Cultivation of the brown alga Sargassum horneri: sexual reproduction and seedling production in tank culture under reduced solar irradiance in ambient temperature

As a large conspicuous intertidal brown alga, individuals of Sargassum horneri can reach a length of more than 7 m with a fresh weight of 3 kg along the coasts of the Eastern China Sea. The biomass of this alga as a vital component in coastal water ecology has been well documented. In recent years, a steady disappearance of the algal biomass along the once densely populated coastal areas of the Eastern China Sea has drawn attention in China. Efforts have been made to reconstruct the subtidal algal flora or even to grow the alga by use of long-lines. As part of the efforts to establish an efficient technique for producing seedlings of S. horneri, in this investigation a series of culture experiments were carried out in indoor raceway and rectangular tanks under reduced solar irradiance at ambient temperature in 2007-2008. The investigation demonstrated that: (1) sexual reproduction of S. horneri could be accelerated in elevated temperature and light climates, at least 3 months earlier than in the wild; (2) eggs of S. horneri had the potential to be fertilized up to 48 h, much longer than that of known related species; (3) suspension and fixed culture methods were both effective in growing the seedlings to the long-line cultivation stage; and (4) the life cycle of S. horneri in culture could be shortened to 4.5 months, thus establishing this alga as an appropriate model for investigating sexual reproduction in dieocious species of this genus.

Transforming kelp into a marine bioreactor

The past decade has seen the genetic engineering of various types of seaweed. To date, genetic transformation studies have been carried out in several seaweeds, including the red seaweeds Porphyra, Gracilaria, Grateloupia, Kappaphyclus and Ceramium and the green seaweed Ulva. A genetic transformation model system has been established in the most commonly cultivated seaweed, the brown seaweed Laminaria japonica (kelp), based on the transfer of technology used in land plant transformation and also by modulating the seaweed life cycle. This model showed the potential for application of transgenic kelp to the production of valuable products and an indoor cultivation system for transgenic kelp was proposed, taking into account necessary factors for bio-safety. In this review, the establishment at use of the kelp transformation model is introduced, highlighting the potential for transforming kelp into a marine bioreactor.

Cultivation of the brown alga Hizikia fusiformis (Harvey) Okamura: enhanced seedling production in tumbled culture

The reuse of holdfasts for regeneration of young seedlings or using wild juvenile plants as the seedling source has played the major role in commercial cultivation of the brown alga Hizikia fusiformis in East Asia over the past 20 years. The possibility of employing zygote-derived germlings for producing seedlings has been discussed in the literature, but has not yet become a reality. Three main obstacles have limited the use of zygotes as a main source of seedlings, (1) the dioecious nature of the algal life cycle which may lead to asynchronous male and female receptacle development and thus different timing of egg and spermatozoa expulsion, (2) the low attachment rate when using zygote-derived germlings with developed rhizoids from wild parental plants for seeding production, and (3) the problem of culturing young germlings in regions where water temperature is high in summer. In this investigation, shifting the timing of receptacle formation earlier than in nature was performed by tumbling the algae in a long-day tank (16-h light per day). Synchronization of egg and spermatozoa expulsion and thereafter fertilization were conducted in indoor tanks. Receptacle formation in constant long days could be shifted by 20 days earlier than in plants cultured on long lines in the open sea, or I month earlier than in plants growing on intertidal rocks. Synchronized expulsion of eggs and spermatozoon led to a high rate of fertilization. This was achieved by tumbling the male and female receptacle-bearing branchlets in the same tank at low density in high irradiance. In two independent trials, a total of 1,400,000 zygote-derived germlings were obtained from 620 g (fresh weight) female sporophytes. The germlings shed from the receptacles were at an identical developmental stage indicating high synchronization of expulsion of eggs and spermatozoon followed by fertilization. Approximately 63% ( +/-9.6%) of the germlings were shed from the receptacle between 16 and 24 It after fertilization and 20% ( +/-11.9%) remained on the receptacle for 3 days after fertilization. Germlings were seeded on string collectors before rhizoids started to elongate and the attachment efficiency was enhanced. Young seedlings reached 800 ( +/-50) mum in length in 25 days at 25 degreesC before they were transferred to open sea cultivation. These results provide the basis of a practical way of seedling production by use of zygote-derived germlings in the commercial cultivation of Hizikia fusiformis. (C) 2004 Elsevier B.V All rights reserved.

Photoperiodic long-day control of sporophyll and hair formation in the brown alga Undaria pinnatifida

Two photoperiodic responses, the development of sporophylls and hairs, have been quantified in sporophytes of the brown alga Undaria pinnatifida. In a final experiment, the algae were cultivated in outdoor, 2000-L seawater tanks in a greenhouse for up to 12 weeks, and daylength was regulated by automatic blinds mounted on top of the tanks. Vegetative young sporophytes were treated under short-day (SD; 8 h light per day) or long-day conditions (LD; 16 h light per day), at 12 h light per day or in a night-break regime (NB; 8 h light per day, 7.5 h dark, 1 h light, 7.5 h dark). The earliest sporophyll development was observed 6, 7 or 9 weeks under LD, NB or SD conditions, respectively. After 12 weeks the sporophylls were significantly longer and wider under LD or NB conditions than in the SD regime, and only half of the experimental algae had formed sporophylls under SD conditions, but all algae under LD or NB conditions. In a foregoing 7-week culture experiment performed in 300-L indoor tanks, enhanced sporophyll formation had also been observed under LD and not under SD conditions (NB omitted). In both experiments, blade elongation rates remained high until the end of the experiments in SD, but declined during sporophyll initiation in LD, NB or at 12 h light per day. Another difference caused by photoperiod was observed in regard to the development of surface hair spots which occurred in both experiments on the blades in LD, NB or at 12 h light per day with identical densities, but were completely lacking under SD conditions. It is concluded that U. pinnatifida is a facultatative long-day plant in regard to reproduction forming vigorously sporophylls in long days, and an obligate long-day plant in regard to hair formation.

Cultivation of the brown alga Hizikia fusiformis (Harvey) Okamura: stress resistance of artificially raised young seedlings revealed by chlorophyll fluorescence measurement

Commercial farming of the intertidal brown alga Hizikia fusiformis (Harvey) Okamura in China and South Korea in the sea depends on three sources of seedlings: holdfast-derived regenerated seedlings, young plants from wild population and zygote-derived seedlings. Like many successfully farmed seaweed species, the sustainable development of Hizikia farming will rely on a stable supply of artificial seedlings via sexual reproduction under controlled conditions. However, the high rate of detachment of seedlings after transfer to open sea is one of the main obstacles, and has limited large-scale application of zygote-derived seedlings. To seek the optimal condition for growing seedlings on substratum in land-based tanks for avoidance of detachment in this investigation, young seedlings were grown in both outdoor tanks exposed directly to sunlight and in indoor raceway tanks in reduced, filtered sunlight. Results showed that young seedlings, immediately after fertilization, could withstand a daily fluctuation of direct solar irradiance up to a level of 1800 mu mol photons m(-1)s(-1), and maintained a faster growth rate than seedlings grown in indoor tanks. Detailed experiments by use of chlorophyll fluorescence measurements further demonstrated that the overnight (12 h) recovery of optimal fluorescence quantum yield (F-v/F-m) of seedlings after 1 h treatment at 40 degrees C was 98%, and the 48 h recovery of F-v/F-m of seedlings after 1 h exposure to 1800 mu mol m(-2)s(-1) was 92%. Forty-one-day-old seedlings showed no significant decrease of optimal fluorescence quantum yield at salinity ranging from 30 to 5 ppt for a treatment up to 17 h. Six-hour desiccation treatment did not have any influence on the optimal fluorescence quantum yield. Exposure to 18 mmol L-1 sodium hypochlorite for 10 min did not damage the PSII efficiency, and thus could be used to remove epiphytic algae. The strong tolerance of young seedlings to high temperature, high irradiance, low salinity and desiccation found in this investigation supports the view that mass production of Hizikia seedlings should be performed in ambient light and temperature instead of in shaded greenhouse tanks.

Characterization of the life history of Bangia fuscopurpurea (Bangiaceae, Rhodophyta) in connection with its cultivation in China

Bangia fuscopurpurea (Rhodophyta) was cultivated in Putian (Fujian province, China). The characteristics of the life history concerned with cultivation were investigated and the cultivation procedure was presented. The gametophytic phase (thallus) and the sporophytic phase (conchocelis) occurred alternately in the life history of B. fuscopurpurea. Young thalli produced archeospores, and the number depended on the environmental factors. Temperature affected the number of archeospore release and percent of germination, and photo flux density (PFD) mainly affected the time of spore release and germination. Thalli matured from December to February and developed into the conchocelis phase through sexual reproduction. The conchocelis grown in shells had three developmental stages: vegetative conchocelis, conchosporangiall formation and conchospore formation. Pit-connections were present in the first 2 stages but absent after conchospore formation. Vegetative conchocelis and conchosporangial. branches can transform into each other. However, conchospores only developed into the gametophytic phase. Cultivation of B. fuscopurpurea was based on characterization of the life history, consisting of 3 steps: zygotospores collection, indoor cultivation of conchocelis and outdoor cultivation of thalli. Young thalli that developed from conchospores produced numerous archeospores before December. Over 90% of the crop was from the development of archeospores. The results indicated that conchosporelings were a good source of archeospores, and the development of the large quantity of archeospores acted as a more prevailing means to increase the population size. (C) 2008 Elsevier B.V. All rights reserved.

A new method for the estimation of oceanic mixed-layer depth using shipboard X-band radar images

Shipboard X-band radar images acquired on 24 June 2009 are used to study nonlinear internal wave characteristics in the northeastern South China Sea. The studied images show three nonlinear internal waves in a packet. A method based on the Radon Transform technique is introduced to calculate internal wave parameters such as the direction of propagation and internal wave velocity from backscatter images. Assuming that the ocean is a two-layer finite depth system, we can derive the mixed-layer depth by applying the internal wave velocity to the mixed-layer depth formula. Results show reasonably good agreement with in-situ thermistor chain and conductivity-temperature-depth data sets.

Effects of different light sources and illumination methods on growth and body color of shrimp Litopenaeus vannamei

Shrimps Litopenaeus vannamei with initial body weight of 2.108 +/- 0.036 g were sampled for specific growth rates (SGR) and body color measurements for 50 days under different light sources (incandescent lamp, IL; cool-white fluorescent lamp, FL; metal halide lamp, MHL; and control without lamp) and different illumination methods (illumination only in day, IOD, and illumination day and night, IDN). Body color of L. vannamei was measured according to the free astaxanthin concentration (FAC) of shrimp. The SGR, food intake (FI), feed conversion efficiency (FCE) and FAC of shrimps showed significant differences among the experimental treatment groups (P < 0.05). Maximum and minimum SGR occurred under IOD by MHL and IDN by FL, respectively (difference 56.34%). The FI of shrimp for the control group did not rank lowest among treatments, confirming that shrimp primarily use scent, not vision, to search for food. FI and FCE of shrimps were both the lowest among treatment groups under IDN by FL and growth was slow, thus FL is not a preferred light source for shrimp culture. Under IOD by MHL, shrimps had the highest FCE and the third highest FI among treatment groups ensuring rapid growth. FAC of shrimp were about 3.31 +/- 0.20 mg/kg. When under IOD by MHL and IDN by FL, FAC was significantly higher than the other treatments (P < 0.05). To summarize, when illuminated by MHL, L. vannamei had not only vivid body color due to high astaxanthin concentration but also rapid growth. Therefore, MHL is an appropriate indoor light source for shrimp super-intensive culture. SGR of shrimp was in significantly negative correlation to FAC of shrimp (P < 0.05). Thus, when FAC increased, SGR did not always follow, suggesting that the purpose of astaxanthin accumulation was not for growth promotion but for protection against intense light. (c) 2005 Elsevier B.V. All rights reserved.

Corrosion resistance of hot-dipped zinc and zinc alloy coated sheet steels under offshore atmospheric environment

The application of hot-dipped zinc and zinc-aluminum alloy coatings were introduced. Exposure tests of the steels with these coatings were conducted in the offshore atmosphere in Qingdao and Xiamen for 12 years separately. Effects of the coating thickness, alloy composition and atmospheric environment on the corrosion performance were studied. Results of the onsite exposure tests were compared with the results of a previous indoor salt spray accelerated corrosion tests. The study supports that zinc-aluminum alloy coatings are useful in providing better corrosion resistance and can be further developed for future applications.

基于线性不变矩和角度向量的立体匹配算法

针对室内场景双目立体匹配有别于一般场景立体匹配的特殊性,提出了一种计算简便、准确度高的立体图像匹配算法。该算法首先利用canny算子检测物体的边缘,根据边缘的线性不变矩寻找出目标物体,然后提取出目标物体轮廓的特征点,利用角度直方图计算出左右图像的旋转角度,最后利用角度向量实现左右图像的对应像素点的匹配。线性不变矩有效地将计算复杂度由二维降低到一维,大大降低了计算量。角度向量的提出降低了特征点匹配的复杂度,而且计算简便,准确率高。实验表明,该算法对图像的缩放、旋转、平移均免疫,具有较高的识别精度和良好的抗干扰性,计算效率高于传统方法,有着较高的应用价值。

用于移动机器人自定位的视觉路标设计

为了实现室内移动机器人的自定位,提出了一种简易美观的新型视觉人工路标以及基于对数极坐标系投影直方图的路标识别方法,并用基于共面四点的位姿估计算法计算机器人位姿。实验结果说明,路标检测具有很高的鲁棒性;路标识别方法抗噪声和形变的能力强;位姿精度足够满足室内移动机器人自定位的需要。

移动机器人路径规划方法研究

针对室内动态非结构化环境下的移动机器人路径规划问题,提出了一种能够将全局路径规划方法和局部路径规划方法相结合、将基于反应的行为规划和基于慎思的行为规划相结合的路径规划方法.全局路径规划器采用A*算法生成到达目标点的子目标节点序列;局部路径规划器采用改进的人工势场方法对子目标节点序列中相邻两节点进行路径平滑和优化处理.在考虑了移动机器人运动学约束的前提下,该方法不但能够充分利用已知环境信息生成全局最优路径,而且还能及时处理所遇到的随机障碍信息.仿真研究与在室内复杂环境下的实际运行结果验证了该方法的有效性.

基于视觉的室内移动机器人自定位技术研究

在关于移动机器人的诸多研究领域中，机器人自定位是十分关键的技术，是实现机器人自主运动和其他任务的基础，而且涉及领域广泛，有很多难点有待解决，因而是一个具有重要研究价值的课题。 本论文以沈阳新松机器人股份有限公司自主研发的家庭服务机器人为研发平台，系统地研究了基于计算机视觉的室内移动机器人自定位问题，成功设计了基于单目视觉人工路标以及粒子滤波的室内移动机器人自定位系统。 本文首先根据室内移动机器人自主导航定位的要求，设计了一种简易美观的新型视觉人工路标，并且研究与实现了该路标的实时准确检测以及不同路标的识别。 其次，在位姿计算方面，本文研究了共面P4P（4点透视）问题的解法及其在位姿计算方面的应用，并分析比较了两种不同P4P解法的优缺点，成功地将两种算法结合起来用于机器人位姿计算。 最后，在机器人自定位方面，本文将单目彩色摄像机作为传感器，在基于贝叶斯滤波理论的自定位理论框架下，利用粒子滤波自定位方法融合视觉信息与码盘信息，实现了自主移动机器人的自定位。 实践证明，本文设计的基于单目视觉人工路标的自定位系统能够成功地应用在室内移动机器人上，具有较高的应用推广价值。

基于障碍预估与概率方向权值的移动机器人动态路径规划

主要研究了移动机器人在未知动态环境中的路径规划问题.提出一种将障碍预估与概率方向权值相结合的动态路径规划新方法.该方法将卡尔曼滤波引入到规划算法中,使得对障碍物运动状态的实时有效预估成为可能.同时,为实现移动机器人的实时路径规划,提出一种新的概率方向权值方法,基于周期规划将障碍物与目标信息进行融合,能够有效处理室内环境下对于障碍物的速度和运动轨迹均未知的动态路径规划问题.仿真结果以及基于SmartROB2移动机器人平台所进行的实验结果验证了该方法的有效性和实用性.

移动机器人基于激光测距和单目视觉的室内同时定位和地图构建

该文研究了部分结构化室内环境中自主移动机器人同时定位和地图构建问题.基于激光和视觉传感器模型的不同,加权最小二乘拟合方法和非局部最大抑制算法被分别用于提取二维水平环境特征和垂直物体边缘.为完成移动机器人在缺少先验地图支持的室内环境中的自主导航任务,该文提出了同时进行扩展卡尔曼滤波定位和构建具有不确定性描述的二维几何地图的具体方法.通过对应用于SmartROB-2移动机器人平台所获得的实验结果和数据的分析讨论,论证了所提出方法的有效性和实用性.