An assessment of a natural wetland receiving sewage effluent

An assessment of the performance of a wetland dominated by opportunistic weeds in removing nutrients from a secondary sewage effluent was carried out at Thredbo in Kosciusko National Park. Water quality sampling of the inflow and outflow showed a reduction in turbidity, pH and conductivity with passage through the wetland. Dissolved oxygen levels also decreased. In summer 1982, the phosphorus toad of 1.8 kg P day^-1 was reduced by 44% as wastewater moved through the wetland, and the nitrogen load of 6.4 kg N day^-1 by 65%. Winter retentions were 10% and 14% of inflowing loads, respectively. In 1983 there was a net release of phosphorus and reduced retention of nitrogen. This was regarded as being a result of physical disturbance of the wetland. Vegetation downstream of the effluent inflow was dominated by the opportunistic weeds Epilobium sarmantaceum and Rumex crispus. Upstream, Carex gaudichaudiana and Baeckea gunniana dominated. Marked seasonal changes in vigour and biomass were recorded. Plants, but not sediments, downstream of the inflow contained more nutrients than those upstream. Seed bank analysis showed more seeds downstream than upstream. A moist treatment promoted more seed germination than a flooded treatment. E. sarmantaceum and to a lesser extent R. crispus dominated in each treatment. In an effort to promote greater water retention and replacement of the weed species, channels in the wetland have been blocked with gravel and planted with Phragmites australis and Schoenoplectus validus.     

Lack of Effect of Staphylococcal Toxins on Ciliated Protozoa

SYNOPSIS. Highly purified α and β toxins of staphylococci, reported by others to be lethal for paramecia and entamoebae, proved harmless to Paramecium caudatum and Tetrahymena pyriformis.     

THE DISTRIBUTION OF APHID INFESTATION IN RELATION TO LEAF AGE

Infestations of apterous Aphis fabae Scop, on potted sugar beets have been followed in detail for several weeks. The plants were somewhat stunted and their crowns presented an unusually complete series of leaf ages. Records were kept of the changing number and size of the leaves and of their stage of growth. Parallel records were kept of the changing population of aphids on every leaf, and the figures are analysed in various ways to show how suitability for the aphids varied through the life cycle of the leaves.
The leaves were very suitable when young, became unsuitable as they matured, became suitable again just after maturity and then unsuitable again as they senesced. But among leaves at any given stage, those which were growing or senescing rapidly were more suitable than those changing slowly, unless the rate of senescence was very high. The differences of population density on different-aged leaves were due largely to the preferences exercised by the apterous adults. The added effect of differences in the fecundity of these mothers while feeding on different leaves was not excluded, but could not be assessed. It is concluded that the physiological development of the plant as a whole determines, through the growth and senescence among its total complement of leaves, the progress and pattern of its aphid infestation.     

Possible impacts of environmental change on pelagic fish recruitment: modelling anchovy transport by advective processes in the southern Benguela

Climate change may influence pelagic fish by altering advective processes or by changing where fish choose to spawn. Using a simulation model, the effects of altered advection and spatial distribution of spawning by anchovy on recruitment off South Africa were explored. Cape anchovy Engraulis capensis spawn on the region of the Agulhas Bank, south of South Africa. Currents transport eggs and larvae to nursery areas. Transport of eggs and larvae was modelled using a flow field based on averaged Acoustic Doppler Current Profile data, Feasible Scenarious of altered advection were modelled. For modelling purposes, the ocean surrounding South Africa was divided into blocks with dimensions of a quarter-degree latitude by a quarter-degree longitude. Acoustically measured distributions of spawner biomass for the years 1986–92 were used to calculate egg production per block. In the model, batches were released from each of these blocks each day of the spawning season. The modelling study indicates that passive transport of young anchovy may account for a substantial proportion of year-class variability. Model results show that distribution of spawners influences the distribution of young of the year, as well as the number and the location of advective losses across offshore boundaries.     

OLFACTORY INPUTS TO A BURSTING SEROTONERGIC INTERNEURON IN A TERRESTRIAL MOLLUSC

Olfactory fiber tracts in Limax maximus Linnaeus terminate inthe cerebral ganglion, and arborize near the metacerebral giantcell (MGC). In the preparation herein described the serotonergicMGC fires in bursts. Electrical stimulation of an olfactorynerve (OfN) elicits complex postsynaptic potentials (PSPs) inthe ipsilateral MGC that disrupt its bursting. Rigidly controlledstimulation of a nose with natural or synthetic odors elicitsa brief burst of compound action potentials in the ipsilateralOfN (en passant recording). Olfactory stimulation of a noseleads to PSPs in the ipsilateral MGC which can cause an increasein its firing rate and alter the firing pattern of the contralateralMGC. Olfactory stimulation failed to activate the feeding neuralnetwork of which the MGC is part. MGC bursting is discussed. ¹Present address: 2326 Woodglen St., Richardson, Texas, 75081,U.S.A. Send reprint requests to A. Gelperin. (Received 31 January 1980;     

Responses of ant communities to dry sulfur deposition from mining emissions in semi‐arid tropical Australia,with implications for the use of functional groups

Abstract The impact of dry deposition of SO₂ emissions on ant abundance, diversity and composition was investigated at Mount Isa in the semiarid tropics of northern Australia. Forty plots were sampled, stratified at two levels: sulfur deposition zones (high, medium, low, and two control zones) and habitat (Ridge and Plain). The two habitats supported distinctly different ant communities. Ants had clear responses to SO₂ emissions. Ant abundance was lowest in the high and medium sulfur zones in both habitats. Species richness in high SO² plots (up to 5 km from the source) was approximately half that of control plots in Ridge habitat, and was substantially less than controls in the Plain habitat. Ant community composition in the high sulfur zone was clearly separated from those of other zones in ordinations. Vector fitting showed soil SO₄ concentration as a primary correlative factor in this separation. Ant abundance and richness were both negatively correlated with soil SO₄ concentration, and positively correlated with plant species richness and distance away from the smelters. The abundance of 10 of the 21 most common species showed significant responses to emissions. Five species showed positive responses, and all belong to species‐groups known to be abundant at disturbed sites throughout northern Australia. Relative abundance and richness of Eyrean (arid adapted) taxa collectively responded positively to sulfur, and Torresian (tropical) and Widespread species responded negatively. Despite large changes in species composition and abundances, there was relatively little change in the abundance of functional groups that have been widely used in studies of Australian ant communities. Ants are sensitive to SO₂ emissions and appear to be good candidates as an indicator group in this context. However, an alternative functional group framework is required for the identification of recurrent responses of arid zone ant communities to disturbance.     

DEEPER PROBLEMS FOR NOONAN'S PROBABILITY ARGUMENT AGAINST ABORTION: ON A CHARITABLE READING OF NOONAN'S CONCEPTION CRITERION OF HUMANITY

In ‘An Almost Absolute Value in History’ John T. Noonan criticizes several attempts to provide a criterion for when an entity deserves rights. These criteria, he argues are either arbitrary or lead to absurd consequence. Noonan proposes human conception as the criterion of rights, and justifies it by appeal to the sharp shift in probability, at conception, of becoming a being possessed of human reason. Conception, then, is when abortion becomes immoral. The article has an historical and a philosophical goal. The historical goal is to carefully present the probability argument in a charitable manner. The philosophical goal is to offer a unique criticism of Noonan's probability argument against abortion. I argue that, even on a very charitable reading of Noonan's argument for the conception criterion, this criterion is also susceptible to charges of arbitrariness and absurdity. Noonan's claim that probability shifts have anything to do with the moral rights of fetuses cannot be made coherent. I also show that there are problems with Noonan's assumptions about moral rights and the potential to become a being possessed of human reason.     

Aminotransferase and the Production of Alanine During Hyperosmotic Stress in Paramecium calkinsi

When Paramecium calkinsi encounter hyperosmotic stress, intracellular free alanine increases. In vivo assays indicate that the reaction catalyzed by alanine aminotransferase contributes to the build up of alanine in response to hyperosmotic shock. ¹⁴C-pyruvate is converted to ¹⁴C-alanine in cells grown axenically at 200 mosm. When shifted to 600 mosm, the rate of conversion of pyruvate to alanine increases, and conversion at either 200 or 600 mosm is blocked by 1 mM aminooxyacetic acid (AOA), an inhibitor of aminotransferase. Intracellular free alanine increase is partially inhibited by AOA, and AOA prevents cells living in fresh water from acclimating to higher salinities, an indication that the increase in intracellular alanine is physiologically significant.