A simple substrate to produce the tropical epiphytic algae Hypnea pseudomusciformis

The seaweeds Hypnea spp have been used as a direct human food, for carrageenan extraction, and exploitation of chemical compounds of interest. Nevertheless, its culture is still undeveloped because of difficulties in managing the epiphytic habit. Therefore, this study focuses on obtaining a suitable substrate for Hypnea pseudomusciformis settling and developing associated to a simple and efficient system to produce this red alga in tropical coastal regions of South Atlantic. We developed a substrate comprised of a 1 cm diameter polypropylene cable with 60 cm length, which was totally shredded. This structure allows that the epiphytic algae grow settled on the substrates and not only appended to it. A modular long-line structure comprised of 1 m polypropylene braided cables with two substrates spaced 30 cm each. Testing the prototype in a seaweed small-farm resulted in a growth rate of 5.66 % day⁻¹ and a productivity of 0.64 kg m⁻¹ in 45 days. This simple patented technology may base used the development of the culture of H. pseudomusciformis in familiar or industrial scales.     

贝藻处理工厂化养殖废水的研究

研究了常见大型藻类对氮、磷营养盐的去除效果和贝类对悬浮颗粒物的去除效果。结果表明,石莼和海带在同样的实验条件下吸附氮、磷营养盐的效果明显高于鼠尾藻和马尾藻,密度2g/L的石莼和7.52g/L的海带是较好的养殖密度。与扇贝和文蛤比较,牡蛎具有较高的去除悬浮颗粒物的效率,可以在24h内除去养殖废水中93%的悬浮颗粒物。在20L养殖废水中投放1000g牡蛎和40g石莼组成的净化养殖废水的生物滤器对营养盐和悬浮颗粒物具有最好的去除效果,其去除效率分别为PO4P67.8%、NO2N60.2%、NH4N55.8%、NO3N59.0%和SPM82.5%。在20L养殖废水中投放1000g牡蛎和150g海带组成的生物滤器对营养盐和悬浮颗粒物的去除效果较好,其去除效率分别为PO4P62.6%,NO2N55.7%,NH4N46.0%,NO3N56.6%和SPM84.5%。     

钩虾对大型海藻的摄食选择及其潜在的碳汇分析

经食物链形成的“碳封存”和“碳转移”是海洋渔业碳汇的重要方面。大型海藻是海洋生态系统中最主要的初级生产力之一,也是最高效的固碳生物类群之一,端足类是大型海藻群落中非常重要的消费类群,处于食物链物质循环和能量传递的中间环节,承担着“碳转移”的职责。本文以山东半岛端足类中华原钩虾(Eogammarus possjeticus)为实验对象,开展了其对5种大型海藻[浒苔(Ulva prolifera)、肠浒苔(U. intestinalis)、扁浒苔(U. compressa)、线形硬毛藻(Chaetomorpha linum)和丝毛藻(Cloniophora sp.)]的摄食研究,比较了中华原钩虾对5种大型海藻的摄食率,分析了摄食率与海藻的总有机碳(TOC)、总氮(TN)、碳氮比(C/N)和干湿比(DW/FW)等指标的相关性,揭示了中华原钩虾对海藻的摄食选择性特征,初步探讨了钩虾潜在的碳汇影响。结果显示,中华原钩虾对肠浒苔和浒苔具有较高的摄食率,分别为0.81和0.80 g鲜重/(g·d),而对线性硬毛藻摄食率最低,为 0.19 g鲜重/(g·d);中华原钩虾选择栖息于大型海藻的个体数量比例以丝毛藻最高,其次为肠浒苔和浒苔;中华原钩虾的摄食率与海藻TOC含量和C/N呈显著正相关(P<0.05),而与TN含量和DW/FW呈显著负相关(P<0.05)。研究表明,中华原钩虾对大型海藻的摄食选择与海藻TOC、TN、C/N和DW/FW均显著相关,且偏向于在结构复杂、细丝状分枝多而密集的海藻中栖息。钩虾优先选择固碳量较高的浒苔类绿藻,能够快速将其固定的碳向更高营养级传递转移,可加速实现碳封存或碳移出,对海洋渔业碳汇进程可能会产生影响。     

Using a macroalgae Ulva pertusa biofilter in a recirculating system for production of juvenile sea cucumber Apostichopus japonicus

A simple indoor recirculating system for production of juvenile sea cucumber (Apostichopus japonicus) was operated on a commercial scale for 90 days during winter. The system consists of three 70 m³ sea cucumber rearing tanks and one biofilter tank where macroalgae (Ulva pertusa) was used as a biofilter in order to reduce water requirements. Effluent from the sea cucumber tanks drained into the macroalgae biofilter tank and were then returned to the sea cucumber tanks by a discontinuous-flow recirculation system. Survival and growth rates in the sea cucumber culture tanks were similar to those in the control tank (with one water exchange per day). The survival rate averaged about 87%. The average body weight increased from 3.5 ± 0.3 g to 8.1 ± 0.8 g and total sea cucumber biomass production over the experimental period was 745 g m⁻² after initial stocking densities of 375 g m⁻². The growth rate of U. pertusa was 3.3% day⁻¹. U. pertusa was efficient in removing toxic ammonia and in maintaining the water quality within acceptable levels for sea cucumber culture; there were only small daily variations of temperature, pH and DO. The U. pertusa tank removed 68% of the TAN (total ammonia-nitrogen) and 26% of the orthophosphate from the sea cucumber culture effluent; the macroalgae biofilter removed ammonia at an average rate of 0.459 g N m⁻² day⁻¹. It would be efficient to use the U. pertusa biofilter in a recirculating system for production of A. japonicus juveniles in winter.     

基于ArcGIS的南麂列岛潮间带大型底栖藻类研究

根据2013年11月(秋)和2014年2月(冬)、5月(春)、8月(夏)在南麂列岛海洋自然保护区潮间带调查所获大型底栖藻类数据,对南麂列岛海洋自然保护区潮间带大型底栖藻类的种类组成、数量分布、优势种以及多样性进行研究。将调查数据整理并录入到南麂列岛生物多样性地理信息系统,使用Arc GIS软件绘制南麂列岛潮间带调查断面分布图、藻类生物量分布图和调查断面藻类多样性指数专题图。使用Arc GIS软件进行距离分析和地形分析,并分别结合藻类调查数据进行研究。结果表明,调查断面与南麂岛之间的距离和调查断面春季生物量之间存在弱相关关系,而与生物多样性指数之间不存在相关关系。除在10°~20°坡度范围内调查断面的生物量异常外,生物量随着坡度的增加而减少,并且藻类的群落结构随着坡度的改变而发生变化;就全年潮间带大型底栖藻类生物量而言,阴坡坡向藻类生物量阳坡坡向藻类生物量半阳坡坡向藻类生物量半阴坡坡向藻类生物量,并且不同坡向的大型底栖藻类生物量随季节的变化程度存在明显差异。     

不同溶解氧浓度下瓦氏马尾藻碎屑分解规律

大型海藻碎屑是海藻场海域生产力循环过程的重要物质基础,海域环境因素例如溶解氧含量差异,对海藻碎屑分解释放营养盐效率产生影响,由此探究不同溶解氧环境对海藻碎屑分解及营养盐贡献度。在实验室控制条件下,探究低氧(1~4 mg/L)和好氧(5~9 mg/L)条件下瓦氏马尾藻碎屑分解速率(用分解系数k表征)以及碎屑分解释放无机营养盐氮、磷、硅规律。结果表明:在好氧条件下,海藻碎屑剩余物质干重最小,实验结束海藻碎屑失重率为84.699%,在实验初期瓦氏马尾藻碎屑(简称海藻碎屑)分解速率较高(0.110/d);而低氧条件下海藻碎屑实验初期分解速率(0.041/d)与好氧条件下实验末期分解速率(0.049/d)相当;海藻碎屑在好氧条件下易于分解释放硝态氮和亚硝态氮,且两者释放趋势一致,氨氮释放量在低氧条件下较高,且氨氮在海藻碎屑分解释放溶解无机氮中占主导作用,使得低氧条件下单位海藻碎屑分解释放溶解无机氮的累积贡献量(3.811 mg/g)比富氧条件下累积贡献量(1.511 mg/g)高出近一倍;海藻碎屑在不同溶解氧环境下对活性磷酸盐贡献量最大,富氧条件下单位海藻碎屑分解释放活性磷酸盐对水体累积贡献量达到10.143mg/g,无机硅酸盐在低氧条件下累积贡献量为1.091~4.777 mg/g;海藻碎屑受海域溶解氧差异影响,不同程度上改变了海域的能流循环和海域氮、磷、硅等营养盐的贡献度。     

Development of an innovative ring-shaped cultivation system for a land-based cultivation of marine macroalgae

Marine macroalgae become increasingly important as a regenerative source of biomass for the production of food, pharmaceuticals, cosmetics and energy. An increasing and environmentally sound utilization of algae requires a closed, land-based cultivation, not limited to coastal or offshore areas. Within this study, segmental and ring-shaped cultivation vessels were developed and compared to tumble cultivation in a circular tank. The development of these innovative approaches also considered economic efficiency, adaptability, handling and reliability. The growth rates achieved by cultivating the red algae P. palmata and C. crispus and the green alga U. lactuca over a test period of 7 d were used to evaluate these experimental models. Mean growth rates of P. palmata and C. crispus in the ring-shaped cultivation model were slightly decreased whereas growth rate of U. lactuca was similar or increased compared to tank cultivated algae. The developed ring-shaped cultivation system distinctly lowered variable costs by reducing the necessary volume of cultivation medium. An increased control of the cultivation process was achieved by separating the supply of CO₂ and nutrients, and the temperature control from agitation.     

大型海藻吸收氮磷营养盐能力的初步研究

将日本马泽藻Mazzaella japonica、孔石莼Ulva pertusa、鼠尾藻Sargassum thunbergii、红毛菜Bangia fusco-purpurea、蠕枝藻Helminthocladia australis、扇形拟伊藻Ahnfeltiopsis fla-belliformis6种大型海藻培养在富含氮磷海水中72 h,分析海水中氨氮、硝氮和活性磷浓度的变化,目的在于比较它们对营养盐去除效果。实验结果表明,6种海藻对氮磷都有明显的去除作用,日本马泽藻和孔石莼对氨氮、硝氮和活性磷的去除效果最好,分别吸收了培养水体中氨氮初始总量的98.0%和97.1%、硝氮初始总量的76.9%和82.0%、活性磷初始总量的90.8%和86.9%。     

High rate algal pond treatment for water reuse in a marine fish recirculation system: Water purification and fish health

Regardless of the degree of closure of a recirculation system, effluents are produced and replacement water is needed, which limits the possibility of locating a seawater production system away from the shoreline. At the Palavas Ifremer station, in the south of France, a High Rate Algal Pond (HRAP) was operated during several years to treat the effluent from a recirculating aquaculture system before reusing it. The effect of the HRAP-treated water on the recirculation system and on the fish was investigated and the optimal algae growing conditions were defined. The experiments were carried out in three rearing systems: one flow through, one recirculating and one recirculating with a HRAP. The water flow rate, temperature, pH and salinity conditions were similar in all systems.The effect of reusing the HRAP-treated water is very limited (1) on the functioning of the recirculation system and (2) on fish performance, but it allows a significant reduction of the dissolved inorganic nitrogen and phosphorus concentration in the rearing water. HRAP treatment reduced metal accumulation in muscle and liver of RAS fish, except for chromium and arsenic. All biomarkers presented no significant difference between systems, except for Superoxide Dismutase (SOD) and EROD, which showed a higher concentration in RAS and in both recirculating system respectively.     

Hydrodynamic characteristics of a full-scale kelp model for aquaculture applications

Hydrodynamic characteristics are needed to optimize the design of kelp aquaculture systems. To support this need, the objective of this study was to resolve both the normal and tangential drag forces acting on a dense aggregate of kelp blades using full-scale physical model tests. The physical model was designed to match the exposed length, individual blade flexural rigidity, the number of blades per unit width, the mass/length of biomass, and the aggregate mass density of kelp cultured at the University of New England experimental aquaculture lease site in Saco Bay, Maine USA. Tow tests were conducted at the United States Naval Academy in a tank with the dimensions of 116m × 7.9m × 4.9 m. The large tank size enabled the use of the full-scale physical model, minimizing dynamic similarity issues. In a series of tests, the model was towed in orientations both aligned and perpendicular to the tow direction. Horizontal and vertical reaction forces were measured for five tow speeds, along with the deflection of the dense kelp aggregate. With these datasets and the wet weight biomass per length of the model, normal and tangential drag forces were calculated. Drag components were processed into corresponding normal and tangential drag-area values. The drag-area representation was chosen since reference areas were ambiguous for both the actual kelp and model. At the higher speeds, the total horizontal drag in the aligned configuration were slightly lower than for the perpendicular orientation. Normal drag-areas as a function of tow speed ranged from 2.36 m²/m to 1.39 m²/m for the aligned case and from 2.49 to 1.88 m²/m for the perpendicular case. Tangential drag-areas as a function of tow speed ranged from 0.264 m²/m to 0.0325 m²/m for the aligned case and from 0.213 to 0.0415 m²/m for the perpendicular case. A transition from a bluff body to a streamlined body occurred as the tow speeds increased. To investigate this transition, horizontal components of the normal and tangential drag forces were reconstructed with the results of the tow tests. The reconstructed forces were obtained using a force balance system of equations with drag-area values for tow speeds less than 0.25 m/s extrapolated from the experimental datasets. For both aligned and perpendicular orientations, the model-aggregate reconfigured at a threshold of 0.25 m/s. We defined the threshold for reconfiguration as the tow speed at which the horizontal component of tangential drag equaled or exceeded the horizontal component of the normal drag. The drag-area results from this study can be incorporated into a dynamic fluid-structure interaction model representing kelp aggregates as a finite element beam prescribed with in-situ values of length, volume, mass density and flexural-rigidity of kelp material.