Relationship between space distribution of the benthic macroinvertebrates community and trophic state in a Neotropical reservoir (Itupararanga, Brazil)

The purpose of this work was to verify the benthic macroinvertebrates community responses through environmental factors along a headwater tropical reservoir. Samplings were taken with a Van-Veen grab along the reservoir in littoral and profundal regions and in the headwater, next to the dam and the middle of the reservoir. Samples were taken during both wet and dry seasons. Dissolved oxygen concentrations, electric conductivity, temperature and pH near the sediment have been performed in situ, at every sampling station by using a multiprobe and Secchi disc. Total water phosphorus and chlorophyll a concentrations were analyzed to determine the trophic state index. Sediment's organic matter, total phosphorus, nitrogen concentrations and granulometric composition were measured. In order to verify which environmental variables would have more influence over the benthic macroinvertebrates community, a canonical correspondence analysis (CCA) was performed. The total number of recorded taxa was 28. Among them, the family Chironomidae (Diptera) was the richest group (19 taxa). It can be proposed that the benthic macroinvertebrates community may be influenced by environmental conditions such as nutrient and organic matter availability, as well as dissolved oxygen concentration. Macroinvertebrates are adequate bioindicators of water quality due to their sensibility to environmental changes mentioned before. Chironomus sp, Limnodrilus hoffmeisteri and Branchiura sowerbyi comprises a group that can be considered bio-indicators of eutrophic conditions. A second group can be considered as indicator of mesotrophic conditions. The presence of two or more members from that group which comprises Tanytarsini spp, Fissimentum sp, Pelomus sp and Goeldichironomus sp, like predominant taxa, may indicates mesotrophic conditions.

Space-temporal dynamics of limnological variables in a floodplain wetland located at Ribeira do Iguape Valley (São Paulo, Brazil) at different hydrological periods

AIM: The main goal of this research was to investigate the influence of the hydrological pulses on the space-temporal dynamics of physical and chemical variables in a wetland adjacent to Jacupiranguinha River (São Paulo, Brazil); METHODS: Eleven sampling points were distributed among the wetland, a tributary by its left side and the adjacent river. Four samplings were carried out, covering the rainy and the dry periods. Measures of pH, dissolved oxygen, electrical conductivity and redox potential were taken in regular intervals of the water column using a multiparametric probe. Water samples were collected for the nitrogen and total phosphorus analysis, as well as their dissolved fractions (dissolved inorganic phosphorus, total dissolved phosphorus, ammoniacal nitrogen and nitrate). Total alkalinity and suspended solids were also quantified; RESULTS: The Multivariate Analysis of Variance showed the influence of the seasonality on the variability of the investigated variables, while the Principal Component Analysis gave rise in two statistical significant axes, which delimited two groups representative of the rainy and dry periods. Hydrological pulses from Jacupiranguinha River, besides contributing to the inputs of nutrients and sediments during the period of connectivity, accounted for the decrease in spatial gradients in the wetland. This "homogenization effect" was evidenced by the Cluster Analysis. The research also showed an industrial raw effluent as the main point source of phosphorus to the Jacupiranguinha River and, indirectly, to the wetland; CONCLUSIONS: Therefore, considering the scarcity of information about the wetlands in the study area, this research, besides contributing to the understanding of the influence of hydrological pulses on the investigated environmental variables, showed the need for adoption of conservation policies of these ecosystems face the increase anthropic pressures that they have been submitted, which may result in lack of their ecological, social and economic functions.

Meridional and zonal changes in water properties along the continental slope off central and northern Chile

[EN] The Humboldt-09 cruise covered a narrow meridional band along the Chilean continental slope (44?23º S). Here we use physical and biochemical data from a long meridional section (4000 km) and three short zonal sections (100 km) to describe the distribution of the different water masses found in this region. Six water masses were identified: Subantarctic Water (SAAW), Summer Subantarctic Water (SSAW), Subtropical Water (STW), Equatorial Subsurface Water (ESSW), Antarctic Intermediate Water (AAIW), and Pacific Deep Water (PDW). For the first time, a novel set of source water mass properties (or water types) is introduced for SSAW, and nutrient and dissolved oxygen water types are proposed for all the water masses. Optimum multiparameter (OMP) analysis was used through an iterative process to obtain a sound definition of the water types that minimizes the residuals of the method. Both the classic OMP and the quasi-extended OMP models reproduced the data rather well. Finally, the spatial distribution of the different water masses was calculated with the quasi-extended OMP, which is not influenced by the respiration of organic matter. The distribution of the different water masses is presented over the meridional and zonal transects and in property-property diagrams. A smooth meridional transition from subantarctic to tropical and equatorial water masses is observed in this area. This transition takes place in surface, central, and intermediate waters over distances of the order of 1000 km. The meridional transition contrasts with the abrupt zonal changes found in the cross-slope direction, which are of comparable magnitude but over distances of the order of 100 km. Both AAIW and SAAW (fresh and well oxygenated) partially mix with the hypoxic ESSW and, therefore, play an important role in the ventilation of the southern part of the oxygen minimum zone.

Hydrogeochemical characterization of Seehausen territory - Bremen

The aim of this thesis is to provide a geochemical characterization of the Seehausen territory (a neighborhood) of Bremen, Germany. In this territory it is hosted a landfill of dredged sediments coming both from Bremerhaven (North See) and Bremen harbor (directly on the river Weser). For this reason this work has been focused also on possible impacts of the landfill on the groundwaters (shallow and deep aquifer). The Seehausen landfill uses the dewatering technique to manage the dredged sediments: incoming sediments are put into dewatering fields until they are completely dried (it takes almost a year). Then they are randomly sampled and analyzed: if the pollutants content is acceptable, sediments are treated with other materials and used instead of raw material for embankment, bricks, etc., otherwise they are disposed in the landfill. During this work it has been made a study of the natural geology and hydrogeology of the whole area of interest, especially because it is characterized by ancient natural salt deposits. Then, together with the Geological Survey of Bremen and the Harbor Authority of Bremen there have been identified all useful piezometers for a monitoring net around the landfill. During the sampling campaign there have been collected data of the principal anions and cations, physical parameters and stable water isotopes. Data analysis has been focused particularly on Cl, Na, SO4 and EC because these parameters might be helpful to attribute geochemical trends to the landfill or to a natural background. Furthermore dataloggers have been installed for a month in some piezometers and EC, pressure, dissolved oxygen and temperature data have been collected. Finally there has been made a deep comparison between current and historical data (1996 – 2011) and between old interpolation maps and current ones in order to see time trends of the aquifer geochemistry.

Outdoor production of Isochrysis galbana (T-iso) in industrial scale photobioreactors and modelling of its photosynthesis and respiration rate

Isochrysis galbana is a widely-used strain in aquaculture in spite of its low productivity. To maximize the productivity of processes based on this microalgae strain, a model was developed considering the influence of irradiance, temperature, pH and dissolved oxygen concentration on the photosynthesis and respiration rate. Results demonstrate that this strain tolerates temperatures up to 35ºC but it is highly sensitive to irradiances higher than 500 µE·m-2·s-1 and dissolved oxygen concentrations higher than 11 mg·l-1. With the researcher group of the “Universidad de Almeria”, the developed model was validated using data from an industrial-scale outdoor tubular photobioreactor demonstrating that inadequate temperature and dissolved oxygen concentrations reduce productivity to half that which is maximal, according to light availability under real outdoor conditions. The developed model is a useful tool for managing working processes, especially in the development of new processes based on this strain and to take decisions regarding optimal control strategies. Also the outdoor production of Isochrysis galbana T-iso in industrial size tubular photobioreactors (3.0 m3) has been studied. Experiments were performed modifying the dilution rate and evaluating the biomass productivity and quality, in addition to the overall performance of the system. Results confirmed that T-iso can be produced outdoor at commercial scale in continuous mode, productivities up to 20 g·m-2·day-1 of biomass rich in proteins (45%) and lipids (25%) being obtained. The utilization of this type of photobioreactors allows controlling the contamination and pH of the cultures, but daily variation of solar radiation imposes the existence of inadequate dissolved oxygen concentration and temperature at which the cells are exposed to inside the reactor. Excessive dissolved oxygen reduced the biomass productivity to 68% of maximal, whereas inadequate temperature reduces to 63% of maximal. Thus, optimally controlling these parameters the biomass productivity can be duplicated. These results confirm the potential to produce this valuable strain at commercial scale in optimally designed/operated tubular photobioreactors as a biotechnological industry.

Sensitivity of atmospheric CO2 and climate to explosive volcanic eruptions

Impacts of low-latitude, explosive volcanic eruptions on climate and the carbon cycle are quantified by forcing a comprehensive, fully coupled carbon cycle-climate model with pulse-like stratospheric aerosol optical depth changes. The model represents the radiative and dynamical response of the climate system to volcanic eruptions and simulates a decrease of global and regional atmospheric surface temperature, regionally distinct changes in precipitation, a positive phase of the North Atlantic Oscillation, and a decrease in atmospheric CO2 after volcanic eruptions. The volcanic-induced cooling reduces overturning rates in tropical soils, which dominates over reduced litter input due to soil moisture decrease, resulting in higher land carbon inventories for several decades. The perturbation in the ocean carbon inventory changes sign from an initial weak carbon sink to a carbon source. Positive carbon and negative temperature anomalies in subsurface waters last up to several decades. The multi-decadal decrease in atmospheric CO2 yields a small additional radiative forcing that amplifies the cooling and perturbs the Earth System on longer time scales than the atmospheric residence time of volcanic aerosols. In addition, century-scale global warming simulations with and without volcanic eruptions over the historical period show that the ocean integrates volcanic radiative cooling and responds for different physical and biogeochemical parameters such as steric sea level or dissolved oxygen. Results from a suite of sensitivity simulations with different magnitudes of stratospheric aerosol optical depth changes and from global warming simulations show that the carbon cycle-climate sensitivity γ, expressed as change in atmospheric CO2 per unit change in global mean surface temperature, depends on the magnitude and temporal evolution of the perturbation, and time scale of interest. On decadal time scales, modeled γ is several times larger for a Pinatubo-like eruption than for the industrial period and for a high emission, 21st century scenario.

Iodide interaction with natural pyrite

29I is one of the major dose-determining nuclides in the safety analysis of deep storage of radioactive waste. Iodine forms anionic species that hardly sorb on the surfaces of common host-rock minerals. Recently, interest has arisen on the role of pyrite, an accessory mineral capable of binding anionic selenium. Whereas the interaction of selenium with pyrite is well documented, corresponding results on iodine sorption are still scarce and controversial. Pyrite is present in argicilleous rocks which are being considered in many countries as potential host rocks for a radioactive waste repository. The uptake of iodide (I−) on natural pyrite was investigated under nearly anoxic conditions (O2 < 5 ppm) over a wide concentration range (10−11–10−3 M total I−) using 125I as the radioactive tracer. Weak but measurable sorption was observed; distribution coefficients (R d) were less than 0.002 m3 kg−1 and decreased with increasing total iodide concentration. Iodide sorption was connected to the presence of oxidized clusters on the pyrite surface, which were presumably formed by reaction with limited amounts of dissolved oxygen. The results obtained indicated that pyrite cannot be considered as an effective scavenger of 129I under the geochemical conditions prevailing in underground radioactive waste geologic storage.

Physical-Biological Oceanographic Coupling Influencing Phytoplankton and Primary Production in the South China Sea

Two cruises were carried out in the summer and winter of 1998 to study coupled physical-chemical-biological processes in the South China Sea and their effects on phytoplankton stock and production. The results clearly show that the seasonal distributions of phytoplankton were closely related to the coupled processes driven by the East Asian Monsoon. Summer southwesterly monsoon induced upwelling along the China and Vietnam coasts. Several mesoscale cyclonic cold eddies and anticyclonic warm pools were identified in both seasons. In the summer, the upwelling and cold eddies, both associated with rich nutrients, low dissolved oxygen ( DO), high chlorophyll a (Chl a) and primary production ( PP), were found in the areas off the coast of central Vietnam, southeast of Hainan Island and north of the Sunda shelf, whereas in the winter they form a cold trough over the deep basin aligning from southwest to northeast. The warm pools with poor nutrients, high DO, low Chl a, and PP were found in the areas southeast of Vietnam, east of Hainan, and west of Luzon during the summer, and a northwestward warm jet from the Sulu Sea with properties similar to the warm pools was encountered during the winter. The phytoplankton stock and primary production were lower in summer due to nutrient depletion near the surface, particularly PO4. This phosphorus depletion resulted in phytoplankton species succession from diatoms to dinoflagellates and cyanophytes. A strong subsurface Chl a maximum, dominated by photosynthetic picoplankton, was found to contribute significantly to phytoplankton stocks and production.

An evaluation of a Lake Houston tributary, Cypress Creek, for contamination and water quality

Introduction. Lake Houston serves as a reservoir for both recreational and drinking water for residents of Houston, Texas, and the metropolitan area. The Texas Commission on Environmental Quality (TCEQ) expressed concerns about the water quality and increasing amounts of pathogenic bacteria in Lake Houston (3). The objective of this investigation is to evaluate water quality for the presence of bacteria, nitrates, nitrites, carbon, phosphorus, dissolved oxygen, pH, turbidity, suspended solids, dissolved solids, and chlorine in Cypress Creek. The aims of this project are to analyze samples of water from Cypress Creek and to render a quantitative and graphical representation of the results. The collected information will allow for a better understanding of the aqueous environment in Cypress Creek.^ Methods. Water samples were collected in August 2009 and analyzed in the field and at UTSPH laboratory by spectrophotometry and other methods. Mapping software was utilized to develop novel maps of the sample sites using coordinates attained with the Global Positioning System (GPS). Sample sites and concentrations were mapped using Geographic Information System (GIS) software and correlated with permitted outfalls and other land use characteristic.^ Results. All areas sampled were positive for the presence of total coliform and Escherichia coli (E. coli). The presences of other water contaminants varied at each location in Cypress Creek but were under the maximum allowable limits designated by the Texas Commission on Environmental Quality. However, dissolved oxygen concentrations were elevated above the TCEQ limit of 5.0 mg/L at majority of the sites. One site had near-limit concentration of nitrates at 9.8 mg/L. Land use above this site included farm land, agricultural land, golf course, parks, residential neighborhoods, and nine permitted TCEQ effluent discharge sites within 0.5 miles upstream.^ Significance. Lake Houston and its tributary, Cypress Creek, are used as recreational waters where individuals may become exposed to microbial contamination. Lake Houston also is the source of drinking water for much of Houston/Harris and Galveston Counties. This research identified the presence of microbial contaminates in Cypress Creek above TCEQ regulatory requirements. Other water quality variables measured were in line with TCEQ regulations except for near-limit for nitrate at sample site #10, at Jarvis and Timberlake in Cypress Texas.^

Carbonate saturation in the water column of station M8_056 off Cap Sao Vincente, Portugal (Table 1)

Changes in the dissolved oxygen content, the alkalinity, and the pH in sea water near the ocean floor are interpreted in terms of chemical and biochemical processes at the sediment water interface. A simple model provides a plausible explanation of the observed phenomena. Special emphasis is given to the importance of borate corrections in the calculation of the solution effects of calcium carbonate.