Foraging habitats of the seabird community of Europa Island (Mozambique Channel)

We investigated the foraging habitats of the winter breeding community of tropical seabirds from Europa Island (Mozambique Channel) in September 2003. We focused our study on the dominant species of this austral community, the sooty tern (Sterna fuscata), the red-footed booby (Sula sula), and the frigatebirds, including the great (Fregata minor) and the lesser frigatebirds (F. ariel). We considered the at-sea distribution and abundance of these species in relation to chlorophyll concentration, sea-surface temperatures, sea-surface height anomalies, depth of the thermocline, distance to the colony, and presence of surface marine predators, flying fishes and other seabirds. Although the marine environment where seabirds foraged was oligotrophic, it presents the best feeding opportunities for seabirds for the area in winter. Our study demonstrates that the winter-breeding seabird species of Europa Island tend to forage in productive waters in association with other marine predators when possible. Sooty terns and frigatebirds were widely distributed in the whole study area, whereas red-footed boobies were not found farther than 160 km from their colonies and were associated with relatively productive waters. Sooty terns and red-footed boobies were aggregated where flying fishes were abundant. The presence of other marine predators was associated with larger multispecies feeding flocks than when no association occurred. Sooty terns, which are numerically dominant at Europa and adopted network foraging, seem to be catalysts of feeding events, and represented a good target for the other foraging species, especially frigatebirds. However, when possible, frigatebirds favour association with flocks of red-footed boobies.Communicated by S.A. Poulet, Roscoff     

Dairy farm effluent effects on urine patch nitrous oxide and carbon dioxide emissions

Dairy farm effluent (DFE) comprises animal feces, urine, and wash-down water collected at the milking shed. This is collected daily during the milking season and sprayed onto grazed dairy pastures. Urine patches in grazed pastures make a significant contribution to anthropogenic N(2)O emissions. The DFE could potentially mitigate N(2)O emissions by influencing the N(2)O to dinitrogen (N(2)) ratio, since it contains water-soluble carbon (WSC). Alternatively, DFE may enhance N(2)O emissions from urine patches. The application of DFE may also provide a substrate for the production of CO(2) in pasture soils. The effects of DFE on the CO(2) and N(2)O emissions from urine patches are unknown. Thus a laboratory experiment was performed where repeated DFE applications were made to repacked soil cores. Dairy farm effluent was applied at 0, 7, or 14 d after urine deposition. The urine was applied once on Day 0. Urine contained (15)N-enriched urea. Measurements of N(2)O, N(2), and carbon dioxide (CO(2)) fluxes, soil pH, and soil inorganic N concentrations were made. After 43 d the DFE had not mitigated N(2)O fluxes from urine patches. A small increase in the N(2)O flux occurred from the urine-treated soils where DFE was applied 1 wk after urine deposition. The amount of WSC applied in the DFE proved to be insignificant compared with the amount of soil C released as CO(2) following urine application. The priming of soil C in urine patches has implications for the understanding of soil C processes in grazed pasture ecosystems and the budgeting of C within these ecosystems.     

The use of radioactive isotopes to measure the transfer of materials in aquatic food chains

Radioisotopes have been misused extensively by ecologists in transfer studies within food chains. Unless it is known that no recycling of isotope has occurred during the experiment, the assumption of linear uptake when in fact the system is not linear, even over short periods, can lead to significant errors in the estimation of ingestion or feeding. If recycling occurs, at least a 3 or 4-compartment, hydraulic-type model is necessary to even approximate the complicated kinetics of isotopic transfer in a simple aquatic feeding experiment. In any event, it is essential to follow the uptake or loss of an isotope (change in specific activity) as a function of time in at least 1 compartment before deciding on an appropriate model. If experiments are designed so that the maximum number of rate processes are summed or integrated by the animal, the kinetics can be considerably simplified. If the food supply is uniformly labelled, the rate of change of tracer can be used to give a rate of ingestion (grazing). If the predator is labelled with a suitable isotope before starting the experiment, the rate of loss of its isotope burden under different experimental conditions can be used to determine respiration or excretion rates, turnover rates, ingestion, and the size and number of major compartments in the transfer system.Bedford Institute Contribution. Woods Hole Oceanographic Institution Contribution No. 2690.     

A review on thermal analyses of cyclodextrins and cyclodextrin complexes

Environmental Chemistry Letters - Cyclodextrins are valuable natural or synthetically modified cyclic oligosaccharides that are widely used for ameliorating properties of biologically active...     

First occurrence and composition assessment of microplastics in native mussels collected from coastal and offshore areas of the northern and central Adriatic Sea

Environmental Science and Pollution Research - In recent years, the occurrence of microplastics in the aquatic environment has gathered increasing scientific interest. Several studies have shown...     

Reproductive conflict in animal societies: hierarchy length increases with colony size in queenless ponerine ants

Dominance interactions determine reproductive status in many animal societies, including many cooperatively breeding vertebrates and eusocial Hymenoptera without queen-worker dimorphism. Typically, the dominant individual monopolises reproduction, and subordinates behave like helpers. In Dinoponera queenless ants, workers are totipotent females and can potentially reproduce, yet only the top-ranking worker actually reproduces. Individual workers ranked immediately below the dominant breeder worker (gamergate) are hopeful reproductives. Whether or not a worker benefits from joining the hierarchy of high-ranking workers depends on the trade-off between the probability of becoming dominant and reproducing directly, and the colony-level cost of an additional lazy high ranker. Inclusive fitness models predict that the length of the dominance hierarchy depends on relatedness, colony size, and the linearity of the hierarchy. Here, we test the effect of colony size by comparing hierarchy length among three species that differ in colony size (Dinoponera australis: median=14 workers, quartiles=10 and 19 workers; D. gigantea: median=41, quartiles=33 and 74; D. quadriceps: median=78, quartiles=55 and 90). Although difficulties in defining where the hierarchy ends hamper comparisons, the results are in broad agreement with the predictions. Hierarchies are close to the predicted lengths and are longer in species with larger colonies (one, three and three workers in the three species in order from smallest to largest colony vs two, three and four predicted). These conclusions are further supported by determining Kokko and Lindström's λ index of skew, which is smaller (i.e. characteristic of a longer hierarchy) in species with larger colonies.     

The problem of specifying otolith-mass growth parameters in the radiometric estimation of fish age using whole otoliths

A problem in the radiometric estimation of age using whole otoliths is the necessity to specify otolith-mass growth. Unless it can be assumed that otolith-mass growth is linear, parameters describing this growth will occur in the radiometric equation used to estimate age. Previous authors have assumed that the values of these parameters must be known before age can be estimated. This leads to circular reasoning: to estimate the age of a fish (and thus infer its growth) prior knowledge about the growth of the otolith is needed. A reanalysis of published radiometric data for Hoplostethus atlanticus is presented to illustrate two new approaches that avoid this assumption and thus the problem of circular reasoning. The first calculates the age that is most probable for each sample given the radiometric and otolith-mass data; the second estimates a lower bound for the maximum age. These analyses depend on correcting a misinterpretation of the otolith-mass term in a common radiometric equation. The effect of between-individual variability in otolith growth rates on the radiometric method is discussed.     

Evidence for the remobilisation of transuranic elements in the terrestrial environment

The transuranium elements, Np, Pu and Am discharged from the BNFL fuel reprocessing plant at Sellafield have accumulated in the local environment. The processes responsible for their dispersal rely both on physical transportation and their chemical reactivity. The transuranics have a complex chemistry, with multiple oxidation states and a strongly polarising character. In the environment, the particle active III/IV and more mobile VNI oxidation state groups are important and govern their geochemical behaviour and subsequent dispersal. Studies of the behaviour of the transuranics, particularly Pu, in the Irish Sea, have shown that the majority of the radionuclides in the liquid effluent discharged from Sellafield, quickly becomes associated with the marine sediments. Their dispersal and distribution in the environment is then governed primarily by the movement of particulate material and for some sites it has been suggested that sediment profiles preserve the historical record of discharges from the plant. In tidally inundated soils, radionuclide levels are greatly enhanced. These soils are water-logged for long periods of the year, are strongly anoxic and accretion rate are very low. The distribution of Np, Pu and Am in the soil suggests that simple sedimentary accumulation mechanism cannot provide an adequate explanation for the profiles observed. From preliminary studies of soil pore water composition and detailed analysis of the variation of isotopic ratios in the soil cores, it is apparent that a small but significant component of the radionuclide inventory is mobile. In addition, it is clear that the mechanisms responsible for this mobility allows differentiation between the transuranium nuclides.