Effects of Experimental Acidification on Phyto-, Bacterio-and Zooplankton in Enclosures of a Highly Humic Lake

In situ enclosure experiments were performed in a highly humic lake to examine the effects of acidification on phyto-, bacterio- and zooplankton. The acidity of three enclosures was adjusted with H₂SO₄ to pH 3.5, 4 and 5 and one enclosure and the lake served as controls. The diversity of plankton as well as the mean concentration of chlorophyll α, primary production and respiration of plankton decreased with increasing acidity. Bacterial density was slightly lower in the pH 3.5 enclosure than in the other enclosures and in the lake, but there were no differences in the morphological type or mean volume of the cells between different treatments. In the acidified enclosures Cryptomonas ovata and Chlamydomonas spp. were the dominant phytoplankters, while Dinobryon and Mallomonas species seemed to be most sensitive to acidity. Keratella cochlearis, Kellicottia longispina and Bosmina longispina were the most tolerant zooplankton to acidity.     

Associations of Cyanobacterial Toxin,Nodularin, with Environmental Factors and Zooplankton in the Baltic Sea

Concentrations of a cyanobacterial toxin, nodularin, were measured in the Baltic Sea in 1998 and 1999. Statistical associations of nodularin concentrations with environmental factors were tested by multiple regression analysis. To reveal the toxin-producing organism, colonies of Aphanizomenon and filaments of Nodularia were picked and analyzed for peptide toxins. It was also investigated whether there was an association with zooplankton and Nodularia. All the measured seston samples contained nodularin, but other toxins were not detected by the HPLC analysis. In both years, the highest nodularin concentrations were found at the surface water layer. The nodularin concentrations were positively correlated with silicate concentrations in water. High concentrations of silica in surface water may indicate recent upwelling, which in turn renders surface water rich in nutrients. This upwelling is likely to intensify cyanobacterial growth and toxin production, which may explain this rather unexpected result. The picked Aphanizomenon colonies did not contain nodularin and the dissolved nodularin concentrations were below detection limit. Thus it was concluded that most of the nodularin was bound to Nodularia cells. The abundances of zooplankton (copepods, rotifers, and cladocerans) were unrelated to Nodularia, but were positively associated with Aphanizomenon.     

A Quantitative Comparison of Two Zooplankton Sampling Methods,a Plankton Trap and a Towed Net,in the Baltic

A comparison between a large plankton trap with a capacity of 23 litres and a modern towed net was made in the course of zooplankton production studies in the Baltic. On the average, the net efficiency was 75% of that of the trap. Both methods were equally efficient in catching naupliar stages of copepods. The net efficiency was especially low during the zooplankton maximum for adult copepods and cladocerans (41 and 51%, respectively), probably due to the active avoidance of the net by fast swimming species. The net was only about 66% as efficient as the trap for catching rotifers. This difference is probably caused by the loss of small and softbodied forms through the mesh. Only about 65% of the total zooplankton biomass retained in the trap was collected by the net. Net sampling is not recommended for quantitative zooplankton studies.     

Limnological Aspects of Some Moroccon Atlas Lakes,with Reference to Some Physical and Chemical Variables,the Nature and Distribution of the Phyto- and Zooplankton,Including a Note on Possibilities for the Development of an Inland Fishery

Four mountain lakes were studied. Two are eutrophic, one is mesotrophic and one is oligotrophic. The first three have a well-developed phyto- and zooplankton, with a relatively high diversity index. There are differences between the faunas that may be ascribed to differences in surface, depth, altitude and also to biological phenomena such as interspecies competition. The Ifni Lake is a genuine high-mountain lake, subject to severe environmental conditions. It has a very simple food chain: there is only one species of algae, an unicellular blue-green, one copepod species, one rotifer and one fish. In general some features of a definite interest for fundamental limnology were found: the presence of a pelagic Rhabdocoelid in Dayat Ifrah, some particularities in the vertical distribution of a number of plankton species, the existence of a layer of relatively warm water near the bottom of Lake Ifni. The latter is explained by a strong bottom current which flows through the lake between its phreatic in- and outlets. Finally, stress is laid on the under-exploitment of Moroccon inland waters with respect to a freshwater fishery. Yet, perspectives are good and some suggestions are forwarded.     

红树林溶磷菌的初步鉴定、溶磷能力测定及其优化培养

对分离来自华南红树林的溶磷菌进行16S rDNA或ITS等基因水平上的初步鉴定, 测定其溶解无机磷的能力, 并对溶磷菌的生长培养基条件进行优化。结果表明, 溶磷真菌的溶磷效果明显强于溶磷细菌, 且溶磷真菌的溶解无机磷能力与培养液的pH呈极显著负相关, 而溶磷细菌的溶磷能力与pH没显著相关关系。单因素实验表明, 对供试菌株生长的合适碳源为麦芽糖, 氮源为尿素。通过正交实验得到的优化培养基为麦芽糖5 g/L、尿素0.05 g/L、NaCl 5 g/L、pH 5, 在30°C下培养48 h菌落总数可达6.06×     

深圳湾外来红树植物海桑幼苗生长及其影响因子

选取深圳湾红树林的林缘、林窗及郁闭海桑Sonneratia caseolaris林和秋茄Kandelia obovata林等4种环境下自然生长的海桑幼苗,测其生物量、光合特性等指标。结果表明,林缘海桑幼苗生物量累积最大,叶片生物量所占比重最高,幼苗通过提高叶片面积和叶片数量,增加光合速率、水分利用率和光合氮利用率而加速生长。综合分析4种环境的环境因子发现,光照强度是决定幼苗速生并占领生态位的关键生态因子。该结果为研究深圳湾外来种海桑的危害及其防控和管理措施提供参考。     

Zooplankton Distribution Related to Environmental Factors and Phytoplankton in a Shallow Tropical Lake (Lake Guiers,Senegal, West Africa)

The chemical and biological characteristics of Lake Guiers (Senegal) have changed markedly since the impoundment of the Senegal River (Diama and Manantali dams) and subsequent development of irrigated agriculture in the nineteen eighties. On a longitudinal transect of 10 stations (from south to north), the environmental characteristics and the spatial variability of physicochemical variables, phytoplankton and zooplankton communities were studied. Within a marked south‐north gradient, the southern stations were characterized by the highest conductivity and pH and by the lowest values of suspended solids, chlorophyll‐a concentrations and phytoplankton abundance (mainly Chlorophycea, Cyanobacteria and Bacillariophycea). The spatial distribution of zooplankton showed a clear distinction between the southern zone, characterized by the presence of the rotifers Brachionus falcatus and Conochiloides sp., the cladoceran Bosmina longirostris, the cyclopoid Thermocyclops neglectus and the calanoid Pseudodiaptomus hessei. A co‐inertia analysis clearly showed that environmental factors and phytoplankton drives the spatial distribution of zooplankton communities. The comparison of our data with previous studies suggests a marked change in the biological communities since the impoundment of the Senegal River, with rarefaction of P. hessei and proliferation of the cyclopoid Mesocyclops ogunnus. Several hypotheses are discussed to explain these biological changes. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Some Factors Affecting on Dry Weight,Organic Weight and Concentrations of Carbon and Nitrogen in Freshly Prepared and in Preserved Zooplankton

Effects of rinsing and preservation on dry weight, organic weight, and chemical composition were determined on the chaetognath Sagitta nagae and the copepods Calanus sinicus, Pleuromamma xiphias and Acartia tonsa. Samples rinsed with distilled water were always lighter than comparable samples rinsed with seawater, showing apparent decrease in the organic matter and chemical contents (as total carbon and nitrogen) by weight; these losses increased with increasing volume of the rinse water. The volume of distilled water used for rinsing should be less than 0.3 ml per 1 mg dry weight of sample in order to avoid the significant loss of body substances. Isotonic ammonium formate rinse often resulted in the widest range of variation and on an average the organic weight and chemical contents were slightly lower than those of fresh samples rinsed with filtered seawater. Freeze-drying samples resulted in dry and organic weights as well as chemical compositions that were somewhat greater than oven-dried samples. The organic matter and chemical contents by weight decreased significantly within 2.5 days of being placed in Borax-buffered formaldehyde-sea water solution. Loss of organic weight from fresh samples exceeded 20% after one week of the preservation. Hexamine-buffered formaldehyde solution showed a result which was different from the Borax-buffered solution.     

Further Studies on Leptospirosis in Small Rodents and Shrews in Finland. A Report on Investigations Made in 1963-64

In previous investigations on small mammals in Finland (Rislakki & al 1954, Rislakki & Salminen 1955, Salminen 1956), the Leptospira icterohaemorrhagiae-frequency in rats (Rattus norvegicus) was rather high (43.1 %). Leptospira-positive cases were also found in house mice (L. sejroe 23.3 %), harvest mice (L. hataviae 9.0 %), yellow necked field mice (L. poi 12.5 %), common voles (L. sejroe and L. bataviae together 12.1 %), field voles (L. sejroe and L. bataviae together 10.7 %) and in common shrews (L. poi 1.2 %). Specimens of other species sent in for investigation (Norway rat, common red backed vole, large tooth backed vole, northern red backed vole, root vole, water vole, wood lemming, Laxmann's shrew, lesser shrew and water shrew) gave negative results.     

Determination of Key Environmental Factors Responsible for Distribution Patterns of Fiddler Crabs in a Tropical Mangrove Ecosystem

In tropical regions, different species of fiddler crabs coexist on the mangrove floor, which sometimes makes it difficult to define species-specific habitat by visual inspection. The aim of this study is to find key environmental parameters which affect the distribution of fiddler crabs and to determine the habitats in which each species was most abundant. Crabs were collected from 19 sites within the mudflats of Sepang-Lukut mangrove forest. Temperature, porewater salinity, organic matter, water content, carbon and nitrogen content, porosity, chlorophyll content, pH, redox potential, sediment texture and heavy metals were determined in each 1 m² quadrate. Pearson correlation indicated that all sediment properties except pH and redox potential were correlated with sediment grain size. Canonical correspondence analysis (CCA) indicated that Uca paradussumieri was negatively correlated with salinity and redox potential. Sand dwelling species, Uca perplexa and Uca annulipes, were highly dependent on the abundance of 250 μm and 150 μm grain size particles in the sediment. Canonical Discriminative Analysis (CDA) indicated that variation in sediment grain size best explained where each crab species was most abundant. Moreover, U. paradussumieri commonly occupies muddy substrates of low shore, while U. forcipata lives under the shade of mangrove trees. U. annulipes and U. perplexa with the high number of spoon tipped setae on their second maxiliped are specialized to feed on the sandy sediments. U. rosea and U. triangularis are more common on muddy sediment with high sediment density. In conclusion, sediment grain size that influences most sediment properties acts as a main factor responsible for sediment heterogeneity. In this paper, the correlation between fiddler crab species and environmental parameters, as well as the interaction between sediment characteristics, was explained in order to define the important environmental factors in fiddler crab distributions.     

Experimental and Analytical Studies of Pteridophytes: XXXII. Further Investigations on the Effect of Undercutting Fern Leaf Primordia

An account is given of experiments in which young primordiaand primordium sites at the apex of Dryopteris aristata wereisolated basally and laterally by undercutting and deep radialincisions. The treatments had the effect of destroying or severingthe incipient vascular tissue underlying the primordium on itsabaxial and lateral sides. Provided the shoot apex had not beendamaged during treatment, neither buds nor centric (or radial)leaves were induced as a result of the experimental procedureemployed. On the contrary leaves with distended bases, showingan abnormally rapid rate of growth, were usually produced. Theresults obtained are against the view that a leaf-trace, differentiatingacropetally in advance, determines the formation of a primordium;but they support the thesis that the apical cell group exercisesa regulative effect on the growth and morphogenetic activitiesof the apical meristem and young primordia. The evidence alsosupports the view that the incipient vascular tissue is importantin morphogenesis in that it affords a pathway for the translocationof nutrients and hormonal substances.     

Studies on Plankton Parasites: III. Examples of the Interaction between Parasitism and other Factors determining the Growth of Diatoms

This paper deals with the interrelations of populations of planktonorganisms and their parasites in two English lakes. The organismsconsidered are diatoms, mainly Asterionella farmosa but alsoTabellaria fenestrata var. asterionelloides, Fragilaria crotonensis,and Melosira italica, with a blue-green Oscillatoria agardhiivar. isothrix. The parasites are the Chytrids Rhizophidium planktonicumon diatoms and R. megarrhizum on Oscillatoria. The parasites may delay the time of maximum algal number ormay decrease the size of the maximum. Generally parasitism ofone alga favoura the development of others. Various other complexitiesarise from the interaction of these factors with nutritionalconditions.     

Studies on transfer ribonucleic acids and related compounds. VIII(1). Further studies on aromatic phosphoramidates as a protecting group for phosphomonoesters

Stability of aromatic phosphoramidates was studied using 2',3'-O-dibenzoyluridine 5'-phosphoramidates and N,2',3'-O-tribenzoylcytidine 5'-phosphate. The effect of dicyclohexylcarbodiimide in this mixture was investigated. Decomposition of the anilidate was slower in the presence of DCC.Substituted anilidates of uridine 5'-phosphate were synthesized and the stability of these amidates in anhydrous pyridine was studied.2'-O-Benzoyluridine 3'-phosphoranilidate and the corresponding beta-naphthylidate were compared in their stabilities in anhydrous pyridine, 50% aqueous pyridine and 80% acetic acid. 2'-O-Benzoyluridine 3'-phosphoro-beta-naphthylidate was used for synthesis of dinucleotides.