and biological characteristics of stream structures that generate A_s are also relevant for nutrient uptake. We performed 24 additions of phosphate, ammonium, and chloride in four reaches of a man-made channel where we introduced three types of naturally colonized substrata packs (mud, sand and cobbles) to modify A_s. We estimated ammonium and phosphate uptake coefficients in both the main channel and A_s using a solute transport model (OTIS-P) and compared the results among reaches with different substrata types. The introduction of substrata packs decreased water velocity and increased A_s similarly among treatments. Nutrient uptake coefficients in the main channel were similar among reaches with different type substrata packs; however, nutrient uptake coefficients measured in A_s differed among them as well as the ratio between ammonium and phosphorus uptake coefficients in A_s, which were 1.6 in reaches with mud packs and 0.02 in reaches with sand or cobble packs. Results obtained in this study suggest that the contribution of A_s in nutrient uptake not only depends on the size of A_s but on the type of materials used to increase A_s, and thus, have biogeochemical implications on restoration projects aimed to modify channel morphology.     

Abrupt Climatic Changes during the Last Glaciation Based on Pollen Analysis of the Abric Romani, Catalonia, Spain

The Abric Romani continental pollen record provides evidence of abrupt climate variations during the last glaciation. The pollen record reveals a pattern of high-frequency variations similar to that in ice cores as shown by oxygen isotopes or dust content. Analyses of 14 travertine samples yield coherent U-series ages in correct stratigraphic order, ranging from 40,000 to 70,000 yr. According to changes in the composition and structure of the vegetation, five paleoclimatic phases have been differentiated; the oldest, ranging from 70,200 to 65,500 yr ago, records thermophilous taxa which correspond to the last warm events of isotopic stage 5. The next phase, from 65,500 to 56,800 yr, records a cold, humid climate that correlates with isotope stage 4. During the third phase, from 56,800 to 49,500 yr, relatively warm and cold events alternate. The fourth phase, from 49,500 to 46,200 yr, records a cold, dry climate. The fifth phase, ranging from 46,200 to 40,800 yr, records a milder phase that is similar in appearance to the beginning of the Holocene.