Does seston size structure reflect fish-mediated effects on water quality in a degraded semiarid wetland?

This study evaluates whether the size structure of seston (the sum of living and nonliving particles in the water column) reflects the effects of fish on wetland water quality. Using enclosures, we measured water quality and zooplankton community structure in the presence and absence of two fish species with distinct foraging strategies [benthivorous carp (Cyprinus carpio) and planktivorous mosquitofish (Gambusia holbrooki)]. Seston collected from the enclosures was counted and sized automatically with a Coulter counter, and the size structure in the range of 1–60 μm was modelled using the underlying Pareto distribution of particles. Only Cyprinus contributed to a loss of water quality (increased nutrient levels, algal and non-algal turbidity, hypoxia), while both fish species changed zooplankton community composition compared to fishless controls. However, these changes were not reflected in parameters [goodness of fit (r ²) and parameter c (slopes)] of Pareto models. Multivariate statistics suggest that seston size structure responded more to environmental gradients related to water depth but the relationships were also weak. Our overall result contrasts with the regulation of size spectra constructed from living organisms. Although seston integrates many structural and functional features of the water column, the lack of strong relationships between Pareto model parameters and water quality suggests that a size-based approach to characterise seston structure has a limited potential for assessing biota-mediated effects in wetlands in a straightforward manner.     

Effect of combined nitrogen on dinitrogen fixation and productivity in Pisum sativum L. Inoculated with different strains of Rhizobium

This growth chamber study was designed to determine rates of nitrogen fixation, growth, productivity and concentrations of nitrogen and phosphorus during vegetative growth, flowering and the beginning of the fruiting and ripening period in Pisum sativum plants supplied with different concentrations of nitrate and nodulated by various strains of Rhizobium leguminosarum. Noninoculated control plants were grown under the same nutritional conditions. Nodulated and unnodulated plants responded differently to treatment. The effects of inoculation with Rhizobium and the nitrate treatments on the parameters of growth and nitrogen content varied with plant age. Although the presence of nitrate in the culture medium inhibited nodulation and acetylene reducing activity (ARA), the different Rhizobium strains used in the inoculations led to variations in tolerance to combined nitrogen.     

Synthesis of Poly(β-hydroxybutyrate) in Simulated Microgravity: An Investigation of Aeration Profiles in Shake Flask and Bioreactor

The microbial strain Azotobacter vinelandii UWD was grown under conditions of simulated microgravity in the National Aeronautics and Space Administration (NASA) Bioreactor. Bacterial growth in simulated microgravity differed significantly from that observed in conventional shake flask experiments: Cells tended to grow in a cluster-like pattern and polymer production started immediately after exposing them to conditions of simulated microgravity, and no lag time was observed. It was imperative to differentiate between the effects derived from microgravity and those imposed by the altered oxygen supply in the bioreactor. Aeration conditions were studied in both reactor types and a gas supply profile was developed for the bioreactor. This supply profile allowed for similar amounts of dissolved oxygen in the bioreactor and the shake flask in the initial stage of the fermentation and, therefore, for an evaluation of the effects of microgravity on biopolyester-producing bacteria. Since the optical density that is conventionally used as a measure for the cell growth could not be used due to the cluster-like growth pattern of the cells, it was determined that bacterial growth behavior in the bioreactor can be monitored through glucose or oxygen consumption.     

The value of open ocean ecosystems: A case study for the Spanish exclusive economic zone

Valuing goods and services from open oceans provides arguments for the ocean's protection and plays an increasingly important role in debates on the use and management of natural resources. This paper identifies and estimates the monetary value of some of the most important goods and services provided by open oceans. The list of goods and services considered includes food production, raw materials, water supply, CO₂ regulation, bioremediation of waste, biomass and biodiversity conservation. Therefore, not only values associated with productive uses are quantified but also values assigned to other biological ecosystem services. This paper constitutes a first attempt in the open ocean literature at evaluating services such as water supply, biomass and biodiversity conservation. To obtain their monetary value, different techniques, some not applied before in this area, have been used depending on the ecosystem service to be evaluated. As a general criterion we use the concept of net value added (revenues obtained from the services less incurred costs). Our methodology is illustrated by estimating the monetary values of goods and services provided by the open ocean ecosystem of Spain as defined by its exclusive economic zone. The total economic value obtained measures the contribution of oceans to overall welfare and it may be an important instrument in managing open ocean ecosystems and developing environmental policies in the future.     

Environmental hazard of cadmium, copper, lead and zinc in metal-contaminated soils remediated by sulfosuccinamate formulation

Accumulation of metals in soil at elevated concentrations causes risks to the environmental quality and human health for more than one hundred million people globally. The rate of metal release and the alteration of metal distribution in soil phases after soil washing with a sulfosuccinamate surfactant solution (Aerosol 22) were evaluated for four contaminated soils. Furthermore, a sequential extraction scheme was carried out using selective extractants (HAcO, NH(2)OH·HCl, H(2)O(2) + NH(4)AcO) to evaluate which metal species are extracted by A22 and the alteration in metal distribution upon surfactant-washing. Efficiency of A22 to remove metals varied among soils. The washing treatment released up to 50% of Cd, 40% of Cu, 20% of Pb and 12% of Zn, mainly from the soluble and reducible soil fractions, therefore, greatly reducing the fraction of metals readily available in soil. Metal speciation analysis for the solutions collected upon soil washing with Aerosol 22 further confirmed these results. Copper and lead in solution were mostly present as soluble complexes, while Cd and Zn were present as free ions. Besides, redistribution of metals in soil was observed upon washing. The ratios of Zn strongly retained in the soil matrix and Cd complexed with organic ligands increased. Lead was mobilized to more weakly retained forms, which indicates a high bioavailability of the remaining Pb in soil after washing. Comprehensive knowledge on chemical forms of metals present in soil allows a feasible assessment of the environmental impact of metals for a given scenario, as well as possible alteration of environmental conditions, and a valuable prediction for potential leaching and groundwater contamination.     

House sparrows selectively eject parasitic conspecific eggs and incur very low rejection costs

Most host species of obligate interspecific brood parasites are under strong selection because such parasitism, e.g., that involving evictor nestmates, is highly costly. Egg rejection is one of the most efficient host defences against avian brood parasites. Many hosts have thus evolved egg-recognition ability and rejection behaviour. However, this defensive mechanism has not evolved in most species where only intraspecific brood parasitism occurs, probably because (1) the eggs of conspecific females are very similar in appearance, making egg rejection less likely to emerge, and (2) such parasitism is frequently less costly than interspecific parasitism. Using a captive population of house sparrows (Passer domesticus) with a low breeding density, we here provide new evidence showing that this species actually has a fine capacity to discriminate conspecific eggs and to eject them (44.2% of foreign eggs ejected) while incurring very low rejection costs (4.2% of own eggs ejected). This result contradicts those previously found in high-density house sparrow populations in which very high rejection costs and very high clutch desertion rates were reported, probably as a consequence of intraspecific competition and infanticide provoked by the high breeding density. The house sparrow has only rarely been reported as the host of an interspecific brood parasite, which implies that it is a newly described example of an altricial species in which egg ejection has evolved and is maintained in response to intraspecific brood parasitism.