摇蚊幼虫对底泥中氮、磷释放作用的研究

本文研究了摇蚊幼虫对底泥中氮、磷释放的影响,初步探讨了摇蚊在湖泊富营养化过程中的生态作用。结果表明,摇蚊幼虫能明显促进底泥中氮、磷的释放,而释放到水层中的氮、磷又容易被藻类吸收利用,从而促进藻类生长。这利,生态效应与水体营养循环和富营养化的发生及发展过程间存在着重要的关系。     

水动力条件下藻类动态模拟

藻类动态变化是其内部生理特征和外部驱动因素综合作用的结果。除了藻类自身生理因素及光、温度、营养盐等因素,水动力作用使底泥发生再悬浮所造成的营养盐的内源释放对藻类的影响也非常重要。1999年5月8日~6月24日在太湖湖泊生态系统研究站大型生态实验槽中进行了模拟水动力条件下的太湖藻类动态实验,并应用国外先进的PHREEQC软件从生物化学和生态动力学角度建立了藻类生态动力学模型。模型不仅考虑了氮循环及磷循环,还考虑了水动力条件引起的内源释放问题,根据2003年4月26~4月30日在河海大学环形水槽所做的底泥释放实验结果建立了水流和各形态氮磷营养盐释放的定量化关系。由于目前太湖的野外监测资料存在较明显的时空不一致性,模型参数率定的精度受到了较大影响。从室内模拟实验出发,通过对生态槽实验结果的模拟,确定和验证了模型的各参数值,计算结果显示模拟值能较好地拟合实验测量值,表明所建藻类生态动力学模型能较好地描述藻类及各种营养盐的动态变化,这对揭示藻类“水华”暴发机理有一定的意义。     

富营养化水体沉积物中磷的释放及其影响因素

综述了富营养化水体沉积物中磷的化学形态、释放规律及其影响因素。化学形态分为水溶性磷、铝磷、铁磷、钙磷、还原态可溶性磷、闭蓄磷、有机磷等 7种 ,其分布取决于各形态磷的性质。磷释放受 7种因素影响 ,厌氧、高 pH或低 pH值、高温、扰动、生物活动、底泥与水体含磷量的浓度差值以及钙质沉积物组分等因素均能促进沉积物中磷的释放。     

不同岩性湖泊底泥对磷的释放研究

富营养化是最常见的城市内水体污染现象,尽管采取了截留排污、完善城市排水管网建设、污水集中处理等多种措施,但仍然无法杜绝富营养化的产生。研究发现,底泥吸附的磷在一定条件下会释放回上覆水中,这是导致内源型富营养化产生的关键。本文以东北某城市人工湖为研究对象,对人工湖底泥在不同温度、PH下对磷的释放进行研究,为预防和治理东北地区水体富营养化提供理论依据。     

克隆植物乌菱对底泥磷含量及植株密度的表型可塑性响应

植物,尤其是克隆植物,能够通过表型变化来缓解外界压力,提高对环境的适应能力。该文研究了水生克隆植物乌菱(Trapa bicornis)对底泥磷含量(Sediment phosphorus concentration, SP)、植株密度(Plant density, PD) 及两者间交互作用的可塑性响应,探讨可塑性是否能促进其在富营养化环境中的生长。结果显示,底泥磷含量对乌菱的主菱盘叶数、同化根比根长、吸收根比根长以及叶、茎、同化根、吸收根与植株总磷含量等都有显著影响 (p<0.05),而植株密度对乌菱各生长及生理生态参数均无显著作用 (p>0.05);SP与PD的交互作用弱化了底泥磷含量对乌菱的效应。底泥磷含量和植株密度甚至改变了同化根、吸收根、茎、叶与总生物量之间的异速生长关系。研究结果表明:乌菱的表型可塑性变化主要受底泥磷含量的影响,乌菱通过器官生物量分配、形态结构及生理生态特征的调整来响应底泥磷含量的变化;同时,高的植株密度也可以提高其在富营养化生境下的生态适应性。     

水体富营养化过程中氧含量变化问题探讨

随着经济的进一步发展 ,大量含氧、磷肥料的生产和使用、食品加工、畜产品加工等造成的工业废水和大量城市生活废水 ,特别是含磷洗涤剂产生的污水未经处理即行排放 ,使海水、湖水中富含氮、磷等植物营养物质 ,称为水体富营养化。在富营养化的水体中 ,由于有了充足的养料保证 ,藻类等浮游植物一有适宜条件即大量繁殖。此时鱼类等生物的消费能力 (以藻类为食 )赶不上藻类的繁殖速度 ,水中藻类越长越多 ,它使水中氮含量减少 ,导致水中的鱼类等生物大量死亡。在教学过程中 ,发现有许多学生错误认为藻类疯长 ,应该是光合作用增强 ,产生氧气量增多…     

不同磷条件下塔玛亚历山大藻氮的生态幅

藻类氮的生态辐是指在一定氮浓度范围内藻类能生长和繁殖的浓度范围。它由藻类生长的最佳氮浓度、氮适宜生长范围和氮耐受限度构成。为了定量计算藻类的氮生态幅,在室内培养条件下,研究了低磷(0.48 μmol/L)、中磷(0.97 μmol/L)和高磷(1.45 μmol/L)3种不同磷起始浓度条件下不同氮对塔玛亚历山大藻细胞数和最大比生长率的影响,依据Shelford耐受性定律建立了塔玛亚历山大藻生长的氮耐受性模型,并得到了藻类生长的最佳氮浓度、氮适宜生长范围和氮耐受范围的定量表达。结果表明,在低磷、中磷和高磷条件下,当氮浓度小于适合藻类生长的最佳氮浓度时,藻类细胞数和最大比生长率均随着氮浓度的增大而增大;当氮浓度大于适合藻类生长的最佳氮浓度时,藻类细胞数和最大比生长率均随着氮浓度的增大而减小。藻类生长的氮耐受性模型与谢尔福德耐受定律较为吻合,定量得到在低磷、中磷和高磷培养条件下塔玛亚历山大藻的最佳氮浓度分别为30.36、62.07和77.85 μmol/L;氮适宜生长范围分别为18.30-42.42、37.71-86.43和41.52-114.18 μmol/L;氮耐受限度分别为6.24-54.48、13.35-110.79和5.19-150.51 μmol/L。研究显示不同磷起始浓度条件下,藻类的氮生态幅也不相同。     

穗花狐尾藻(Myriophyllum spicatum L.)在不同程度富营养化水体中的营养积累特点及营养分配对策

通过对栽培于3个不同程度的富营养化水体(富营养化程度为水体1<水体2<水体3)中的穗花狐尾藻(MyriophyllumspicatumL.)进行研究,测定了不同时期植物体各个器官的氮磷含量及生物量分配,探讨了富营养化水对其营养积累及分配格局的影响。结果表明,重度富营养化的水体3中穗花狐尾藻组织中的氮含量显著高于其它两个水体;而由于水体1和水体2的氨态氮含量无显著差异,植物组织中的氮含量在水体1和水体2间无显著差异。富营养化程度高的水体2中植物磷的含量显著低于富营养化程度低的水体1中的植物,但在重度富营养化的水体3中,叶子的磷含量却远高于其它两个水体,这是由植物不同部位吸收的磷在各器官间分配不同所造成的。由于底泥的营养含量丰富,在3个不同程度的富营养化水体中,穗花狐尾藻的根冠比并未表现出明显差异。     

穗花狐尾藻(Myriophyllum spicatum L.)在不同程度富营养化水体中的营养积累特点及营养分配对策

通过对栽培于3个不同程度的富营养化水体(富营养化程度为水体1<水体2<水体3)中的穗花狐尾藻(MyriophyllumspicatumL.)进行研究,测定了不同时期植物体各个器官的氮磷含量及生物量分配,探讨了富营养化水对其营养积累及分配格局的影响。结果表明,重度富营养化的水体3中穗花狐尾藻组织中的氮含量显著高于其它两个水体;而由于水体1和水体2的氨态氮含量无显著差异,植物组织中的氮含量在水体1和水体2间无显著差异。富营养化程度高的水体2中植物磷的含量显著低于富营养化程度低的水体1中的植物,但在重度富营养化的水体3中,叶子的磷含量却远高于其它两个水体,这是由植物不同部位吸收的磷在各器官间分配不同所造成的。由于底泥的营养含量丰富,在3个不同程度的富营养化水体中,穗花狐尾藻的根冠比并未表现出明显差异。     

围隔模拟生态系统中藻类生长的磷酸盐浓度阈值研究

藻类的过度生长是湖泊富营养化的显著特征之一。一般认为,在富营养化水体中降低磷的负荷能有效控制藻类生长并改善水体的富营养化状态;在我国巢湖,两次调查显示出总氮与总磷浓度比分别为15.4:1和16.3:1,远远超过巢湖优势藻微囊藻的最适生长氮磷比9:1,说明磷比氮更能限制藻类的生长。然而最近一些研究却显     

Rates of ammonia release from sediments by chironomid larvae

SUMMARY. 1. Microcosms of Lake Balaton mud and sterilized sand and aerated water were used to evaluate ammonia increments in the overlying water as influenced by chironomid density and temperature. In the two approaches, the effects of sediment disturbance and metabolic excretion of chironomids were measured.
2. The activity of larvae increased the ammonia content of the overlying water at temperatures above 10°C. A rise of temperature to 20°C resulted in a 5–20-fold increase in ammonia release in both systems with chironomids.
3. At 10°C combined effects of sediment disturbance and of excretion produced lower release rates than did excretion rates alone (mud-water v. sand-water treatments). At higher temperatures (15 and 20°C) release rates of ammonia by sediment disturbance plus excretion were higher than excretion rates alone. Ammonia excretion contributed significantly to the total release at each temperature.
4. Metabolic mineralization of nitrogen compounds appears to be an important mechanism contributing to nitrogen regeneration from aerobic lake sediments. High N:P ratio (14:1) of chironomid excretion materials supports this interpretation.     

An attempt to trace eutrophication in a shallow lake (Balaton,Hungary) using chironomids

Lake Balaton, the largest shallow lake in Central Europe, is about 20 000 years old. An enormous increase in tourism and the disproportionate building development of the last few decades has resulted in the acceleration of eutrophication in the lake. Widespread research to reveal the causes of water-quality deterioration and possible ways of protection against it have recently started. The investigation of the larvae of non-biting midges (Diptera: Chironomidae) in the sediment of the open-water zone has also begun. The contemporary faunal composition strongly correlates with the trophic gradient along the longitudinal axis of the lake. We therefore supposed that the eutrophication process should be identifiable from the analysis of subfossil chironomid head capsules from the upper (15 cm thick) layer of the sediment. We found that quantitative results could only be obtained when fragments as well as relatively intact head capsules are considered. Our data verify that the originally oligo-mesotrophic community has been gradually replaced by eutrophic species in a west to east direction. Large-bodied larvae belonging to the Chironomus plumosus group mix the sediment down to 15 cm as they build their tubes and consequently alter the original proportions of head capsules at the different levels. So the sequence of communities through the sediment-layers is not quite reliable.     

Ecological background and importance of the change of chironomid fauna (Diptera: Chironomidae) in shallow Lake Balaton

The objectives of this research were to record the changes in composition of the open-water, bottom-dwelling chironomid fauna in Lake Balaton between 1978–1984, to examine the causes of these changes, and to discover their significance in the life of the lake.The spatio-temporal dispersion of larvae is compared with the water and sediment quality of each basin in the lake. It is established that, under present conditions, nutrient status can be regarded as the chief environmental factor.Studies of population dynamics show that chironomids play a highly important role in preserving sediment quality. Chironomids are an essential element in the organic matter circulation of the lake. They dominate a sub-system that retards water quality degradation, and thus they play a prominent role in the natural prevention of eutrophication.     

Twentieth century human and climate impacts on a large mountain lake in southwest China

Subfossil chironomid and sediment geochemistry data from Lugu Lake, a large high-elevation lake in southwest China, were used to assess the influences of climate warming and direct human impacts on the lake through time. A 95-year-long sediment record was recovered from the lake. Principal components analysis (PCA) and redundancy analysis of fossil chironomid data were performed to determine the controlling factors on the chironomid community. The four prominent environmental controls were summer air temperature, organic matter C:N ratio (C_org:N), dry mass accumulation rate (DMAR), and total nitrogen. C_org:N proved to be the most important controlling factor through time. However, C_org:N and summer air temperature were highly co-linear, possibly due to temperature directly impacting lake productivity (and thus C:N ratios) through increased stratification and a longer growing season. PCA Axis 1 scores were a strong predictor of summer temperatures even after DMAR was factored out to account for direct human influences. The strong temperature–chironomid relationship over the last 50 years could be due to the lake becoming more responsive to climate warming after cultural eutrophication of the 1950s, as lakes with higher nutrient loads are shown to be more responsive to the effects of climate warming.     

The effect of tubificids and chironomids on particle redistribution of lake sediment

The effects of chironomid larvae,Chironomus plumosus, and tubificid worms,Limnodrilus spp., on particle redistribution in lake sediment were investigated experimentally using pots containing sediments obtained from Lake Suwa, Japan. The chironomids and tubificids increased the water content of surface sediment. The chironomid larvae had no effect on particle size distribution, while tubificids continuously accumulated small particles on the surface sediment through their selective feeding activity. Particles larger than 0.125 mm were buried at a sediment depth of 6 cm. In Lake Suwa, long diatom frustules, large plant debris and blue-green algal flocs were found to accumulate in the deeper layer of the lake sediment inhabited by tubificids at high density.     

The influence of chironomus plumosus larvae on the exchange of dissolved substances between sediment and water

4th instar Chironomus plumosus larvae (about 1000·m^–2) were added to tubes containing sediment and overlying water. At a temperature of 20°C the larvae greatly increased the trasnport of silica, phosphorus and iron from the sediment to the water. Oxygen concentrations did not influence the exchange of silica. For two non-calcareous sediments the exchange of phosphorus and iron was much higher under anaerobic than under aerobic conditions while the difference was small for sediment from a hardwater lake. Exchange of inorganic nitrogen was little influenced by added chironomid larvae.     

Methane-derived carbon flows through methane-oxidizing bacteria to higher trophic levels in aquatic systems

Recent investigations have shown that biogenic methane can be a carbon source for macro invertebrates in freshwater food webs. Stable carbon isotopic signatures, used to infer an organism's food source, indicated that methane can play a major role in the nutrition of chironomid larvae. However, the pathway of methane-derived carbon into invertebrate biomass is still not confirmed. It has been proposed that chironomid larvae ingest methane-oxidizing bacteria (MOB), but this has not been experimentally demonstrated to date. Using ¹³C-labelled methane we could show for the first time that chironomid larvae assimilate methane-derived carbon through MOB. Chironomid larval biomass was significantly ¹³C-enriched after dwelling for 10 days in lake sediment enriched with labelled methane. Moreover, phospholipid fatty acids diagnostic for MOB were detected in larval tissue and were significantly ¹³C-enriched, which encompasses the ¹³C-uptake predicted for a methane-based nutrition. Additionally, chironomid larvae fed on sediment and water-column derived MOB biomass.     

乌梁素海沉积物中有机质和全氮含量分布特征

针对乌梁素海富营养化日趋严重和湿地面积逐渐萎缩,系统地研究了其生态环境地球化学效应.结果表明,乌梁素海表层沉积物中的全氮含量存在明显的经向和纬向分异特征;沉积物中全氮养分含量与有机质含量显著相关(r＞0.93);沉积物中C/N的平均值介于12.07～19.95之间,表明有机质主要来源于湖中水生植物,水体富营养化具有显著的内源性.TN和有机质在不同粒级表层沉积物中的粒度效应明显,且TN和有机质在IV粒级的含量分别为I粒级的3.1～7.6倍和2.5～8.0倍.     

The chironomid‐temperature relationship: expression in nature and palaeoenvironmental implications

Fossils of chironomid larvae (non‐biting midges) preserved in lake sediments are well‐established palaeotemperature indicators which, with the aid of numerical chironomid‐based inference models (transfer functions), can provide quantitative estimates of past temperature change. This approach to temperature reconstruction relies on the strong relationship between air and lake surface water temperature and the distribution of individual chironomid taxa (species, species groups, genera) that has been observed in different climate regions (arctic, subarctic, temperate and tropical) in both the Northern and Southern hemisphere. A major complicating factor for the use of chironomids for palaeoclimate reconstruction which increases the uncertainty associated with chironomid‐based temperature estimates is that the exact nature of the mechanism responsible for the strong relationship between temperature and chironomid assemblages in lakes remains uncertain. While a number of authors have provided state of the art overviews of fossil chironomid palaeoecology and the use of chironomids for temperature reconstruction, few have focused on examining the ecological basis for this approach. Here, we review the nature of the relationship between chironomids and temperature based on the available ecological evidence. After discussing many of the surveys describing the distribution of chironomid taxa in lake surface sediments in relation to temperature, we also examine evidence from laboratory and field studies exploring the effects of temperature on chironomid physiology, life cycles and behaviour. We show that, even though a direct influence of water temperature on chironomid development, growth and survival is well described, chironomid palaeoclimatology is presently faced with the paradoxical situation that the relationship between chironomid distribution and temperature seems strongest in relatively deep, thermally stratified lakes in temperate and subarctic regions in which the benthic chironomid fauna lives largely decoupled from the direct influence of air and surface water temperature. This finding suggests that indirect effects of temperature on physical and chemical characteristics of lakes play an important role in determining the distribution of lake‐living chironomid larvae. However, we also demonstrate that no single indirect mechanism has been identified that can explain the strong relationship between chironomid distribution and temperature in all regions and datasets presently available. This observation contrasts with the previously published hypothesis that climatic effects on lake nutrient status and productivity may be largely responsible for the apparent correlation between chironomid assemblage distribution and temperature. We conclude our review by summarizing the implications of our findings for chironomid‐based palaeoclimatology and by pointing towards further avenues of research necessary to improve our mechanistic understanding of the chironomid‐temperature relationship.