Distribution of endosulfan in water, sediment and fish from Warri river, Niger delta, Nigeria

This article presents the first attempt to quantify the levels and distribution pattern of endosulfan, an organochlorine pesticide in surface water, sediment and fish ( Chrysichthys furcatus and Tilapia zilli ). The samples were collected from three stations (Ovwian, Ekakpamre and Ovu) of Warri River in the western Niger Delta of Nigeria in 2006 during the dry and wet seasons (January–August). A total of 96 samples made up of 24 samples each for water, sediment and fish were analysed in this study. The pesticide levels were analysed using high performance liquid chromatography (HPLC model CECIL 1010) to elucidate its distribution in various environmental compartments. The ranges of concentrations of the pesticide in the matrices were: 0.01–9.23 μg/l (water), 0.06–11.98 μg/gdw (sediment), 0.01–15.06 μg/gdw ( Chrysichthys furcatus) and 0.01–1.80 μg/gdw ( Tilapia zilli ). From this result, decreasing order of occurrence of the pesticide is as follows: fish > sediment > water. The concentrations observed in fish ( Chrysichthys furcatus ) were higher than the levels observed in sediment and water suggesting bioaccumulation of the pesticide by the fish. Spatial variations occurred with downstream stations having statistically higher concentrations in all matrices at P  < 0.05. Seasonal variations occurred with higher concentrations in dry season for water and sediment only, while the fish species had higher concentrations in the wet season. The observed values of endosulfan were above the ecological bench marks (0.02 μg/l) recommended by Nigeria Environmental Protection Agency and European Union. They were also relatively higher than those in previous studies on the Nigerian environment, an observation that calls for regular monitoring of the Niger Delta water bodies.     

Microbial Community Profile and Water Quality in a Protected Area of the Caatinga Biome

The Caatinga is a semi-arid biome in northeast Brazil. The Paraguaçú River is located in the Caatinga biome, and part of its course is protected by the National Park of Chapada Diamantina (PNCD). In this study we evaluated the effect of PNCD protection on the water quality and microbial community diversity of this river by analyzing water samples obtained from points located inside and outside the PNCD in both wet and dry seasons. Results of water quality analysis showed higher levels of silicate, ammonia, particulate organic carbon, and nitrite in samples from the unprotected area compared with those from protected areas. Pyrosequencing of the 16S rRNA genes revealed that Burkholderiales was abundant in samples from all three sites during both seasons and was represented primarily by the genus Polynucleobacter and members of the Comamonadaceae family (e.g., genus Limnohabitans). During the dry season, the unprotected area showed a higher abundance of Flavobacterium sp. and Arthrobacter sp., which are frequently associated with the presence and/or degradation of arsenic and pesticide compounds. In addition, genes that appear to be related to agricultural impacts on the environment, as well as those involved in arsenic and cadmium resistance, copper homeostasis, and propanediol utilization, were detected in the unprotected areas by metagenomic sequencing. Although PNCD protection improves water quality, agricultural activities around the park may affect water quality within the park and may account for the presence of bacteria capable of pesticide degradation and assimilation, evidencing possible anthropogenic impacts on the Caatinga.     

Diurnal activity budget of African buffalo (Syncerus caffer Sparrman, 1779) in Chebera Churchura National Park,Ethiopia

One of the fundamental questions in animal ecology concerns the activity pattern of animals and the environmental and intrinsic factors that influence such dynamics. This study tested the hypotheses that activity time budgets of the African buffalo appeared to vary by season and times of day and predicted that buffalo would express unequal proportion of time for different activity patterns during the wet and dry seasons in Chebera Churchura National Park (CCNP). An investigation on the diurnal activity budget of the African buffalo was carried out during the wet and dry seasons of 2012–2014 in the Chebera Churchura National Park, Ethiopia, using focal‐animal sampling method. Buffalo spent a greater proportion of the time in feeding and resting/ruminating activities in both the wet and dry seasons. Feeding and resting (lying down and standing) were the predominant activities (87.14% of the diurnal active period), 48.95% time spent feeding during the dry season and 44.91% during the wet season. There was a significant decrease in feeding and an increase in resting from dry seasons to wet seasons. Daytime grazing and resting periods during the wet season were estimated to be 5.39 h and 4.98 h, respectively. Morning and the late afternoon activity peaks were more pronounced during the dry season than the wet season. Therefore, feeding and resting time was influenced by the time of day and the seasons. But there were no significant difference in time allocation for other activities in both the wet and dry seasons. The study has implications for understanding animal activity budget across species, particularly relationships between temperature and season.     

Variations in oil palm (Elaeis guineensis Jacq.) progeny response to high aluminium concentrations in solution culture

Aluminium (Al) phytotoxicity is an important soil constraint that limits crop yield. The objectives of this study were to investigate how growth, physiology, nutrient content and organic acid concentration is affected by Al, and to assess the degree of Al tolerance in different oil palm progeny (OPP). Four OPPs ['A' (Angola dura × Angola dura), 'B' (Nigerian dura × Nigerian dura), 'C' (Deli dura × AVROS pisifera) and 'D' (Deli dura × Dumpy AVROS pisifera)] were grown in different Al concentrations (0, 100 and 200 μm) in aerated Hoagland solution, pH 4.4, for 80 days. We observed a severe reduction (57.5%) in shoot dry weight, and root tips were reduced by 46.5% in 200 μm Al. In 'B' and 'C', the majority of macro- and micronutrients in plants were reduced significantly by 200 μm Al, with Mg being lowered by more than 50% in roots and shoots. The 200 μm Al treatment resulted in a 56.50% reduction in total leaf area, a 20% reduction in net photosynthesis and a 17% reduction in SPAD chlorophyll value in the third leaf. Root tips (0-5 mm) showed a significant increase in oxalic acid content with increasing Al concentration (～ 5.86-fold); progeny 'A' had the highest concentration of oxalic acid. There was a significant interaction between Al concentration × OPP on total leaf number, root volume, lateral root length, Mg and K in root and shoot tissues, and Ca and N in shoots. The OPPs could be ranked in their tolerance to Al as: 'A' > 'D' > 'B' > 'C'.     

Isotopic values of plants in relation to water availability in the Eastern Mediterranean region

Plant C and N isotope values often correlate with rainfall on global and regional scales. This study examines the relationship between plant isotopic values and rainfall in the Eastern Mediterranean region. The results indicate significant correlations between both C and N isotope values and rainfall in C₃ plant communities. This significant relationship is maintained when plant communities are divided by plant life forms. Furthermore, a seasonal increase in C isotope values is observed during the dry season while N isotope values remain stable across the wet and dry seasons. Finally, the isotopic pattern in plants originating from desert environments differs from those from Mediterranean environments because some desert plants obtain most of their water from secondary sources, namely water channeled by local topographic features rather than direct rainfall. From these results it can be concluded that water availability is the primary factor controlling C and N isotope variability in plant communities in the Eastern Mediterranean.     

流溪河水库敞水区轮虫多样性与群落的动态特征

流溪河水库是位于北回归线上的大型峡谷型供水水库,于2013—2014年对该水库敞水区轮虫群落及其环境因子进行观测,分析敞水区轮虫多样性与群落动态特征。流溪河水库介于贫营养到中营养水平之间,丰水期(5月—9月)的总磷、透明度均高于枯水期(10月—4月),两年的总磷的平均值为0.019mg/L,透明度为2.55m。两年共检出轮虫40种,单月检出物种数波动范围为8—19种,月均检出轮虫13种。螺形龟甲轮虫、真翅多肢轮虫、沟痕泡轮虫和胶鞘轮虫是主要优势轮虫。2013、2014年轮虫年均总丰度分别为68.9、66.9个/L,两年物种丰富度在丰水期大于枯水期,但枯水期轮虫群落Simpson多样性指数均大于丰水期。采用Bray-Curtis距离测度群落之间的相异性,计算表明两年的枯水期轮虫群落之间的平均距离均大于丰水期,即丰水期时轮虫群落相似性较高,枯水期时轮虫群落变异较大。丰水期的水温和水质参数的变化相对稳定,种类的优势度更为明显,导致丰水期群落之间更为相似。主成分分析表明,无柄轮属、胶鞘轮属、多肢轮属、异尾轮属、泡轮属、晶囊轮属和皱甲轮属的主要种类的全年分布有较大的差异,而其余多数轮虫种类全年分布差异较小,反映了我国南亚热带地区水温全年变幅小,可维持较多的全年性种类共存。群落的方差解析与RDA分析表明,相对于生物与化学变量,物理环境变量主导了流溪河水库敞水区轮虫群落的变异,就单个变量而言,水温和食物是影响流溪河水库敞水区轮虫群落结构的重要因素,降雨则是影响轮虫群落结构变异的宏观因素。绝大多数轮虫为滤食性的,处于食物链底端,个体小、生活史短,轮虫群落在对环境因子变化的响应上与浮游植物具有相似性。     

Environmental constraints on the foraging behaviour of a dwarf antelope (Madoqua kirkii)

Dik-diks (Madoqua sp.) inhabit semi-arid regions and experience very different conditions of food availability and quality between wet and dry seasons. By comparing the behaviour of dik-diks between these two seasons, we identified environmental constraints affecting their feeding strategies. In both seasons foraging time was limited by high mid day temperatures. In the wet season a high intake rate compensates for the loss in foraging time, but in the dry season water and protein become limiting. To meet minimum daily water requirements in the dry season dik-diks fed on plant species that they avoided during the wet season. Analysis at the plant species level showed higher species selectivity in the wet season than in the dry season. In a multiple regression analysis food species preferences were best explained by relative abundance and water content in the dry season, and by dry matter content in the wet season. In the wet season the daily dry-matter intake of dik-diks in the field was only about 10% higher than the theoretically predicted minimum for a ruminant of this body weight, while protein and water intake were about 3 times as high. This suggests that the most limiting dietary component in the wet season is energy. In the dry season the daily intake of all dietary components is lower than the theoretical minimum required, and also lower than the values suggested by laboratory studies of dik-diks. This dry season deficit is presumably met from body reserves. Dry season water intake was approximately 30% of the intake observed in laboratory studies indicating that dikdiks are even better adapted to arid conditions than suggested by physiological experiments.     

Water relations and gas exchange in Coespeletia moritziana (Sch. Bip) Cuatrec., a giant rosette species of the high tropical Andes

Giant rosettes are ones of the most striking features of the vegetation in the high tropical Andes, with Coespeletia moritziana reaching the highest altitudes up to 4,600 m a.s.l. Different from other giant rosettes, this species grows on rock outcrops with poorly developed soils and where water availability may be limited. Two questions are addressed in this study: How does this species respond in terms of water relations to maintain favorable gas-exchange conditions? Considering that adult plants rely on a water-reserving central pith, how do early stages respond to this environment??s extreme conditions? Water relations and gas-exchange studies were carried out on juveniles, intermediate and adult C. moritziana plants during wet and dry seasons in Páramo de Piedras Blancas at 4,200 m a.s.l. Adult plants maintained higher leaf water potentials (??_L) during the wet season, however, no differences between stages were found for the dry season. Minimum dry season ??_L were never near the turgor loss point in any of the stages. Juveniles show a more strict stomatal control during the dry season to maintain a favorable water status. Net photosynthesis significantly decreased in intermediate and juvenile stages from wet to dry seasons. Our results suggest that C. moritziana resists more extreme conditions compared to other Andean giant rosettes     

Leaf Litter Dynamics and Its Use by Invertebrates in a High‐Altitude Tropical Andean Stream

This study evaluates litter dynamics and its relation to macroinvertebrate communities (assemblages and feeding habits) at Piburja stream (3300 m, Ecuador). Annual litterfall (216 g AFDM/m²) was not related to rainfall, but differed significantly between months. Transport of Coarse Particulate Organic Matter (CPOM) did not differ between seasons, but retention was higher during the dry season. Thus, CPOM standing stock was higher in the dry (125.28 g AFDM/m²) compared to the wet season (12.27 g AFDM/m²). Macroinvertebrate richness and diversity were positively related to Coarse Benthic Organic Matter (CBOM) especially during the wet season. Gut content analysis revealed that, regardless of season, CPOM and Fine Particulate Organic Matter (FPOM) were the most important food items in the diet of most invertebrate taxa, including those that are not considered shredders or gathering collectors in the literature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Direct and circulatory paths of Permethrin (NRDC-143) causing histopathological changes in the gills of rainbow trout, Salmo gairdneri Richardson

Rainbow trout were exposed to sublethal concentrations of Permethrin in water (0.09, 0.18 and 0.35 μg l⁻¹) and in food (85, 180 and 350 μg kg⁻¹ dry diet) in 20–0 day experiments. Histological changes in the gills included epithelial separation or necrosis, mucus cell hyperplasia, clubbing of epithelial cells or hyperplasia and fusion of adjacent secondary lamellae. These changes were noted in all fish, suggesting that the pesticide or its metabolites reached the gills not only directly through the water, but also indirectly via the circulation.     

Seasonal metabolism of a small, arboreal monitor lizard, Varanus scalaris, in tropical Australia

The field metabolic rates (FMR) and water fluxes of Varanus scalaris were measured during the wet and dry seasons by the doubly-labelled water technique. Seasonal measurements of standard (night-time) metabolism (SMR) and resting (daytime) metabolism (RMR) were made in the laboratory at 18, 24, 30 and 36°C, and maximal oxygen consumption was measured at 36°C on a motorized treadmill. This population was active throughout the year. In the wet season, the mean FMR was 7.8 kJ day⁻¹ (128.0 kJkg⁻¹ day⁻¹; mean mass = 66.4 g, n = 13), and during the dry season the mean was 5.0 kJ day⁻¹ (67.6 kJ kg⁻¹ day⁻¹; mean mass = 77.4 g, n = 17). The mean water flux rates for these animals were 3.6 and 1.2 ml day⁻¹, respectively (60.4 and 16.6 ml kg⁻¹ day⁻¹). The seasonal means of FMR and water flux were significantly different by ANCOVA ( P < 0.0001). Measurements of SMR and RMR were significantly higher in the wet season (ANCOVA: P < 0.0001), but we found no difference in the maximal oxygen consumption between seasons (ANCOVA: P = 0.6). The maximal oxygen consumption of the lizards on the treadmill (2.9 ml min⁻¹= 1.8 ml g⁻¹ h⁻¹), mean mass = 97.4 g, n = 16) was 20 times that of the SMR at the same temperature during the dry season, and 11 times that of the SMR during the wet season. The seasonal differences in FMR were attributable to: changes in SMR (12.2%) and RMR (16.4%); differences in night-time body temperatures (11.3) and daytime body temperatures (16.4%); and activity (broadly defined to include locomotion, digestion, and reproductive costs (43.7%).     

Seasonal water use patterns of woody species growing on the continuous dolostone outcrops and nearby thin soils in subtropical China

In karst regions, forests often grow on bedrock outcrops, however the water sources used by the forest vegetation are not known. This study aimed at investigating whether there were seasonal shifts (dry/wet season) of water sources for plants growing on the continuous dolostone outcrops, and comparing their differences with those growing on nearby thin soils in karst areas of southwest China. Rainwater, soil water within 0–30 cm depths, spring water (as a reflection of local deep water sources) and plant xylem water were sampled in March (late dry season) and July (mid rainy season) 2009, respectively. A direct inference approach and the IsoSource mixing model were used to estimate the contributions of different sources to the plant xylem water. On the outcrops, the deciduous tree species Radermachera sinica mainly used deep water sources during the dry season and a mixture of rainwater and deep water sources during the wet season. By contrast, the deciduous small shrub Alchornea trewioides largely relied on recent rainwater during both dry and wet seasons. Three non-deciduous species (Sterculia euosma, Schefflera octophylla and Ficus orthoneura) appear to rely on deep water sources during the wet seasons. In nearby thin soils, R. sinica mainly utilized deep water in the dry season and a mixture of soil water and deep water in the wet season. A. trewioides relied on the same water sources (rainwater-derived soil water) in the different seasons. The above results indicate that inter-specific differences in rooting patterns and leaf phenologies may lead to the differences in the sources of water used by coexisting plant species in karst regions.     

Inner‐crown Microenvironments of Two Emergent Tree Species in a Lowland Wet Forest1

Vascular epiphyte communities, comprising up to 25 percent of tropical forest flora, contribute to plant diversity and thus ecosystem‐level processes; however, one of the proximal determinants of those communities, microclimate, is little studied. Here we present the first comprehensive study of microclimates in the inner crowns of two emergent tree species, Hyeronima alchorneoides and Lecythis ampla, at La Selva Biological Station, Costa Rica. We examined photon flux density, temperature, vapor pressure, and humidity in inner‐crown branches during the wet and dry seasons and during the wet‐season leafless phase of Lecythis. In both seasons, the percentage daily PFD in foliated Lecythis crowns (9%, wet season; 11%, dry season) was significantly higher than in Hyeronima crowns (5%, both seasons), with the leafless wet‐season PFD of Lecythis reaching 23 percent of full sun. Temperature and vapor pressure varied less in Hyeronima than in Lecythis crowns during the dry season. Microenvironmental conditions for epiphytes within Hyeronima crowns were more spatially and temporally homogeneous and were more buffered from ambient conditions than within Lecythis crowns. Growing conditions within the crowns of the same trees and among different trees were measurably different and are likely to affect the structure and composition of the resident epiphyte communities.     

Fungal endophyte communities in two tropical forests of southern India: diversity and host affiliation

Fifteen tree species from a tropical dry thorn forest and fifteen tree species from a tropical dry deciduous forest in the Mudumalai Wildlife Sanctuary, Nilgiri Biosphere Reserve, southern India, were surveyed for their foliar endophyte communities during the dry and wet seasons. Surface sterilized leaf segments of uniform dimension were plated on nutrient agar and culturable endophytes growing from the segments were identified. Endophyte diversity was greater in the dry thorn forest than in the dry deciduous forest in the dry season. Although the isolation frequency of culturable endophytes increased for both forests during the wet season, the assemblages were represented not by any unique fungal species but by the commonly occurring ones. Furthermore, although individual leaves were densely colonized by endophytes, only a few species of endophytes colonized the whole leaves; and, only a few fungal species dominated the foliar endophytic communities and were common for both forests during both dry and wet seasons. Thus, even under wet conditions that favour dispersal and infection by fungi, the endophyte diversity increased only marginally, an indication that certain tropical forests are not hyperdiverse with reference to fungal endophytes. This should be considered when using culturable endophyte diversity as a surrogate for estimating global fungal diversity.     

鄱阳湖湿地水土环境中微塑料的时空分布及多源性

淡水湿地中日益严重的微塑料(MPs)污染已引起全球关注。为了解鄱阳湖典型湿地微塑料的时空动态特征,相继于丰水期和枯水期采集鄱阳湖流域五河入湖段和鄱阳湖汇入长江出湖段的水体和沉积物样品,分别采用消解抽滤法和浮选分离-消解抽滤法分离水体和沉积物中的微塑料,采用显微镜、傅里叶变换红外光谱仪和扫描电镜鉴定分析微塑料表征。结果表明: 鄱阳湖各区域丰水期水体和沉积物微塑料丰度范围分别为32.1～127.3 n·L^-1和533.3～1286.6 n·kg^-1,枯水期分别为87.1～295.5 n·L^-1和460.0～1368.0 n·kg^-1,与其他淡水湿地相比,鄱阳湖具有较高的微塑料丰度,且各区域间呈时空差异性。研究区微塑料的主要形态有微球、碎片、薄膜和纤维等,相应聚合物成分主要为聚苯乙烯(PS)、聚丙烯(PP)和聚乙烯(PE)等;水体中微塑料以微球类(丰水期35.7%,枯水期52.0%)为主要形态,沉积物中以碎片类(丰水期45.8%,枯水期69.7%)为主要形态;两个水期水体和沉积物中均以小粒径(<0.1 mm)微塑料占优势(>50%),不同粒径微塑料丰度随粒径增大呈减少趋势。鄱阳湖湿地微塑料的潜在主要来源包括工业废水排放、城乡生活污水处理厂排放、农业和渔业活动以及生活垃圾处理不当。     

降雨量改变对常绿阔叶林干旱和湿润季节土壤呼吸的影响

通过野外原位试验,研究降雨量改变对华西雨屏区常绿阔叶林干旱和湿润季节土壤呼吸速率的影响。采用LI-8100土壤碳通量分析系统(LI-COR Inc.,USA)测定干旱和湿润季节对照(CK)、增雨10%(LA)、增雨5%(TA)、减雨10%(LR)、减雨20%(MR)、减雨50%(HR)6个处理水平的土壤呼吸速率,并通过回归方程分析温度和湿度与土壤呼吸速率间的关系。结果表明:湿润季节土壤呼吸速率高于干旱季节,HR处理对干旱季节土壤呼吸速率影响较大,而LA处理对湿润季节土壤呼吸速率的影响较大。TA和LR处理使土壤呼吸的温度敏感性增加,而HR、LA和MR处理使土壤呼吸的温度敏感性降低,干旱季节Q10值高于湿润季节。各处理湿润季节土壤微生物量碳氮含量显著高于干旱季节,HR、MR和LA处理减少土壤微生物生物量碳、氮的含量,而TA和LR处理增加土壤微生物生物量碳、氮的含量。与湿润季节相比,干旱季节土壤水分对土壤呼吸速率的影响较大;而与土壤温度相比,土壤水分对土壤呼吸速率的影响较小。在降雨量改变的背景下,华西雨屏区常绿阔叶林无论是干旱还是湿润季节,适当增雨和减雨都会促进土壤呼吸速率,而较高量的增雨和减雨会抑制土壤呼吸速率。     

三峡库区古夫河水质时空分异特征

以湖北省神农架林区和兴山县境内长江三峡库区香溪河支流古夫河为研究对象,于2010年8月-2011年7月在整条河流中选取20个采样点,进行样本采集,并测定溶解氧、碱度、硬度、电导率、总磷、总氮、化学需氧量、二氧化硅、总有机碳共9项水质指标,运用多元统计方法,分析水质的时空分异特征.依据研究区土地利用类型差异,将20个采样点分成4组,即森林(A组)、耕地(B组)、水库(C组)和村镇(D组);根据该区域的水文节律,将5-10月归为湿季,其余月份为干季.判别分析和方差分析结果表明,古夫河水质具有时空显著性差异:总磷、二氧化硅、电导率、化学需氧量、总硬度和总碱度等指标具有空间显著性差异;总氮、化学需氧量、溶解氧、二氧化硅和总有机碳与季节存在显著相关性,所测9项水质指标在不同空间类别上呈现出显著的季节变化.主成分分析表明,不同空间类别上的干湿季节引起水质变化的主导因子是不同的:A组中,湿季主要体现为二氧化硅和总有机碳,干季主要体现为总磷、二氧化硅、总有机碳和化学需氧量,该组水质主要受地表径流、地质成因和风化作用等自然因素的影响;B组中,湿季主要体现为硬度和总有机碳,干季主要体现为总磷、化学需氧量、总碱度和总硬度,该组除了受自然因素的影响,还受如农业径流、未处理的生活污水排放等人为因素影响;C组中,湿季主要体现为二氧化硅、总氮和总磷,干季主要体现为总氮、总有机碳和二氧化硅,该组主要受农业径流、地表径流以及未经处理的生活污水等的影响;D组中湿季主要体现为二氧化硅、总氮和总磷,干季主要体现为碱度、硬度、总氮和总有机碳,该组主要受村镇生活污水和农业径流等的影响.结果表明,古夫河水质受自然和人为因素影响而发生变化,其中受人为因素影响更大.因此,加强水资源的管理和保护,改善水质,做好水源地的长期水质监测显得尤为重要.     

Seasonality in foraging behaviour of Constrictotermes cyphergaster (Termitidae, Nasutitermitinae) in the Caatinga of Northeastern Brazil

The foraging activity of Constrictotermes cyphergaster was investigated in the Caatinga of Northeast Brazil. Eight colonies were monitored for seven days, during both dry and wet seasons. Foraging activity occurred in exposed columns at night, generally between 22:00 and 05:00 h. During the wet season, foraging activity was significantly higher, with one bout every 1.6 ± 0.2 days, than the dry season, when foraging bouts were performed every 1.9 ± 0.3 days. Foraging activity throughout the study colonies presented high temporal synchronization. In both seasons, foraging was negatively correlated with air temperature and positively correlated with humidity. The foraging trails were often re-utilized and ranged from 1 to 18.5 meters in length. No difference between seasons in the area potentially utilized by the study colonies was observed. Approximately 51000 individuals participated in the foraging bout during the dry season, whereas some 87000 individuals participated in the foraging bout during the wet season. This corresponds to 43 and 74% of the estimated total nest population for the dry and wet seasons respectively. The average ratio soldiers:workers during foraging was 1:1.2 in the dry season and 1:2 in the wet season. The higher frequency and number of individuals foraging during the wet season in the present study are likely to be a strategy from C. cyphergaster to store energy reserves to be utilized during the dry season. Received 28 November 2005; revised 29 May 2006 and 16 August 2006; accepted 1 September 2006.     

Effect of salinity variation and pesticide exposure on an estuarine harpacticoid copepod, Microarthridion littorale (Poppe), in the southeastern US

The harpacticoid copepod Microarthridion littorale (Poppe) was tested for interaction effects between salinity change and acute pesticide exposure on the survival and genotypic composition of a South Carolina population. Previous data suggested a significant link between a combined exposure to chlorpyrifos (CHPY) and dichloro-diphenyl-trichloroethane (DDT) and mitochondrial haplotype in the cytochrome b apoenzyme for this euryhaline species when exposed at 12-ppt salinity seawater. Our tests demonstrate a significant non-linear survival response for M. littorale to short-term immersion (24 h) in 3-, 12- and 35-ppt seawater, with copepods transferred to 12-ppt seawater having the lowest survival. There was significant statistical interaction between salinity and pesticide exposure for the dependent variable “survival.” However, changes in genetic composition of survivors were not significant, and they were complicated by extremely low survival in the pesticide/3 ppt and pesticide/36 ppt treatments. As noted for many studies of harpacticoids, males faired worse than females in all treatments, with none surviving pesticide exposure at 45 μg/l CHPY and 6 μg/l DDT.     

Isolation and identification of Burkholderia pseudomallei from soil using selective culture techniques and the polymerase chain reaction

An environmental soil survey to detect Burkholderia pseudomallei was performed during the dry and wet seasons in Darwin, Northern Territory, Australia. Soil was sampled at regular intervals during a 15-month period at different depths from areas which were representative of the local, soil environment. Selective culture techniques using Ashdown's and Galimand and Dodin's methods and the polymerase chain reaction (PCR) using specific 16S rRNA primers were used to detect and identify the organism and determine its distribution within the soil stratum over the change in seasons. Results showed that Ashdown's method gave higher isolation rates in the dry season, and Galimand and Dodin's method gave higher isolation rates during the wet season. PCR of the soil enrichment proved to be a more sensitive method than culture and was also a useful confirmatory test in determining the identification of isolates where biochemical tests gave inconsistent results. The PCR primers were specific and able to detect 10¹ cfu g^-1 soil and 10⁴ cfu g^-1 of soil using Ashdown's enrichment broth and Galimand and Dodin's broth, respectively. Overall the isolation of B. pseudomallei was greatest during the dry season and at the higher and lower soil depths, which is contradictory to epidemiological evidence that melioidosis occurs primarily during the wet season among patients exposed to contaminated surface soil and water.