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.     

C/N ratio control and substrate addition for periphyton development jointly enhance freshwater prawn Macrobrachium rosenbergii production in ponds

The present research investigated the effect of carbon/nitrogen ratio (C/N ratio) control in ponds with or without substrate addition for periphyton development on production of giant freshwater prawn. C/N ratios of 10, 15 and 20 were investigated in 40 m^− 2 ponds stocked with 2 prawn juveniles (5.023 ± 0.02 g) m^− 2 with or without added substrates for periphyton development. The various treatment combinations of C/N ratio and periphyton substrate addition are abbreviated as ‘CN10’, ‘CN15’, ‘CN20’, ‘CN10 + P’, ‘CN15 + P’ and ‘CN20 + P’, P representing periphyton substrate. A locally formulated and prepared feed containing 30% crude protein with C/N ratio10 was applied. Tapioca starch was used as carbohydrate source for manipulating C/N ratio and applied to the water column separately from the feed. Increasing the C/N ratio from 10 to 20 reduced (P < 0.001) the total ammonia-nitrogen (TAN), nitrite–nitrogen (NO₂–N) and nitrate–nitrogen (NO₃–N) in water column and total Kjeldahl nitrogen (TKN) in sediment. The addition of substrates only influenced the NO₂–N concentration in the water column (P < 0.001). Increasing the C/N ratio raised the total heterotrophic bacterial (THB) population in the water column, sediment and periphyton (P < 0.001). It also increased the dry matter (DM), ash free dry matter (AFDM), and chlorophyll a content of periphyton (P < 0.001). The lowest specific growth rate (SGR), the highest food conversion ratio (FCR), and the lowest protein efficiency ratio (PER) were recorded in treatment CN10 (P < 0.05). The addition of substrates did not influence size at harvest (P > 0.05) but improved the survival from 62.8 to 72% (P < 0.001). Increasing the C/N ratio from 10 to 20 increased the net yield by 40% and addition of substrate increased the net yield by 23%. The combination of C/N ratio control and substrate addition increased the net yield by 75% from 309 (CN10) to 540 (CN20 + P) kg ha^− 1 (120 days)^− 1. This 75% higher production concurred with (1) a lower inorganic nitrogen content in the water column, (2) a higher THB abundance supplying additional single cell protein to augment the prawn production, and (3) an improved periphyton productivity and quality.     

Nitrogen removal techniques in aquaculture for a sustainable production

As the aquaculture industry intensively develops, its environmental impact increases. Discharges from aquaculture deteriorate the receiving environment and the need for fishmeal and fish oil for fish feed production increases. Rotating biological contactors, trickling filters, bead filters and fluidized sand biofilters are conventionally used in intensive aquaculture systems to remove nitrogen from culture water. Besides these conventional water treatment systems, there are other possible modi operandi to recycle aquaculture water and simultaneously produce fish feed. These double-purpose techniques are the periphyton treatment technique, which is applicable to extensive systems, and the proteinaceous bio-flocs technology, which can be used in extensive as well as in intensive systems. In addition to maintenance of good water quality, both techniques provide an inexpensive feed source and a higher efficiency of nutrient conversion of feed. The bio-flocs technology has the advantage over the other techniques that it is relatively inexpensive; this makes it an economically viable approach for sustainable aquaculture.     

Planktonic and Biochemical Composition of Periphyton Grown on Some Biodegradable and Non-Degradable Substrates

ABSTRACT

Ten locally available substrates, five biodegradable and five non-degradable, were evaluated for their potential to harbor periphyton in cement tanks fertilized with poultry manure. The tanks were fertilized regularly and the periphyton was allowed to grow for 70 days. Weekly samples of periphyton and plankton were collected for enumeration and biochemical analyses. Among the substrates, earthen tiles harbored negligible amount of periphyton. The phytoperiphyton genera encountered on the substrate belonged mainly to Chlorophyceae (14 genera), followed by Cyanophyceae (2 genera), Chrysophyceae (1 genus), Bacillariophyceae (1 genus), and Dinophyceae (1 genus). Nauplius, Keratella, Diaptomus, Cyclops, Moina, Chironomus and insect eggs were the zooplankton encountered on substrates. Phytoplankton density was higher on tyre (86,426 cells or colonies/cm²) and palm leaf (85,808 cells or colonies/cm²) and lowest on ceramic tile (21,081 cells or colonies/cm²). Glass plates harbored the highest number of zooplankton species per unit area (1050 cells or colonies/cm²), while arecanut leaf-sheath had the lowest (210 cells or colonies/cm²). All five families of phytoplankton present on the substrates were also present in tank water. While periphyton contained 26 genera, tank water had only 24. Periphytic dry matter, ash, ash-free dry matter, plankton density on substrates and water showed a general increase with respect to time. Polyvinyl chloride (PVC) (0.972 mg/cm²), glass (0.913 mg/cm²), and bamboo (0.897 mg/cm²) had higher periphytic dry matter and ceramic tile (0.262 mg/cm²) the lowest. All the proximate composition parameters of periphyton, except nitrogen free extract (NFE) varied significantly (P < 0.05) between the substrates. The moisture content of periphyton ranged from 85.58% (bamboo) to 95.27% (arecanut leaf-sheath). Crude protein was high in periphyton from bamboo (3.77%) and tyre (3.66%) and low in that from arecanut leaf-sheath (0.99%).     

Formation of periphyton biofilm and subsequent biofouling on different substrates in nutrient enriched brackishwater shrimp ponds

Periphyton grown on substrates is known to improve water quality in aquaculture ponds. Five different substrates, (i) bamboo pipe (ii) plastic sheet (iii) polyvinylchloride (PVC) pipe (iv) fibrous scrubber, and, (v) ceramic tile were evaluated for the formation of biofilm in this experiment. The substrates were suspended 25 cm below the water surface. Each type of substrate was collected fortnightly to analyze the abundance and biomass of different periphytic algae and of the biofouling organism. The study was terminated after 60 days due to severe fouling by polychaete. Results showed that pond water nutrients were high on day 60 with mean total ammonia-N, nitrite-N and soluble reactive phosphorus concentrations of 309.6 ± 8.6 μg L^− 1, 26.0 ± 2.7 μg L^− 1 and 87.2 ± 7.1 μg L^− 1 respectively. During the first two weeks the substrates were colonized by 19 periphytic algae. The most abundant family was Bacillariophyta (8 genera) followed by Chlorophyta (7 genera) and Cyanophyta (4 genera). Periphyton colonization on bamboo pipe showed the highest (p < 0.05) biomass in terms of chlorophyll a amongst all the substrates used. The biomass varied from 179 to 1137 μg m^− 2 with mean values of 1137.2 ± 0.6, 929.6 ± 0.6, 684.2 ± 1.2, 179.1 ± 0.6 and 657.0 ± 0.6 μg m^− 2 on bamboo pipe, PVC pipe, plastic sheet, fibrous scrubber and ceramic tile respectively for the first 15 days. From 3rd week, polychaetes began to form tubes on the substrate. By day 60, the whole surface of all substrates was covered with tightly packed polychaete tubes with mean densities of 168.0 ± 15.4, 121.0 ± 13.5, 72.8 ± 9.8, 72.4 ± 7.4 and 56.0 ± 6.8 polychaete tubes cm^− 2 for bamboo, PVC, plastic, fibrous scrubber and ceramic tile respectively. This study illustrated the invasive nature of attached polychaete thus hampering the formation of periphyton biofilm on substrates which could have been used for improving water quality in enriched brackishwater shrimp ponds.     

不同稻田生态系统周丛生物对水稻种子萌发和幼苗生长的影响

周丛生物广泛分布于稻田生态系统淹水环境中,直接影响稻田养分的迁移转化过程及其生物有效性,但其是否影响水稻的生长、发育却鲜有报道。通过室内控制试验,利用延边（YB）、鹰潭（YT）和镇江（ZJ）的水稻土培养周丛生物,并研究了三种周丛生物对水稻种子萌发和幼苗生长的影响。结果表明,不同类型土壤培养的周丛生物主要由变形菌门（Proteobacteria）、蓝细菌门（Cyanobacteria）和拟杆菌门（Bacteroidetes）组成;三种周丛生物的多样性存在显著差异,其中延边周丛生物（YBP）的物种数和Chao1指数显著高于其他两组处理（P <0.05）。皮尔森（Pearson）相关性分析结果表明,周丛生物群落物种组成和多样性与土壤pH、全磷、总有机碳和全锰含量呈显著正相关（P <0.01）。此外,三种周丛生物的碳代谢活性存在显著差异（P <0.05）。其中,延边周丛生物（YBP）在整个检测期内的碳代谢活性最高,鹰潭周丛生物（YTP）的碳代谢活性最低。种子萌发试验结果显示周丛生物的存在显著提高了水稻种子的萌发率（最高18%）和α-淀粉酶活性（P <0.05）,同时提高...     

周丛生物对稻田氨挥发的影响研究

摘要：[目的] 周丛生物是一种普遍生长在稻田水-土界面中的微生物聚集体,在调节稻田氮循环中起重要作用。本研究旨在通过研究周丛生物对氨挥发的影响,分析田间氨挥发通量与周丛生物微生物群落结构、田面水理化性质之间的关系,为控制稻田氨排放提供理论指导和技术支持。[方法] 通过野外田间微区试验研究稻田周丛生物对氨挥发的影响,分别设置了周丛生物正常生长以及添加特丁净（C10H19N5S）调控周丛生物生长2个处理,每个处理3个重复,分别于基肥（BF）、分蘖肥（SF1）、穗肥（SF2）施加后测定周丛生物影响下的氨挥发速率,计算整个水稻生长期内的氨挥发通量,分析不同稻田周丛生物的微生物群落结构、田间理化性质与土壤氨挥发的关系,构建基于周丛生物的稻田氨挥发预测模型。[结果] 结果表明：周丛生物正常生长状态下基肥和分蘖肥时期氨挥发累计损失量分别达到24.8±1.1 kg?hm-2,10.9±0.1 kg?hm-2,添加了C10H19N5S后氨挥发累积量分别降低了71.3%,39.3%,穗肥期氨挥发差异不显著。淡色藻门Ochrophyta（8.1%~~67.6%）、隐真菌门Cryptomycota（3.9%~~54.8%）、线虫动物门Nematoda（0.6%~42.6%）为周丛生物中真核微生物优势门,变形菌门Proteobacteria（52.1%~23.7%）、拟杆菌门Bacteroidetes（58.1%~16.8%）、绿湾菌门Chloroflexi（14.6%~0.8%）、酸杆菌门Acidobacteria（11.0%~3.3%）为原核微生物优势门。相关性分析表明,周丛生物生物量,田面水氮素含量,风速是影响日氨挥发通量的关键因素。综上所述,使用C10H19N5S调控周丛生物生长能够有效的降低基肥以及分蘖肥期间稻田土壤氨挥发,减缓因氨挥发造成的氮肥损失问题。     

Submersion time, depth, substrate type and sampling method as variation sources of marine periphyton

Periphyton is an additional food source in African and Asian brackish and freshwater fish ponds. The present study was a preliminary assessment of periphyton development on artificial substrates in temperate marine ponds. The effects of submersion time, substrate type, water depth, and total or partial sampling methods on the quantity and quality of periphyton collected, were evaluated. Four types of substrate (W: wooden poles, S: smooth fiber-glass strips, m: mosquito screen (1 mm-mesh) and M: garden netting (5 mm-mesh)) were deployed in a marine pond, and periphyton was collected 15 and 30 days later. The total amount of periphyton per substrate unit was collected as one sample or as 5 sub-samples. Results showed that (i) periphyton biomass in a marine pond increased between day 15 and day 30, (ii) more periphyton was collected on mosquito screen than on wooden poles, fiberglass strips and garden netting, (iii) periphyton biomass increased with submersion depth, (iv) sub-sampling leads to an underestimate compared to whole unit sampling, and (v) a correction of periphyton weight must be carried out considering the dissolved inorganic salts present in periphyton samples from marine and brackish ponds. Whole substrate unit sampling using a tube and stopper is recommended to avoid underestimation of periphyton development. Finally, the autotrophic fraction in the periphyton communities was very low compared to periphyton developed on biodegradable substrates in fertilized tropical ponds. Studies on fertilization and use of biodegraded substrates (i.e. long-time submerged wood) are recommended to further optimize periphyton development in temperate marine ponds.     

新疆伊犁河周丛藻类群落结构及其水质生物学评价

周丛藻类是新疆跨境河流土著、特有鱼类重要的基础饵料资源,研究其种群结构及评价水质,以保护该地区渔业资源与生态环境。2013年5、7、9、10 月,在新疆跨境河流——伊犁河全流域选择8个样点,对周丛藻类群落结构进行了系统的调查分析。结果表明,伊犁河周丛藻类隶属5门41属145种,其中硅藻门种类数最多,113种（占77.9%）,依次是蓝藻门14种（9.7%）、绿藻门13种（9.0%）、裸藻门4种（2.8%）和黄藻门1种（0.7%）。优势种主要为硅藻门的嗜盐舟形藻、偏肿桥弯藻、普通等片藻以及蓝藻门的皮状席藻等。研究期间,伊犁河周丛藻类的密度和生物量的均值分别为1331.7×106 ind/m2、1908.5 mg/m2。Simpson多样性指数、Shannon-Wiener多样性指数、Pielou均匀度指数和Margalef丰富度指数的平均值分别是0.73、3.24、0.60和3.91。Pearson相关性分析显示,伊犁河周丛藻的密度与流速呈极显著的负相关,与总氮呈极显著的正相关,与水温、盐度、氟化物、总硬度、钙离子呈显著的正相关;周丛藻类的生物量与流速呈极显著的负相关,与水温、硝态氮、氟化物、总氮呈显著的正相关。基于生物多样性指数（Shannon-Wiener、Margalef、Pielou）、指示生物法与硅藻耐受性指数等方法的水质评价结果大体上一致,综合评价结果：昭苏解放大桥、雅玛渡和伊犁河大桥水质相对较差为β-中污型,其余采样点水质均处于较好状态为寡污型。整体上伊犁河流域水质趋于良好。