Integrated Membrane Bioreactor for Water Quality Control in Marine Recirculating Aquaculture Systems

The aquaculture live feed organisms Acartia tonsa (a calanoid copepod, experiment 1) and Brachionus “Cayman” (a rotifer, experiment 2) were cultivated in marine recirculating aquaculture systems (RAS), respectively. The pilot plant was built as a combination of conventional RAS (cRAS) and as a modified RAS which implemented an ultrafiltration membrane bioreactor (MBR) for the removal of fine suspended solids and colloidal particles as part of the treatment system (mRAS). The two treatment schemes were connected to the same biofilter (a moving bed bioreactor). In the first experiment, the membrane was operated with no extraction of concentrate, and hydraulic retention time (HRT) of 6 hours (i.e., water exchange in the cultivation tanks of 4 times per day). In the second experiment, the membrane was operated with daily extraction of concentrate, and HRT of 12 hours. Results show that the MBR option is more efficient in removing particles from the recycle stream than conventional RAS. However, the impact this has on the number of particles in the live feed cultivation tanks is not readily apparent based on particle analysis. The amount of suspended solids added during feeding exceeds the amount removed in the recycle system. This requires a higher recirculation rate and different membrane operating conditions.     

Use of Copper to Selectively Inhibit Brachionus calyciflorus (Predator) Growth in Chlorella kessleri (Prey) Mass Cultures for Algae Biodiesel Production

A single Brachionus rotifer can consume thousands of algae cells per hour causing an algae pond to crash within days of infection. Thus, there is a great need to reduce rotifers in order for algal biofuel production to become reality. Copper can selectively inhibit rotifers in algae ponds, thereby protecting the algae crop. Differential toxicity tests were conducted to compare the copper sensitivity of a model rotifer—B. calyciflorus and an alga, C. kessleri. The rotifer LC₅₀ was <0.1 ppm while the alga was not affected up to 5 ppm Cu(II). The low pH of the rotifer stomach may make it more sensitive to copper. However, when these cultures were combined, a copper concentration of 1.5 ppm was needed to inhibit the rotifer as the alga bound the copper, decreasing its bioavailability. Copper (X ppm) had no effect on downstream fatty acid methyl ester extraction.     

Rotibot: Use of Rotifers as Self‐Propelling Biohybrid Microcleaners

Self‐propelled biohybrid microrobots, employing marine rotifers as their engine, named “rotibot,” are presented and their practical utility and advantages for environmental remediation are demonstrated. Functionalized microbeads are attached electrostatically within the rotifer mouth and aggregated inside their inner lip. The high fluid flow toward the mouth, generated by the strokes of rotifer cilia bands, forces an extremely efficient transport of the contaminated sample over the active surfaces of the functionalized microbeads. The reactive particles confined around the rotifer's lip are thus exposed to a high flow rate of the pollutant solution, resulting in dramatically accelerated decontamination processes, without external mixing or harmful fuels. Theoretical simulations, modeling the greatly enhanced fluid dynamic associated with such built‐in mixing effect, correlate well with the experimental observations. The rotibot thus proves to be an effective, versatile, and robust dynamic microcleaning platform for removing diverse environmental pollutants. Microbeads functionalized with lysozyme and organophosphorus hydrolase enzymes are shown to be extremely useful for enzymatic biodegradation of Escherichia coli and the nerve agent methyl paraoxon, respectively, while ligand (meso‐2,3‐dimercaptosuccinic acid) modified beads are used for removing heavy metal contaminants. Rotifer‐based biohybrid microrobots hold considerable promise as self‐propelling dynamic pumps for diverse large‐scale environmental remediation applications.     

不同温度对小种轮虫产生休眠卵影响的研究

在 10 0 0ml的圆锥形玻璃罐中 ,在盐度为 2 5‰ ,小种轮虫每天的投喂量为 2万个小球藻 /轮虫的相同条件下 ,通过控制不同的温度 (2 2℃、2 5℃、2 8℃、32℃ )研究其对小种轮虫产生休眠卵的影响。实验结果表明 :在高温 (2 8℃、32℃ )条件下所产生的休眠卵量明显高于低温 (2 2℃、2 5℃ )条件下所产生的体眠卵量 (P <0 .0 1) ,在 2 8℃条件下所产生的休眠卵量最高达到 5 90 0 0± 910 0个 /l。此结果为大规模生产小种轮虫休眠卵提供了科学依据     

Recruitment of Heliozoa, rhizopods and rotifers from the sediments of an extremely acidic lake during spring and early summer

The goal of this study was to investigate the recruitment of zooplankton from the littoral sediment of Lake 111, an acidic lake in north‐east Germany, in April (spring) and June (early summer), and its role in coupling the benthos and the pelagic. Maximum heliozoan and rhizopod recruitment occurred in early summer from sediment cores incubated at ambient water temperatures (20°C). Conversely, recruitment of the rotifer Cephalodella sp. was highest in spring at ambient spring temperatures of 12°C. A combination of passive and active recruitment processes is likely responsible. The seasonal abiotic and biotic sediment characteristics were relatively constant and therefore not likely responsible for the observed temporal recruitment pattern. The sediment water and carbon content ranged from 20 to 50% (mean = 29 ± 6% standard deviation) and 2–12% (mean = 5 ± 2% standard deviation), respectively. Similarly, there was little variation in the chlorophyll‐a (mean = 0.2 ± 0.2 µg Chl‐a g^?1 dry weight ≡ 6.1 ± 3.9 mg Chl‐a m^?2). The in situ sediment bacterial density (0.82 × 10⁹ ± 0.26 × 10⁹ g^?1 dry weight ≡ 1.01 × 10⁹ ± 0.34 × 10⁹ cells cm^?3) was high. In contrast, the abundance of zoobenthos and their resting stages was low (< 25 individuals cm^?3, and mean of 90 ± 75 cysts cm^?3, respectively), with no temporal pattern being observed. Temperature was the only abiotic factor influencing recruitment. This study suggests that, even in relatively young, chemically extreme lakes, the benthos can play an important role in whole lake microbial processes and zooplankton community composition. Such benthic repositories of resting stages potentially provide protection against adverse environmental changes.     

A critical body size for use of pheromones in mate location

Pheromones have demonstrated importance in mate location in many insect species. Because chemoreception is the most universal sense, it has been assumed that pheromones also are important in aquatic organisms, including bacteria, but few have been found. The physical limits on effective strategies for organisms to come into contact for mating were modeled with assumptions appropriate for organisms less than a millimeter in size in an open aquatic environment. One sex was assumed to be motile, while the other sex was passive or devoted energy to locomotion or to diffusible pheromone production. Assuming spherical organisms, random locomotion by the second sex at the same velocity as the first sex increases the chances of contact by a factor of 4/3 over being passive; this ratio is independent of size. For detection by contact, the effectiveness of searching increases with the third power of the radius of the organisms; for detection by pheromones, search effectiveness increases with the seventh power of the radius above a critical size. Diverting energy from motility to pheromone production is not productive for organisms smaller than the critical size, which corresponds to a radius of 1.8 times the square root of the diffusion coefficient of the pheromone times the threshold concentration for detection divided by the rate of pheromone production per unit volume of organism. Thus, pheromone production is very favorable for organisms much above the critical size, which appears to be between 0.2 and 5 mm in water. On the other hand, bacteria are probably too small to use diffusable pheromones for mate location; most protozoans and rotifers may also be too small.     

淮北采煤塌陷区两个小型湖泊轮虫的群落结构特征

于2017年4月、7月、10月和2018年1月对淮北采煤塌陷区东湖和刘桥湖两个小型湖泊进行采样调查,探讨轮虫群落结构的季节变化及其与环境因子的关系。东湖共记录轮虫13科15属32种,刘桥湖共记录10科12属25种。东湖轮虫的年平均密度和生物量(2 722个/L和3.04 mg/L)明显高于刘桥湖(1 311个/L和1.30 mg/L);东湖主要优势种为刺盖异尾轮虫、暗小异尾轮虫、长肢多肢轮虫、长三肢轮虫、广布多肢轮虫和螺形龟甲轮虫,刘桥湖主要优势种为暗小异尾轮虫、长肢多肢轮虫、小链巨头轮虫、广布多肢轮虫、螺形龟甲轮虫和迈氏三肢轮虫;东湖和刘桥湖水体呈中度富营养状态;水温、总氮、总磷和叶绿素a质量浓度是影响两湖轮虫群落结构变化的重要因素,鲢、鳙鱼的捕食压力间接影响了两湖轮虫群落结构的变化。     

The relationship of the environmental effect of surfactants to their interfacial properties

In an investigation of possible relationships between interfacial properties of surfactants and their environmental effect, using several anionic and nonionic surfactants, a linear correlation was found between the parameters, ΔG ⁰ _ad/A _min, and rotifer toxicity. ΔG ⁰ _ad is a standard free energy of adsorption at the air/aqueous solution interface, and A _min is the minimal hydrated cross-sectional area of the surfactant molecule. Both quantities were evaluated from surface tension data. This correlation is much better than attempted correlations of the toxicity with the negative logarithm of the critical micelle concentration (−log CMC) or with ΔG ⁰ _ad or A _min alone. The ΔG ⁰ _ad/A _min correlation with rotifer toxicity is also better than the correlation with the analogous parameter, Δ _s ^| G _ads ^0| A_min, obtained from adsorption isotherms of the surfactants on a solid immobilized membrane simulating a cell membrane. The data support our hypothesis that toxicity is determined both by adsorption tendency and ease of cell membrane penetration.     

连云港轮虫种类初步调查分析

2007年5月初到8月底,利用浮游生物网在野外采集含有轮虫的水体,通过对轮虫标本活体形态和固定后形态的观察,初步调查了连云港地区的轮虫种类组成情况。采样地点包括连云港新浦区、连云区、东海县、赣榆县、灌云县、灌南县共6个县区,其中连云区包括淡水区和海水区,其它均为淡水区。共发现15种轮虫,隶属于6个属。海洋轮虫种类中,只发现褶皱臂尾轮虫(Brachionus plica-tilis)。对轮虫种类和数量分布的多样性分析表明,臂尾轮虫属是连云港地区的优势种属。