Estat de conservació de les praderies de Posidonia oceanica (Linnaeus) Delile, 1813 dins la Badia de Portocolom (Mallorca)

[cat] Posidonia oceanica (Linnaeus), Delile, 1813 és una fanerògama marina endèmica del Mediterrani que proporciona gran quantitat de serveis ecosistèmics i és clau per a la conservació de la biodiversitat. Com la majoria de la vegetació marina està en greu recessió. Una de les principals amenaces que afecten aquesta planta, juntament amb l’eutrofització i l’escalfament global, és el fondeig incontrolat. En aquest estudi fem una avaluació de l’estat de conservació de la praderia de P. oceanica situada davant la platja de s’Arenal a la badia de Portocolom afectada per fondeig incontrolat. La mitjana del percentatge de cobertura entre una fondària de 2 i 4.8 metres va ser de 44.2 ± 13.6 %, cobertures inferiors a les reportades anteriorment per aquesta zona. Les densitats van variar entre 392 i 576 feixos/m2, amb una mitjana de 508 ± 31 feixos/m2. Aquesta praderia té molt baixa densitat, o densitat anormal, indicant que està sotmesa a pressions que posen en perill el seu estat de conservació. Vam poder estimar el nombre de feixos arrabassats per una àncora d’un vaixell d’uns 15 metres d’eslora, que va ser de 165 ± 31 feixos. Aquesta praderia necessitaria 5 anys en condicions òptimes per poder recolonitzar l’àrea arrabassada per aquesta àncora. Una estima del carboni alliberat per l’efecte del fondeig d’aquesta àncora revelaria que 915 g de carboni quedaria disponible i podria ser alliberat a l’atmosfera.[eng] Posidonia oceanica (Linnaeus), Delile, 1813 is an endemic Mediterranean seagrass that provides multiple ecosystem services and is a key species for biodiversity conservation. Like most submerged vegetation, this key habitat is regressing alarmingly. One of the main threats affecting this seagrass, together with eutrophication and global warming, is uncontrolled anchoring. Here, we evaluate the conservation status of the P. oceanica meadow in front of s’Arenal beach in Portocolom Bay that is affected by uncontrolled anchoring. The mean cover percentage at depths between 2 and 4.8 meters was 44.2 ± 13.6 %, lower than previously reported for this area. Densities varied between 392 and 576 shoots/m2, with an average of 508 ± 31 shoots/m2. This is a very low, or even an abnormal, density, indicating that this meadow is subject to pressures that are threatening its conservation. We could estimate the number of shoots that were torn off by the action of anchoring of a 15 m long boat: 165 ± 31 shoots. This meadow would require 5 years of optimal conditions to be able to recolonize the area removed by the action of this anchoring. An estimate of the carbon released by the action of this anchoring was 915 g of carbon that could become available and could be released to the atmosphere

Geochemical exploration in the Montseny Mountains (NE Spain)

A five year program of systematic multi-element geochemical exploration of the Catalonian Coastal Ranges has been initiated by the Geological Survey of Autonomic Government of Catalonia (Generalitat de Catalunya) and the Department of Geological and Geophysical Exploration (University of Barcelona). This paper reports the first stage results of this regional survey, covering an area of 530 km2 in the Montseny Mountains, NE of Barcelona (Spain). Stream sediments for metals and stream waters for fluoride were chosen because of the regional characteristics. Four target areas for future tactic survey were recognized after the prospect. The most important is a 40 km* zone in the Canoves-Vilamajor area, with high base metal values accompanied by Cd, Ni, Co, As and Sb anomalie

Setting conclitions, Petrology ancl Geochemistry of calc-alkaline rhyolites, stephanian-permian, in the iberian chains

[Resumen] Se exponen los caracteres del emplazamiento, la composición petrológica y geoquímica de unos sills riolíticos que, con afinidad calco-alcalina, se emplazaron, bajo un ambiente sin-colisional, en diversos sectores de la Cadena Ibérica. Estas riolitas representan un origen crustal, con baja tasa de fusión, previo a un magmatismo calco-alcalino de origen subcrustal.[Abstract] The setting characters, the petrological and geochemical composition are exposed for sorne rhyolitic sills, with calc-alkaline affinity, which were set, in a syncollisional environment, in several areas of the Iberian Chains. These rhyolites represent a crustal origin, with a low degree of fussion, previous to a calc-alkaline magmatism of subcrustal origino

Contamination des milieux aquatiques Camarguais par les résidus de produits phyto sanitaires

Les auteurs font état des résultats qu’ils ont obtenu au terme de deux années de recherches sur la contamination des milieux aquatiques cam arguais par les résidus de produits phytosanitaires. En Camargue, les techniques culturales employées, notam ment en riziculture : irrigation intensive et extensive, lutte chimique contre les parasites, menacent de pollution l’ensemble des milieux aquatiques et plus particulièrement les étangs de la Réserve Naturelle Zoologique et Rotanique. Les polluants sont d’origine rhodanienne ou proviennent des traitements agricoles, herbicides et insecticides. L’étude concernant les herbicides est délicate à mener et les résultats obtenus jusqu’à présent sont trop fragmentaires pour pouvoir être interprétés. Des résultats plus complets concernant les insecticides montrent que la contamination de l’eau est encore très faible, mais que l’accumulation des résidus organochlorés aux différents échelons trophiques des biocœnoses présente un réel danger. Les pesticides les plus fréquemment rencontrés sont alpha HCH (d’origine rhodanienne), gamma HCH (d’origine rhodanienne et agricole). La présence à des doses décelables de DDT est moins courante. D’autres résidus ne sont soupçonnés dans l’eau que du fait de leur présence dans les tissus animaux (dieldrine). D’autres enfin ne sont décelés qu’en période de traitement des cultures (les organophosphorés et notamment le parathion), ou à la faveur de circonstances particulières (polychlorocamphane) . Les polychlorobiphényles présents dans le milieu posent un problème. Leur origine est probablement mixte (Rhône et spé cialités commerciales de pesticides agricoles où ils servent d’adjuvant). Ces organochlorés très stables sont accumulés à des taux relativement importants aussi bien dans les sédiments que dans les végétaux et les animaux aquatiques et présentent un réel danger pour la conservation des milieux naturels. La conciliation de l’agriculture et de la conservatoin de la nature en Camargue est subordonnée à deux conditions : le rejet au Rhône de toutes les eaux de drainage des cultures jusqu’à présent déversées dans le Vaccarès et la recherche de pratiques culturales moins polluantes que celles actuellement employées.Results are given of a two year study on the pollution by pesticide-residues of the aquatic environment in the Camargue. The agricultural techniques employed, notably in rice-growing (intensive and extensive irrigation, chemical control of pests) threaten the whole aquatic environment in the Camargue with pollution, particularly the lakes situated in the « Réserve Naturelie Zoologique et Botanique ». These pollutants originate from the Rhône river and from agricultural treatments using herbicides and insecticides. Herbicide studies have proved difficult to conduct and results obtained to date are too fragmentary to allow a clear interpretation. More detailed results on insecticides show that water pollu tion is still very low but that the accumulation of organo- chlorides at the different trophic levels of the ecosystem presents a real threat. The pesticides most frequently recorded are alpha HCH (BHC) (Rhone origin) and gamma HCH (Rhone and agricultural origin). Detectable doses of DDT are less frequently recorded. Other residues are only suspected in water because of their presence in animal tissues (dieldrin). Lastly, others are only revealed during the period when crops are treated (organophosphates and espe cially parathion) or as a result of very particular circumstances (polychlorocamphene) . The presence of polychlorobiphenyls in the environment raises a special problem. They probably have a mixed origin (Rhone and commercial types of agricultural pesticides where they serve as an adjuvant). These very stable organochlorides are accumulated at relatively high rates in sediments as well as in aquatic plants and animals, and present a real danger to the conservation of natural habitats. The conciliation of agriculture and nature conservation in the Camargue is dependent on two conditions : return into the Rhone of all run-off water from crops, at present discharged into the « Etang du Vaccarès », and research into cultural methods which produce less pollution than those in current use

Nacra de roca (Pinna rudis)

En prens

Preliminary comparison of magmatic manifestations, calc-alkaline affinity and stephanian-permian age, in the Iberian Chain

[Resumen] En este trabajo se estudian, de forma sintética y actualizada, las manifestaciones (hipovolcánicas y volcanoclásticas) calco-alcalinas que, con carácter epizonal, pluriepisódico y edad Stephaniense-Pérmico, afloran en la Cadena Ibérica. El estudio del magmatismo en la cuenca de Sauquillo de Alcázar (Soria) permite identificar la geometría y la modalidad de este magmatismo con mayor precisi6n, respecto a lo obtenido en los cuatro afloramientos volcano-clásticos seleccionados. Los resultados obtenidos facilitan realizar consideraciones sobre el estudio espacio-temporal de este magmatismo..[Abstract] A synthetic and actualized study of several magmatic calc-alkaline manifestations of Stephanian-Permian age, of the Iberian Chain, is proposed in this papero The Sauquillo de Alcázar (Soria) outcrop allows a more complete study (with drilling logs and a surface profile) giving improved spacetime information on the geometry and evolution of this magmatism. Four pyroclastic outcrops are integrated in this compariso

Triassic tholeiitic dolerites («ophites») of the El Grado diapir (Pyrenees, Huesca, Spain): emplacement and composition

Mesozoic dolerites in the south Pyrenean sector of El Grado (Huesca, Spain) preserve emplacement structures (fluidity structures at the top and load structures at the base) developed during their intrusion into unconsolidated marly-evaporitic Triassic sediments (Keuper facies). By analogy with other dolerites in the south Pyrenean domain, their emplacement age is equivalent to the uppermost Keuper facies terms, but prior to the final Triassic-early Liassic carbonated sediments. Radiometric ages (187-197±7 Ma) show that the emplacement occurred during the lower Liassic. The petralogical differentiation from the chilled margin facies to the central facies, and also to the late pegmatitoids, is consistent with that obtained from major elements, trace elements and REE. Their tholeiitic affinity, as defined by their geochemical composition, is equivalent to that of similar racks in the Pyrenean domain. However, the rocks analyzed here, which are located at the external sector of this domain, display a greater petralogical and geochemical differentiation as compared to similar rocks in the central sectors of the Pyrenean domain.Las doleritas mesozoicas del sector surpirenaico de El Grado (Huesca) conservan estructuras de emplazamiento (con desarrollo del movimiento de lava fluida al techo y de carga en su base) desarrolladas al instruir en los sedimentos margo-evaporíticos en facies Keuper, todavía inconsolidados. Por similitud con otras doleritas del dominio surpirenaico, la edad del emplazamiento es equivalente a la de los términos superiores de la facies Keuper y previa a la sedimentación carbonatada del Trías terminal-Lías inferior. Las determinaciones de edades radiométricas (187-197±7 Ma) indican que el emplazamiento debió tener lugar durante el Lías inferior. La diferenciación petralógica, desde la facies del borde enfriado a la central y, también, al posterior diferenciado pegmatoide concuerda con la obtenida con elementos mayores, trazas y REE. Su afinidad toleítica, definida por su composición geoquímica, coincide con la obtenida en rocas análogas para el dominio pirenaico; no obstante, estas rocas situadas en el borde más externo de dicho dominio representan una mayor diferenciación (petralógica y geoquímica) respecto a la obtenida, hasta el momento, para rocas análogas situadas en sectores más centrales del citado dominio pirenaico

The triassic alkaline dolerites of the Valacloche-Camarena Area (SE-Iberian Chain, Teruel): Geodynamic implications

The dolerite sills outcropping in the Valacloche-Camarena area (SE Iberian Chain), are the expression of an alkaline magmatism, emplaced in Keuper facies sedimentary rocks. Their pre-Hettangian age is deduced from the development of fluidality structures at the top of the sills together with the very low grade contact metamorphism of the host rocks. A differentiation trend, represented by two rock-types, with variable Ti-augite content, is confirmed by geochemical data (REE). The alkaline composition of this magmatism is close to that of the OIB type. Crust-derived enclaves (metapelites and granitoids) are common in these sills, suggesting that magma ascent took place through a fracture system, related to a distensive tectonic regime, that affected different levels of the crust. This magmatism was one of the expressions of the triassic rifting events that are well represented in the SE border of the Iberian Chain.Un magmatismo alcalino, emplazado en sedimentos triásicos en facies Keuper, está bien representado en los sills doleríticos del área de Valacloche-Camarena (SE de la Cordillera Ibérica). La edad pre-Hettangiense ha sido deducida a partir de la presencia de estructuras de fluidalidad y de un metamorfismo de contacto de grado muy débil. Petrológicamente se identifica una fraccionación según dos litotipos (con contenido variable en Ti-augita) que está corroborada por los datos de composición geoquímica (en tierras raras); la composición alcalina de este magmatismo es próxima a la del tipo OIB. La presencia, frecuente, de enclaves de corteza (metapelitas y granitoides) indica una fracturación que, en condiciones distensivas, afectó a distintos niveles de dicha corteza. Este magmatismo está ligado al rifting triásico que está bien expresado en el borde SE de la Cordillera Ibérica

Warming effect on nitrogen fixation in Mediterranean macrophyte sediments

The Mediterranean Sea is warming faster than the global ocean, with important consequences for organisms and biogeochemical cycles. Warming is a major stressor for key marine benthic macrophytes. However, the effect of warming on marine N2 fixation remains unknown, despite the fact that the high productivity of macrophytes in oligotrophic waters is partially sustained by the input of new nitrogen (N) into the system by N2 fixation. Here, we assess the impact of warming on the N2 fixation rates of three key marine macrophytes: Posidonia oceanica, Cymodocea nodosa, and Caulerpa prolifera. We experimentally measured N2 fixation rates in vegetated and bare sediments at temperatures encompassing current summer mean (25 and 27&thinsp;∘C), projected summer mean (29 and 31&thinsp;∘C), and projected summer maximum (33&thinsp;∘C) seawater surface temperatures (SSTs) by the end of the century under a scenario of moderate greenhouse gas emissions. We found that N2 fixation rates in vegetated sediments were 2.8-fold higher than in bare sediments at current summer mean SST, with no differences among macrophytes. Currently, the contribution of N2 fixation to macrophyte productivity could account for up to 7&thinsp;%, 13.8&thinsp;%, and 1.8&thinsp;% of N requirements for P. oceanica, C. nodosa, and C. prolifera, respectively. We show the temperature dependence of sediment N2 fixation rates. However, the thermal response differed for vegetated sediments, in which rates showed an optimum at 31&thinsp;∘C followed by a sharp decrease at 33&thinsp;∘C, and bare sediments, in which rates increased along the range of the experimental temperatures. The activation energy and Q10 were lower in vegetated than bare sediments, indicating the lower thermal sensitivity of vegetated sediments. The projected warming is expected to increase the contribution of N2 fixation to Mediterranean macrophyte productivity. Therefore, the thermal dependence of N2 fixation might have important consequences for primary production in coastal ecosystems in the context of warming.</p

Precipitation characteristics and associated weather conditions on the eastern slopes of the Canadian Rockies during March–April 2015

Precipitation events that bring rain and snow to the Banff–Calgary area of Alberta are a critical aspect of the region's water cycle and can lead to major flooding events such as the June 2013 event that was the second most costly natural disaster in Canadian history. Because no special atmospheric-oriented observations of these events have been made, a field experiment was conducted in March and April 2015 in Kananaskis, Alberta, to begin to fill this gap. The goal was to characterize and better understand the formation of the precipitation at the surface during spring 2015 at a specific location in the Kananaskis Valley. Within the experiment, detailed measurements of precipitation and weather conditions were obtained, a vertically pointing Doppler radar was deployed and weather balloons were released. Although 17 precipitation events occurred, this period was associated with much less precipitation than normal (−35&thinsp;%) and above-normal temperatures (2.5&thinsp;°C). Of the 133&thinsp;h of observed precipitation, solid precipitation occurred 71&thinsp;% of the time, mixed precipitation occurred 9&thinsp;% and rain occurred 20&thinsp;%. An analysis of 17&thinsp;504 precipitation particles from 1181 images showed that a wide variety of crystals and aggregates occurred and approximately 63&thinsp;% showed signs of riming. This was largely independent of whether flows aloft were upslope (easterly) or downslope (westerly). In the often sub-saturated surface conditions, hydrometeors containing ice occurred at temperatures as high as 9&thinsp;°C. Radar structures aloft were highly variable with reflectivity sometimes  &gt; 30&thinsp;dBZe and Doppler velocity up to −1&thinsp;m&thinsp;s−1, which indicates upward motion of particles within ascending air masses. Precipitation was formed in this region within cloud fields sometimes having variable structures and within which supercooled water at least sometimes existed to produce accreted particles massive enough to reach the surface through the relatively dry sub-cloud region.</p