氮及氮磷比对附着藻类及浮游藻类的影响

2005年5月至11月,在河北省YH水库选取5个具有代表性的样点,进行了微囊藻毒素-LR的调查,同时,测定了相应各样点的TN,TP,NH4-N,NO3-N和PO4-P.结果显示,水库中微囊藻毒素-LR(MC-LR)随季节发生变化,其中,7-10月期间相对较高,且大部分超过了生活饮用水地表水标准限值(1 μg/L);MC-LR与水体中的N、P之间的相互关系表明,5-7月期间,水库MC-LR与TP呈正相关,与NH4-N和TN/TP呈负相关;8-9月期间,水库中TP逐渐降低,但其它降低速率低于TN,造成TN/TP明显降低,MC-LR与TP和TN/TP呈正相关,与NH4-N呈负相关;10-11月期间,大量藻细胞死亡,释放到水体中MC-LR也逐渐下降,这时,大量外源营养盐也进入水库,造成微囊藻毒素-LR的变化与TN、NH4-N、NO3-N呈显著或极显著负相关.这说明在不同季节下,微囊藻毒素-LR与营养盐的关系不同,必须视实际情况而定.     

铜绿微囊藻在竞争生长条件下对氧化还原电位降低的响应

在室内研究了有、无伊乐藻存在条件下,不同水平的氮及氮磷比(N/P)对实验体系中附着藻类和浮游藻类生长的影响,结果表明:1)在有沉水植物的体系中,当氮浓度较高时(5 mg/L),浮游藻类对N/P的变化比附着藻类更为敏感;而当氮浓度较低时(2 mg/L),浮游藻类与附着藻类对N/P的响应则没有显著的差异;2)在有沉水植物的体系中,当N/P为15时,随水体中氮浓度的升高,附着藻类的生物量显著增加,但浮游藻类的变化不显著.当N/P为25时,随水体中氮浓度的升高,浮游藻类及附着藻类的生物量均显著升高;3)附着藻类的生物量在无沉水植物(伊乐藻)存在的情况下要比有沉水植物(伊乐藻)存在时高得多,且随氮浓度升高,其生物量的增加量也远高于后者.而对浮游藻类而言,情况则完全相反.     

Substrate influence and temporal changes on periphytic biomass accrual and metabolism in a tropical humic lagoon

We performed a field experiment in a tropical humic coastal lagoon to evaluate periphyton biomass accrual and metabolism on three different substrates (1) plastic ribbons, (2) green and (3) senescent leaves of the emergent macrophyte Typha domingensis) over 30 days. The contribution of autotrophic biomass decreased as total biomass increased over the time. Mean periphytic ash free dry weight ranged from 0.8 to 5.6 mg cm⁻², but periphyton chlorophyll a concentrations presented shorter amplitudes, which oscillated from 0.12 to 0.44 μg cm⁻² throughout the experiment. Periphyton metabolism was overall heterotrophic on all substrates, especially on senescent leaves. Our data show that substrate type influenced both biomass accrual and periphyton net productivity and respiration rates throughout periphyton development and highlighted the dominance of heterotrophic metabolism. The periphyton respiration may be subsidized by both water- and substrate-derived allochthonous energy pathways, shedding light on the role of periphytic assemblages to the carbon cycling, as a source of CO₂ to the system.     

Effects of sedimentation and periphyton communities on embryonic Rainbow Smelt, Osmerus mordax

The decline in anadromous rainbow smelt (Osmerus mordax) populations may be due to anthropogenic causes including spawning habitat degradation. The purpose of this study was to assess the survival of rainbow smelt embryos incubated under sediment layers of different depths (0.00, 0.25, 1.00, and 6.00 g/45.6 cm²) and in contact with periphyton communities of different biomass. Embryo survival was also assessed when cultured on periphyton in combination with sterilized sediment or eutrophying compounds (nitrates and phosphates). Oxygen consumption was monitored from embryos cultured alone, on periphyton layers, and under a sediment layer. Survival was significantly reduced under the highest sediment treatment and attributed to low oxygen availability to the embryos. Embryonic survival was also significantly reduced when incubated on the highest periphyton biomass. Embryos under the sediment layer consumed oxygen at a significantly greater rate than the controls, and the dissolved oxygen concentration below the sediment–water interface decreased to near anoxic. These results suggest that embryonic survival could be impacted in rivers with heavy sedimentation or a high standing biomass of periphyton.     

Periphyton communities in Amazonian black- and whitewater habitats: Community structure, biomass and productivity

Chlorophyll a-concentrations, AFWD (ash-free-dry-weight) and photosynthesis rates were estimated for periphyton assemblages in Amazonian black-and white-water habitats over 14 months. Cellulose-acetate strips were incubated in situ and showed few major differences in periphyton quality as compared to natural substrata. The only exceptions were submersed Igapó forest leaves, which exhibited higher proportions of green algae and cyanobacteria though not producing differences in total periphyton biomass. Enclosure experiments showed a considerable nutrient release by inundated non-senescent Igapó forest leaves. Periphyton biomass and productivity were found to be highest in black-and white water mixing zones, where biomass peaked at 41.6 mg Chla/m² and 19.8 g/m² AFDW. Production was estimated to be 380 gC/m²·a. Maximum biomass of periphyton in floating meadows was 46 mg Chla/m² and 10.6 g/m² AFDW, with an annual production of 170 gC/m²·a. Solimões main channel periphyton values were low: maximum Chla was 7.1 mg/m², AFDW 0.8 g/m² and annual production was estimated to be 30 gC/m². Blackwater periphyton values were lower compared to whitewater and mixed water values but an enlarged trophogenic zone has to be taken into account. Highest Chla content reached 30.9 mg/m², AFDW 1.43 g/m². Estimated annual production was 110 gC/m². Observed mean periphyton productivity of Amazonian blackwater habitats approximately corresponded to mesotrophic attached algae productivity in temperate zones, whereas productivity of whitewater periphyton approached those of temperate eutrophic lakes. The role of periphyton in the Amazon food web is discussed.     

Phytoplankton and periphyton production and its relation to temperature in a humic lagoon

To analyse the existence of interactive competition between phytoplankton and periphyton, we studied their photosynthesis–irradiance (P–E) response during one year in a humic lagoon. Lake production was dominated by phytoplankton, which followed seasonal changes in temperature. Periphyton primary production and algae biomass increased in winter, when phytoplankton biomass and production were lower. In this study we show that even in conditions of phytoplankton dominance, the habitat coupling between phytoplankton and periphyton can still be noticed.     

The effect of periphyton on the light environment and production of Potamogeton perfoliatus L. in the mesotrophic basin of Lake Balaton

Light within the littoral zone affects the productivity and interaction between periphyton and its macrophyte substrate. The effect of periphyton on macrophyte photosynthesis, seasonal variation and vertical distribution of periphyton on artificial substrates (plastic strips), and the effect of periphyton on the light environment was studied in Lake Balaton. Data showed that an average of 4.1 ± 0.4 mg (dry weight) cm^?2 of periphyton had accumulated on the plastic strips after 8.8 ± 0.4 days. This biomass corresponded to 294 ± 30 μg m^?2 chl-a of epiphytic algae and blocked 92.3 ± 0.8 % of the depth specific radiation. Seasonal variation and specific vertical distribution of periphyton were observed. The most active time of periphyton accumulation corresponded to spring up until mid-June. Later in the year, the amount of periphyton significantly decreased. The optimal conditions for periphyton accumulation were at 30–40 cm depth. Most of the light reaching the adaxial leaf surface was attenuated by periphyton, decreasing the production of Potamogeton perfoliatus by 60–80 %. This increased the importance of backscattered light that corresponded to 10–15 % of the macrophyte production. A smaller part of the periphyton consisted of precipitated inorganic material, while epiphytic algae, making up the majority of the periphyton, were connected to both benthic (dominantly benthic penales) and pelagic (very close seasonal dynamics of pelagic and epiphytic biomass) algae. Periphyton affects macrophyte production especially in spring and in the upper water layers even in a mesotrophic water body. This increases the importance of the light absorbed through the abaxial side of the leaf and confirm the role of periphyton in transition from clear to turbid water states.     

Evidence for ecosystem engineering in a lentic habitat by tadpoles of the western toad

A number of aquatic organisms have demonstrated an ability to modulate sediment deposition in tropical and temperate stream systems, but little is known about the impact of similar benthic grazing processes in temperate pond systems. Using exclosure experiments in mesocosms, we used tadpoles of the western toad (Anaxyrus boreas) to investigate two questions: (1) can grazing activities of tadpoles of the western toad in ponds reduce sediment accrual on grazing surfaces (e.g. via bioturbation or ingestion); and (2) do these grazing activities contribute to enhanced periphyton biomass and chlorophyll a content of benthic matter. Mesocosms received pulses of fine sediment weekly over 8 weeks to simulate allochthonous surface inputs following rainstorms. Accumulated sediment and periphyton matter on exposed and grazing-restricted substrate surfaces were measured weekly. Tadpole grazing activity significantly reduced the standing stock of periphyton on open grazing surfaces by 80% in controls. Under sediment-additions, tadpoles effectively removed settled particulate matter from exposed grazing surfaces, but no corresponding increase in periphyton biomass was observed. These results suggest that tadpoles can impact the dynamics of sediment distribution in ponds as well as streams, providing support for a role as “ecosystem engineers” in these habitats.     

太湖蓝藻碎屑对水质及附着藻和水丝蚓生物量的影响

富营养化是现今各国面临的主要水环境问题,其中蓝藻水华暴发是全球富营养化水体最常见的现象之一.蓝藻水华将产生大量的蓝藻碎屑,其对水质及生物的影响还尚不清楚.本研究通过向中宇宙系统添加微囊藻碎屑,分析其对水体不同形态营养盐及水生生物生物量的影响.结果表明:微囊藻碎屑加入后,水体不同形态的营养盐浓度均在短期内迅速增加,其中水体总氮和总磷平均浓度最高分别达到3.86和0.36 mg/L;浮游植物生物量(用叶绿素a表示)在前9天随营养盐浓度的升高而增加,随后逐渐下降至实验初始水平.此外,附着藻类生物量在微囊藻碎屑加入后呈逐渐下降趋势,这可能与浮游植物快速增殖引起的水体透明度下降有关.微囊藻碎屑加入后,水丝蚓生物量随微囊藻碎屑的分解持续增长,在第20天达到生物量最大值.本研究通过模拟太湖梅梁湾生态系统,探讨微囊藻碎屑对水质及水生生物生物量的影响,结果有助于进一步了解蓝藻水华对水生态系统影响的途径及机理,为富营养化湖泊管理提供理论依据.     

鳑鲏对“蚌-草”关系的影响

重建沉水植物群落是修复浅水富营养化湖泊的关键.河蚌可改善水下光照条件、促进沉水植物生长,因此放养河蚌常被用于沉水植物群落恢复的并行手段.河蚌是鳑鲏产卵的重要基质,因此河蚌可能促进鳑鲏种群发展,而鳑鲏对水生态系统的影响还尚不清楚.本研究以密刺苦草、大鳍鱊和背角无齿蚌为研究对象,通过中宇宙试验研究河蚌和鳑鲏对附着藻的影响,以及鳑鲏对水质和沉水植物生长的影响及机理.结果发现：鳑鲏显著增加了水体总磷、总溶解性磷、总悬浮物和叶绿素a浓度,而对总氮和总溶解性氮浓度的影响不显著.河蚌对苦草的相对生长率、总株数、根冠比及苦草最大叶长均无显著影响,而显著增加了苦草的单株平均生物量,这可能与河蚌组较高的附着藻生物量有关.鳑鲏未显著影响河蚌与苦草间的关系,但鳑鲏的出现显著增加了附着藻类生物量;此外,鳑鲏还降低了苦草的根冠比,而增加了苦草的最大叶长,这可能与鳑鲏引起的营养盐和叶绿素a浓度升高,以及植物表面附着藻生物量显著升高有关.鳑鲏属于小型杂食性鱼类,在长江中下游地区分布广泛,与沉水植物关系密切,且易在修复后的湖泊中形成优势鱼类,因此在湖泊修复和管理中应加强此类小型杂食性鱼类的监测与管理.     

Characterization of the light attenuation by periphyton in lakes of different trophic state

In order to measure the attenuation of light by periphyton a method has been developed which assures that natural periphyton architecture and therefore its optical characteristics remain preserved. This method has been applied to analyze the transmittance of periphyton of four lakes of different tropic states situated in the Osterseen Lake District (Upper Bavaria, Germany). The seasonal variation of the periphyton's transmittance has been studied using standard microscope glass slides exposed 1 m beneath the water surface within macrophyte beds. The study ran from February to November 1997 in two eutrophic lakes (Lake Waschsee, Lake Sengsee) and from May to November 1997 in the meso-oligotrophic Lake Eishaussee and in the oligotrophic Lake Herrensee.Generally the exposure-period, the seasonality, and the tropic state of the habitat affected the transmittance spectra of the periphyton. In all lakes the attenuation by periphyton increased with longer colonization times but at a different time scale. The periphyton of the nutrient-rich and the nutrient-poor lakes differed clearly in composition and architecture. The eutrophic lakes were characterized by a relatively thick but loosely attached, unstable periphyton community, which was translucent to a certain degree even at the end of the growth period. The transmittance of this periphyton fluctuated considerably and high percentages of filamentous green algae in this periphyton contributed to attenuation maxima within the range 400-500 nm and 650-700 nm due to photosynthetic pigments. By contrast, the periphyton of the meso-oligotrophic and of the oligotrophic lake was quite compact and nearly impervious to light.     

菹草(Potamogeton crispus)附着物对水体氮、磷负荷的响应

通过实验模拟了10组氮、磷负荷对菹草(Potamogeton crispus)生长期和衰亡期茎叶附着物的影响.结果显示:随着水体氮、磷浓度的升高,菹草附着物的叶绿素a(Chl.a)含量、附着有机物量、附着无机物量和附着物总量均增加,在氮、磷浓度最高的T10组(总氮12.0 mg/L,总磷1.0 mg/L),附着物的总量达到高峰,附着物的Chl.a含量为2.005~4.765mg/g(DW),附着有机物的量为29.027~94.886 mg/g(DW),附着无机物的量为176.881~397.750 mg/g(DW),附着物总量为205.909~492.636 mg/g(DW).在菹草的快速生长期、稳定期和衰亡期,附着物的Chl.a含量、附着有机物量、附着无机物量和附着物总量均存在显著差异,均表现为衰亡期 >稳定期 >快速生长期,且在各营养盐浓度下均存在这一趋势.菹草衰亡期附着物的Chl.a含量、附着有机物量、附着无机物量和附着物总量分别为稳定期的1.046~1.826、1.046~1.638、1.029~1.858和1.106~1.717倍,为快速生长期的2.324~4.059、2.323~3.640、2.101~3.792和2.280~3.584倍.结果表明水体氮、磷负荷的增加促进了菹草茎叶附着物的生长和积累,加速了沉水植物衰亡.     

Temporal patterns in macrograzer effects on epilithic algae and meiofauna: a comparative approach to test for single species and whole grazer community effects

Within the shallow littoral zones of lakes, periphyton is an essential component, representing an important source of primary production and a food resource for herbivores. Periphytic communities are abundantly inhabited by meiofaunal organisms, which are mostly dominated by nematodes. During the last 3 decades, consumer–resource interactions between herbivore consumers and periphytic components (mainly algae) have been intensively studied. Although whole grazer community and single species effects on periphyton are known from field and laboratory experiments, the importance of single, dominant grazer taxa in direct comparison to whole community impacts is unknown. To investigate the continuity of grazing effects of a single, dominant macrograzer (Theodoxus fluviatilis, Gastropoda, Prosobranchia) on epilithic meiofauna and algae with respect to the whole grazer community, a temporally structured field experiment was carried out in Lake Erken (Sweden). Grazer impacts on periphytic algae and meiofauna were tested by controlling macrograzer access to littoral periphyton communities for 8 weeks in an exclosure/enclosure experimental design. Overall, the results showed macrograzer presence to have temporally constant, strongly negative effects on algal biomass as well as meiofaunal abundance and community composition. Moreover, T. fluviatilis alone accounted for up to 80% of the grazing effects, indicative of their ability to regulate periphytic communities in lakes. The present study yields new insights into the effects of a single grazer species and stressed temporal patterns of consumer–resource interactions in freshwater lakes.     

天津团泊洼水库水体生物生产力与渔业开发利用

天津市团泊洼水库属华北平原滨海盐碱性水库。1989年多学科综合调查的结果表明:该水体中营养盐类含量氮高磷低,挺水植物藨草、芦苇为主要初级生产者,浮游生物种类贫乏,现存量不高,周丛生物丰富。结果还表明,该水体仍有较大渔产潜力。应从调整鱼类种群结构着手,充分而合理地利用水体中的可更新资源,使渔业、环境协调发展。     

贵州草海湿地不同生境周丛生物碳、氮、磷生态化学计量学

为深入了解湿地周丛生物碳(C)、氮(N)、磷(P)生态化学计量的变化规律及其影响因素,对贵州草海湿地4种不同生境(湖滨带、人工湿地、农田沟渠、污水处理厂)中周丛生物两个生长阶段(生长期和衰老期)的C、N、P生态化学计量学进行了研究.结果表明:水体营养指数依次为污水处理厂(51.55±4.50)＞农田沟渠(50.41±4...     

极端洪水导致的湖泊水位抬升和氮磷输入增加对苦草(Vallisneria natans)的复合影响

据全球气候变化模型预测,未来极端洪水事件将呈现增多和加剧态势。极端洪水对沉水植物功能性状、生长发育状况及整个生态系统均有深远的影响,研究极端洪水对沉水植物生长发育的影响对理解和预测气候变化过程中水生态系统的变化具有重要意义。本文针对极端洪水事件引起的水位急剧上升和营养负荷量增加双重效应,在实验周期90 d内设置对照(水位保持75 cm)、2种极端洪水条件(水位在第1天从75 cm快速上升至150 cm + NP输入、水位从75 cm逐步上升至150 cm + NP输入)以及水位保持75 cm + NP输入4项处理(后3项处理中营养输入总量相同),研究了极端洪水对沉水植物苦草(Vallisneria natans)生长、繁殖对策及生物量分配的影响,实验过程中还同步监测了浮游植物、附着藻类和水体营养状况(TN和TP)。在苦草的17个测定指标中,只有根生物量分配和有性繁殖分配在4个处理下无明显变化。从水位的单独作用看,相对于营养增加且水位恒定的处理,两种洪水条件(水位急剧上升和逐步上升)均降低了苦草的分株数、叶片数、间隔子数、间隔子总长、最大根长、花果数以及各器官生物量和总生物量,促进了人工基质表面附着藻类的生长。水位急剧上升时,植株对间隔子的生物量投资倾向于最小,而株高和植株对叶的生物量投资倾向于最大。从营养负荷的单独作用来看,相对于对照组,营养增加且水位恒定的处理中水体N浓度显著增加,促进浮游植物和苦草表面附着藻类的生长,但是从二者的Chl.a浓度来看,浮游植物遮光作用相对较大,抑制了苦草叶、根和间隔子的生长,但有性繁殖生物量无明显变化。从水位和营养负荷联合作用的模式来看,水位上升和营养负荷两个环境因素的联合作用会使入湖营养负荷加强水位上升对沉水植物生长的影响效应,二者的联合作用使叶、根、间隔子和有性繁殖生物量均大大降低。因此,极端洪水对沉水植物的不利影响较大,一方面水位抬升会直接影响沉水植物,另一方面会通过浮游植物间接影响沉水植物生长发育。     

Influence of slight differences in environmental conditions (light, hydrodynamics) on the structure and function of periphyton

Small streams are ecosystems mainly controlled by physical factors. Minor differences in these factors can affect periphyton, which are key functional communities in these ecosystems. Eight different environmental conditions combining two types of current, two flow velocities and two light intensities were produced and controlled in artificial channels. Their impact on young and mature periphyton was investigated during a 6-week exposure period. The two different levels of light intensity produced early effects on the algal community. In young periphyton, the lower level of light intensity enhanced the number of algal cells, and this community appeared to be significantly structured by light. As the periphyton matured, the effects of physical factors became more marked. At this later stage, both the bacterial and algal communities began to be affected. Both function (primary production) and structure began to respond to differences in light and in flow velocity. Small differences in low-level environmental factors, such as light and flow, had an effect both on the structure of periphyton and its functional capacities. Keeping in mind the close link between diversity and function in microbial communities, periphyton confronted to various environmental stresses (pollution, flooding) in the field may behave differently due to minor differences in physical factors.     

磷在"沉积物-自然生物膜-上覆水"三相体系中的迁移转化

地表水体中沉积物表面通常会附着一层自然生物膜,对上覆水-沉积物界面化学物质的迁移转化有着重要的影响.以往研究往往会忽略这一生物层面,因而,开展磷在"沉积物-自然生物膜-上覆水"三相界面之间的迁移转化研究具有重要的实际意义.以软性填料表面形成的自然生物膜模拟沉积物表层以及悬浮颗粒物表层的自然生物膜,开展磷在沉积物-自然生物膜-上覆水之间的迁移转化过程研究.结果表明:有无曝气情况下,自然生物膜界面的存在均能够显著降低上覆水中总磷、溶解态总磷、溶解态无机磷的含量,明显抑制沉积物中可交换态磷向上覆水释放.研究证明自然生物膜在水体磷的迁移转化中起着不可忽视的作用,在研究沉积物-上覆水界面之间磷的迁移转化行为时,要充分考虑自然生物膜界面的存在.