In situ nutrient enrichment experiments with periphyton in agricultural streams

The abundance, composition and seasonal distribution of planktonic protozoans and physical and chemical variables such as temperature, dissolved oxygen content, pH, and chlorophyll a concentration were analyzed monthly from February 1985 to January 1986 in eutrophic Rio Grande Reservoir. Analyses were performed on water samples collected at the surface and bottom (0.5 m above the sediment) in three stations, and individual distribution profiles were constructed for the major species. Dominant protozoan taxa included Codonella cratera, Coleps amphacantus, Coleps hirtus, Halteria grandinella, Mesodinium pulex, Tintinnidium sp., Urotricha spp., Vorticella spp., and Difflugia sp.. The distribution of some species was probably related to temperature and dissolved oxygen content.     

黄渤海甲壳类的分类多样性

为了解黄渤海甲壳类的分类多样性特征, 我们统计了2010-2015年中国水产科学研究院黄海水产研究所调查捕获的黄渤海甲壳类(软甲纲: 十足目与口足目)物种名录。结合历史文献, 进一步系统整理得到黄渤海甲壳类物种总名录。基于这2个名录, 应用分类阶元包含指数(the inclusion index at taxonomic level, TINCL_i)、平均分类差异指数(average taxonomic distinctness index, Δ⁺)和分类差异变异指数(variation in taxonomic distinctness index, Λ⁺)研究了其分类多样性特征。结果显示: 2010-2015年调查名录中, 甲壳类共93种, 隶属于2目39科66属, 其中10种为新分布种; 对虾科、藻虾科、长臂虾科、梭子蟹科和弓蟹科的物种数最多, 合计占总物种数的38.71%; TINCL_i分别为1.41种/属和2.38种/科; Δ⁺和Λ⁺分别为50.25和35.20。总名录中, 甲壳类共228种, 隶属于2目53科123属, 其中藻虾科、豆蟹科、对虾科、弓蟹科和鼓虾科的物种数最多, 合计占总物种数的30.70%; TINCL_i分别为1.85种/属和4.30种/科, Δ⁺和Λ⁺分别为50.18和30.87。对虾科的相对丰富度指数(the relative richness index, R_r)最高(100), 其次是梭子蟹科(71.43)和长臂虾科(62.50), 豆蟹科最低(6.25)。黄渤海甲壳类的平均分类差异指数(Δ⁺)明显小于鱼类(P < 0.05)。2010-2015年调查的Δ⁺计算值高于理论值, 且在理论值的95%置信区间内, 说明黄渤海甲壳类群落正处在中等程度的干扰中。     

黄渤海海域口虾蛄野生资源的种群遗传学研究

本研究通过扩增测序共获得了148条口虾蛄线粒体COⅠ基因序列,定义了52个单元型,其中存在63个变异位点。在黄渤海海域中,盐城口虾蛄种群的遗传多样性最高;渤海与黄海海域口虾蛄群体间遗传分化指数(Fst)为0.006 12。经MEGA 4.0软件计算得知11个种群间的遗传距离为0.0009~0.0057,而渤海与黄海两大海域间的遗传距离为0.0043。系统发生关系显示,渤海与黄海海域的单倍型呈交错聚集状态,说明两大海域间不存在显著的遗传分化。本次研究初步评估了两个海域的口虾蛄种群的遗传多样性水平,为渤海海域与黄海海域口虾蛄种质资源保护提供了基础资料。     

黄渤海海水养殖自身污染的评估

探讨了投饵和非投饵两种养殖方式自身污染对海洋环境的影响.结果表明,海水养殖产量与营养盐类、COD和赤潮发生次数均呈正相关关系,其中无机氮含量和赤潮发生次数与虾养殖产量有显著正相关关系,说明海水养殖自身污染对邻近海域富营养化及赤潮发生有一定影响.通过黄渤海海水养殖向海洋排泄氮、磷、COD等污染物估算,分别占相应陆源污染物排海量的2.8%、5.3%、1.8%.虽然与人类其他活动向海洋排污量相比,水产养殖的排污量所占比重还不算大,对于某些局部水域,特别是海水养殖密集区,将对海洋环境的影响产生叠加作用,很可能成为刺激近海富营养化和赤潮发生的一个重要因素,应引起足够的重视.     

In situ methane enrichment in anaerobic digestion

A major cost consideration in the use of anaerobic digestion to convert biomass and waste to utility-grade gas is the expense of separating CO(2) from the product gas. Anaerobic digestion has a number of inherent properties that can be exploited to increase the methane content of the gas directly produced by the digester, the most important of which is the high solubility of CO(2)(40-60 times that of methane) in water under digestion conditions. The methane enrichment concept examined in this study involved the recirculation of a liquid stream from the digester through a CO(2) desorption process and the return of the liquid stream back to the digester for absorption of additional CO(2) produced by the conversion of organic materials. A steady-state equilibrium model predicted that a digester gas methane content exceeding 94% could be achieved with this scheme using modest recirculation rates provided a desorption process could be designed to achieve a 60+% CO(2) removal efficiency in the degassing of the liquid recycle stream. Using fixed-film laboratory digesters operated on synthetic feedstocks, the technique of methane enrichment was tested under pressurized and unpressurized conditions. A 93 + 2% methane gas stream was produced from a volatile-acid-fed bench-scale digester simulating the methanogenic stage of two-phase digestion under conditions of (1) a pH swing achieved without caustic addition that allowed digestion at pH 7. 5 and air stripping at pH 6. 5-7. 0, (2) digester pressurization to 30 psig, and (3) a recycle rate of 0. 33 L/L reactor/day. Significant but lower levels of methane enrichment were achieved with the single-stage digester at the low experimental recycle rate. However, the narrow range among all experiments of CO(2) desorption efficiencies achieved in air stripping the recycle stream (35-60% CO(2) removal) suggests that comparable methane enrichment-may be achieved with unpressurized single-stage digestion using greater recycle rates. A materials balance analysis of data from an unpressurized, single-stage digester employing no chemical addition and using laboratory degassing efficiencies indicated that 94% methane could be produced at recycle rates of less than 1. 4 L/L reactor/day with a methane loss of less than 2%.     

黄海和渤海沿海地区生态系统健康评价

随着社会经济的发展,环境问题得到广泛的关注和重视,生态系统健康评价成为近年来生态环境领域的研究热点。本文以黄海和渤海沿海地区为研究区,以131个县区为评价单元。基于压力、状态和响应(PSR)模型,从人口、社会、经济、环境、景观、政策等方面综合考虑,根据社会经济统计数据和景观格局指数,构建了符合黄海和渤海沿海地区特点的生态系统健康评价模型,并计算出各评价单元的生态系统健康指数。结果表明:黄海和渤海沿海地区有84.73%的地区健康状况达到合格及以上水平;黄海和渤海沿海地区生态系统整体健康状况较好,系统对于自然和人工干扰有一定的抵抗力和恢复力,具备一定的自我调控能力。本文还分析了该地区所面对的各种潜在的压力,针对现状,结合这些潜在压力,提出了提高生态系统健康水平的建议。     

Immigration and zooplankton community responses to nutrient enrichment: a mesocosm experiment

Dispersal can be an important determinant of local diversity and species composition, but evidence for effects of the regional species pool on local zooplankton communities has been mixed. Theory and experiments suggest that immigration will be necessary for maintenance of community diversity and functioning during periods of environmental change; conversely, fluctuating resource levels may increase the likelihood of invasion success. We conducted a factorial-design mesocosm experiment to test the effects of a nutrient pulse and weekly immigration from other lakes on the diversity and composition of a pelagic zooplankton community. Contrary to expectations, there were no interactive effects of nutrient enrichment and immigration on any measure of diversity, and the initial shift in community composition in response to the nutrient pulse did not depend on the introduction of new species or genotypes from more productive lakes. Although immigration increased species richness in enclosures, success of most colonising species was poor. However, the dispersal treatment appears to have enabled a stronger predator response to increased herbivore numbers in nutrient-pulsed enclosures, leading to an eventual decline in the abundance of some herbivorous species in response to immigration. We conclude that community invasibility was not influenced by productivity, and that dispersal limitation did not strongly constrain the response of the zooplankton community to our applied disturbance. This indicates an unexpected resistance to change in species composition and diversity in spite of disturbance, and suggests that, in our study system, changes in the abundance of resident species are more important than introductions of new species in the community response to short-term environmental change.Electronic Supplementary Material Supplementary material is available to authorized users in the online version of this article at .     

Distinct seasonality of chytrid-dominated benthic fungal communities in the neritic oceans (Bohai Sea and North Yellow Sea)

Benthic fungal diversities in Bohai Sea and North Yellow Sea were investigated using pyrosequencing of 18S rDNA. Overall, Chytridiomycota dominated, followed by Basidiomycota, Ascomycota and Cryptomycota, in terms of alpha diversities and relative abundance. The beta diversity of benthic fungi showed a significant seasonality but no regional differences, accounted for by contrasting relative abundances of Chytridiomycota and Basidiomycota. Significantly seasonal changes in Chytridiomycota and Basidiomycota assemblage structure were also observed, but not for Ascomycota and Cryptomycota. Environmental filtering was more important than water depth and geographic distance in shaping the distribution of benthic fungi in the neritic oceans. The overall fungal beta diversity co-varied with concentration of chlorophyll a, pH, and salinity, distance from land, and water depth. The assemblage structure of benthic Chytridiomycota, Basidiomycota, Ascomycota and Cryptomycota co-varied with different sets of environmental parameters, suggesting their niche differentiations in the coastal sediments.     

Impacts of nutrient enrichment and sediment on phytoplankton community structure in the northern Baltic Sea

A three-week mesocosm experiment was conducted in order to study the effects of bottom sediment and nutrient enrichment on phytoplankton and zooplankton community structure in the Archipelago Sea, northern Baltic Sea. The transparent polyethylene enclosures included the whole water column and varied in volume from 30 to 40 m³. There were two types of enclosures: some with natural sediment as a bottom and others with a plastic bottom. The experiment was a 2 × 2 factorial design with presence of sediment and nutrient enrichment as treatment factors. Both the sediment presence and nutrient enrichment significantly increased water nutrient concentrations and the rate of primary production. However, external nutrient enrichment and the presence of sediment stimulated the growth of different phytoplankton groups, indicating that the effect of sediment was not related to nutrient fluxes alone, but involved more complex interactions. External nutrient enrichment was primarily channelled to picoplanktonic cyanobacteria, the biomass of which increased four- to fivefold due to enrichment. The presence of sediment increased the biomass of cryptophytes, chrysophytes and prasinophytes, but decreased the biomass of N₂-fixing cyanobacteria. Zooplankton biomass increased during the experiment, but was not affected by the treatments. The study shows that sediment plays a significant role in phytoplankton dynamics, underlining the importance of including sediment in shallow-water mesocosm experiments. Handling editor: J. Padisak     

Phytoplankton and periphyton responses to in situ experimental nutrient enrichment in a shallow subtropical lake

Experiments were performed in situ in shallow, subtropical LakeOkeechobee (Florida. USA) to quantify and compare the responsesof phytoplanklon (in 20 I clear polycarbonate carboys) and periphyton(on nutrient-diffusing clay substrates) to additions of nitrogenand/or phosphorus. During early and late summer. 1994, bothassemblages were nitrogen limited or co-limited by nitrogenand phosphorus, indicating the potential for competition betweenbenthic and planktonic communities. During late summer, therewas evidence that high phytoplankton biomass reduced light penetrationthrough the water column and may have suppressed periphytongrowth. The similar phytoplankton and periphyton taxonomic structures,both dominated by Lyngbya sp. and pennate diatoms, suggestedthat in shallow regions of this lake, resuspended meroplanktonmight account for a large portion of phytoplankton biomass.This phenomenon has been observed in other shallow, wind-drivenFlorida lakes.     

In situ removal and purification of biosurfactants by automated surface enrichment

Erysipelothrix rhusiopathiae, the causative agent of swine erysipelas, was cultivated in a 5-L stirred and aerated bioreactor under different dissolved oxygen tensions (0%, 5%, and 30% of saturation) for evaluation of the influence of oxygen on cell growth as well as on the production of the main antigenic component of the vaccine against erysipelas, a 64–69 kDa protein (SpaA). The microorganism presented different growth profiles for different aeration conditions. However, at the end of the batch cultivations, similar cell concentrations were obtained under the studied conditions. In order to maximize biomass titers and antigen production, the microorganism was cultivated in fed-batch operation mode under aerobic conditions. Under this condition, there was a fivefold increase in biomass production in comparison to the results attained in batch cultivations. To follow up antigen expression, samples collected during batch cultivations were concentrated and treated with choline for antigen extraction. Antigen expression was then assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and by murine immunization tests. It was observed a direct influence of oxygen availability upon antigen expression, which is favored in the presence of oxygen. Analysis of the samples collected throughout the fed-batch process also revealed that antigen production is growth associated.     

Response to nutrient enrichment by the plankton of Antarctic coastal lakes and the inshore Ross Sea

Summary Water samples from coastal lakes and ponds on Ross Island (77°S) and from the adjacent Ross Sea were analyzed to determine nutrient supply relative to the population size of planktonic algae and bacteria. An enrichment test was applied to each water to measure N and P accumulation by the seston as a guide to nutrient demand and deficiency. In all waters, including the sea, the dissolved inorganic N-to-P ratios were low, but inorganic nitrogen was generally present at concentrations that satisfied or exceeded the current growth requirements of the algae. None of the samples responded to added P, and only 3 of the 13 plankton assemblages tested responded positively to nitrogen enrichment. These waters are therefore characterized by an abundance of resources relative to demand. This apparently r-selecting coastal environment contrasts markedly in many ecosystem properties with the inland meromictic lakes of Antarctica.     

Fish and nutrient enrichment effects on rotifers in a Mediterranean shallow lake: a mesocosm experiment

A mesocosm experiment was conducted “in situ” in a Chara dominated shallow lake near Valencia (Spain) to study top–down and bottom–up effects on rotifers by means of nutrient and fish additions. Both processes were important in determining rotifer abundance, biomass and diversity. A total of 36 mesocoms were established with triplicate treatment combinations of three fish levels (from no fish to 45 individuals of Gambusia holbrooki males) and four nutrient enrichment levels (from no additions to 10 mg l⁻¹ nitrate-N and 1 mg l⁻¹ phosphate-P). The main effect was a notable increase of planktonic and plant associated rotifers densities with fish. Rotifers benefited from mosquitofish predation on microcrustaceans and chironomids. The results showed a marked negative relationship between rotifer and cyclopoid abundances, indicating the importance of the predatory pressure of cyclopoids on rotifers. Effects on rotifer diversity were also evident, in general rotifer diversity decreased with nutrients and increased with fish. The effects of nutrients analysed at species level showed two contrasting density responses: an increase or a decrease with nutrients, which levelled off at high nutrient concentrations. High-level nutrient additions (from 5 mg l⁻¹ nitrate-N and 0.5 mg l⁻¹ phosphate-P) induced a switch to a turbid state with macrophyte disappearance. Most planktonic rotifer species, as well as plant associated ones, diminished when the turbid state was well established, especially in the mesocosms without fish. In the turbid mesocosms, relative abundance of plant-associated rotifers (as a whole) was higher than that of planktonic rotifers. The changes in rotifer species composition after the switch from a clear to a turbid water state are also described. Species of the genus Anuraeopsis, Trichocerca and Hexarthra, dominant in the clear water state, practically disappeared in the turbid water state, in which Proalides tentaculatus and Lecane nana were the main species. Guest editors: S. S. S. Sarma, R. D. Gulati, R. L. Wallace, S. Nandini, H. J. Dumont & R. Rico-Martínez Advances in Rotifer Research     

Response of zooplankton to nutrient enrichment and fish in shallow lakes: a pan-European mesocosm experiment

1. Responses of zooplankton to nutrient enrichment and fish predation were studied in 1998 and 1999 by carrying out parallel mesocosm experiments in six lakes across Europe. 2. Zooplankton community structure, biomass and responses to nutrient and fish manipulation showed geographical and year‐to‐year differences. Fish had a greater influence than nutrients in regulating zooplankton biomass and especially the relative abundances of different functional groups of zooplankton. When fish reduced the biomass of large crustaceans, there was a complementary increase in the biomasses of smaller crustacean species and rotifers. 3. High abundance of submerged macrophytes provided refuge for zooplankton against fish predation but this refuge effect differed notably in magnitude among sites. 4. Large crustacean grazers (Daphnia, Diaphanosoma, Sida and Simocephalus) were crucial in controlling algal biomass, while smaller crustacean grazers and rotifers were of minor importance. Large grazers were able to control phytoplankton biomass even under hypereutrophic conditions (up to 1600 μg TP L^?1) when grazer biomass was high (>80–90 μg dry mass L^?1) or accounted for >30% of the grazer community. 5. The littoral zooplankton community was less resistant to change following nutrient enrichment in southern Spain, at high temperatures (close to 30 °C), than at lower temperatures (17–23 °C) characterising the other sites. This lower resistance was because of a greater importance of nutrients than zooplankton in controlling algal biomass. 6. Apart from the reduced role of large crustacean grazers at the lowest latitude, no consistent geographical patterns were observed in the responses of zooplankton communities to nutrient and fish manipulation.     

Length‐weight relationships of flatfish species caught by bottom trawl in the Yellow Sea and the Bohai Sea,China

This study determined the length–weight relationships of five flatfish species from the Yellow Sea and the Bohai Sea in China. Two of the species (Cynoglossus semilaevis and Verasper variegatus) had no previous length‐weight estimates.     

黄渤海海草分布区日本鳗草根际微生物群落结构特征及其功能分析

日本鳗草(Zostera japonica)是亚洲特有的海草种类,具有重要生态价值。近年来,黄渤海海草分布区中的日本鳗草海草床持续退化,引起了研究人员的广泛关注。【目的】基于根际微生物的分布与日本鳗草的健康生长密切相关的设想,本文旨在探究黄渤海海草分布区日本鳗草根际细菌群落结构多样性并分析其与海草健康生长的内在联系。【方法】选取黄渤海海草分布区中东营、威海、大连3个地点的日本鳗草根际与非草区表层沉积物,采用高通量测序技术(Illumina HiSeq PE300)解析根际微生物群落特征,并结合相关环境参数分析其环境功能。【结果】日本鳗草根际表层沉积物中主要存在的细菌类群有:变形菌门(Proteobacteria)所占比例为41.1%,蓝细菌门(Cyanobacteria)占15.4%,拟杆菌门(Bacteroidetes)占12.6%,放线菌门(Actinobacteria)占9.3%。不同地点之间以及样品类型(海草床根际与非根际)之间的微生物群落存在显著差异,主要表现为根际富含硫酸盐还原菌和固氮菌。环境因素:TN (total nitrogen)、TC (total carbon)、TOC (total organic carbon)、黏土(Clay)、砷(As)与根际群落组成与分布显著相关。【结论】从功能的角度来看,不同地点、不同样品类型之间的差异物种多与硫、氮代谢相关,硫酸盐还原菌对维持日本鳗草的生态健康起关键作用;日本鳗草根际微生物群落分布与环境因子、空间分布有一定相关性。     

In situ determination of slurry nutrient content by electrical conductivity

Land application of animal slurries has both agronomic and environmental implications. It can be supported by the quantification of available nutrients in the field. A prototype device for indirect measurement of the nutrient content of slurry based on electrical conductivity (EC) was calibrated on manure samples collected from farms with different livestock typologies. The resulting correlations between EC and nutrient contents of slurries from laboratory analyses have shown good agreement (r(2) from 0.73 to 0.95) with total and ammoniacal nitrogen and, with some exception, Potassium, but failed to demonstrate any significant relationship with total phosphorous. The mean errors obtained using the device in field conditions for nitrogen content were always lower or equal to 10%, while the standard deviations were 12-13% for pig and calf slurries, and 20-21% for dairy cow slurry. The results obtained suggest that the equipment, provided the regression line used to convert EC readings to nutrient contents is related to the livestock typology under observation, can provide good support to practical slurry spreading, even though it does not reach an accuracy comparable to laboratory methods and does not give reliable information on phosphorus.     

Effect of nutrient enrichment on bacterioplankton biomass and community composition in mesocosms in the Archipelago Sea, northern Baltic

Effects of nutrient enrichment on the biomass and communitycomposition of heterotrophic bacteria and picocyanobacteriawere studied in large (42 m³) mesocosms in the brackish-waterArchipelago Sea (Baltic Sea) in late summer 2000 using cellcounts and denaturing gradient gel electrophoresis (DGGE) ofpolymerase chain reaction (PCR)-amplified 16S rRNA gene fragments.The identity of the major DNA bands was determined by sequencing.The obtained sequences were related to - and -proteobacteria,actinobacteria, verrucomicrobia and cyanobacteria. Nitrogenand phosphorus additions increased the biomasses of heterotrophicbacteria and picocyanobacteria and caused significant changesin their community composition judging from the DGGE bandingpatterns. Most verrucomicrobial bands had their highest relativeintensity in the control treatment and their lowest in the highernutrient addition treatment, whereas most Synechococcus-relatedbands had their lowest relative intensity in the lower nutrientaddition treatment. The responses of proteobacteria and actinobacteriawere more variable. The presence of both freshwater and marinesequences among the closest relatives to our sequences highlightsthe intermediate character of the Archipelago Sea between afreshwater and truly marine environment.