Boosted Regression Tree Models to Explain Watershed Nutrient Concentrations and Biological Condition

Boosted regression tree (BRT) models were developed to quantify the nonlinear relationships between landscape variables and nutrient concentrations in a mesoscale mixed land cover watershed during base‐flow conditions. Factors that affect instream biological components, based on the Index of Biotic Integrity (IBI), were also analyzed. Seasonal BRT models at two spatial scales (watershed and riparian buffered area [RBA]) for nitrite‐nitrate (NO₂‐NO₃), total Kjeldahl nitrogen, and total phosphorus (TP) and annual models for the IBI score were developed. Two primary factors — location within the watershed (i.e., geographic position, stream order, and distance to a downstream confluence) and percentage of urban land cover (both scales) — emerged as important predictor variables. Latitude and longitude interacted with other factors to explain the variability in summer NO₂‐NO₃ concentrations and IBI scores. BRT results also suggested that location might be associated with indicators of sources (e.g., land cover), runoff potential (e.g., soil and topographic factors), and processes not easily represented by spatial data indicators. Runoff indicators (e.g., Hydrological Soil Group D and Topographic Wetness Indices) explained a substantial portion of the variability in nutrient concentrations as did point sources for TP in the summer months. The results from our BRT approach can help prioritize areas for nutrient management in mixed‐use and heavily impacted watersheds.     

LCA of the South African sugar industry

A life cycle assessment of sugar produced in South Africa evaluates the environmental impacts and energy consumption of the different life cycle phases of sugar production. The system studied includes sugar cane farming, fertiliser and herbicide manufacture, cane burning, sugar cane transportation and sugar manufacture. Inventory and impact assessment results show that non-renewable energy consumption is 5350 MJ per tonne of raw sugar produced and 40% of this is from fertiliser and herbicide manufacture. Reduction in the use or impact of fertiliser for cane farming could bring considerable savings in terms of fossil energy consumption and a reduction in greenhouse gas emissions.     

三峡库区水华优势藻类生长动力学的普适性研究

从蓝绿藻中选取绿藻门的普通小球藻(Chlorella vulgaris,CV藻)为研究对象,应用Monod方程考察氮、磷营养盐对CV藻生长的影响,分别计算出CV藻对TP、TN的半饱和常数KSP和KSN结果表明KSN>>KSP,说明TP对CV藻生长的影响明显大于TN.CV藻生长速率对磷质量浓度反应很灵敏:与空白值相比,在0.002 mg·L-1的低浓度下u就有提高,而浓度到0.2 mg.L-1时,u明显增大;但在0.000-0.050 mg·L-1氮浓度范围内u几乎没有变化.通过系统比较CV藻与优势蓝绿藻,甚至海水藻的生长动力学特征,探讨了CV藻与其它蓝绿藻的动力学普适性和共同性,证实这些藻类都具有非常类似的生长动力学和生态学特征.因此,推测CV藻生长动力学模型可以从整体上反映和代表库区优势蓝绿藻的生长行为.同时分析和归纳了蓝绿藻生长模型的相似性和规律性,得出三峡库区优势藻类生长行为存在普遍一致性的初步结论.     

Review of historical aquatic toxicity and bioconcentration data for the brominated flame retardant tetrabromobisphenol A (TBBPA): effects to fish,invertebrates, algae,and microbial communities

This paper summarizes the historical and recent research on the aquatic toxicology and bioconcentration potential of tetrabromobisphenol A (TBBPA), a major flame retardant in electronics. Historical studies on TBBPA are presented in detail, and are compared with more recent research. The historical studies have not been published to date, though they were pivotal in regulatory assessments by the European Union, Canada, and the USA. These assessments have enabled the use of TBBPA as a flame retardant in electronic applications, to the present. The studies were conducted under a Test Rule by the US Environmental Protection Agency in 1987, and were sponsored by member companies of the North American Flame Retardants Alliance (NAFRA) through the American Chemistry Council. The studies were conducted under Good Laboratory Practice procedures, and include 6 acute toxicity tests of TBBPA with fish, invertebrates, algae, and microbes, eight chronic tests, and three bioconcentration studies with fish and invertebrates. Methods and empirical data for each study are detailed in an electronic supplement. Results of the NAFRA studies are compared with recent findings on TBBPA toxicity. Molluscan shell growth may be uniquely sensitive to TBBPA, more sensitive than chronic fish or crustacean toxicity endpoints. Several of the NAFRA studies and several independent studies have reported toxicities exceeding the empirical water solubility limits of TBBPA (in the range of 2.0 mg/L depending on pH). The validity of these results is discussed.     

Aggresive competition and individual food consumption in wild brown capuchin monkeys (Cebus apella)

Summary The impact of aggresive competition on food intake at all the resources used is analysed for every member of a group of brown capuchin monkeys (Cebus apella) in the Manu National Park, Peru, where they live in groups of 8–14 animals. An individual's food intake at a given tree was affected independently both by its domirance rank (Fig. 1) and by how much aggression it received (Table 5). Food intake was not strongly affected by body size when dominance rank was held constant by partial correlation. At food sources where high rates of fighting occurred, an individual's food intake depended more on its domirance status than on the rate of aggression it received (Fig. 2). However, food intake at resources where rates of fighting were low depended mostly on the rate of aggression received. When aggression over food was absent, the food intakes of dominants and subordinates were equal. Dominants had significantly greater total energy intake (20.5% more) than did subordinates, even though more than one third of their diet came from food sources where little or no fighting occurred (Fig. 3). Energy intake was also significantly greater for individuals that received little aggression. The only adult that emigrated from the main study group was the individua with the lowest energy intake. Competition for food within groups was more than ten times as intense as competition between brown capuchin groups.     

Annual migrations,diving behavior,and thermal biology of Atlantic bluefin tuna, <Emphasis Type="Italic">Thunnus thynnus</Emphasis>, on their Gulf of Mexico breeding grounds

Electronic tags were used to examine the biology of Atlantic bluefin tuna (Thunnus thynnus L.) on their breeding grounds in the Gulf of Mexico (GOM). The hypothesis that movement patterns, diving behavior, and thermal biology change during different stages of the breeding migration was tested. Mature Atlantic bluefin tuna tagged in the western Atlantic and the GOM, were on their breeding grounds from February to June for an average of 39 ± 11 days. The bluefin tuna experienced significantly warmer mean sea surface temperatures (SSTs) within the GOM (26.4 ± 1.6°C) than outside the GOM (20.2 ± 1.9°C). As the bluefin tuna entered and exited the GOM, the fish dove to daily maximum depths of 568 ± 50 and 580 ± 144 m, respectively, and exhibited directed movement paths to and from the localized breeding areas. During the putative breeding phase, the bluefin tuna had significantly shallower daily maximum depths (203 ± 76 m), and exhibited shallow oscillatory dives during the night. The movement paths of the bluefin tuna during the breeding phase were significantly more residential and sinuous. The heat transfer coefficients (K) were calculated for a bluefin tuna in the GOM using the recorded ambient and body temperatures. The K for this fish increased rapidly at the high ambient temperatures encountered in the GOM, and was significantly higher at night in the breeding phase when the fish was exhibiting shallow oscillatory dives. This suggests that the fish were behaviorally and physiologically thermoregulating in the Gulf of Mexico. This study demonstrates that the movement patterns, diving behavior, and thermal biology of Atlantic bluefin tuna change significantly at different stages of the breeding migration and can be used to define spawning location and timing. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Genetic evidence of multiple parentage in broods of cliff swallows

Summary Parental exclusion analyses based on allozyme data were performed on 105 families of cliff swallows (Hirundo pyrrhonota) from southwestern Nebraska, USA. The protein products of seve polymorphic loci were resolved from blood, and at least one parental exclusion occurred at six of these loci. One or both putative parents were excluded for 35 nestlings from 22 different families. The mean number of non-kin nestlings in these families was 1.59. Non-kin nestlings were found in families with brood sizes ranging from two to five. A greater percentage of families in an 1100-nest colony had non-kin offspring than in two smaller colonics, although the difference was not statistically significant. Application of genetic models to these data and the observed distribution of parental exclusions suggested that multiple parentage in cliff swallows results more often from intraspecific brood parasitism than from forced extra-pair copulations. Based on the calculated probabilities of detecting non-kin, we estimate that 23.7% of all nestlings in our population are not the offspring of one or both of their putative parents. We estimate that about 43% of all cliff swallow nests in Nebraska contain at least one offspring resulting from intraspecific brood parasitism, and that about 6% of nests might contain offspring resulting from extra-pair copulations.     

Disposition of vanadium in rat tissues at different age

Tissue vanadium levels were determined in rats of different age by neutron activation analysis. The vanadium concentrations in the tissues of rats 21 days old are of the order of few tens of ng/g. Significant depletions of these concentrations were observed in kidney, liver lung and spleen at 115 days postnatal period. At this time the vanadium content in all tissues analysed did not exceed 10 ng/g.