Temporal changes in the trophic ecology of the asymbiotic gorgonian Leptogorgia virgulata

Gorgonians are widespread sub-littoral benthic suspension feeders in the world oceans. However, data on their trophic ecology and role in benthic–pelagic coupling and biogeochemical cycles remain limited. This study assesses the trophic ecology of Leptogorgia virgulata in the Skidaway River estuary, USA (31.9896N, 81.0242W) by analysing carbon and nitrogen isotopic signatures of its soft tissue and different-sized fractions of particulate organic matter (POM) in its environment. Samples were taken in 5 April, 2 August, and 15 October 2012 and 11 January 2013. Results support a distinct temporal shift in the diet of L. virgulata from the POM fraction <10 µm (i.e. pico- and nanoplankton) to the 10–63-µm fraction (i.e. microplankton). This trophic regime is likely associated with the natural abundance of prey items within these size classes, thus suggesting that L. virgulata may be an opportunistic feeder, and seasonal shifts in food availability in the water column affect its diet. As such small prey items affect the bioenergetics of L. virgulata, it is important to understand the implications of changes in food availability associated with environmental drivers on the physiology and population dynamics of this dominant species in the western Atlantic Ocean.     

Effect on benthic communities of a major input of organic matter and other pollutants (coast off Barcelona,Western Mediterranean)

Benthic communities on soft bottoms off Barcelona, at and around two main pollution sources, the mouth of the Besòs River and the outlet of the submarine pipeline draining wastewater and organic sludges from the wastewater treatment plant of Sant Adrià del Besòs, have been studied. Samples were obtained with a Van Veen grab from 36 stations covering a 100 km² grid, between 10 and 70 m in depth. The effect of both pollution sources is clearly seen both at the species (the following macrofauna groups have been studied: Polychaeta, Mollusca, Echinodermata and Crustacea Decapoda) and community levels. The distribution of species and individuals numbers, species diversity and a pollution index, and of some selected (indicator) polychaeta species, all clearly define the degree of environmental degradation and the extent of the areas under the influence of the organic pollution.     

Genetic structure of wild European populations of the invasive Pacific oyster Crassostrea gigas due to aquaculture practices

As a result of aquaculture activities, Pacific oysters Crassostrea gigas (Thunberg, 1793) have invaded European coasts. Using seven microsatellites, we found virtually no genetic differentiation between natural populations throughout the European range (from the south of the Wadden Sea (the Netherlands) to the south of France) and French cultivated oysters. The genetic homogeneity of Pacific oyster samples appears to be the result of repeated transfers from same seed stocks made for aquaculture and, to a lesser extent, widespread dispersal due to specific biological traits of this species. The only genetic differentiation of Sylt population in the north of the Wadden Sea (Germany) suggests a stronger, persistent impact of ongoing supply of new genetic material from hatchery production, corresponding to seeds selection made by breeders. All of our genetic data highlighted the importance of aquaculture practices on the genetic structure of the keystone invader C. gigas in Europe.     

Vegetation succession and impacts of biointrusion on covers used to limit acid mine drainage

A cover with capillary barrier effects (CCBE) was constructed in 1998 on the abandoned Lorraine mine tailings impoundment to limit the generation of acid mine drainage. The Ministry of Natural Resources and Fauna of Quebec (MRNF) is responsible for the site and for all restoration works on it, including CCBE construction. The CCBE is made up of three layers: a 0.3-m layer of sand used as a support and capillary break layer; a moisture-retaining layer with a thickness of 0.5 m (this layer is constructed of a nonplastic silt); and a 0.3-m sand and gravel layer on top. The main objective of the CCBE is to maintain one (or more) of the layers at a high degree of water saturation to impede oxygen migration and acid generation. Vegetation succession on the Lorraine CCBE results in an improvement in soil conditions, leading to the installation of deep-rooted species, which could represent a risk to CCBE long-term performance. Hence, the characterization of vegetation succession is an important aspect of the monitoring strategy for the Lorraine CCBE. Species occurrence was documented, and depth of tree roots was measured by excavation on a regular basis. Eight functional groups of plants were identified; herbaceous plants were the most abundant ecological plant groups. Tree ring counts confirmed that tree colonization started the year of CCBE construction (1999). Of the 11 tree species identified, the most abundant were poplar (Populus spp.), paper birch (Betula payrifera Marsh.), black spruce (Picea mariana Mill.), and willow (Salix spp.). Significant differences in occurrence related to environmental conditions were observed for most functional groups. Root excavation showed that tree roots exceeded the depth of the protective layer and started to reach the moisture-retaining layer; in 2008, root average depth was 0.4 m and the maximal root depth was 1.7 m.     

Paving the Way for Invasive Species: Road Type and the Spread of Common Ragweed (<Emphasis Type="Italic">Ambrosia artemisiifolia</Emphasis>)

Roads function as prime habitats and corridors for invasive plant species. Yet despite the diversity of road types, there is little research on the influence of these types on the spread of invaders. Common ragweed (Ambrosia artemisiifolia), a plant producing large amounts of allergenic pollen, was selected as a species model for examining the impact of road type on the spread of invasive plants. We examined this relationship in an agricultural region of Quebec, Canada. We mapped plant distribution along different road types, and constructed a model of species presence. Common ragweed was found in almost all sampling sites located along regional (97%) and local paved (81%) roads. However, verges of unpaved local roads were rarely (13%) colonized by the plant. A model (53% of variance explained), constructed with only four variables (paved regional roads, paved local roads, recently mown road verges, forest cover), correctly predicted (success rate: 89%) the spatial distribution of common ragweed. Results support the hypothesis that attributes associated with paved roads strongly favour the spread of an opportunistic invasive plant species. Specifically, larger verges and greater disturbance associated with higher traffic volume create propitious conditions for common ragweed. To date, emphasis has been placed on controlling the plant in agricultural fields, even though roadsides are probably a much larger seed source. Strategies for controlling the weed along roads have only focused on major highways, even though the considerable populations along local roads also contribute to the production of pollen. Management prioritizations developed to control common ragweed are thus questionable.     

Floral scent variation in two <Emphasis Type="Italic">Antirrhinum majus</Emphasis> subspecies influences the choice of naïve bumblebees

Two wild subspecies of snapdragon, Antirrhinum majus, subspecies pseudomajus and striatum, differ in floral color and can be visually discriminated by insect visitors. The extent to which olfactory cues derived from floral scents contribute to discrimination between snapdragon subspecies is however unknown. We tested whether these two subspecies differ in floral scent and whether these olfactory differences are used by bumblebees (Bombus terrestris) to discriminate between them. We grew individuals of both subspecies, collected from a total of seven wild populations, under controlled conditions. We quantified the volatile organic compounds (VOCs) emitted by the flowers using gas-chromatography/mass-spectrometry/flame-ionization-detection. We studied antennal detection of VOCs by bumblebees, by means of electroantennogram study (EAG). We also performed behavioral experiments in a Y-maze to determine the innate response of bumblebees to the main floral VOCs emitted by our snapdragon subspecies. The floral scent of Antirrhinum majus pseudomajus contained three volatile benzenoids absent in the floral scent of Antirrhinum majus striatum. One of them, acetophenone, contributed over 69% of the absolute emissions of A. majus pseudomajus. These benzenoids elicited a significantly higher EAG response compared with other VOCs. In the Y-maze, bumblebees were significantly less attracted by acetophenone, suggesting an aversive effect of this VOC. Our findings indicate that bumblebees are able to discriminate between the two Antirrhinum majus subspecies. Differences in flower scent between these subspecies and olfactory bumblebee preferences are discussed in the light of biochemical constraints on VOCs synthesis and of the role of flower scent in the evolutionary ecology of A. majus.     

Determination of resin acids during production of wood pellets--a comparison of HPLC/ESI-MS with the GC/FID MDHS 83/2 method

Resin acids are constituents of natural and technical products of widespread use. Exposure is known to cause health effects in the airways and on the skin. Liquid chromatography/positive ion electrospray-mass spectrometry (HPLC/pos ESI-MS) was investigated for determination of 7-oxodehydroabietic (7-OXO), dehydroabietic (DHAA) and abietic acid (AA) in wood dust-containing air samples as a derivatisation-free alternative to the GC/FID HSE method 83/2, developed by the Health and Safety Executive UK. The resin acid 7-OXO was measured as a marker for oxidised resin acids, which are known to be the main contact allergens in colophonium. The found detection limits were 0.42 ng m(-3) for 7-OXO, 5.2 ng m(-3) for DHAA and 9.4 ng m(-3) for AA, respectively, which are considerably lower than with the GC/FID method (24, 115 and 89 ng m(-3)). The two methods correlated well, although consistently and significantly lower concentrations of 7-OXO were detected with LC/MS. The higher concentration of this compound with MDHS 83/2 is suggested to be an artefact from the derivatisation step in the presence of soluble wood dust remains.     

Pesticide toxicity towards microalgae increases with environmental mixture complexity

Environmental Science and Pollution Research - Effect-directed analysis (EDA) aims at identifying the compound(s) responsible for toxicity in a complex environmental sample where several dozens of...