210Po bioaccumulation in coastal sand dune wild legumes--Canavalia spp. of southwest coast of India

In view of considerable natural background radioactivity reported from southwest coast of India, the current study documents bioaccumulation of 210Po in two dominant coastal sand dune perennial mat-forming wild legumes, Canavalia cathartica and C. maritima. Root, stem, leaf, mature beans, dry seeds and rhizosphere sand were analyzed for 210Po concentration. 210Po activity decreased in the order of leaves > roots > seeds > stems > beans. The highest 210Po activity was recorded in rhizosphere sand samples (5.78-5.88 Bq kg(-1)) followed by the leaf samples (3.27-3.07 Bq kg(-1)), while it was lowest in mature beans (0.13-0.20 Bq kg(-1)). 210Po activities or tissue moisture between plant species were not significantly different (p > 0.05; t-test). But 210Po activity vs. moisture differed significantly in all tissues (p = 0.0001), vegetative tissues (root, stem and leaf) (p = 0.0016), seeds (p = 0.0393) and proteins in seeds (p = 2.355 x 10(-6)) indicating the importance of moisture and protein in 210Po accumulation. Although 210Po has affinity for proteins, it did not concentrate too much in seed proteins of Canavalia. Concentration of 210Po in mature beans is at safe levels as fisher folk only consume tender pods occasionally. 210Po activity in Canavalia is compared with other plant materials. As the landraces of C. cathartica and C. maritima are distributed throughout pantropical coastal areas, the current study emphasizes on considering them as bioindicators to monitor 210Po in coastal sand dune biomes and in turn the health of coastal population.     

Impacts of Climate Change on Hydrology and Water Resources in the Boise and Spokane River Basins1

Jin, Xin and Venkataramana Sridhar, 2012. Impacts of Climate Change on Hydrology and Water Resources in the Boise and Spokane River Basins. Journal of the American Water Resources Association (JAWRA) 48(2): 197‐220. DOI: 10.1111/j.1752‐1688.2011.00605.x Abstract: In the Pacific Northwest, warming climate has resulted in a lengthened growing season, declining snowpack, and earlier timing of spring runoff. This study characterizes the impact of climate change in two basins in Idaho, the Spokane River and the Boise River basins. We simulated the basin‐scale hydrology by coupling the downscaled precipitation and temperature outputs from a suite of global climate models and the Soil and Water Assessment Tool (SWAT), between 2010 and 2060 and assess the impacts of climate change on water resources in the region. For the Boise River basin, changes in precipitation ranged from ?3.8 to 36%. Changes in temperature were expected to be between 0.02 and 3.9°C. In the Spokane River region, changes in precipitation were expected to be between ?6.7 and 17.9%. Changes in temperature appeared between 0.1 and 3.5°C over a period of the next five decades between 2010 and 2060. Without bias‐correcting the simulated streamflow, in the Boise River basin, change in peak flows (March through June) was projected to range from ?58 to +106 m³/s and, for the Spokane River basin, the range was expected to be from ?198 to +88 m³/s. Both the basins exhibited substantial variability in precipitation, evapotranspiration, and recharge estimates, and this knowledge of possible hydrologic impacts at the watershed scale can help the stakeholders with possible options in their decision‐making process.     

Using intra-flock association patterns to understand why birds participate in mixed-species foraging flocks in terrestrial habitats

Bird species are hypothesized to join mixed-species flocks (flocks hereon) either for direct foraging or anti-predation-related benefits. In this study, conducted in a tropical evergreen forest in the Western Ghats of India, we used intra-flock association patterns to generate a community-wide assessment of flocking benefits for different species. We assumed that individuals needed to be physically proximate to particular heterospecific individuals within flocks to obtain any direct foraging benefit (flushed prey, kleptoparasitism, copying foraging locations). Alternatively, for anti-predation benefits, physical proximity to particular heterospecifics is not required, i.e. just being in the flock vicinity can suffice. Therefore, we used choice of locations within flocks to infer whether individual species are obtaining direct foraging or anti-predation benefits. A small subset of the bird community (5/29 species), composed of all members of the sallying guild, showed non-random physical proximity to heterospecifics within flocks. All preferred associates were from non-sallying guilds, suggesting that the sallying species were likely obtaining direct foraging benefits either in the form of flushed or kleptoparasitized prey. The majority of the species (24/29) chose locations randomly with respect to heterospecifics within flocks and, thus, were likely obtaining antipredation benefits. In summary, our study indicates that direct foraging benefits are important for only a small proportion of species in flocks and that predation is likely to be the main driver of flocking for most participants. Our findings apart, our study provides methodological advances that might be useful in understanding asymmetric interactions in social groups of single and multiple species.     

Lake pollution in Ibadan,Nigeria

An investigation was made of the sources and degree of pollution of Ogunpa lake, situated in Ibadan, Nigeria. It was shown that the lake receives a variety of waste effluents from domestic and industrial sources which discharge into the Ogunpa stream. These waste effluents have caused an odour nuisance in the lake, and little or no dissolved oxygen is present. The discharge of nutrients (N and P) to the lake has resulted in excessive growth of aquatic weeds. All these impacts on the lake have resulted in a reduced fish production. Some suggestions for the prevention of pollution and the recovery of the lake are presented.     

Methaemoglobin levels in infants receiving low dietary nitrates in eastern Nigeria

Methaemoglobin levels in 154 normal infants from Aba, Imo State, Eastern Nigeria were determined. In the population 53% showed methaemoglobin levels 0–2%, 32% showed 3–8% and 15% showed 9‐23%. The nitrate levels in the tap waters, boreholes and rivers ranged between 1.10–48.4 mg/1 with a mean of 10.20 mg/1. The breast milk showed 0.5–40.6 mg/1 with a mean of 18.1 mg/1 and the commercial milk formulae and a local food prepared from maize (pap) showed a range of 87.1–700 mg/lOOOg with a mean of 360mg/1000g on dry basis. There was no significant association between the high methaemoglobin levels in the blood and the levels of nitrates they ingested. A more intensive data collection is recommended in view of the increasing threat of nitrates in the waters from indiscriminate disposal of wastes and agricultural runoffs.     

Modeling the Spatially Varying Water Balance Processes in a Semiarid Mountainous Watershed of Idaho1

Stratton, Benjamin T., Venakataramana Sridhar, Molly M. Gribb, James P. McNamara, and Balaji Narasimhan, 2009. Modeling the Spatially Varying Water Balance Processes in a Semiarid Mountainous Watershed of Idaho. Journal of the American Water Resources Association (JAWRA) 45(6):1390‐1408. Abstract: The distributed Soil Water Assessment Tool (SWAT) hydrologic model was applied to a research watershed, the Dry Creek Experimental Watershed, near Boise Idaho to investigate its water balance components both temporally and spatially. Calibrating and validating SWAT is necessary to enable our understanding of the water balance components in this semiarid watershed. Daily streamflow data from four streamflow gages were used for calibration and validation of the model. Monthly estimates of streamflow during the calibration phase by SWAT produced satisfactory results with a Nash Sutcliffe coefficient of model efficiency 0.79. Since it is a continuous simulation model, as opposed to an event‐based model, it demonstrated the limited ability in capturing both streamflow and soil moisture for selected rain‐on‐snow (ROS) events during the validation period between 2005 and 2007. Especially, soil moisture was generally underestimated compared with observations from two monitoring pits. However, our implementation of SWAT showed that seasonal and annual water balance partitioning of precipitation into evapotranspiration, streamflow, soil moisture, and drainage was not only possible but closely followed the trends of a typical semiarid watershed in the intermountain west. This study highlights the necessity for better techniques to precisely identify and drive the model with commonly observed climatic inversion‐related snowmelt or ROS weather events. Estimation of key parameters pertaining to soil (e.g., available water content and saturated hydraulic conductivity), snow (e.g., lapse rates, melting), and vegetation (e.g., leaf area index and maximum canopy index) using additional field observations in the watershed is critical for better prediction.     

PREDICTION OF STREAM TEMPERATURE IN FORESTED WATERSHEDS1

ABSTRACT: Removal of streamside vegetation changes the energy balance of a stream, and hence its temperature. A common approach to mitigating the effects of logging on stream temperature is to require establishment of buffer zones along stream corridors. A simple energy balance model is described for prediction of stream temperature in forested headwater watersheds that allows evaluation of the performance of such measures. The model is designed for application to “worst case” or maximum annual stream temperature, under low flow conditions with maximum annual solar radiation and air temperature. Low flows are estimated via a regional regression equation with independent variables readily accessible from GIS databases. Testing of the energy balance model was performed using field data for mostly forested basins on both the west and east slopes of the Cascade Mountains, and was then evaluated using the regional equations for low flow and observed maximum reach temperatures in three different east slope Cascades catchments. A series of sensitivity analyses showed that increasing the buffer width beyond 30 meters did not significantly decrease stream temperatures, and that other vegetation parameters such as leaf area index, average tree height, and to a lesser extent streamside vegetation buffer width, more strongly affected maximum stream temperatures.     

A System Dynamics Model for Conjunctive Management of Water Resources in the Snake River Basin

The Pacific Northwest is expected to witness changes in temperature and precipitation due to climate change. In this study, we enhance the Snake River Planning Model (SRPM) by modeling the feedback loop between incidental recharge and surface water supply resulting from surface water and groundwater extraction for irrigation and provide a case study involving climate change impacts and management scenarios. The new System Dynamics‐Snake River Planning Model (SD‐SRPM) is calibrated to flow at Box Canyon Springs located along a major outlet of the East Snake Plain Aquifer. A calibration of the model to flow at Box Canyon Springs, based on historic diversions (1950‐1995) resulted in an r² value of 0.74 and a validation (1996‐2005) r² value of 0.60. After adding irrigation entities to the model an r² value of 0.91, 0.88, and 0.87 were maintained for modeled vs. observed (1991‐2005) end‐of‐month reservoir content in Jackson Lake, Palisades, and American Falls, the three largest irrigation reservoirs in the system. The scenarios that compared the impacts of climate change were based on ensemble mean precipitation change scenarios and estimated changes to crop evapotranspiration (ET). Increased ET, despite increased precipitation, generally increased surface water shortages and discharge of springs. This study highlights the need to develop and implement models that integrate the human‐natural system to understand the impacts of climate change.     

Uptake and transformation of perchlorate by vascular plants

Phytoremediation is a promising new method that uses green plants to cleanse soil and water contaminated with organic or inorganic pollutants. In this study, the uptake and transformation of sodium perchlorate (NaClO₄) using four vascular plant species were examined in batch experiments. The species include two trees, cabbage gum (Eucalyptus amplifolia) and eastern cottonwood (Populus deltoides), a herbaceous wetland plant, perennial glasswort (Salicornia virginica), and a herbaceous aquatic plant, waterweed (Elodea canadensis). Perchlorate was depleted from solution in the presence of all but one species (waterweed). Depletion was calculated as a first‐order kinetics reaction with k values in the range of 0–0.013 per day and accumulation of perchlorate was between 3.2 and 3138 mg/kg. Perchlorate and transformation metabolites (chlorate, chlorite, chloride) were observed in all plant tissues (e.g., roots, stems, leaves) analyzed. Results suggest that significant influences on perchlorate uptake include: (1) plant species present, (2) concentration of perchlorate, (3) sand versus hydroponic treatments, (4) the presence or absence of plant nutrients or competing ions, (5) stage of plant maturity.