Ecophysiological Studies on Size-fractionated Phytoplankton Populations by Tracer Technique in Wadi el Majanin Dam,Libya

Wadi el Majanin, one of the largest hydraulic structures in Libya was studied for ecophysiological aspects in relation to ambient environment. The waterbody is alkaline (pH=7.2) and characteristic of hydrogen-carbonate (144.8 mg L^–1 CaCO₃) system. Vertical extinction coefficients (> 4.8) indicate very high (biogenic) turbidity. Conspicuous variations of a quantitative kind in algal development (e.g., Pediastrum bloom) together with abundant diatom populations (chlorococcales-diatom assemblage), apart from very common occurrence of cyanobacteria and euglenoids show eutrophic water condition. Winter-summer alternation induced pronounced seasonal variability in the rates of in situ planktonic algal photosynthetic activities (285.7...1305 mg m^–3 d^–1 C). Dark fixation activity, attributed largely to bacterial production, oscillated by order of 2-fold magnitude, characterized by summer maxima (47.6 mg m^–3 d^–1 C). Size-fractional analysis established that smaller forms (< 60 μm), broadly regarded nanno-phytoplankton, frequently dominated (c. 70%) overall algal productivity.     

Differences in stable isotope compositions of freshwater snails from surface sediments of two Polish shallow lakes

The study reports and discusses the differences in δ¹³C and δ¹⁸O values of shells between several species of freshwater snails. Shells were derived from sediment samples collected from depths of 0.5, 1, 2 and 3 m along transects in two shallow eutrophic lakes located in mid-western Poland. Mean δ¹³C values of the shells ranged between −7.5 and −3.8‰ in Lake Jarosławieckie and between −8.1 and −5.2‰ in Lake Rosnowskie Duże, whereas mean δ¹⁸O values ranged between −2.2 and −0.2‰ and between −2.2 and 0.4‰ respectively in the studied lakes. A similar order of species in terms of shell isotope values, from least to most ¹³C and ¹⁸O-depleted was observed in both lakes and seems to indicate constancy of the factors controlling the stable isotope compositions of snail shells. We postulate that the nearly 4‰ difference in the mean carbon stable isotope values between the species was primarily controlled by the amount of metabolic carbon incorporated into the shells and the δ¹³C values of the snail food. Different growth cessation temperatures and microhabitats of the species studied result in temporally and spatially varied DIC δ¹³C values, water δ¹⁸O values and water temperature of shell precipitation, and may thus differentiate the δ¹³C and δ¹⁸O values of shells. The range of δ¹³C and δ¹⁸O values of individual shells from a sediment sample (mean 2.35 and 2.15‰, respectively) is interpreted as reflecting an intraspecific variability of isotope compositions in shells from a population and changes of the ambient conditions during the accumulation of the sediment layer. The species-specificity and intraspecific variability in C and O isotopic compositions of shells allow concluding that in palaeolimnological studies, stable isotope analyses should be performed on a set of mono-specific shells representing mean isotope compositions of the species for the interval studied rather than single shells or multispecific bulk shell material.     

西藏地区现代沉积物中介形类环境指示意义初探

于2008和2012年先后2次从西藏阿里和那曲地区61个不同水体,包括不同盐度的湖泊、湿地、浅水坑和河流等,共采集了78个水体表层沉积物样品,用以研究该地区现生介形类的生态分布及其环境指示意义.经鉴定,阿里和那曲地区现生介形类共计11属38种.除Ilyocypris neoaspera等5个种外,本次调查的介形类各属种均在湖泊中出现,尤以Limnocythere dubiosa的总壳瓣数最为丰富.Ilyocypris属中除Ilyocypris subdunshanensis和Ilyocypris xizangensis外,其余各种均喜浅水坑的小型浅水环境.Leucocythere dilitata、Limnocythere dubiosa、Limnocytherellina kunlunensis和Eucypris rischtanica为该地区的广盐种.其中Limnocythere dubiosa和Leucocythere dilitata适应盐度范围最广,在不同盐度的各类水体中均有出现.本次研究中的介形类均喜碱性水体,在p H值为8~9的水体中介形类各属种的丰度值达到最大.     

Fatty Acid Composition of Plankton and Bighead Carp (Aristichthys nobilis) in Freshwater Ponds

The community structure and fatty acid composition of plankton in broodstock ponds were studied at the Bishui Fisheries Company in the Liaoning Province, northeast China, between May and December 2002 and in March 2003. The Fatty acid analysis of bighead carp larvae and plankton in the fry pond occurred during June, July, and September 2002. The fatty acid composition of the plankton varied with seasonal changes in the community structure. When blue‐green algae dominated the broodstock ponds in spring and summer, the percentage of saturated fatty acids (SFA) (especially 16:0) was high. When diatoms and cryptophytes dominated in autumn and winter, the percentage of polyunsaturated fatty acids (PUFAs) (mainly n–3 PUFA) was high. Similarly, a high content of docosahexaenoic acid (DHA) occurred in autumn and winter when DHA‐rich copepods became an important group of zooplankton. In addition, environmental factors, especially water temperature, influenced the fatty acid composition of plankton. 16:0, DHA, and 18:1n–9 were dominant fatty acids of bighead carp larvae during ontogeny. 16:0, C18 unsaturated fatty acids, and eicosapentaenoic acid (EPA) were major fatty acids of plankton in the fry pond. Analysis of the relationship between the fatty acids of the larvae and those of plankton showed that the fatty acid profiles of the larvae did not always agree with those of plankton.     

Impact of Estuarine Outflow on Coastal Upwelling

A two-dimensional numerical model is developed facilitating the locationwise study of coastal upwelling. The coastal rigid boundary in the model is replaced with an open boundary to understand the dynamical response of the coastal ocean in the presence of an estuary. The model is applied to the east coast of India in a plane perpendicular to the coast of Kakinada where the Godavari river joins the Bay of Bengal. The model is driven, starting from a state of rest, by the combined effect of the wind stress forcing and the freshwater discharge from the estuary. Two numerical experiments were conducted to study the effect of the variation in the freshwater discharge on upwelling. It is found that the freshwater discharge from the Godavari estuary suppresses the upwelling off Kakinada.     

Lacustrine ostracodes as hydrochemical indicators in lakes of the north-central United States

The modern ostracode distribution in lakes of the north-central United States shows how ostracode abundances are related to concentrations of major ions such as calcium, sulfate, and bicarbonate. These relationships are quantified for species living in lakes that range from fresh water (200 S cm^-1) to saline water (17 000 S cm^-1). Lakes located in the Minnesota forests have different ostracode assemblages and different water chemistry than lakes located on the prairie of North Dakota and South Dakota. These differences are attributed to differences in precipitation and rock-water interactions. Multivariate analyses of the ostracode and water chemistry data set indicate that different ostracode species are associated with different water types. For example, Limnocythere sappaensis and Heterocypris glaucus are found in bicarbonate-enriched sulfate-dominated waters, whereas Limnocythere staplini is found in bicarbonate-depleted sulfate-dominated waters. Candona ohioensis and Limnocythere itasca are found in fresh water, and Candona rawsoni is eurytopic and found in both bicarbonate-enriched and bicarbonate-depleted sulfate-dominated waters. Ostracodes can be used to identify changes in both ionic composition (solutes) and ionic concentration.This publication is the second of a series of papers presented at the Conference on Sedimentary and Paleolimnological Records of Saline Lakes. This Conference was held August 13–16, 1991 at the University of Saskatchewan, Saskatoon, Canada. Dr Evans is serving as Guest Editor for this series.     

New records of temperate mollusks in two Late Pleistocene terrestrial localities from northeastern Oaxaca,Southern Mexico

The Mixteca Alta Oaxaqueña is in the state of Oaxaca, southern Mexico. This region is characterized by numerous Pleistocene fossiliferous localities. The objective of this study is to describe a diverse assemblage of Late Pleistocene freshwater and terrestrial mollusks in two localities from northeastern Oaxaca, Coixtlahuaca District. We identified 10 taxa of gastropods and one of bivalves. By the sedimentological characteristics and the mollusks assemblage, it is possible to relate the first locality with meandriform river deposits, without vegetation. The second locality was associated with a floodplain with short-lived associated vegetation. Five identified species constitute the most austral records of these taxa in Neartic Realm. In all the taxa, the Late Pleistocene occurrences constitute the last records of the identified mollusks in the study zone.     

Effects of sewage discharges on lipid and fatty acid composition of the Patagonian bivalve Diplodon chilensis

Lipid and fatty acid (FA) composition and selected oxidative stress parameters of freshwater clams (Dipolodon chilensis), from a sewage-polluted (SMA) and a clean site, were compared. Trophic markers FA were analyzed in clams and sediment. Saturated FA (SAFA), and bacteria and sewage markers were abundant in SMA sediments, while diatom markers were 50% lower. Proportions of SAFA, branched FA, 20:5n − 3 (EPA) and 22:6n − 3 (DHA) were higher in SMA clams. Chronic exposure of D. chilensis to increasing eutrophication affected its lipid and FA composition. The increase in EPA and DHA proportions could be an adaptive response, which increases stress resistance but could also lead to higher susceptibility to lipid peroxidation TBARS, lipofuscins (20-fold) and GSH concentrations were higher in SMA clams. FA markers indicated terrestrial plant detritus and bacteria are important items in D. chilensis diet. Anthropogenic input in their food could be traced using specific FA as trophic markers.     

曹娥江流域的淡水贝类

报告了自１９８１年以来历次对曹娥江流域淡水贝类的调查结果。标本经鉴定计有５２种，其中腹足纲６科１３属３２种，瓣鳃纲４科１１属２０种。分析了流域中淡水贝类与栖息环境的关系。探讨了流域中淡水贝类的分布区划及经济意义。     

The provenance,petrology and sedimentology of building stone in Bromyard,Herefordshire, UK

A multi-disciplinary study was undertaken of the Lower Old Red Sandstone building stones of Bromyard, Bromyard Downs and Bringsty Common, Herefordshire, UK, to trace their original quarry sources. 196 stone structures were recorded in detail and 3 broad lithological groups recognised. Combining old maps, archival sources, Light Detection and Ranging (LiDAR) data and testimony of local residents, the historic quarries in the area have been mapped. Field studies of the geology of quarries and outcrops have established the area of origin of two distinctive coarse grained lithologies. Intraformational conglomerates have been demonstrated, with some confidence, to be derived from Bromyard itself. Coarse, pebbly, quartzose sandstones have been traced to Bringsty Common and shown to be used only in the church in Bromyard before the 20th century. The origins of fine grained sandstone are found to be more complex. Through a combination of fieldwork and archival research, Clater Park Quarry is indicated as the origin of high quality green sandstones in Bromyard. 15 samples of sandstone from the Bromyard Downs, have been petrographically analysed by point counting to determine their clastic and mineralogical proportions. Early results of this analysis are presented which show modal variation in lithics, feldspars and cements that may serve to link quarries to buildings. Finally, it is suggested that at least some of the diversity of stone present in Bromyard is the result of slight variation in depositional processes in the immediately underlying bedrock.