Fish recruitment, dispersal, and trophic interactions in a heterogeneous lotic environment

I examine how dispersal of juvenile creek chubs (Semotilusatromaculatus) from beaver ponds into adjacent stream environments interacts with temporal abiotic variability to influence fish foraging, growth, and long-term persistence in the lotic ecosystem. Minnow trapping in upstream and downstream beaver ponds, along with weir traps used to monitor directional movement, indicated that most chubs colonized the stream from the downstream beaver pond. Large annual fluctuations in density of age 0 creek chubs occurred in the stream over a 10-year sampling period. Multiple regression analysis indicated that stream temperature, precipitation, and the density of reproductive creek chubs were not correlated with summer density of age 0 chubs in the stream. The factor most strongly associated with increased density of age 0 creek chubs was creation of the downstream beaver pond during the 6th–7th years of the study, suggesting dispersal from the pond was the primary factor determining age 0 fish density in the stream. Most individuals in the strong year classes neither persisted in the stream through their first winter nor resulted in an increased abundance of older age classes in later years. Comparison of age 0 fish density in summer to the proportion of fish surviving to age 1 in spring suggested that overwinter mortality was density dependent. Furthermore, a comparison of the size structure for age 0 individuals in summer to age 1 individuals the following spring indicated that winter mortality was size dependent. Experiments in an artificial stream adjacent to the natural channel revealed that fish growth was strongly density dependent, decreasing as fish density increased across both spring and summer, and elevated and low discharge. The decline in invertebrate prey captured by the fish and the subsequent decline in fish growth appeared to be particularly pronounced under low discharge in summer. Changes in juvenile creek chub density had no significant effect on benthic insect or crustacean abundance, suggesting that exploitative competition for limited invertebrate drift resources was a more important cause of density- dependent growth than depressed local benthic invertebrate abundance. These results suggest that lotic regions adjacent to beaver ponds act as potential reproductive “sinks” for dispersing juveniles confronting seasonal and flow-mediated restrictions on resource acquisition and growth, and the occurrence of seasonal bottlenecks to their survival, especially harsh winter conditions. Received: 9 September 1996 / Accepted: 8 August 1997     

池塘桡足类休眠卵对浮游种群的潜在补充及其影响因素

休眠卵是桡足类的重要生存策略,其在沉积物中的丰度对水体种群的补充具有重要意义.干塘是池塘养殖管理的重要措施,对池塘生态系统具有重要影响.2014年2月15日(干塘前)和3月2日(干塘后),分别采集广州市南沙区养殖池塘内表层沉积物,研究沉积物中桡足类休眠卵对浮游种群的潜在补充及影响因素.结果表明: 干塘前未冷藏沉积物样品在盐度20时的潜在补充量和孵化率最高,4 ℃冷藏4周后最高值出现在盐度为15的处理组.干塘后未冷藏沉积物样品在盐度15时的潜在补充量和孵化率最高,冷藏4周后最高值出现在盐度为20的处理组.这说明干塘前桡足类休眠卵的潜在补充量显著高于干塘后,且干塘对沉积物中休眠卵的持续孵化时间有影响.     

Optimization and effect of dairy industrial waste as media components in the production of hyaluronic acid by Streptococcus thermophilus

Hyaluronic acid (HA) production using a dairy industrial waste is a more cost-efficient strategy than using an expensive synthetic medium. In this study, we investigated the production of HA using Streptococcus thermophilus under shake flask conditions using dairy industrial waste as nutritional supplements, namely whey permeate (WP) and whey protein hydrolysate (WPH). Preliminary screening using Plackett–Burman design exhibited WP, WPH, initial pH, and inoculum size as significant factors influencing HA titer. Response surface methodology design of four factors was formulated at three levels for enhanced production of HA. Shake flask HA fermentation by S. thermophilus was performed under global optimized process conditions and the optimal HA titer (342.93?mg?L^?1) corroborates with Box–Behnken design prediction. The molecular weight of HA was elucidated as 9.22–9.46?kDa. The ultralow-molecular weight HA reported in this study has a potential role in drug and gene delivery applications.     

Population genetics and reproductive strategies of two Notostraca (Crustacea) species from winter ponds in Israel

Fluorescent-amplified fragment length polymorphism (FAFLP) fingerprinting assay was used to compare the genetic diversity within and between tadpole shrimps (Notostraca) populations of Lepidurus apus (n=7) and Triops cancriformis (n=2) from rain pools in Israel. Each ephemeral water body has revealed a unique fingerprint pattern with an entailed genetic drift between nearby ponds. High similarity of genotypic diversity within each geographic area led to three clusters of water bodies, north, south and center of Israel. FAFLP assays on several newly hatched individuals of T. cancriformis revealed high identity amongst kin, as compared to L. apus where newly hatched from the same maternal source showed high diversity. Results indicate that T. cancriformis populations from Israel are probably parthenogenetic as indicated by clonal structures. The higher genetic variability in the L. apus populations and in laboratory-hatched specimens indicates the existence of sexual reproduction.     

A comparison of thermal treatment processes for hazardous waste

This paper (the second in a series of three) compares incineration options for hazardous waste with LCA. Provided that acceptance criteria are met with regard to metals, PAHs and chlorine, Dutch Municipal Solid Waste Incinerators (MSWls) appeared to be preferable above rotary kilns since they have a better energy recovery and — unlike rotary kilns — produce reusable slags. The position of the cement kiln relative to the MSWI and rotary kiln depends on the allocation method chosen. System enlargement, which may be most highly defensible, tends to give cement kilns the advantage. Yet, two key concerns which are unsolvable by LCA make final conclusions impossible. First, an input of highly contaminated waste leads to an enrichment of cement with metals. Long-term consequences are not known, so the incineration of waste with a high metal content will inevitably be controversial. Second, no convincing proof was found that cement kilns would not produce additional hazardous process emissions (e.g. dioxins) when using waste instead of fuel. The precautionary principle demands that such proof be provided before cement kilns can be considered for the incineration of waste with a composition other than their regular fuel.     

Selection and characterization of a proteo-chitinolytic strain of Bacillus thuringiensis,able to grow in shrimp waste media

This paper reports the selection and characterization of Bacillus thuringiensis strains, with ability to grow in a proteo-chitinaceous substrate (milled shrimp waste) as the sole ingredient. Selected strains were able to produce crystal proteins, as well as proteases and chitinases as fermentation by-products. By a preliminary, qualitative screening of 152 B. thuringiensis strains, grown on media rich in protein and chitin, eight strains were selected. These strains were cultured in a liquid medium containing milled shrimp waste and their kinetics of protease production were followed. The two most active proteolytic strains (Bt-103 and Bt-112) were characterized by their crystal protein content, plasmid profiles, crystal ultrastructure, and toxicity towards Manduca sexta, Aedes aegypti and Leptinotarsa texana. The only activity recorded in these species was moderate toxicity of strain Bt-112 against Manduca sexta first instar larvae, as well as the highest proteolytic and chitinolytic activities. Its bipyramidal crystals were associated with semi-cuboidal inclusions and although its crystal proteins were similar to those of B. thuringiensis kurstaki (HD-1), its plasmid content was quite different. Serotyping of Bt-112 indicated that it belongs to serovar. tolworthi. Further studies with a similar strategy might render more strains with ability to grow in a rich waste by-product like the shrimp waste, which may show not only higher insecticidal activity, but also with the ability to produce extracellular enzymes with biotechnological applications.     

大气质量提高与农业中的硫肥需求

论述了植物对硫素的生理需求,大气中含硫化合物的来源、组成与含量以及对植物生态系统的硫素补充作用,植物对气态硫化物的吸收、同化能力及适宜浓度等．近年来由于人类健康与生态环境的需要,世界各国纷纷通过法律体制对工业含硫废气的排放标准进行了严格控制,却导致了作物缺硫现象的频繁发生,在某些地区硫已成为限制农业生产的最重要肥料限制因素．为此,全球农业中硫肥的需求量猛增且有效性范围不断扩大,进而对硫肥的研究与开发利用提出了新的要求     

Physio-chemical characterization of indigenous agricultural waste materials for the development of potting media

Organic residues are an important factor that directly affects fruiting tree seedlings' health at earlier stages. It provides a suitable environment for seedling growth by providing better nutrient ions, water, and aeration. However, low organic contents and high shrinkage of most organic materials mostly deteriorate ideal potting media characteristics. Low aeration, high water, and nutrients leaching decrease seedling growth and cause a significant loss of valuable resources. That is why the current study was conducted to screen out the best indigenous materials based on particle size to produce good characteristics bearing potting media. For that, eight different ingredients, i.e., “sugarcane”, “coconut coir”, “wheat straw”, “rice straw”, “corn cob”, “leaf litter”, “farmyard manure”, and “sunflower heads” were collected. Initially, all the materials were air-dried and processes as per requirement. After grinding, three particles size (fine = < 2 mm, medium = 3 mm and coarse = 5 mm) were separated by sieving. Results showed that decreasing particle size in “rice straw”, “corn cob”, “farmyard manure,” and “sunflower head” decreased leachate pH. Higher EC in leachates was negatively correlated with particle size in all potting media ingredients. Except for farmyard manure, fine particle size increases the water-holding ability of potting media ingredients. However, air-filled porosity was associated with a decrease in particle size of potting media in gradients. In conclusion, farmyard manure, “sunflower heads”, “leaf litter” and “sugarcane” should be incorporated while making a combination for potting media. More investigations are suggested by mixing different particle size ingredients to prepare potting media.     

Fluorescent carbon dots synthesized by waste wind turbine blade for photocatalytic degradation

Developing novel waste recycling strategies has become a feasible solution to overcome environmental pollution. In this work, a method of using waste wind turbine blade (WTB) as a carbon source to synthesize blue fluorescent carbon dots (B-CDs) by hydrothermal treatment is proposed. B-CDs are spherical and have an average particle size of 5.2 nm. The surface is rich in C–O, C=O, −CH₃, and N–H bond functional groups, containing five elements: C, O, N, Si, and Ca. The optimal emission wavelength of B-CDs is 463 nm, corresponding to an excitation wavelength of 380 nm. Notably, a relatively high quantum yield of 29.9% and a utilization rate of 40% were obtained. In addition, B-CDs can serve as a photocatalyst to degrade methylene blue dye, with a degradation efficiency of 64% under 40-min irradiation conditions. The presence of holes has a significant influence on the degradation process.     

The Succession of Bacterial Community Structure in Groundwater from a 250-m Gallery in the Horonobe Underground Research Laboratory

We investigated the change in bacterial community structure after drilling boreholes, 09-V250-M02 and 09-V250-M03, in the 250-m deep research gallery of the Horonobe Underground Research Laboratory. In the 09-V250-M02 borehole, ?-Proteobacteria were predominantly detected in the clone library analyses of the groundwater samples conducted immediately after drilling. All the ?-Proteobacteria clones were closely related to Arcobacter spp., which are known to be sulfide-oxidizing chemoautotrophic bacteria. After 4 years, the microbial structure drastically changed, and most detected operational taxonomic units were uncultured species such as candidate division OP9 and Chloroflexi relatives, which are frequently detected in deep sea sediments. The results indicated that the microbial community structure was drastically affected by borehole drilling and was concomitant with oxidation perturbation. However, these disturbed microbial communities changed within a few years to a microbial community composed of uncultivated species such as OP9 and Chloroflexi.