Seasonal variation and diversity of rotifers in Ehoma lake, Nigeria

The zooplankton and physicochemistry of Ehoma lake were studied from March 2005 to August 2006 in order to evaluate seasonal trend in species composition and abundance in relation to water quality. Forty two (42) species of rotifers dominated by Keratella tropica tropica were encountered. Species richness declined by nearly 50% from dry season values during the rainy season. Species richness was higher in the littoral zone during the dry season, the reverse was the case during the rainy season. Species abundance followed similar trend as species richness. Abundance was closely associated with dissolved oxygen, biological oxygen demand and width of the lake and these in turn varied significantly between seasons. Shannon-Weaver diversity varied from 2.2 to 3.8 bit ind(-1) and significantly between seasons (p<0.05). Anuraeopsis navicula navicula and Euchlanis dilatata dilatata Ehrenbreg were the only species gained during the flood periods.     

Seasonal succession and diversity of phytoplankton in a eutrophic lagoon (Liman lake)

The seasonal succession, composition and diversity of phytoplankton in a eutrophic lagoon (Liman lake) were studied between January 2002 and November 2003. Samples were collected from surface water and deeper (1 m depth) at stations and species diversity (Shannon-Weaver, H) and evenness were calculated. Shannon Diversty was similar at Station 1 and Station 2. Minimum and maximum diversity values (0.101 and 0.765 bits. mm3) were recorded in June and July 2003 at Station 2. Cluster analysis and NMDS (Non metric multidimensial scaling) were applied to the phytoplankton community. The lagoon exhibits high conductivity (7211-10757 microScm(-1)), mean temperature of 17.7 degrees C, varying concentrations of dissolved oxygen (3.3-8.4 mg l(-1)). Light, temperature, rainfall, turbidity and salinity were expected to be the main factors affecting the seasonal succession. The seasonal succession of phytoplankton were similar at surface water and 1 m depth. A total of 130 taxa belonging to Bacillariophyta, Chlorophyta, Euglenophyta, Cyanophyta, Dinophyta, Xantophyta, Chrysophyta and Cryptophyta divisions were identified. Pseudanabaena limnetica, Kirchneriella obesa, Kirchneriella lunaris, Ankistrodesmus falcatus and Ankistrodesmus spiralis were highly represented.     

Seasonal variations in physicochemical characteristics and cyanobacterial diversity of a lake in Northern India

Physicochemical analyses and cyanobacterial diversity of Ramgarh Lake water were performed at five sampling sites during winter, summer, and monsoon seasons. Higher load of solids, carbon, and nutrients were persistent throughout the analysis that indicates the conversion of lake from oligotrophic to eutrophic nature. High nutrients load enhanced cyanobacterial biomass, while low nutrients load produced relatively less biomass. The physicochemical parameters of water samples revealed minimum 2.9 mg L^?1 dissolved oxygen (DO) at site-1 during summer, while maximum (5.6 mg L^?1) at site-4 in monsoon season. Maximum biochemical oxygen demand (BOD) (40 mg L^?1) and chemical oxygen demand (COD) (126 mg L^?1) were recorded at site-1 during summer, whereas minimum BOD (18 mg L^?1) and COD (52 mg L^?1) were evident at site-3 in monsoon season. Minimum concentration of nitrate (0.72 mg L^?1) was recorded at site-3 in summer, whereas maximum 2.7 mg L^?1 was present at site-5 in winter season. The phosphate concentration was maximum (0.52 mg L^?1) at site-5 in summer, and minimum (0.18 mg L^?1) was observed at site-4 in monsoon season. Cyanobacterial diversity was higher during all the seasons, and dominated by the species of Microcystis at all the five sampling sites.     

Independent gradients of producer, consumer, and microbial diversity in lake plankton

Interactions between trophic levels during food web assembly can drive positive correlations in diversity between producers, consumers, and decomposers. However, the contribution of trophic interactions relative to local environmental factors in promoting species diversity is poorly understood, with many studies only considering two trophic levels. Here we examine correlations in diversity among zooplankton, phytoplankton, and bacteria in the pelagic zone of 31 lakes in British Columbia, Canada. We sampled species diversity of zooplankton and phytoplankton through morphological identification, and bacterial genetic diversity was estimated by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA polymorphisms. We looked for correlations in diversity that were independent of the abiotic environment by statistically controlling for 18 limnological variables. No significant correlations were found between the diversity of zooplankton, phytoplankton, and bacteria. In addition, the physical factors that were associated with species composition in one trophic level were independent of those that were important for another. Our results provide no support for the importance of direct feedbacks between producers, consumers, and decomposers in maintaining diversity. Zooplankton, phytoplankton, and bacterial diversity and composition are regulated independently from one another and respond to different environmental variables. These results suggest that species of lake plankton show loose trophic associations with one another due to broad diets in consumers and decomposers.     

金银花根围AM真菌多样性的季节性变化研究

为了探明金银花根围AM真菌季节性变化规律及其影响因素,2011年3月、6月、9月和12月在河北省安国市中药材基地分0-10、10-20和20-30 cm 3个土层采集金银花(Lonicera japonica)根围土壤,应用PCR-DGGE技术研究AM真菌多样性季节变化规律及其与土壤因子相关性。4个季节共分离出15种AM真菌分子种,AM真菌丰富度、香农-威纳指数和均匀度从春季到冬季先降后升,夏季最低。土壤采样深度对AM真菌多样性有显著影响,随土层加深AM真菌多样性指数降低。聚类分析表明,不同季节AM真菌群落组成差异显著,但总体来说冬季和春季群落结构相似,夏季和秋季相似。主成分和相关性分析表明,丰富度和香农-威纳指数与土壤速效P和全N显著正相关,与pH显著负相关,辛普森多样性指数与土壤全N显著正相关,与pH显著负相关,其中全N影响最大,随全N含量升高,AM真菌丰富度、多样性指数先升后降。说明金银花根围AM真菌多样性具有明显的季节性变化规律,这种变化与土壤因子密切相关,这为深入了解AM真菌、宿主植物和土壤环境之间关系,利用菌根生物技术提高金银花产量和品质提供了依据。     

Evaluating the trophic status of a shallow polluted lake,lake Ioannina,Greece

Lake Ioannina in western Greece is a shallow lake, charged by springs as well as untreated discharges of the nearby urban area. Physicochemical and biological parameters have been evaluated verifying the deterioration of the lake aquatic environment. The water quality and the trophic status of the lake are greatly altered during the last ten years while the total phosphorus critical loading is already at a dangerous state.     

Seasonal variation in the diversity and abundance of pelagic larvae of Antarctic marine invertebrates

Most marine benthic macroinvertebrate species reproduce via a larval phase but attempts to explain the occurrence of different larval strategies (feeding or non-feeding, pelagic or benthic) in different habitats have been largely inconclusive. There have been very few year-round surveys of meroplankton at any latitude and in consequence fundamental data on the diversity, abundance, and timings of larval life history phases are lacking. There has been considerable debate regarding the viability of pelagic larvae in cold waters with highly seasonal primary production but there has been only one year-round study of meroplankton in the Southern Ocean, and that was outside of the Antarctic Circle. We present data from the first year-round survey of meroplankton assemblages at a location within the Antarctic Circle. We surveyed abundances of meroplanktonic larvae over 1.5 year at Rothera Point, West Antarctic Peninsula (67°34′S, 68°07′W). Larvae were collected in monthly diver-towed net samples close to the seabed at 20 and 6 m total water depths at each of three locations and were identified and counted live immediately after sampling. A total of 99 operationally defined taxonomic types representing 11 phyla were recorded but this is likely to be an underestimate of true diversity because of inherent difficulties of identification. Larvae were present in all months of the year and although planktotrophic larvae were more abundant in summer, both feeding and non-feeding types were present in all months. Comparisons of seasonal larval abundances with data from a settlement study at the same sites and from the literature show that larvae of mobile adults settle in summer regardless of developmental type, whereas sessile taxa settle in all seasons. We suggest that this is a consequence of differences in the food requirements of mobile and sessile fauna and that the availability of food for post-larval juveniles is more critical for survival than factors affecting the larval stage itself.     

Seasonal variation of fish abundance and biomass in gillnet catches of an East Mediterranean lake: Lake Doirani

The seasonal variation of fish species composition and abundance in gillnet catches (14-90 mm knot-to-knot) from the Greek part of the transboundary Lake Doirani was studied during the period 2006-2007. A total of 8,419 specimens weighing 182.3 kg and belonging to 9 species were caught. Catch composition differed with season. Thus, Rhodeus meridionalis dominated in terms of NPUE the spring, Perca fluviatilis the summer and Albumus macedonicus the autumn and winter catches. Cyprinids were generally the most abundant, with the cyprinids:percids biomass ratio ranging from 1.7 in summer to 14.8 in winter, supporting the eutrophic character of the lake. Richness and Shannon-Wiener diversity and evenness indices differed seasonally (ANOVA; p < 0.05). The abundance-biomass comparative (ABC) curves showed that fish communities were dominated by one or a few opportunistic species (e.g. Rhodeus meridionalis, Albumus macedonicus), which while dominated in number did not dominate in biomass, being small bodied.     

Assessment of bio-medical waste management in three apex government hospitals of Agra

Waste management practices in three apex government hospitals of Agra viz., Sarojini Naidu Medical College, Lady Lyall Maternity Hospital and District Hospital were studied during January 2004-January 2005. Data were collected with the help of (i) personal observations of the waste treatment and disposal practices and (ii) assessment of knowledge, attitude and practices of working personnel with the help of questionnaires. The results obtained indicated lack of knowledge and awareness regarding legislations on bio-medical waste management even among qualified hospital personnel. None of these hospitals were equipped with higher technological options e.g. incinerator autoclave, microwave and had no facilities to treat the liquid waste generated inside the hospital. It is concluded that generation and implementation of a waste management policy institutiona/organizational set up, training and motivation must be given paramount importance to meet the current needs and standards of bio-medical waste management in these hospitals.     

Phytoplankton dynamics and species diversity in a shallow eutrophic,natural mid-altitude lake in Himachal Pradesh (India): role of physicochemical factors

Rewalsar Lake, a mid-altitude, shallow and recreational water body located in the north-western Himalayas, Himachal Pradesh (India) was studied through monthly surveys in two consecutive years (March 2008 to February 2010). Forty-seven species belonging to seven groups of phytoplankton were identified from the lake. Microcystis aeruginosa and Synedra ulna exhibited a perennial habit. Ankistrodesmus falcatus, Chlorella vulgaris, Scenedesmus bijugatus, Chlamydomonas reinhardi, Eudorina elegans, Navicula cuspidate, Synedra ulna, Euglena acus, Euglena oxyuris, Spirulina gomontii, Oscillatoria princeps and Arthrospira khannae were abundant, and Oscillatoria limosa and Microcystis aeruginosa were highly abundant. Twenty-one important criteria were studied, for example, temperature, free carbon dioxide, biochemical oxygen demand, total alkalinity, nitrate, silicate and phosphate, which provide an idea of the portability of water for irrigation and drinking purposes as per the permissible limits given in World Health Organization, Indian Council of Medical Research and Indian Standards Institute standards. Pearson's correlation revealed a significant relationship between physicochemical parameters and different algal groups. Both plankton and chlorophyll a showed a bimodal pattern of fluctuation. High annual mean concentrations of chlorophyll a (mg L^?1) were recorded as 11.44 in 2008–09, and 11.04 in 2009–10. As per the Palmer pollution index, 13 pollution-tolerant algal species with a pollution score of 37 were observed. The Central Pollution Control Board categorised the water at Rewalsar Lake as ‘D–E’.     

Chemical characterization and health risk assessment of soil and airborne particulates metals and metalloids in populated semiarid region,Agra, India

Rapid industrialization and urbanization have contaminated air and soil by heavy metals and metalloids from biogenic, geogenic and anthropogenic sources in many areas of the world, either directly or indirectly. A case study was conducted in three different microenvironments, i.e., residential sites, official sites and official sites; for each sites, we choose two different locations to examine the elemental concentration in fine particulate matter and soil and health risk assessment. The concentration values of heavy metals and metalloid in the air and soil in the Agra region were measured using inductively coupled plasma-atomic emission spectrophotometry. The exposure factor and health risk assessment for carcinogenic and non-carcinogenic effects due to heavy metals and metalloid contaminants have been calculated for both children and adults by following the methodology prescribed by USEPA. For the elements As, Cr, Cd, Ni and Pb selected for the carcinogenic health risk assessment, the calculated results lie above the threshold ranges. We observed the lifetime exposure to heavy metals through mainly three pathways, ingestion, inhalation and dermal contact of soil and air from that particular area. Therefore, the overall hazard quotient (HQ) values for children are more than that of adults. The assessment of health risk signifies that there were mainly three exposure pathways for people: ingested, dermal contact and inhalation. The major exposure pathway of heavy metals to both children and adults is ingestion. The values of HQ are higher than the safe level (=1), indicating a high risk exists in present condition. Meanwhile, HQs value for children is higher than that for adults, indicating that children have higher potential health risk than adults in this region.

     

Tracking the metal distribution in the tropical Valencia lake catchment: Soil, rivers and lake

In tropical areas, the relations between soil, rivers, and lakes are poorly understood as regard to the physicochemical transformation that occurs when solid materials are transferred among them. In order to ascertain the natural dynamics of Na, K, Mg, Ca, Al, Fe, Mn, Pb, Zn, Cu, Ni, Cr, and Co, as well as the perturbations by human activity, soils and sediments from a tropical catchment were studied. To accomplish the above mentioned objective, the Valencia Lake catchment was subdivided into three systems, i.e. soils, rivers and lakes. Original data and those previously published by Mogolló;n and Bifano (1994), and Mogolló;n et al. (1995, 1996) were used to establish the numerical relation between the average concentration in the three systems. The percentage labile fraction and metal distribution in different particle size fractions were studied in selected samples. A total of 410 samples was analysed.Lithology and topography are the main factors that differentiate the physicochemical characteristics of soils and sediments. Processes coupled with solid material transport from the upland to lowland area cause the increase of the HNO₃ (1M) extractable metal concentration, and of the percentage labile fraction, metal redistribution towards fine particle fraction. In spite of the tropical climate, the pedogenesis of exposed sediments and the transport along the river courses, have very low influence. Most of the transformations seem to occur during the soils – river transfer of materials. The carbonate precipitation in the lake causes further increase of metal concentration and the percentage labile fraction. The pollutant input increases metal concentration, the percentage labile fraction and the trend of accumulation toward fine particles.     

Seasonal density dependence, timing of mortality, and sustainable harvesting

Birth-pulse populations are often characterized with discrete-time models, that use a single function to relate the post-breeding population size to the post-breeding size of the previous year. Recently, models of seasonal density dependence have been constructed that emphasize interactions during shorter time periods also. Here, we study two very simple forms of density-dependent mortality, that lead to Ricker and Beverton-Holt type population dynamics when viewed over the whole year. We explore the consequences of harvest timing to equilibrium population sizes under such density dependence. Whether or not individual mortality compensates for the harvested quota, the timing of harvesting has a strong impact on the sustainability of a harvesting quota. Further, we show that careless discretization of a continuous mortality scheme may seriously underestimate the reduction in population size caused by hunting and overestimate the sustainable yield. We also introduce the concept of the demographic value of an individual, which reflects the expected contribution to population size over time in the presence of density dependence. Finally, we discuss the possibility of calculating demographic values as means of optimizing harvest strategies. Here, a Pareto optimal harvest strategy will minimize the loss of demographic value from the population for a given yield.     

Evaluation of physical, chemical and microbiological properties of lake Uluabat, Turkey

Lake Uluabat, known for its scenic beauty and richness of aquatic life, is situated in Marmara Region, Bursa (Turkey). On account of its importance, lake Uluabat was designated by the Ministry of Environment as a Ramsar site in 1998. Physical, chemical and microbiological parameters of the aquatic ecosystem in lake Uluabat were measured monthly at five stations from February 2003 to January 2004. The results showed that lake Uluabat can be classified as Class I with respect to temperature (16.36 +/- 7.47 degrees C), nitrate nitrogen (0.63 +/- 0.50 mgl(-1)), sodium (9.64 +/- 2.78 mgl(-1)), chloride (20.45 +/- 4.59 mgl(-1)), sulphate (54.80 +/- 29.97 mgl(-1)); as Class II with respect to dissolved oxygen (7.62 +/- 1.99 mgl(-1)), ammonium nitrogen (0.52 +/- 0.49 mgl(-1)), chemical oxygen demand (35.74 +/- 10.66 mgl(-1)), total coliform (2027 MPN100 ml(-1) (average value)); as Class III with respect to pH (8.69 +/- 0.16) and as Class IV with respect to total nitrogen (84.94 +/- 66.13 mgl(-1)), total phosphorus (1.11 +/- 3.01 mgl(-1)), biochemical oxygen demand (21.21 +/- 6.60 mgl(-1)) according to TWPCR (Turkey Water Pollution Control Regulation). The nutrient content of lake waterapparently indicated that lake had an eutrophic characteristic. Phosphorus was determined as a limiting factor in lake. The measured hardness values (140.94 +/- 14.61 CaCO3 mgl(-1)) indicated that lake water was classified as soft/hard during the study period. Eutrophic characteristic of the lake and contaminant accumulation in water will probably affect the future use of the lake. Therefore, pollution parameters must be regularly monitored and evaluated according to aquatic living and local regulations.     

Temporal, spatial, and between-host comparisons of patterns of parasitism in lake zooplankton

In nature, multiple parasite species infect multiple host species and are influenced by processes operating across different spatial and temporal scales. Data sets incorporating these complexities offer exciting opportunities to examine factors that shape epidemics. We present a method using generalized linear mixed models in a multilevel modeling framework to analyze patterns of variances and correlations in binomially distributed prevalence data. We then apply it to a multi-lake, multiyear data set involving two Daphnia host species and nine microparasite species. We found that the largest source of variation in parasite prevalence was the species identities of host-parasite pairs, indicating strong host-parasite specificity. Within host-parasite combinations, spatial variation (among lakes) exceeded interannual variation. This suggests that factors promoting differences among lakes (e.g., habitat characteristics and species interactions) better explain variation in peak infection prevalence in our data set than factors driving differences among years (e.g., climate). Prevalences of parasites in D. dentifera were more positively correlated than those for D. pulicaria, suggesting that similar factors influenced epidemic size among parasites in D. dentifera. Overall, this study demonstrates a method for parsing patterns of variation and covariation in infection prevalence data, providing greater insight into the relative importance of different underlying drivers of parasitism.     

广州流花湖底泥磷的垂直变化特征

广州流花湖是典型的城市景观浅水湖泊。应用经改进的Psenner连续提取法,分析了广州市流花湖底泥中各形态磷的垂直分布。结果表明,不同采样点底泥的理化性质和磷的形态垂直变化存在较大的差异;不同形态磷的质量分数由小到大的顺序是NaOH-P,Org-P,HCl-P,BD-P,NH4Cl-P,其中NaOH-P和Org-P是底泥磷的主要赋存形态,分别占底泥总磷质量的47.28%和24.23%,说明了流花湖底泥人为污染较严重;底泥生物可利用磷的质量分数在0.50～1.45 mg.g-1,平均质量分数为0.93 mg.g-1,约占总磷的58.57%,表明流花湖底泥的磷具有较好的生物可利用性,将为水体藻类大量繁殖提供潜在的有利条件。流花湖底泥中有机磷、金属结合态磷和生物可利用磷垂直方向上的分布变化规律较复杂。     

Modeling the annual thermal regime of lake Ohrid,Yugoslavia, using daily weather data

The time-dependent characteristics of the five weather variables which control the annual thermal response of Lake Ohrid are analyzed in detail. These are daily values for solar radiation, air temperature, humidity, wind speed and cloud cover. A simple numerical model of the lake's thermal response, forced by thermally driven density mixing, is developed and tested using observed thermal profiles for verification. The numerical model successfully reproduces the major features of the lake's thermal regime over a 6 y period from 1972 to 1977, the average root mean square value for the simulated profiles being 1.2°C with extremes of 2.2 and 0.3°C and a standard deviation of 0.4°C.     

Seasonal variation of heavy metals in sediment of Lake Ulansuhai,China

Sediment samples were collected from 10 sites in Lake Ulansuhai during summer and winter 2009 to reveal seasonal variations in sediment heavy metal levels. The geoaccumulation index (GI) was calculated to assess the severity of metal pollution. The GI values suggest that, in winter, the lake sediments were polluted slightly with Cu (GI=0.66–1.34), Zn (GI=0.59–1.35), Cr (GI=0.49–0.82) and Pb (GI=0.60–0.96), and moderately with Cd (GI=1.03–4.23). The degree of pollution was higher in winter than in summer. By contrast, the degree of pollution was higher in summer than in winter for Hg and As. Correlation analysis can be used to identify factors influencing seasonal variations in heavy metals. The concetrations of Cu, Zn, Pb, Cr and Cd were negatively correlated with water temperature and hydrodynamic conditions, but positively correlated with organic matter concentration in the sediments and with a sediment particle size of<63 μm (p<0.01). Meanwhile, Hg and As concentrations were affected by redox state and salinity. Among the metals tested, Hg and Cd posed a more serious pollution risk.     

Seasonal variation in paediatric blood lead levels in Syracuse,NY, USA

Venous blood lead values for 2,633 children aged 0–4 years in Syracuse, New York, collected between 1 April 1992 and 31 March 1993 were summarised by census tract for study of geographic variability. A demographic exposure model is presented showing housing stock and SES (socioeconomic status) parameters as the most significant predictor variables. A seasonal trend in blood lead levels was observed with late summer values about 40% higher than late winter values for census tracts with the highest geometric mean PbB levels. Seasonal variation is compared with a biokinetic uptake model to examine hypotheses about temporal variations in soil and dust lead exposure patterns.