Egg laying and embryonic-larval development in the snail<Emphasis Type="Italic"> Thais (Stramonita) chocolata</Emphasis> (Duclos, 1832) with observations on its evolutionary relationships within the Muricidae

Oviposition and embryonic-larval development are described for the muricacean snail Thais (Stramonita) chocolata from the Southeast Pacific coast. As with numerous other muricacean snails, this species engages in communal egg laying, with females depositing egg capsules in clusters on subtidal rocks. Each cluster of capsules contains 100–150 pedunculate, ampulliform egg capsules, with each capsule containing an average of 2,600 small (130 m) eggs. Intracapsular development was followed using light and scanning electron microscopy to describe the successive embryonic stages of the species. Free-swimming veliger larvae of about 225 m length were released from capsules after 49 days incubation at 13.6°C. The planktotrophic larvae were cultured in seawater aquaria by feeding with pure cultures of phytoplankton, recording growth and form of the larvae. Larvae reached competence after 4 months at 22°C, at 1,450–1,740 m in size, and a few larvae were observed through metamorphosis and early definitive growth. The embryonic-larval development of T. chocolata coincides with the general characteristics of the ontogeny observed in other Thais species as well as of other genera of the Rapaninae such as Concholepas. This lent support to grouping these genera into a single clade. The lack of knowledge of the development of free larvae of Thais spp. means that we do not know whether these similarities also include an extensive larval phase as generally characteristic of other members of the clade. The mode of development may be useful in characterizing some clades of this family. Thus for example, the transference of some Thais to the genus Nucella (Subfamily Ocenebrinae) is supported by differences in the mode of embryonic development, which differentiates these subfamilies. Paleobiological data reported for Neogastropoda allow postulation of primitiveness in planktotrophic larval development compared to more recent developmental strategies such as direct development of different types, which characterize various clades of this family.Communicated by O. Kinne, Oldendorf/Luhe     

Utilisation of mangroves and seagrasses by fishes in the Negombo Estuary,Sri Lanka

In two years of sampling, 10 287 fishes belonging to 62 species (39 families) were collected from mangroves and seagrasses of the Negombo Estuary. Of the species collected, 70% were marine, 27% estuarine and 3% freshwater. Aplocheilus melastigma, Ambassis dayi, Etroplus suratensis, E. maculatus, Bathygobius fuscus and Arothron immaculatus constituted 90% of the catch. Sixteen species were caught only from mangroves, 6 only from seagrasses, and 40 from both. The number of species, individuals, biomass and diversity were higher in seagrasses than in mangroves. Gobies and some siganids moved to the mangrove habitat as they grew, but cichlids, triacanthids, some eleotrids and tetraodontids preferred seagrasses. The number of species and individuals caught increased at the beginning of the north-east monsoon when the rainfall was low. The number of species and individual numbers were positively correlated with salinity and dissolved oxygen and negatively correlated with water temperature. Of the 33 species examined, seagrasses formed >25% of the gut content in juvenile Lates calcarifer, Apogon thermalis, E. suratensis, E. maculatus, Siganus javus, Butis butis and Bathygobius fuscus. Mangrove litter was the main gut content of the family Syngnathidae. E. suratensis, E. maculatus and S. javus from seagrasses contained more filamentous algae than seagrasses in their stomachs. S. javus collected from mangroves also contained more seagrasses in their stomachs than mangrove litter, indicating that the association of juvenile fishes with mangroves or seagrasses may not be obligate in estuaries subject to low tidal fluctuations.     

Growth,mortality and recruitment of the yellow clam Mesodesma mactroides on Uruguayan beaches

We studied some aspects of the population dynamics of the yellow clam Mesodesma mactroides (Deshayes, 1854) which inhabits the eastern sandy beaches of Uruguay. Observations were made from March 1983 through March 1985 (harvesting season), and additional data from January 1988 to December 1989 (closed season) were also included in the analyses. Parameters of growth and mortality were estimated by methods that make use of age or length information. An age/length relationship was constructed by counting growth rings. Results were consistent with those obtained with modal class progression analysis and other length/frequency methods. The growth curve obtained from the age/length relationship did not account for seasonality in growth rate, and a seasonal growth model explained growth oscillations in a better way. The instantaneous coefficient of natural mortality (M) estimated for the closed season was 1.64, whereas an increase in fishing mortality (F) was observed during 1984. Age composition did not change during the 2 yr of study, and the first 6 mm class accounted for over 50% of the population. The main contribution of recruits was observed between late summer and early fall (February to April), and the recruitment pattern suggested one main settlement period per year. Growth and recruitment success appeared to be regulated by density-dependence processes. Some implications for management are considered in this context. Methodological aspects concerning the reliability of empirical equations and programs for estimating growth and mortality are discussed.     

Brazil's Electric Power Choices and Their Corresponding Carbon Emissions Implications

This study analyzes the options for meeting power demand in the Brazilianpower sector through the year 2015. Three policy cases are constructedto test economic and environmental policy measures against a baseline:advanced technologies scenario, environmental control scenario and carbon(C) elimination scenario. Least-cost modeling simulated these scenarios throughchanges in emissions fees and caps, costs for advanced technologies,demand side efficiency, and clean energy supplies. Results show that, in theabsence of alternative policies, new additions to Brazil's electric powersector will shift rapidly from hydroelectricity to combined-cycle natural gasplants. When the cost of environmental impacts are incorporated in theprice of power, the least-cost mix of electric power generation technologycould change in other ways. In all scenarios, energy efficiency andcogeneration play an important role in the least-cost power solution. Savingelectricity through increased efficiency offsets the needs for new supply andhas enormous potential in Brazil's industrial sector. Efficiency also reducesthe environmental burden associated with electricity production andtransmission, without compromising the quality of the services demandedby end users. Interesting enough, carbon dioxide (CO₂) emissions will remainrelatively low under almost every conceivable scenario.     

The assessment of water quality in the Lower Luján River (Buenos Aires,Argentina): phytoplankton and algal bioassays

The monitoring of river phytoplankton and several hydrological, physical and chemical variables, in combination with bioassays using Selenastrum capricornutum Printz, allowed the characterisation of three distinct reaches of the Lower River Luján. The upstream stretch, characterised by the lowest depth and discharge, registered the highest nutrient, dissolved heavy metal and chlorophyll a concentrations in accordance with low phytoplankton diversity and the occurrence of several species typical of organically polluted lowland rivers. A downstream improvement, concomitant to increasing river discharge, is revealed by a progressive decrease of organic pollution parameters even though algal toxicity is registered through bioassays. The water input from the Parana River through the G. Arias Channel plays an important role in the regulation of the limnology of the Lower Luján River. As a result of marked increasing discharge, depth and width, there is a decrease in nutrient concentration and phytoplankton density and an increase in dissolved oxygen concentration. Likewise, algal growth rates in the bioassays showed less toxic effect.     

A practical method for quantification of phosphorus- and glycogen-accumulating organism populations in activated sludge systems.

Enhanced biological phosphorus removal (EBPR) from wastewater relies on the enrichment of activated sludge with phosphorus-accumulating organisms (PAOs). The presence and proliferation of glycogen-accumulating organisms (GAOs), which compete for substrate with PAOs, may be detrimental for EBPR systems, leading to deterioration and, in extreme cases, failure of the process. Therefore, from both process evaluation and modeling perspectives, the estimation of PAO and GAO populations in activated sludge systems is a relevant issue. A simple method for the quantification of PAO and GAO population fractions in activated sludge systems is presented in this paper. To develop such a method, the activity observed in anaerobic batch tests executed with different PAO/GAO ratios, by mixing highly enriched PAO and GAO cultures, was studied. Strong correlations between PAO/GAO population ratios and biomass activity were observed (R2 > 0.97). This served as a basis for the proposal of a simple and practical method to quantify the PAO and GAO populations in activated sludge systems, based on commonly measured and reliable analytical parameters (i.e., mixed liquor suspended solids, acetate, and orthophosphate) without requiring molecular techniques. This method relies on the estimation of the total active biomass population under anaerobic conditions (PAO plus GAO populations), by measuring the maximum acetate uptake rate in the presence of excess acetate. Later, the PAO and GAO populations present in the activated sludge system can be estimated, by taking into account the PAO/GAO ratio calculated on the basis of the anaerobic phosphorus release-to-acetate consumed ratio. The proposed method was evaluated using activated sludge from municipal wastewater treatment plants. The results from the quantification performed following the proposed method were compared with direct population estimations carried out with fluorescence in situ hybridization analysis (determining Candidatus Accumulibacter Phosphatis as PAO and Candidatus Competibacter Phosphatis as GAO). The method showed to be potentially suitable to estimate the PAO and GAO populations regarding the total PAO-GAO biomass. It could be used, not only to evaluate the performance of EBPR systems, but also in the calibration of potential activated sludge mathematical models, regarding the PAO-GAO coexistence.     

Leaching and degradation of corn and soybean pesticides in an Oxisol of the Brazilian Cerrados

Pesticide pollution of ground and surface water is of growing concern in tropical countries. The objective of this pilot study was to evaluate the leaching potential of eight pesticides in a Brazilian Oxisol. In a field experiment near Cuiabá, Mato Grosso, atrazine, chlorpyrifos, lambda-cyhalothrin, endosulfane alpha, metolachlor, monocrotofos, simazine, and trifluraline were applied onto a Typic Haplustox. Dissipation in the topsoil, mobility within the soil profile and leaching of pesticides were studied for a period of 28 days after application. The dissipation half-life of pesticides in the topsoil ranged from 0.9 to 14 d for trifluraline and metolachlor, respectively. Dissipation curves were described by exponential functions for polar pesticides (atrazine, metolachlor, monocrotofos, simazine) and bi-exponential ones for apolar substances (chlorpyrifos, lambda-cyhalothrin, endosulfane alpha, trifluraline). Atrazine, simazine and metolachlor were moderately leached beyond 15 cm soil depth, whereas all other compounds remained within the top 15 cm of the soil. In lysimeter percolates (at 35 cm soil depth), 0.8-2.0% of the applied amounts of atrazine, simazine, and metolachlor were measured within 28 days after application. Of the other compounds less than 0.03% of the applied amounts was detected in the soil water percolates. The relative contamination potentials of pesticides, according to the lysimeter study, were ranked as follows: metolachlor > atrazine = simazine > monocrotofos > endsulfane alpha > chlorpyrifos > trifluraline > lambda-cyhalothrin. This order of the pesticides was also achieved by ranking them according to their effective sorption coefficient Ke, which is the ratio of Koc to field-dissipation half-life.     

Immission patterns of airborne pollutants in Argentina and Germany II. Biomonitoring of organochlorine compounds and polycyclic aromatics

The air pollution profiles of organic xenobiotics (including chlorinated insecticides and benzenes, PCBs and PAHs) were comparatively analyzed in the climatically different regions of Leipzig-Halle (Germany) and Greater Mendoza (Argentina) using two-year-old pine needles (Pinus sylvestris L.) as passive biomonitors. In addition to total compound contents, the levels of potentially bioavailable fraction in the inner needle compartment were determined. The peak levels of chlorinated insecticides and PAHs in an urban park in Mendoza were found to exceed the maximum levels in the Leipzig-Halle region by one to two orders of magnitude, indicating the recent substantial tropospheric input of the compounds from local sources. Bioavailable fractions were observed to exhibit considerable variations for some of these compounds, which became even more distinct when needle samples from Germany and Argentina were compared. Generally speaking, an increase in permeability under semiarid climatic conditions was observed for most of the xenobiotics examined. The discussion of the results reflects the problems associated with using biomonitoring for semivolatile compounds. Interpretation takes into account pollution measurements in the air at Argentine and German reference sites.     

Electrochemical degradation of chlorophenoxy and chlorobenzoic herbicides in acidic aqueous medium by the peroxi-coagulation method

The degradation of 4-chlorophenoxyacetic acid (4-CPA), 4-chloro-2-methylphenoxyacetic acid (MCPA), 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) as chlorophenoxy herbicides, as well as of 3,6-dichloro-2-methoxybenzoic acid (dicamba) as chlorobenzoic herbicide, has been studied by peroxi-coagulation. This electrochemical method yields a very effective depollution of all compounds in acidic aqueous medium of pH 3.0 working under pH regulation, since they are oxidized with hydroxyl radicals produced from Fenton's reaction between Fe(2+) and H(2)O(2) generated by the corresponding Fe anode and O(2)-diffusion cathode. Their products can then be removed by mineralization or coagulation with the Fe(OH)(3) precipitate formed. Both degradative paths compete at low currents, but coagulation predominates at high currents. The peroxi-coagulation process of dicamba at I>or=300 mA leads to more than 90% of coagulation, being much more efficient than its comparative electro-Fenton treatment with a Pt anode and 1 mM Fe(2+), where only mineralization takes place. For the chlorophenoxy compounds, electro-Fenton gives a slightly lower depollution than peroxi-coagulation, because more easily oxidable products are produced. Oxidation of chlorinated products during peroxi-coagulation is accompanied by the release of chloride ion to the solution. The efficiency of this method decreases with increasing electrolysis time and current. The decay of all herbicides follows a pseudo-first-order reaction, with a similar constant rate for 4-CPA, MCPA, 2,4-D and 2,4,5-T, and a higher value for dicamba.     

Culturability and concentration of indoor and outdoor airborne fungi in six single-family homes

In this study, the culturability of indoor and outdoor airborne fungi was determined through long-term sampling (24-h) using a Button Personal Inhalable Aerosol Sampler. The air samples were collected during three seasons in six Cincinnati area homes that were free from moisture damage or visible mold. Cultivation and total microscopic enumeration methods were employed for the sample analysis. The geometric means of indoor and outdoor culturable fungal concentrations were 88 and 102 colony-forming units (CFU) m(-3), respectively, with a geometric mean of the I/O ratio equal to 0.66. Overall, 26 genera of culturable fungi were recovered from the indoor and outdoor samples. For total fungal spores, the indoor and outdoor geometric means were 211 and 605 spores m(-3), respectively, with a geometric mean of I/O ratio equal to 0.32. The identification revealed 37 fungal genera from indoor and outdoor samples based on the total spore analysis. Indoor and outdoor concentrations of culturable and total fungal spores showed significant correlations (r = 0.655, p<0.0001 and r = 0.633, p<0.0001, respectively). The indoor and outdoor median viabilities of fungi were 55% and 25%, respectively, which indicates that indoor environment provides more favorable survival conditions for the aerosolized fungi. Among the seasons, the highest indoor and outdoor culturability of fungi was observed in the fall. Cladosporium had a highest median value of culturability (38% and 33% for indoor and outdoor, respectively) followed by Aspergillus/Penicillium (9% and 2%) among predominant genera of fungi. Increased culturability of fungi inside the homes may have important implications because of the potential increase in the release of allergens from viable spores and pathogenicity of viable fungi on immunocompromised individuals.