Effect of Integrated Nutrient Management on Rice Yield,Soil Nutrient Profile,and Cyanobacterial Nitrogenase Activity under Rice–Wheat Cropping System

We assessed the cyanobacterial inoculation, green manure (GM) application, and chemical nitrogen (N) fertilization on grain/straw yield, nutrient balance, and nitrogenase activity under individual and integrated nutrient management mode in a rice–wheat cropping sequence. Individual and integrated application of cyanobacterial biofertilizer (CB) and GM with chemical fertilizer improved the soil health and production of rice crop. Integration of cyanobacterial and green manure resulted in a savings of 50 kg N ha^?1. Functional relationships (R2, –83.5 to 95.7%) between the different sources of nutrients revealed that the maximum positive contribution of cyanobacteria was on final available N (45.2%) and available phosphorus (P, 18.5%). Green manure had the greatest contribution to total N, total P, zinc, iron, and manganese (Mn). However, cyanobacteria had a negative relationship with Mn and sodium (Na, –30.19%). A negative relationship with Na indicates the possibility of using cyanobacteria as an ameliorating agent for salt-affected soil.     

Inferring biological soil crust successional stage using combined PLFA, DGGE, physical and biophysiological analyses

Arid areas are highly sensitive to climate change and are ideal model systems to study the potential impact of climate change on species' community structure. Biological soil crust (BSC) formation plays an ecological role in a number of key processes in the development of dry ecosystems. It was hypothesized that BSC succession and function are affected by aridity level and limited by rainfall. Furthermore, it is possible to infer the direction of the BSC succession based on aridity level, and the latter can imitate future climate change scenarios. The objectives of this study were to investigate the microbial biomass and diversity of the BSC structure in three sites differing in aridity level (semiarid, arid and hyper-arid), by combining physical and biophysiological measurements with 16S rRNA gene fragment and phospholipid fatty acid (PLFA) analyses. Physical and biophysiological parameters of the BSC were significantly influenced by aridity level. Total protein and polysaccharide contents were strongly correlated with total PLFA-based microbial biomass. Gram-positive biomarkers and microbial biomass were significantly higher in the wettest (semiarid) site than in the driest (hyper-arid) one. Multivariate-analysis based ordination of the PLFA data segregated the cluster of semiarid data from that of the hyper-arid site, while data from the arid site were dispersed between the two. The phylogenetic distribution of prominent 16S rRNA bacterial gene sequences along the aridity levels was in agreement with the PLFA analysis: the hyper-arid site was dominated by the cyanobacterium Microcoleus vaginatus, while diverse populations of cyanobacteria and soil bacteria were found in the other sites. These complementary tools allowed a simple and sensitive measurement of the influence of aridity levels on BSC successional stage. The results demonstrate that different aridity levels correspond to different BSC successional stages and those differences can be used as parameters for global change scenarios.     

A review of cyanobacterial odorous and bioactive metabolites: Impacts and management alternatives in aquaculture

Increased demand has pushed extensive aquaculture towards intensively operated production systems, commonly resulting in eutrophic conditions and cyanobacterial blooms. This review summarizes those cyanobacterial secondary metabolites that can cause undesirable tastes and odors (odorous metabolites) or are biochemically active (bioactive metabolites) in marine and freshwater, extensive and intensive aquaculture systems. For the scope of this paper, biochemically active metabolites include (1) toxins that can cause mortality in aquaculture organisms or have the potential to harm consumers via accumulation in the product (hepatotoxins, cytotoxins, neurotoxins, dermatoxins, and brine shrimp/molluskal toxins), (2) metabolites that may degrade the nutritional status of aquaculture species (inhibitors of proteases and grazer deterrents) or (3) metabolites that have the potential to negatively affect the general health of aquaculture species or aquaculture laborers (dermatoxins, irritant toxins, hepatotoxins, cytotoxins). Suggestions are made as to future management practices in intensive and extensive aquaculture and the potential exposure pathways to aquaculture species and human consumers are identified.     

Seasonal changes in periphyton nitrogen fixation in a protected tropical wetland

Cyanobacteria are important for global nitrogen cycle and often form complex associations referred to as cyanobacterial mats or periphyton that are common in tropical, limestone-based wetlands. The objective of this study was to monitor the nitrogen fixation rate using the acetylene reduction assay of these cyanobacterial mats in a tropical, unfertilized, and protected wetland. To account for temporal and spatial variation of nitrogenase activity, we were interested in seasons in a hydrological cycle (dry, rains, and end of rains), sites with different vascular vegetation, and rates of nitrogenase activity in a 24-h cycle. The annual average of nitrogenase activity was 22 nmol C₂H₄ cm⁻² h⁻¹, with a range of <6 to 35 nmol C₂H₄ cm⁻² h⁻¹, and the annual nitrogen fixation rate of our study site (9.0 g N m⁻² year⁻¹) is higher than similar estimates from other freshwater wetlands. There was a clear temporal pattern in nitrogenase activity with a maximum rate occurring during the rainy season (August) and a maximum nitrogenase activity occurring between 0600 and 1200 hours. We found spatial differences in nitrogenase activity among the four sites that could be attributed to variations in species composition within the periphyton.     

Significance of old aspen (Populus tremula) trees for the occurrence of lichen photobionts

In the boreal forest landscape, aspen has been effectively selected against in favour of conifers. The decrease in aspen is of particular concern, since it has more host-specific species associated with it than any other boreal tree species. Recently, forest management systems have begun to include green-tree retention in order to maintain structural diversity. Earlier studies have focused on the importance of remnant aspen trees for lichen species prevalence. We have focused on the occurrence of free-living photobionts, i.e. cyanobacteria and green-algae, since a successful establishment of sexually dispersed lichens will depend upon the presence of the photobiont. Our study shows that the abundances of Gloeocystis, Nostoc, Scytonema and Trentepohlia increased with stand age, while the abundance of Trebouxia decreased. The response to clear-felling differed between genera. The two cyanobacterial genera were able to persist in clear-cuts, although they were more abundant on the northern side of the remnant trees. The green-algae showed no consistent pattern, Trentepohlia was affected while Trebouxia was unaffected. Our study indicates that the prerequisites for new-establishment for spore dispersed lichen species, on remnant aspen, may be fulfilled in terms of availability of free-living photobionts on the northern side of the trunks. In support of this interpretation we found that the occurrence of cyanolichens was positively correlated with the occurrence of free-living cyanobacteria in the clear-cuts. We conclude that tree retention is likely to provide a useful tool for increasing biodiversity in managed forest landscapes provided that source populations still exist in the surrounding landscape.     

The effect of surface growth of blue-green algae and bryophytes on some microbiological,biochemical, and physical soil properties

Summary The influence of surface growth of inoculated cyanobacteria (blue-green algae) on subsurface properties of a brown earth, silt loam soil was studied in reconstituted flooded soil columns. One blue-green algae species, Nostoc muscorum, become dominant within the first 7 days of inoculation. In light control columns (not inoculated) a bryophyte, Barbula recurvirostra, was dominant although significant growth of indigenous blue-green algae occurred. The blue-green algae counts were in the range of 1×10⁶ g^-1 dry soil in the surface layer (0–0.7 cm) in both columns. Any effect of surface phototrophic growth on soil properties was restricted to the surface layer. In inoculated columns there was a twofold increase in microbial biomass and an eightfold increase in bacterial numbers by week 13. However, bacterial numbers declined so that there was only a 2.8-fold increase by week 21. Dehydrogenase (x2.1), urease (x2.8) and phosphatase (x3.1) activities and polysaccharides (+69%) increased by week 21 as a result of the blue-green algae inoculation along with a significant improvement in soil aggregation. However, similar increases occurred in the light control columns, indicating that given appropriate conditions of light and moisture indigenous species may be ultimately as effective as introduced species in bringing about biochemical and microbiological changes to soil.     

蓝藻厌氧发酵控制因素与反应器应用研究进展

蓝藻厌氧发酵生产沼气是蓝藻资源化利用的一个重要方式。综述了蓝藻厌氧发酵产沼过程的控制因素和厌氧反应器的应用,为从工程上实现蓝藻发酵制沼气提供参考。     

蓝藻大量堆积、死亡与黑水团形成的关系

经过多年治理,太湖水环境状况得到一定程度的改善,但大部分湖区仍处于富营养化状态,夏季水华很严重,在适宜的环境条件下会诱发黑水团。2011年8月28日至9月27日在太湖梅梁湖杨湾水域进行为期1个月的原位蓝藻堆积围隔试验,分析蓝藻大量堆积、死亡过程中水体关键环境要素的变化趋势,并基于试验结果初步分析了其与黑水团形成之间的关系。结果表明,蓝藻积聚死亡会导致水体处于缺氧状态,水体溶解氧浓度基本在0.2mg/L上下波动;同时,水体主要营养盐浓度会在短时间内迅速上升,TN、NH4+-N和TP浓度最高值分别为初始值的16、48和46倍。高温时段打捞水体表面积聚的蓝藻是防止蓝藻死亡进一步恶化环境的有效措施。蓝藻死亡的同时会促进致黑物质的产生,丰富的有机污染底泥的参与对于黑水团的形成有决定作用,但形成典型的黑水团需要一定水平的风浪扰动。     

Effects of insecticide acetamiprid on photosystem II (PSII) activity of Synechocystis sp. (FACHB-898)

Effects of insecticide acetamiprid on photosystem II (PSII) activity of Synechocystis sp. were investigated by a variety of in vivo chlorophyll fluorescence tests. Acetamiprid exposure increased the proportion of inactivated PSII reactive centers (PSII_X) and led to loss of active centers (PSII_A). High concentration (1.0 mM) acetamiprid decreased amplitude of the fast phase and increased the slow phase of fluorescence decay during reoxidation. The electron transport after Q_A was hindered by high concentration acetamiprid and more Q_A had to be reoxidized through S₂(Q_AQ_B)⁻ charge recombination. Acetamiprid decreased the density of the active reaction centers, electron transport flux per cross section and the performance of PSII activity but had little effect on dissipated energy flux per reaction center, antenna size and the maximum quantum yield for primary photochemistry (F_v/F_m). The target site of acetamiprid toxicity to the PSII of Synechocystis sp. was electron transfer on the acceptor side.