Effects of periodic hypoxia on distribution of demersal fish and crustaceans

Effects of periodic hypoxia (O₂ < 2 mg l^–1) on distribution of three demersal fish species, spot (Leiostomus xanthurus), hogchoker (Trinectes maculatus) and croaker (Micropogonias undulatus), and of two crustacean species, mantis shrimp (Squilla empusa) and blue crab (Callinectes sapidus), were investigated in the lower York River, Chesapeake Bay, USA. Trawl collections were made in four depth strata (5 to 10, 10 to 14, 14 to 20 and > 20 m) during normoxia and hypoxia from 26 June to 20 October 1989. Three periods with hypoxia in the bottom water (below 10 m depth) occurred in mid-July, early August and early September, each with a duration of 6 to 14 d. The demersal fish and crustaceans studied were all affected by hypoxia, and a general migration from deeper to shallower water took place during July and August. However, when oxygen conditions improved after a hypoxic event all species, exceptS. empusa, returned to the deeper areas. The degree of vertical migration was related to levels of oxygen concentration and varied for the different species.M. undulatus was the most sensitive species to low oxygen, followed byL. xanthurus andC. sapidus. T. maculatus andS. empusa were more tolerant and survived in 14 to 25% oxygen saturation by increasing ventilation rate and, forS. empusa, by also increasing blood pigment (haemocyanin) concentration. Periodic hypoxia driven by the spring-neap tidal cycle may represent a natural phenomenon with which the fishes and crustaceans are in a delicate balance. Areas experiencing periodic short-lived hypoxia may be good nursery grounds for fisheries species, and there is no indication that the habitat value in the study area of lower York River is lessened. However, if eutrophication lengthens the time of hypoxia or brings the system closer to anoxia the system may change and become characteristically stressed. The migratory and physiological responses of these species to hypoxia are good indicators of the severity of oxygen stress and could be used as part of an early warning monitoring system for changes in environmental quality.Contribution of the Virginia Institute of Marine Science     

Development,local livelihoods,and vulnerabilities to global environmental change in the South American Dry Andes

Climate change will increasingly impact large areas of South America, affecting important natural resources and people’s livelihoods. These impacts will make rural people disproportionately more vulnerable, given their dependency on ecosystem services and their exposure to other stressors, such as new rules imposed by agribusiness and trends toward the commodification of natural resources. This paper focuses on the vulnerability of rural communities in Andean drylands of Argentina, Bolivia, and Chile, showing how different economic and political pathways lead to different levels of vulnerability. The paper begins with a brief discussion of the methodological and theoretical concept of vulnerability, which framed the research. Starting from the premise that global environmental change impacts are strongly linked to styles of development, the discussion explores the diverse institutional capital and governance schemes as well as different development styles in the case studies and their role in increasing or reducing local vulnerability to climate and water scarcity. Using a comparative perspective, the exposures and adaptive capacities of rural actors in three river basins are discussed, emphasizing situations that speak for the ways in which development styles counteract or magnify conditions of vulnerability. The analysis considers irrigated and non-irrigated agriculture, water property interests, different productive structures (viticulture, horticulture, etc.), producer typologies (large/small, export, etc.), and geographical location. Finally, the paper offers some insights about development style and adaptive capacities of rural people to overcome those vulnerabilities.     

Contrasting behaviour of cadmium and zinc in a soil-plant-arthropod system

This study investigates the transfer of Cd and Zn from a soil amended with sewage sludge at rates up to 100 t ha(-1) through a multi-trophic system consisting of barley, the aphid Sitobion avenae and the larvae of the lacewing Chrysoperla carnae. Results show marked differences in the transfer of the two metals. Cadmium was freely accumulated in barley roots, but accumulation in the shoot was restricted to a concentration of around 0.22 mg kg(-1) (dry weight). This limited the transfer of Cd to higher trophic levels and resulted in no significant accumulation of Cd in S. avenae or in C. carnae. Zinc transfer in the system was largely unrestricted, resulting in significant accumulation in roots and shoots, in S. avenae and in C. carnae. Cadmium biomagnification occurred in lacewing pupae, with concentrations up to 3.6 times greater than in aphids. S. avenae biomagnified Zn by a factor of ca. 2.5 at low sludge amendment rates, but biomagnification decreased to a factor of 1.4 at the highest amendment rate. Biomagnification of Zn did not occur in C. carnae, but concentrations were up to 3.5 time higher than in soil. Results are discussed in light of the mechanisms regulating transfer of the two metals in the system.     

Pharmazeutische Wirkstoffe und Umweltschutz

On 26 April this year the German Environmental Advisory Council (SRU) published a statement on ‘Pharmaceuticals in the environment’ and pointed considerable need for action to understand and to reduce the risks from diffuse pharmaceutical inputs in the environment. On the one hand, it is urgently necessary to improve the database for environmental risk assessments; on the other hand measures should already be taken to minimize harmful inputs. Fortunately, the new regulations for an application for an authorization to market new pharmaceuticals require an environmental risk assessment. However, there is a lack of information on possible impacts from long time admitted medicines which may be responsible for harmful active substances detectable in the environment. To remove this data deficit, a European programme for risk evaluation of old pharmaceuticals should be established. It is necessary for an adequate risk assessment to look at all impacts of one active substance or all substances same-directed in their active potential summativ and to generate regularly consumption data in particular for the use of veterinary products. The hot spots of contamination are the introduction of large scale volumes of active pharmaceutical ingredients for human use like diclofenac and carbamazepin as well as hormones into surface waters, as well as the application of antibiotics-loaded economic fertilizers on soils. Not to be neglected is the application of antiparasitics in animals kept on pasture. With the assessment of the use of pharmaceuticals for all purposes special attention is needed on antibiotic resistance. For the mitigation of environmental exposures there are exposures measures necessary to reduce use of antibiotics in farming, for the application of new effective technologies in treatment sewage — as for example ozonation, filtration with activated carbon or membrane filtration — as well as for the labelling of environmentally harmful medicinal products.     

The role of tyramine and octopamine in the regulation of reproduction in queenless worker honeybees

In honeybees, workers under queenless condition compete for reproduction and establish reproductive dominance hierarchy. Ovary activation is generally accompanied by the expression of queen-like pheromones. Biogenic amines (BAs), in particular dopamine, are believed to be involved in this process by regulating ovarian development. However, the role of BAs in establishing reproductive dominance or their effect on queen-like pheromone production was not investigated. Here, we explored the effect of octopamine (OA) and tyramine (TA) oral treatments on the propensity of treated bees to become reproductively dominant and produce queen-like pheromones in Dufour’s and mandibular glands. One bee in a pair was treated with either OA or TA while the other was fed sugar solution. TA was found to enhance ovary development and the production of esters in the Dufour’s gland and 9HDA (queen component) in the mandibular glands, thus facilitating worker reproductive dominance. OA, on the other hand, did not enhance ovarian development or ester production, but increased the production of 10HDA (worker major component) in the mandibular glands of their sugar-paired mates. OA is known to induce foraging behavior by workers, while increased production of 10HDA characterizes nursing workers. Therefore, we suggest that TA induces reproductive division of labor, while OA treatment results in caste differentiation of workers to foragers and nurses.