Riverine Zone Research Articles

Perennial transmission of malaria in the low altitude areas of Baringo County, Kenya

BackgroundMalaria causes the greatest public health burden in sub-Saharan Africa where high mortality occurs mainly in children under 5 years of age. Traditionally, malaria has been reported mainly in the lowlands endemic regions of western Kenya, while the highlands of the Rift Valley have been relatively free except for the sporadic epidemics in some areas. Baringo County is located in the Kenyan highlands. The county generally experiences seasonal transmission of malaria. A few hotspots which experience continuous malaria transmission in the county do however exist. The objective of this study was to assess malaria infection status and identify areas with continuous transmissions with a view to mapping out probable transmission hot spots useful in mounting focused interventions within the county.MethodsSystematic sampling was employed to identify 1668 primary school pupils from fifteen primary schools located in 4 ecological zones (lowland, midland, highland and riverine) of three sub-counties of Baringo. Finger prick blood sampling was done every 4 months (during the dry season in February/March, after the long rains in June/July and short rains in November 2015). Malaria occurrence was tested using rapid diagnostic test kit (CareStart HRP-2 Pf). Microscopic examination was done on all RDT positive and 10% of negative cases.ResultsA total of 268 (16.1%), out of 1668 pupils tested positive for Plasmodium falciparum by RDT; 78% had a single episode, 16.8% had 2 episodes, 4.9% had 3 episodes and 0.4% had 4 episodes. The riverine zone had the highest malaria cases (23.2%) followed by lowlands (0.9%). No malaria cases were detected in the midland zone while highland zone recorded only few cases during the third follow up. Up to 10.7% of malaria cases were reported in the dry season, 2.9% during the long rains and 5.7% in short rains season.ConclusionsMalaria infection was prevalent in Baringo County and was mainly restricted to the riverine zone where transmission is continuous throughout the year. High malaria prevalence occurred in the dry season compared to the wet season. Even though malaria transmission is relatively low compared to endemic regions of Kenya, there is a need for continued monitoring of transmission dynamics under changing climatic conditions as well as establishing expanded malaria control strategies especially within the riverine zone which would include an integrated mosquito control and chemotherapy for infected individuals.

Effect of climatic variability on malaria trends in Baringo County, Kenya

BackgroundMalaria transmission in arid and semi-arid regions of Kenya such as Baringo County, is seasonal and often influenced by climatic factors. Unravelling the relationship between climate variables and malaria transmission dynamics is therefore instrumental in developing effective malaria control strategies. The main aim of this study was to describe the effects of variability of rainfall, maximum temperature and vegetation indices on seasonal trends of malaria in selected health facilities within Baringo County, Kenya.MethodsClimate variables sourced from the International Research Institute (IRI)/Lamont-Doherty Earth Observatory (LDEO) climate database and malaria cases reported in 10 health facilities spread across four ecological zones (riverine, lowland, mid-altitude and highland) between 2004 and 2014 were subjected to a time series analysis. A negative binomial regression model with lagged climate variables was used to model long-term monthly malaria cases. The seasonal Mann–Kendall trend test was then used to detect overall monotonic trends in malaria cases.ResultsMalaria cases increased significantly in the highland and midland zones over the study period. Changes in malaria prevalence corresponded to variations in rainfall and maximum temperature. Rainfall at a time lag of 2 months resulted in an increase in malaria transmission across the four zones while an increase in temperature at time lags of 0 and 1 month resulted in an increase in malaria cases in the riverine and highland zones, respectively.ConclusionGiven the existence of a time lag between climatic variables more so rainfall and peak malaria transmission, appropriate control measures can be initiated at the onset of short and after long rains seasons.

Monitoring spatiotemporal variations in nutrients in a large drinking water reservoir and their relationships with hydrological and meteorological conditions based on Landsat 8 imagery

Nutrient enrichment is a major cause of water eutrophication, and variations in nutrient enrichment are influenced by environmental changes and anthropogenic activities. Accurately estimating nutrient concentrations and understanding their relationships with environmental factors are vital to develop nutrient management strategies to mitigate eutrophication. Landsat 8 Operational Land Imager (OLI) data is used to estimate nutrient concentrations and analyze their responses to hydrological and meteorological conditions. Two well-accepted empirical models are developed and validated to estimate the total nitrogen (TN) and total phosphorus (TP) concentrations (CTN and CTP) in the Xin'anjiang Reservoir using Landsat 8 OLI data from 2013 to 2016. Spatially, CTN decreased from the transition zone to the riverine zone and the lacustrine zone. On the other hand, CTP decreased from the riverine zone to the transition zone and the lacustrine zone. Temporally, CTN displayed elevated values during the late fall and winter and had lower values during the summer and early fall, whereas CTP was higher during the spring and lower during the winter. Among the environmental factors, the rainfall and the inflow rate have strong positive correlations with the nutrient concentrations. TN is more sensitive to meteorological factors (wind speed, temperature, sunshine duration), and the spatial driving forces vary among the different sections of the reservoir. However, TP is more easily influenced by human activities, such as fishery and agricultural activities. Current results would improve our understanding of the drivers of nutrients spatiotemporal variability and the approach in this study can be applicable to other similar reservoir to develop related strategies to mitigate eutrophication.

Addressing uncertainties in the environmental sustainability of limno‐reservoirs: insights from the synthesis of multidisciplinary research

AbstractLarge reservoirs in the Mediterranean area exhibit a variety of negative impacts resulting from exploitation of their water, many a result of large water‐level fluctuations. Water managers in Spain have implemented various mitigation measures to reduce these negative impacts. One such measure is construction of small dams in the riverine zone of large reservoirs to create a small waterbody with a constant water level (i.e. a ‘limno‐reservoir’) to provide the environmental and recreational services that the main reservoir cannot provide due to water‐level variations. To this end, the Pareja Limno‐reservoir was built in 2006 in a sidearm of the Entrepeñas Reservoir (Guadalajara, central Spain). As its environmental sustainability was not assessed prior to construction, however, there are some uncertainties about the ability of the limno‐reservoir to provide the expected environmental and recreational services. Accordingly, a multidisciplinary study was conducted on the Pareja Limno‐reservoir to shed on its environmental sustainability. This study addressed three relevant issues associated with the limno‐reservoir, focusing on water availability, water quality and the risk of sediment filling. This study reviews the research conducted to date, including an integrative discussion that endeavours to address these issues. The Pareja Limno‐reservoir is currently a successful tourist and recreational aquatic resource. The results of this study, however, reveal its recreational and environmental value may be reduced, especially as a constant water level at the maximum capacity of the limno‐reservoir cannot be guaranteed. The conclusions of this study may be useful for reservoir managers by providing guidelines for assessing the environmental sustainability of limno‐reservoirs.

Distribution and ecological preferences of the freshwater lineage LimA (genus Limnohabitans) revealed by a new double hybridization approach.

The ecological relevance and factors shaping dynamics of Limnohabitans sp. have been largely studied by fluorescence in situ hybridization with a 16S rRNA probe targeting the R-BT group (lineages LimBCDE), but not lineage LimA. Consequently, ecology and distribution of LimA remained unknown. We developed a double hybridization strategy using a novel 23S rRNA probe specifically targeting LimA and LimE that in combination with the existing R-BT probe can discriminate LimA populations. This technique was applied for more than 1000 samples from 46 freshwater sites including long-term data sets from oligo-mesotrophic Lake Zurich, CH and meso-eutrophic Římov reservoir, CZ. LimA was ubiquitously distributed and highly abundant. Observed ecological preferences of LimA in Lake Zurich were in general similar to already reported for Limnohabitans with highest numbers in surface waters during growing seasons. Three times higher densities of LimA were detected in Římov reservoir, where they were significantly more abundant at the riverine zone especially after flood events that introduced fresh terrestrial DOM (dissolved organic matter). Moreover,statistical analyses of biological and physicochemical parameters obtained from small dynamic water bodies confirmed a correspondence between LimA and allochthonous DOM, in opposite to R-BT that was more related to algal primary production.

English

Over the years, there is a direct linkage of township drains and streams to the Opa reservoir, Obafemi Awolowo University, Nigeria. Hence the spatial and temporal variations of the reservoir’s water quality were studied between November 2012 and October 2013 to investigate the effect of these discharges on these.  Physical, chemical as well as the oxygen parameters of the water were investigated using standard techniques. The parameters determined revealed considerable temporal variations with the rainy season averaged concentration of COD, TOC, OM, TSS, TS, turbidity, apparent colour, true colour, sodium, and phosphate significantly higher (p<0.05) than those of the dry season. Spatially, DO, TSS, TS, organic matter and TOC decreased significantly (p<0.05) from riverine to the lacustrine (dam site). However, calcium, sulphate, and electrical conductivity showed significant increases (p<0.05) from the riverine zone section towards the dam site. Vertically, sulphate, bicarbonate, COD, TOC, chloride, TSS, TS, turbidity, apparent colour, true colour and sodium ion values increased significantly (p<0.05) from the surface down to the bottom. Conversely, magnesium, total hardness, nitrate, BOD, DO, electrical conductivity, acidity, carbonate, alkalinity, TDS and pH values decreased (p<0.05) from water surface to the bottom of the reservoir. Therefore, the discharges from the catchment area of Opa reservoir could pose a level of risk to the aquatic ecosystem as well as the community if not well treated before being supplied. Key words: Spatial, temporal, water quality, zones, risk level, source.

Malaria Vector Species Distribution and Seasonal Population Dynamics across Varied Ecological Zones in Baringo County, Kenya

Vector populations fluctuate on a seasonal basis annually. Knowledge on seasonal abundance and distribution of vector species at the local level would improve vector control programmes and contribute to malaria prevention. Despite this, information on malaria vector species distribution and seasonal fluctuations in Baringo County is scarce. This study examined distribution and seasonal abundance of malaria vector species in Baringo. The study area was stratified into four ecological zones namely; lowland, riverine, midland and highland. Monthly collection of outdoor and indoor mosquitoes was conducted between June 2015 and May 2016 using CDC light traps and pyrethrum spray collection respectively. A total of 6,113 anopheline mosquitoes belonging to four species were collected across the four ecological zones. Anopheles gambiae was the most abundant malaria vector species accounting for (93.8%) while An. pharoensis and An . funestus accounted for 4.8% and 1.1% respectively. Mosquitoes were mainly collected from lowlands (79.8%) and riverine (19.0%) zones. Malaria vector abundance was higher in the dry season compared to the rainy season. Anopheles gambiae abundance showed high positive correlation with rainfall in the riverine zone only (r=0.7). Knowledge gained from this study, on malaria vector species distribution and seasonal abundance at local level, is important in implementation of control strategies against malaria by the Baringo County Health Department. The findings highlight the seasons when malaria cases are likely to be higher due to vector abundance and also inform specific areas to target for intervention.

EFFECT OF RIVER SUPPLY ON THE DISTRIBUTIONOF MACROELEMENTS IN THE SEDIMENTS OF A RETENTION RESERVOIR - A CASE STUDY OF LOJE RESERVOIR

The aim of the studies was to evaluate the influence of the 30-year operation of a small retention reservoir fed with water from a forest-agricultural catchment area on the contents of selected mineral elements substances in bottom deposits. The studies were carried out in the Loje dam reservoir (N 53o7 28 , E 20o48 20 ), supplied by the regulated Loj wka stream. Deposit samples were collected in four transects perpendicular to the reservoir axis in the center of riverine and lacustrine zones and two transects in the transitional zone. In the sediment samples, the following parameters were determined: dry matter content, pH (in H2O) and the concentrations of organic matter, organic carbon, total nitrogen, total phosphorus, potassium, calcium, sodium, magnesium, iron, sulfur, chlorides, copper, manganese and zinc. Changes in the reservoir were evaluated with the use of geochemical indicators (C:N, Fe:Ca, Fe:Mn, Cu:Zn, Ca:Mg). The results showed the highest content of organic matter and its components (Ntot., Ptot., Ca, Na and Mg) in deposits sampled along the course of the main water stream flowing through the reservoir. In deposits sampled from the reservoir's riverine and transitional zones, the predominant macroelement was Ca, and in samples from the lacustrine zone Fe. On average, the content of the analyzed macroelements in deposits sampled from various zones created the following descending order: Ca > S > Ntot. > Fe > Mg > K > Ptot. > Na. Our results indicate that the accumulated deposits had been formed in shallow waters and that organic matter originated mainly from macrophytes and higher plants rich in cellulose.

Textural Features - Indicators of Pollution

The dynamic estuarine environment influences the sedimentary processes like physical and chemical characteristics of sediments. The dominant factor in sediment transport is the motion of water. The particles are moved by the current of water in the way of sliding, rolling, siltation and suspension. Texture a peculiar feature of the sediment which describes the nature of soil. In the water bodies, the textural characteristics reflect how long the sedimentary particles are affected by organic and inorganic contaminants. For the present study three different estuaries namely Kadinamkulam backwater, Veli Lake and Poonthura backwater around the Trivandrum city of Kerala were chosen as study sites. From each estuary three stations such as riverine zone, middle zone and bar mouth zone were fixed for collection of samples. Monthly collection of sediment for a period of one year from April-2014 to March 2015 was carried out. Regular analysis of texture was done and calculated the results. The observations from the present study showed that most of the months and in all the selected stations sandy soil dominates. The clayey and silty soil was reported in certain stations in specific seasons.

О водохозяйственных проблемах на примере Оренбуржья

Interconnection of water/economic problems with a region forest content and necessity of forest/melioration measures and actions on water protection against pollution and depletion on the basis of the advanced techniques application has been shown. 337 water intake wells located mostly in the riverine zones where the main resources of fresh water situated have been tested. The investigation object was a zone of active water exchange of the regional hydrosphere with macro- and mezzo-basins of water runoff. It has been stated that the increasing scales of the technogenic processes cause negative geo/dynamic phenomena, growing natural disasters and hazardous risks. Measures on mitigation and prevention of the negative geo/dynamic processes have been vindicated and developed. Some methods of assessment of groundwater formation processes, as well as laboratory, calculation/graphic and experimental methods have been applied. Geological/geophysical and hydro/geological information with the results of physical/chemical analysis of natural and waste water samples (> 2000 samples) have been summarized. Some cases of technogenic disturbance of the balance-unbalance water-rock-gas-living being system have been investigated. It has been concluded that it is necessary to stop deforestation, plowing up, dam construction and any other construction but water/protective one in river floodplains to preserve water resources. It is recommended to apply barrier techniques to protect water resources against pollution and to purify water.

Прибрежная травяная растительность пойм рек Вычегда и Печора. Класс Phragmito–Magno-Caricetea Klika in Klika et Novák 1941

The present study continues a series of publications by the authors on the diversity of the herb vegetation in the floodplains of the Vychegda and Pechora rivers and their tributaries (Komi Republic). The floristic classification of the orders Molinietalia Koch 1926 and Arrhenatheretalia R. Tx. 1931 was published earlier (Shushpannikova, Yamalov, 2013, 2014). The results of classification of communities belonging to the class Phragmito–Magno-Caricetea Klika in Klika et Novák 1941 are discussed in this paper in accordance with principles of the Braun-Blanquet approach (Braun-Blanquet, 1964; Mirkin, Naumova, 1998). Analysis was based on 268 relevés made in 1981–2016. The assessment of environmental parameters was performed by ecological methods by L. G. Ramensky (Ramensky et al., 1956). Syntaxonomic diversity of the vegetation of the class Phragmito–Magno-Caricetea in the floodplain of rivers Vychegda and Pechora is presented by 3 orders (Phragmitetalia W. Koch 1926, Oenanthetalia aquaticae Hejny in Kopecky et Hejny 1965 and Magno-Caricetalia Pignatti 1953), 4 alliances (Phragmition communis W. Koch 1926, Nardosmion laevigatae Klotz et Köck 1986, Equisetion arvensis Mirkin. et Naumova in Kononov et al. 1989 emend. Taran 1995 and Magnocaricion elatae Koch 1926) and 13 associations. The communities of the class Phragmito–Magno-Caricetea, as well as the order Molinietalia of Molinio–Arrhenatheretea, are located at all levels of the floodplains and are characterized by a variety of humidification conditions. However, the communities of the class Phragmito–Magno-Caricetea are characterized by higher humidification indices (72.2–86.3) compared to meadow vegetation the order Molinietalia of the class Molinio-Arrhenatheretea of (68.8–74.4). A lot of associations, heterogeneous in their floristic composition, can be divided into 9 subassociations and 10 variants. New 4 subassociations (caricetosum vesicariae, equisetosum fluviatilis, persicaretosum amphibiae and lysimachetosum vulgaris), are included into ass. Caricetum gracilis Savich 1926. The peculiarities of the floristic composition of the above mentioned associations, as well as their distribution and ecology are discussed. The distinguished associations are well differentiated by their elevation position on the floodplains. The communities of the ass. Caricetum gracilis are located at all levels of the floodplainons; these of Agrostio stoloniferae–Equisetetum arvensis — on the highest ones; Equisetetum fluviatilis — on the lowest part of the floodplains in the riparian zone. The described communities are located on the soils with various ecological indi­cators. The distinguished associations are differentiated by the levels of humidification (65.9–89.9), mean figures — 70.3–86.3. The communities of the ass. Agrostio stoloniferae–Equisetetum arvensis occupy the driest sites (65.9–72.9); these of associations ­Equisetetum fluviatilis and Nardosmietum laevigatae — the wettest ones (80.7–87.8). The ass. Caricetum aquatilis has a wide range of humidification (72.7–89.9). The variability of humidification varies from alternating to high values (6.4–12.0). The ­greatest differences in humidification are experienced by the communities of the ass. Caricetum gracilis (5.5–12.0). Тhe communities of the ass. Agrostio stoloniferae–Equisetetum arvensis occupy the richest (10.5–15.0) and alluvial soils (4.0–5.0). They are located on the low level in the riverine and middle zone of the floodplain and are formed by annual flooding on alluvial deposits. The distinguished associations are differentiated by pH (3.0–8.0), mean figures — 4.5–7.0. The communities of the associations Caricetum juncellae, Caricetum gracilis and Caricetum acutae–rostratae are located on the most acidic soil; these of the ass. Equisetetum fluviatilis — on the neutral ones. The associations are distributed by the scale of pasture digression in range 2.5–4.5, mean figures — 3.0–3.9. The communities are used for hay-making. The question of the boundary between the meadow vegetation, lowland swamp and semi-aquatic vegetation remains unsolved. The communities of the class Phragmito–Magno-Caricetea described in this paper belongs to meadows. Ass. Nardosmietum laevigatae (previously referred to the class Galio-Urticetea Pass. 1967) is included into the order Phragmitetalia W. Koch 1926. The communities of the ass. Agrostio stoloniferae–Equisetetum arvensis have a mesophilic species composition and low moisture values, so they represent a transition between the class Molinio-Arrhenatheretea order Molinietalia and class Phragmito–Magno-Caricetea. A comparison of species composition of the syntaxa in Komi Republic and that in other regions of the Eastern Europe and the Asian part of Russia showed that the semiaquatic communities of the Komi Republic have low species diversity. It is less than 16 species on sample plot. The richest are communities of the associations Caricetum gracilis and Carici acutae–Phalaroidetum arundinaceae. 101 vascular plant species are recorded in 268 geobotanical relevés of the class Phragmito–Magno-Caricetea. The aboveground phytomass varies from 30–80 g/m2 (Agrostio stoloniferae–Equisetetum arvensis) to 420 г/м2 (Phalaroidetum arundinaceae).

Temporal and spatial fluctuations of heavy metals in Opa Reservoir, Ile-Ife, Nigeria

The Opa Reservoir, established for water supply to the Obafemi Awolowo University community, over the years has received direct linkage to township drains as a result of the widening and dredging of its river channels. The current study aimed at documenting monthly heavy metal loads at its riverine, transition and lacustrine zones in 2012–2013. Most of the heavy metals, analysed using an atomic absorption spectrophotometer, occurred within wide ranges, with coefficients of variation ranging from 60% to 300%, although the differences in heavy metal loads between the different zones were statistically insignificant at both the surface and bottom levels. The overall order of dominance of the metals was Ni > Cu > Fe > Zn > Cd = Cr > Pb, with nickel concentration being very high throughout. Heavy metal total mean concentration was higher during the rainy season (1.889 mg l−1) than the dry season (1.503 mg l−1) irrespective of sampling sites, having highly significant seasonal differences (p < 0.001) in Ni, Cd, Fe and Cu concentrations. The mean concentrations of Zn (0.074 mg l−1), Fe (0.176 mg l−1), Cu (0.507 mg l−1) and Pb (0.004 mg l−1) were within the WHO acceptable limit. However, the recorded levels of toxic elements Cd (0.031 mg l−1) and Ni (0.905 mg l−1) pose potential health risk to water consumers.

Impoundments affect fish reproduction regardless of reproductive strategy

AbstractMajor changes to local river habitats, after impoundment, are expected to restrict the reproductive activity of fishes with migratory strategies, although the changes are not expected to have relevant effects on fishes with other strategies. The reproductive activity of fishes with different reproductive strategies was evaluated along a longitudinal gradient before, and after, the formation of a reservoir on the Tocantins River (Tocantins State, Brazil). Samples were collected at six sites distributed along 80‐km stretch of the reservoir (R1 to R6 in the upstream–downstream direction) before and after the impoundment. The highest mean values of the reproductive activity index (RAI), considering all species in the river phase, were recorded for the intermediate segments (R4). The reproductive activity was classified as intense at the two sites located further upstream (R2 and R1). The highest mean RAI value after impoundment was observed for the site further upstream (R1). The reproductive activity was classified as intense, however, at every site, except for R6. Regardless of the reproductive strategy, mean RAI values were higher in this phase at site R1, particularly for long‐distance migratory species (LDM). The most lacustrine area (R6) was only relevant for the group of species with parental care. For non‐long‐distance migratory species, without parental care, the reproductive activity was intense at every site, except for R6. Overall, after the impoundment, the fish species tended to seek more lotic environments to spawn, including the riverine zone of the reservoir and side tributaries, regardless of the reproductive strategy. The results of this study provide evidence that impoundments affect the reproduction of the fish, independent of the reproductive strategy, although the intensity of the effect is different for each group.

Hydrological controls on cascade reservoirs regulating phosphorus retention and downriver fluxes.

Many coastal rivers have a system of cascade reservoirs, but the role of these reservoirs in regulating nutrient transport from watershed to coast is still unknown. In this study, phosphorus (P) in surface water and top sediment was investigated along the North Jiulong River (southeast China) under three hydrological conditions (high flow, medium flow and low flow) in 2012-2013, and P dynamics in a cascade reservoir (Xipi Reservoir) were studied on a monthly scale. Results showed that the concentrations of dissolved reactive phosphorus (DRP) consistently decreased longitudinally in the upper river with the lowest values observed in the section of cascade reservoirs, likely due to tributary inputs and in situ uptakes. The decrease was most rapid during base flow when DRP was highest in the free-flowing river section and lowest in cascade reservoirs. Results from monthly monitoring on the Xipi Reservoir showed general downriver decreases in DRP, total particulate phosphorus (TPP) and total phosphorus (TP) in the riverine zone and transition zone. Mass balance results on an annual basis suggest that the Xipi Reservoir (lacustrine zone) was an overall sink for TPP (6% retention) but somewhat a source of DRP (-0.3%) with TP retention (1%). Even scaled up to the whole cascade reservoir system, P retention was low compared with worldwide reservoirs, which we ascribe to the high P loading and short hydraulic residence time. Nevertheless, major processes controlling P retention in coastal rivers with cascade reservoirs varied from sedimentation in the dry-cold season to biotic transformation in the wet-warm season, thereby affecting loading and composition of P from watershed to the coast. This study highlights the hydrological controls on the role of cascade reservoirs in regulating P retention and downriver fluxes in different seasons.

Metal Signature of Atmospheric Aerosol from Kochi, the Queen of Arabian Sea, Kerala, India

The present research article highlights the metal (Cd, Cu, Pb, Zn and Fe)distribution pattern in the RSPM generated in different hot spot sites located at Kochi, theQueen of Arabian Sea. These sampling sites are categorized under three different zonesas estuarine, riverine, and coastal. Two sampling phases are selected in order to check theconsistency in pollution trend after a two year gap and are described in Phase I and PhaseII, respectively. Metals are noticed to be intensely concentrated in the post monsoonmonths in both phases. Among the metals, Fe is revealed as the prominent metal at theestuarine sites. Estuarine and riverine zone expresses the overall enrichment pattern withslight difference at coastal regime in phase I. In phase II, insignificant metal load withirregular pattern is observed. Source apportionment study reveals that major sources ofmetals are from automobile exhausts and the estuarine zone is entangled with 45.9%.

Metals in sediments: bioavailability and toxicity in a tropical reservoir used for public water supply.

Sediments may be a repository of contaminants in freshwater ecosystems. One way to assess the quality of this compartment, in terms of potentially bioavailable metals, is by the analysis of acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM). In order to investigate the bioavailability, toxicity, and compartmentalization of different metals (Cd, Cr, Cu, Ni, Pb, Zn), sampling of surface sediments was performed at nine stations along the Paiva Castro reservoir (São Paulo, Brazil). The metals were analyzed using atomic absorption spectroscopy. Sediment organic matter (OM), organic carbon (OC), and grain size were also measured. The parameters pH, EH, temperature, and dissolved oxygen were determined at the sediment-water interface. Chronic and acute toxicological tests were performed with sediments from the area where water was extracted for the public water supply. Low levels of OM, associated with loss of stratification in the water column, explained the relatively low AVS values. The molar ratio ∑[SEM]-[AVS]/fOC was less than 130 mmol/kg(-1) for all the sampling stations, indicating that the metals were not bioavailable. With the exception of Cd, metal levels were in accordance with background concentrations and the threshold effect level (TEL) established by the Canadian Council of Ministers of the Environment. The ecotoxicological tests confirmed the absence of toxic effects to biota. Application of principal component analysis indicated the presence of four compartments along the reservoir: (1) a riverine zone, potentially threatened by contamination with Cd; (2) an intermediate zone; (3) a limnic area; and (4) the area where water was taken for the public water supply.

Manejo y aprovechamiento de la agrobiodiversidad en el sistema milpa del sureste de México

&lt;p&gt;En este trabajo, se describió y clasificó la agrobiodiversidad del sistema milpa en la región tropical de San Felipe Usila, Oaxaca, México, a partir de la percepción de agricultores sobre la diversidad fenotípica y usos de la variabilidad intraespecífica y biodiversidad recolectada a nivel de parcela. Bajo un enfoque de agroecosistemas, se obtuvo información de tres sistemas de producción, denominados: laderas pedregosas (&amp;gt; 18° de pendiente), lomeríos irregulares y pedregosos con pendientes entre 6 y 18°, y terrenos planos (&amp;lt; 6°) de zonas ribereñas. Así, con el objetivo de registrar la percepción de diversidad y usos de la agrobiodiversidad, se aplicaron entrevistas a 200 agricultores de once comunidades indígenas Chinantecas de San Felipe Usila, mediante un cuestionario semiestructurado. En el análisis de ji-cuadrada, se determinaron relaciones significativas (P &amp;lt; 0.05) entre agroecosistemas y variantes fenotípicas de frijol y maíz, cultivos intercalados, regímenes de humedad para la siembra, superficie sembrada y fechas de siembra, de floración y cosecha de maíz. En el análisis de correspondencia múltiple, se distinguen patrones de diversidad, uso y manejo en relación a regiones geográfico-culturales de localización de los agroecosistemas y parcelas. En las parcelas de producción se siembran, cultivan y recolectan hasta 26 especies, las principales son: maíz (cinco variantes fenotípicas), frijol (21 variedades y poblaciones nativas), calabaza (cuatro variantes) y yuca (tres variantes). También fue notorio el alto uso de pesticidas y fertilizantes químicos, hasta 22 productos diferentes.&lt;/p&gt;

Salinity variation in the macrotidal mixing zone: the Paracauari River estuary, Marajó Island (Northern Brazil)

ABSTRACT Monteiro, S.M. and Robrini, M., 2016. Salinity variation in the macrotidal mixing zone: the Paracauari River estuary, Marajo Island (Northern Brazil). In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 93–97. Coconut Creek (Florida), ISSN 0749-0208. The objective of this study is to delineate the estuarine zones (Riverine Zone – RZ, under river influence; Mixing Zone – MZ, under marine influence) across different seasonal periods in the macrotidal Paracauari River estuary – Marajo Island (Northern Brazil). We measured salinity (S) and electric conductivity (EC) in the water column using a multi-parameter probe. We also collected data on suspended particulate matter (SPM – gravimetric estimation) along 40 km of the estuary during higher rainfall (660 mm), transitional (260 mm), and lower rainfall (10 mm) periods in 2008. The first sampling st...

Spatio-temporal variabilities of nutrients and chlorophyll, and the trophic state index deviations on the relation of nutrients-chlorophyll-light availability

The object of this study was to determine long-term temporal and spatial patterns of nutrients (nitrogen and phosphorus), suspended solids, and chlorophyll (Chl) in Chungju Reservoir, based on the dataset of 1992 – 2013, and then to develop the empirical models of nutrient-Chl for predicting the eutrophication of the reservoir. Concentrations of total nitrogen (TN) and total phosphorus (TP) were largely affected by an intensity of Asian monsoon and the longitudinal structure of riverine (Rz), transition (Tz), and lacustrine zone (Lz). This system was nitrogen-rich system and phosphorus contents in the water were relatively low, implying a P-limiting system. Regression analysis for empirical model, however, showed that Chl had a weak linear relation with TP or TN, and this was mainly associated with turbid, and nutrient-rich inflows in the system. The weak relation was associated with non-algal light attenuation coefficients (Kna), which is in versely related water residence time. Thus, values of Chl had negative functional relation (R 2 = 0.25, p 0] and the effects of zooplankton grazing were also minor [TSI (Chl) – TSI (TP) > 0; TSI (SD) – TSI (Chl) > 0].

Spatial variations in fish assemblage structure in a southeastern Brazilian reservoir.

We assessed the fish assemblage structure and composition of Nova Ponte Reservoir (Araguari River, Upper Paraná Basin, Brazil). We observed significant differences in abundance (p = 0.0003), richness (p = 0.0005) and diversity (p = 0.02) between lacustrine and riverine zones of the reservoir. Nine species were significantly more abundant in the riverine region: Astyanax altiparanae, Astyanax gr. fasciatus, Galeocharax knerii, Hoplias intermedius, Hypostomus sp., Leporinus friderici, Leporinus obtusidens, Pimelodus maculatus and Schizodon nasutus. The results indicated a longitudinal gradient in the composition and abundance of fishes in Nova Ponte Reservoir, reinforcing the importance of freely flowing riverine reaches for conserving native neotropical ichthyofauna and reflecting the strong adaptation of these species to riverine systems.