Biosorption of Uranium Ions by Marine Macroalga Padina pavonia          下载免费PDF全文

Sule Aytas  Elif Gunduz  Cem Gok 《洁净——土壤、空气、水》2014,42(4):498-506

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Microfossils from the Arymas and Debengda formations, the Riphean of the Olenek Uplift: Age and presumable nature     

A. M. Stanevich  E. N. Maksimova  T. A. Kornilova  D. P. Gladkochub  A. M. Mazukabzov  T. V. Donskaya 《Stratigraphy and Geological Correlation》2009,17(1):20-35

Studied assemblages of diverse organic-walled microfossils separated from the Arymas and Debengda formations of the Olenek Uplift include several paleobiological groups of microorganisms. Sufficiently large morphotypes of the first group are identified with remains of cyanobacteria. Morphotypes of variable spiral structure, which dwelt in association or in symbiosis with cyanobionts, are attributed to the same bacterial community. The other group includes a series of different acritarch genera whose characters suggest their affinity with green algae of the order Desmidiales. It is very likely that this group coexisted on siliciclastic shoals with large ancestral forms of the present-day brown algae. Several microfossil taxa have been known before from the Neoproterozoic deposits only. With due regard for the relatively gradual accumulation of sedimentary succession lacking large hiatuses and for the regular series of K-Ar dates characterizing three Riphean formations of the Olenek Uplift, it is possible to suggest that there was the Arymas-Debengda-Khaipakh cycle of long-lasted, almost uninterrupted sedimentation within the time span of 1250–900 Ma. It is also admissible that age ranges of some Late Precambrian microfossils are much larger than their distribution intervals postulated formerly.  相似文献   

Bottom-up control of phytoplankton growth in spring blooms in Central Yellow Sea,China     

《Deep Sea Research Part II: Topical Studies in Oceanography》2013

The source and significance of three nutrients – nitrogen, phosphorous and silicon – were investigated by a modified dilution method performed on seawater samples from the Central Yellow Sea (CYS), in spring blooming period of 2007. This modified dilution method accounted for the phytoplankton growth rate, microzooplankton grazing mortality rate, the internal and external nutrient pools, as well as nutrients supplied through remineralization by microzooplankton grazing. The results indicate that phytoplankton growth during the bloom is mostly contributed by internal nutrient pools (K_I=0.062–1.730). The external nutrient pools (K_E=<0–0.362) are also of importance for phytoplankton growth during the bloom at some sampling sites. Furthermore, the contribution of the recycled-nutrient pool by remineralization (K_R=<0–0.751) is significant when microzooplankton grazing rate was higher than 0.5 d⁻¹ during the spring phytoplankton blooms in the Central Yellow Sea. Compared with internal phosphorus, internal nitrogen and silicon contribute more to the phytoplankton production at most sampling stations.  相似文献   

Kelp forests in False Bay: urchins vs macroalgae in South Africa’s southwest coast biogeographical transition zone     

《African Journal of Marine Science》2013,35(4):395-406

Kelp forests along South Africa's southwest coast occur in a region of biogeographical overlap. Commonly referred to as transition-zone kelp forests, these dynamic ecosystems are particularly susceptible to grazing from species such as urchins. This study explores relationships between urchins and macroalgae in transition-zone kelp forests along the western side of False Bay. Six kelp forests in this region were sampled. At each site, the urchin Parechinus angulosus and kelp Ecklonia maxima were counted, percentage cover of understorey algae was recorded, and drift algae were collected. Despite variability in urchin and algal cover across sites, kelps generally increased from north to south, while urchins did the opposite. Urchins were negatively associated with macroalgae, although this relationship was weak. A localised threshold of 50 urchins m^–2 was identified, above which kelp density failed to increase above 10 m^–2 and percentage cover of understorey algae usually remained below 20%. Surprisingly, no relationship was discovered between drift algae and attached algae. The findings highlight the complexity of these cool-water environments. To better understand the role of urchins in this system, particularly under changing climate trends, experimental research into the feeding behaviour and possible effects of urchins on attached algae in the presence/absence of drift algae is advised.  相似文献   

Insights into zooplankton‐cyanobacteria interactions derived from enclosure studies     

Carolyn W. Burns 《新西兰海洋与淡水研究杂志》2013,47(3):477-482

Few workers have used enclosures specifically to study interactions between zoo‐plankton and cyanobacteria. Differences among studies in enclosure size, nutrient level, plankton abundance and species composition, presence or absence of fish, and length of experiments make generalisations difficult. Zooplankton had no direct effect on the growth of ungrazed cyanobacteria (Anabaena flos‐aquae, Aphanizomenon flos‐aquae, large Microcystis colonies) in short‐term (<5 days) and long‐term (> 1 month) enclosure studies. When large cyanobacteria were abundant, some Daphnia spp. snowed reduced reproduction and development. When large grazers were abundant they suppressed the growth of edible, colonial cyanobacteria (Aphanizomenon elenkinii, small Microcystis colonies). By altering the ambient light and nutrient environment, large zooplankton may suppress cyanobacteria; evidence for the importance of grazers in promoting cyanobacterial dominance by removing competing phytoplankton species is equivocal. Zooplankton may suppress nitrogen fixation by cyanobacteria through ammonia excretion and may promote a change in dominance from diatoms to cyanobacteria through recycling phosphorus but not silicon.  相似文献   

Light‐dependence of photosynthesis and growth in cyanobacteria: Implications for their dominance in eutrophic lakes     

Max M. Tilzer 《新西兰海洋与淡水研究杂志》2013,47(3):401-412

In eutrophic lakes cyanobacteria are favoured relative to other phytoplankton, both under stratified and mixed conditions. During stratification, gas vacuole formation allows the accumulation of dense surface scums which attain the highest possible area‐specific photosynthetic rates in aquatic environments owing to high irradiances, near‐complete harvesting of impinging light, and minimal light inhibition and photo‐oxidation. During moderate mixing, high yields of biomass can be achieved by effective light harvesting for photosynthesis (aided by phycobilin pigments) and low maintenance energy requirements at low mean irradiances. Howevrr, nitrogen fixation competes for energy and reductant with photosynthesis, and leads to a decline of light‐saturated maximum growth rates. Wind‐driven vertical mixing and lateral advection are the main causes for the instability of cyanobacterial blooms in hyper‐eutrophic lake ecosystems.  相似文献   

Culture observation and molecular phylogenetic analysis on the blooming green alga Chaetomorpha valida (Cladophorales, Chlorophyta) from China     

邓蕴彦  汤晓荣  詹子锋  滕林宏  丁兰平  黄冰心 《中国海洋湖沼学报》2013,31(3):552-559

The marine green alga Chaetomorpha valida fouls aquaculture ponds along the coastal cities of Dalian and Rongcheng, China. Unialgal cultures were observed under a microscope to determine the developmental morphological characters of C. valida. Results reveal that gametophytic filaments often produce lateral branches under laboratory culture conditions, suggesting an atypical heteromorphic life cycle of C. valida between unbranched sporophytes and branched gametophytes, which differs from typical isomorphic alternation of Chaetomorpha species. The shape of the basal attachment cell, an important taxonomic character within the genus, was found variable depending on environmental conditions. The 18S rDNA and 28S rDNA regions were used to explore the phylogenetic affinity of the taxa. Inferred trees from 18S rDNA sequences revealed a close relationship between C. valida and Chaetomorpha moniligera. These results would enrich information in general biology and morphological plasticity of C. valida and provided a basis for future identification of green tide forming algae.  相似文献   

Comparing long term sediment records to current biological quality element data - Implications for bioassessment and management of a eutrophic lake     

Tommi Kauppila  Antti Kanninen  Matias ViitasaloJohanna Räsänen  Kristian MeissnerJukka Mattila 《Limnologica》2012,42(1):19-30

Defining reference conditions for lakes situated in areas of human settlement and agriculture is rarely straightforward, and is especially difficult within easily eroding and nutrient rich watersheds. We used diatoms, cyanobaterial akinetes, remains of green algae and chironomid head capsules from sediment samples of Lake Kirmanjärvi, Finland, to assess its deviation from the initial ecological status. These site-specific records of change were compared to current type-specific ecological status assessment. All paleolimnological data indicated deviation from natural conditions and mirrored the current, monitoring-based assessment of “moderate” ecological lake status. However, the sediment data showed that the lake should be re-typified as a naturally eutrophic lake. Sediment records as well as current monitoring data indicated temporary improvement in water quality in response to extensive fish manipulation. Our results suggest that paleolimnological records can be used to derive site-specific reference conditions and that extensive restoration efforts can result in gradual, observable improvements of water quality and ecological status.  相似文献   

Dynamics of phytoplankton associations in three reservoirs in northeastern Brazil assessed using Reynolds’ theory     

Ênio Wocyli Dantas  Maria do Carmo Bittencourt-OliveiraAriadne do Nascimento Moura 《Limnologica》2012,42(1):72-80

The aim of the present study was to evaluate the influence of seasonality on the behavior of phytoplankton associations in eutrophic reservoirs with different depths in northeastern Brazil. Five collections were carried out at each of the reservoirs at two depths (0.1 m and near the sediment) at three-month intervals in each season (dry and rainy). The phytoplankton samples were preserved in Lugol's solution and quantified under an inverted microscope for the determination of density values, which were subsequently converted to biomass values based on cellular biovolume and classified in phytoplankton associations. The following abiotic variables were analyzed: water temperature, dissolved oxygen, pH, turbidity, water transparency, total phosphorus, total dissolved phosphorus, orthophosphate and total nitrogen. The data were investigated using canonical correspondence analysis. The influence of seasonality on the dynamics of the phytoplankton community was lesser in the deeper reservoirs. Depth affected the behavior of the algal associations. Variation in light availability was a determinant of changes in the phytoplankton structure. Urosolenia and Anabaena associations were more abundant in shallow ecosystems with a larger eutrophic zone, whereas the Microcystis association was more related to deep ecosystems with adequate availability of nutrients. The distribution of Cyclotella, Geitlerinema, Planktothrix, Pseudanabaena and Cylindrospermopsis associations was different from that seen in subtropical regions and the substitution of these associations was related to a reduction in the eutrophic zone rather than the mixture zone.  相似文献   

海南清澜港水母暴发期间浮游生物生态特征研究   总被引：2，自引：0，他引：2  

岑竞仪  欧林坚  吕淑果  张云  李霞  江涛  吕颂辉 《海洋与湖沼》2012,43(3):595-601

自2010年12月-2011年5月,调查研究了海南清澜港海域的浮游生物群落特征,重点跟踪监测了2011年5月黄斑海蜇(Rhopilema hispidum)暴发期间海水营养盐水平及浮游生物群落结构变化。通过样品分析,共鉴定出浮游植物111种(变种和变型),细胞密度范围为(2.25×104)-(8.19×108)cells/L,浮游动物36种,丰度范围为19.39-25798.74ind/L,其中浮游动物以桡足类为优势种群,浮游植物以硅藻为主要优势种。在水母暴发期间浮游植物以热带骨条藻(Skeletonema tropicum)为主,浮游动物以桡足类为主。清澜港养殖区为水母水螅体提供生长发育的环境和水母暴发前期浮游植物大量增殖,为浮游动物提供充足的食物,在一定程度上促进了水母的暴发。  相似文献