竹叶眼子菜居群遗传多样性和克隆结构

采用ISSR技术对长江中游南岸豹澥湖和大冶湖不同生境中的竹叶眼子菜(Potamogeton malaianus)居群的遗传多样性及克隆结构进行了研究.结果表明,在两居群的106株个体中,利用6条ISSR引物共得到40条符合3/N标准并无连锁不平衡的清晰位点,竹叶眼子菜具有较高的遗传多样性,其多态位点百分率为75.0％,Shannon多样性指数为0.3736, 两居群的遗传分化很小.竹叶眼子菜的克隆多样性很高(D=0.9917),两居群间的克隆分化很大,不具有共有的基因型.竹叶眼子菜的基株分布为游击型构型,位于湖心的大冶居群克隆距离(3.0～31.5 m)明显地大于湖岸豹澥居群(2.4～6.7 m).     

南极冰下水生态系统微生物与生源元素循环研究进展

南极大陆冰盖下存在液态水,形成了由冰下湖、冰下河/溪、冰封湖和冰架下水体等组成的冰下水生态系统,具有低温、黑暗和寡营养等极端的环境条件特征。微生物主导了南极冰下水生态系统,其具有丰富多样的种群构成、功能形式和独特的适应机制,在生源元素生物地球化学循环过程中起了重要作用。研究南极冰下微生物群落的生态特征及其参与的生源元素地球化学循环过程,可为揭示地球生命演化和探索外星生命提供指示,具有重要的科学意义。本文综述了南极冰下水生态系统的极端环境条件、冰下微生物的多样性、冰下微生物参与的生物地球化学循环以及冰下微生物的适极机理,最后基于研究现状展望了南极冰下微生物的未来研究方向。     

三江平原小叶章湿地生态系统硫的生物地球化学循环

以三江平原小叶章湿地生态系统为研究对象,应用分室模型研究了硫在大气-土壤-植物系统各分室中的分布及循环过程。结果表明,在植物-土壤系统内,土壤是主要的贮存库和流通介质,有97.78%的硫贮存在土壤中,且主要以有机硫的形态存在,2.22%的硫贮存在植物中。在植物亚系统中,根是主要的贮库,79.60%的硫贮存在根中。湿地植物地上部分吸收的总S量为0.75gS/m^2;向地下再转移的总S量为0.24gS/m^2,向枯落物S库转移的总S量为0.51gS/m^2;根吸收的总S量为3.76gS/m^2;根向土壤S库转移的总S量为3.07gS/m^2;现存枯落物中的总S量为0.75gS/m^2;枯落物向土壤S库的转移量最低为0.52gS/m^2·a。输入和输出过程的研究表明,小叶章湿地生态系统在生长季（5-9月份）向大气排放H2S的量为1.42mgS/m^2,从大气吸收COS的量为1.83mgS/m^2;通过大气降水输入到生态系统中的硫为4.85mgS/m^2,其差值为5.26mgS/m^2,这表明硫在小叶章湿地生态系统中处于累积状态,湿地存在潜在的酸化趋势。     

外来植物对陆地生态系统氮循环的影响途径

外来植物的引种和入侵已成为一个全球性的重要问题.许多外来植物不仅可以改变陆地生态系统的氮输入、输出,而且还可以通过改变氮素吸收、再利用,凋落物质量,土壤环境,土壤生物等因子影响陆地生态系统内都氮循环.在概述陆地生态系统氮循环基础上,系统综述了外来植物对陆地生态系统氮循环的影响方式和途径以及可能造成的生态后果,并对将来研究方向进行了展望:应更多考虑外来植物影响机制的复杂性、不同养分元素循环的相互作用和新技术手段的应用.     

“双季稻-鸭”共生生态系统稻季磷循环

稻鸭共生是对中国传统农业稻田养鸭的继承与发展。在长江流域双季稻主产区湖南布置了稻田养鸭田间对比试验,以常规稻作为对照,采用投入产出法,分析"稻鸭共生"生态系统P的输入输出及循环情况。结果表明:"早稻-鸭"共生生态系统P输出为52.28kg·hm-2,其中鸭产品P为1.71kg·hm-2;"晚稻-鸭"共生生态系统P输出为83.24kg·hm-2,其中鸭产品P为6.17kg·hm-2;在早、晚稻两季,"稻鸭共生"系统在目前的P养分投入水平下,降低了土壤P的亏缺量;鸭子系统P输入主要来自系统外投入的饲料P;鸭粪P在系统内循环利用,两季循环率分别为12.5%和13.5%;两季稻作后,"稻鸭共生"土壤截存的P量为195.41kg·hm-2,比常规稻作显著提高了36.9%;"稻鸭共生"可对稻田土壤增加鸭粪P为17.75kg·hm-2。     

海南岛海莲红树林的钙镁累积和循环

本文是海南东寨港红树林研究的一部分,主要讨论55年生海莲林的Ca、Mg元素的累积和生物循环。试验结果表明,在海莲群落现存量中,含有Ca、Mg总量分别为3258.1和597.9kg·ha~(-1),其中地上部分别为1891.9和247.1kg·ha~(-1),地下部分别为1366.2和350.8kg·ha~(-1)。该群落的Ca、Mg元素的生物循环中,年吸收量分别为382.0和100.4kg·ha~(-1),存留量131.3和20kg·ha~(-1),归还量为250.7和80.4kg·ha~(-1)。Ca的周转期为13年,较Mg8年为慢。     

海南岛海莲红树林的钾钠元素的累积和循环

本文是海南东寨港红树林研究的一部分,主要讨沦55年生海莲林的K、Na元素的累积和生物循环。试验结果表明：在海莲群落现存量中,含有K、Na总量分别为669.9和2951.3kg／ha;其中地上部分别为425.6和908.9kg／ha,地下部分别为244.3和2042.4kg／ha。该群落的k、Na元素的生物循环中,年吸收量分别为89.6和204.4kg／ha,归还量为49.0和99.8kg／ha,存留量为40.6和104.6kg／ha。K的周转期为14年比Na30年为快。     

水分再分配对土壤-植物系统养分循环的生态意义

水分再分配(hydraulic redistribution, HR)作为一个普遍存在的生物物理过程, 在缓解植物干旱胁迫、调节植物种间关系和群落组成、影响生态系统水碳平衡等方面具有重要的生态意义。近年来, 同位素标记示踪技术的应用促进了HR的深入研究, 该文综述了HR对土壤-植被系统养分循环的影响。HR能改善干燥土层的水分状况, 防止根系栓塞, 促进细根存活与生长, 提高微生物活性, 从而促进植物对表层土壤养分(尤其是氮)的吸收; HR还通过水分下传作用促进植物对深层土壤中磷和金属离子的吸收。HR促进土壤养分库的上下交换与流动, 调节植物与土壤的氮磷比, 因此其影响可能具有全球意义。在全球变化(如氮沉降)背景下, 有必要深入探索HR在生物地球化学循环过程中的影响和作用, 并将其纳入生态系统模型中。     

箱体特征对箱式法观测水-气界面CO2和CH4通量的影响

箱式法是广泛运用于内陆水体CO₂和CH₄通量监测的重要方法,但各研究中使用的箱体特征存在差异,箱体设计缺少统一标准,从而会影响观测结果。为明确箱体透光性、箱体内外气压差以及箱体内气体混合状态对水-气界面CO₂和CH₄通量观测的影响,本研究基于多通道闭路式动态箱观测系统,分别对比明箱和暗箱、箱体是否配备气压平衡阀及风扇对养殖塘水-气界面CO₂和CH₄通量观测的影响。结果表明: 夏季白天观测期间,与可观测CO₂实际通量的明箱相比,当CO₂呈现排放状态时,暗箱高估了90%的CO₂通量;当CO₂呈现吸收状态时,暗箱低估了50%的CO₂通量。暗箱测得的CH₄扩散通量比明箱低40%。箱体内气压是否与外界气压保持平衡对CO₂和CH₄通量影响均不显著。无风扇的箱体观测的CO₂通量代表性较差,在本研究中较有风扇的箱体高20%。无风扇的箱体难以区分不同途径排放的CH₄通量。在运用箱式法观测水-气界面CO₂、CH₄通量时,应使用透明箱体,并在其中安装风扇辅助气体混合。     

连栽第1和第2代杉木人工林养分循环的比较

森林生态系统的养分循环是生态系统的重要功能过程之一,直接影响着森林的生产力,很大程度上影响和制约着林地的肥力水平,而且人工林连栽地力衰退和生产力下降现象普遍存在,寻求杉木林连栽两代杉木人工林养分循环差异与连栽林分生产力下降的关系,无疑具有重要的现实意义。利用30多年连续定位的测定数据,分析了连栽第1、2代杉木人工林在物质生产养分利用有效性、生物地球化学循环、地球化学循环的差异。结果表明,杉木速生阶段,第2代林每生产1 t干物质需要的养分比第1代林多1.58-3.29 kg,干材生长阶段,第2代林每生产1t所需养分比第1代林多4.23-5.92kg;速生阶段生物地球化学循环的养分利用系数第2代林比第1代林分下降19.7%-22.8%,养分循环系数下降12.8%-15.6%,干材生长阶段养分利用系数比第1代林分下降35.3%-36.2%,养分循环系数下降23.2%-27.0%,养分周转利用的生物地球化学循环功能第2代林比第1代林差;由干材生长进入成熟阶段的生长期内,伴随水文学过程的养分地球化学循环中,第2代杉木人工林生态系统的养分积累的地球化学循环的能力下降,养分流失率是第1代林的2倍左右,养分的积累率还不到第1代林的60%,对森林地力的维持和林木生长都是不利的。从生态系统水平上定位研究,定量分析了杉木连栽两代人工林养分循环功能过程,研究成果为我国南方人工林持续经营措施的制定提供了理论指导和科学依据。     

Nutrient limitation in Ellis Fjord,eastern Antarctica

The occurrence of high chlorophyll-a concentrations (up to 11.6gl^–1) at shallow depths within Ellis Fjord, eastern Antarctica, during spring and summer, coincided with the development of a stratified water column. Macronutrient concentrations during periods of high chlorophyll-a levels were very low. Phosphate concentrations decreased to 0.2 M, nitrate to 0.4 M and silicate to 3.9 M. High rates of nutrient depletion early in the season can be explained by strong sea-ice algal mat development. An SiNP uptake ratio of 25.513.81 indicates a strong demand for silicate. Minimum silicate levels were below those necessary for maximum diatom growth and probably contributed to the successional shift from diatoms to phytoflagellates.     

Nutrient and flow vector dynamics at the hyporheic/groundwater interface and their effects on the interstitial fauna

Environmental conditions in the interstices beneath streams and rivers with porous beds are unlike those found either on the bed surface or in the true groundwater. For most of the year, in many streams, the bulk of the water in the hyporheic zone is provided by baseflow but, as it passes across the hyporheic/groundwater interface, the physical and chemical nature of this groundwater changes, probably in response to mixing with surface water. Factors promoting the influx of surface water are associated with features of the bed and channel morphology. The upper and lower boundaries of the hyporheic zone are thought to vary in time, but at any instant they can be defined. As a habitat, the hyporheic zone fits the definition of an ecotone, although certain adverse features may result in reduced species diversity. There are limited, correlative, data available on the relationship of the fauna (hyporheos) to interstitial conditions and further study of the general biology of both species and populations is needed. In an attempt to stimulate future research on these systems, some preliminary models of hyporheic dynamics are proposed.     

Exchange of phosphorus across the sediment-water interface

In this article, principles of phosphorus retention and phosphorus release at the sediment-water interface in lakes are reviewed. New results and hypotheses are discussed in relation to older models of phosphorus exchange between sediments and water. The fractional composition of sedimentary phosphorus is discussed as a tool for interpretation of different retention mechanisms. Special emphasis is given to the impact of biological, particularly microbial, processes on phosphorus exchange across the sediment-water interface and to the significance of biologically induced CaCO₃ precipitation to phosphorus retention in calcareous lakes.     

Seasonal cycle of the microbial plankton in Crooked Lake,Antarctica

Summary Changes in the abundance of the components of the microbial plankton between July 1990 and March 1991 in Crooked Lake, one of the largest and deepest freshwater lakes in Antarctica, are described. Chlorophyll a concentration is low (0.2–0.4g·1^–1) and there is no discernable spring increase. The phytoplankton is largely dominated by flagellates. Bacterioplankton exhibits a seasonal pattern of abundance ranging from 1.0 × 10⁸·1^–1 in July to 3.25 × 10⁸·1^–1 in September. Changes in bacterial abundance probably relate to temperature and grazing by heterotrophic and mixotrophic flagellates. Total flagellated protozoan concentrations ranged between 25–136 × 10²·l^–1. Autotrophic and heterotrophic flagellate abundances were coupled and peaks in their abundance oscillated with peaks in bacterioplankton concentration. Four species of ciliated protozoa, dominated by oligotrichs, particularly the plastidic Strombidium, inhabit the lake. The plankton is characterised by the presence of floes which act as loci for bacteria, flagellates and amoebae and feeding sites for the ciliates and the two sparce metazoan components of the plankton. Crooked Lake is extremely oligotrophic but nonetheless supports a plankton community with a low species diversity and simple trophodynamics.     

Nutrient dynamics at the interface between surface waters and groundwaters

1. The surface water/groundwater (SW/GW) interface is a crucial control point for lateral nutrient fluxes between uplands and aquatic ecosystems and for upstream/downstream (longitudinal) processes in lotic ecosystems. 2. Hydrological and biogeochemical dynamics of the SW/GW ecotone are linked to the degree of channel constraint and the sediment characteristics of the floodplain and stream bed. 3. The availability of specific chemical forms of electron donors and electron acceptors affects the spatial distribution of biogeochemical processes at the SW/GW interface. Temporal change in discharge is also a major factor affecting the rate and extent of these processes. 4. The magnitude of SW/GW interactions in lotic ecosystems is predicted to be a major determinant of solute retention. Channel morphology, stream bed composition and discharge are predicted to be important controls on SW/GW interactions. 5. Interdisciplinary research involving hydrologists, geomorphologists, aquatic ecologists, microbial ecologists and landscape ecologists is needed to further our present understanding of this critical interface linking terrestrial and aquatic ecosystems.     

Engineering microalgae for water phosphorus recovery to close the phosphorus cycle

As a finite and non-renewable resource, phosphorus (P) is essential to all life and crucial for crop growth and food production. The boosted agricultural use and associated loss of P to the aquatic environment are increasing environmental pollution, harming ecosystems, and threatening future global food security. Thus, recovering and reusing P from water bodies is urgently needed to close the P cycle. As a natural, eco-friendly, and sustainable reclamation strategy, microalgae-based biological P recovery is considered a promising solution. However, the low P-accumulation capacity and P-removal efficiency of algal bioreactors restrict its application. Herein, it is demonstrated that manipulating genes involved in cellular P accumulation and signalling could triple the Chlamydomonas P-storage capacity to ~7% of dry biomass, which is the highest P concentration in plants to date. Furthermore, the engineered algae could recover P from wastewater almost three times faster than the unengineered one, which could be directly used as a P fertilizer. Thus, engineering genes involved in cellular P accumulation and signalling in microalgae could be a promising strategy to enhance P uptake and accumulation, which have the potential to accelerate the application of algae for P recovery from the water body and closing the P cycle.     

The role of zooplankton in the intrabiocoenotic phosphorus cycle and factors affecting phosphorus excretion in a lake

The temporal and spatial excretion rates of specific size groups of limnetic zooplankton were studied by measuring changes in soluble reactive phosphorus following incubation. Animals were collected in the epilimnion and hypolimnion of Stonehouse Pond, New Hampshire from August, 1972 to July, 1973 and separated into > 0.308 and < 0.308 (mm) size groups. Temporal excretion rates varied considerably within groups, however, similar patterns were observed in both strata. Peak excretion rates were observed in the spring and fall with a low in winter months. In addition, smaller animals excreted at higher rates and excretion rates of both size groups in the epilimnion exceeded those in the hypolimnion.The phosphorus uptake of natural seston relative to the amount released by zooplankton is considered using mass balance equations and kinetic analyses. During the spring of 1973 excretion rates increased, however, this increase was offset by an even greater rise in the rate of phosphorus uptake by the seston. This suggests that during this period the phosphorus excretions of zooplankton were not sufficient to meet the amount of phosphorus being removed by the seston.The experimental work was based on a thesis submitted to the Graduate School of the University of New Hampshire in partial fulfillment of the requirements for the degree of Doctor of Philosophy.     

Periphyton as a potential phosphorus sink in the Everglades Nutrient Removal Project

Phosphorus uptake and release by periphyton mats were quantified in the Everglades Nutrient Removal Project (ENRP) to evaluate the potential for periphyton P removal. Short-term P uptake rates were determined by incubating cyanobacteria (Oscillatoria princeps and Shizothrix calcicola) and Chlorophycean (primarily Rhizoclonium spp.) algal mat samples for 0.5–2 h under ambient conditions in BOD bottles spiked with soluble reactive P (SRP). Cyanobacterial mats removed P more than twice as fast (80–164 μg P h⁻¹ g⁻¹ AFDM) as Chlorophycean mats (33–61 μg P h⁻¹ g⁻¹ AFDM) during these incubations. In a longer term study, fiberglass cylinders were used to enclose 1.8 m² plots within the wetland and were dosed weekly for 7 weeks with: (1) no nutrients; (2) SRP (0.25 g P m⁻² week⁻¹); or (3) SRP plus nitrate (0.42 g N m⁻² week⁻¹) and ammonium (0.83 g N m⁻² week⁻¹). Phosphorus uptake rates by this periphyton assemblage, which was dominated by the chlorophytes Stigeoclonium spp. and Oedogonium spp., were measured weekly and were similar among nutrient treatments on most dates, indicating that the algal storage compartment for P was not saturated despite repeated P additions. Decomposition rates and P loss by cyanobacteria and Chlorophycean mats were determined by measuring biomass loss and SRP release in darkened BOD bottles over 28–42 day periods under anaerobic and aerobic conditions. First-order aerobic and anaerobic decomposition rates for cyanobacterial mats (k = 0.1095 and 0.1408 day⁻¹, respectively) were 4–20-fold higher than rates for Chlorophycean mats (k = 0.0066 and 0.0250 day⁻¹, respectively) and cyanobacteria released considerably more P back to the water column. Our findings suggest that periphyton can be an important short-term sink for P in treatment wetlands and that retention is strongly affected by the taxonomic composition of the periphyton assemblage.