Spatial Interaction Among Nontoxic Phytoplankton, Toxic Phytoplankton, and Zooplankton: Emergence in Space and Time

In homogeneous environments, by overturning the possibility of competitive exclusion among phytoplankton species, and by regulating the dynamics of overall plankton population, toxin-producing phytoplankton (TPP) potentially help in maintaining plankton diversity—a result shown recently. Here, I explore the competitive effects of TPP on phytoplankton and zooplankton species undergoing spatial movements in the subsurface water. The spatial interactions among the species are represented in the form of reaction-diffusion equations. Suitable parametric conditions under which Turing patterns may or may not evolve are investigated. Spatiotemporal distributions of species biomass are simulated using the diffusivity assumptions realistic for natural planktonic systems. The study demonstrates that spatial movements of planktonic systems in the presence of TPP generate and maintain inhomogeneous biomass distribution of competing phytoplankton, as well as grazer zooplankton, thereby ensuring the persistence of multiple species in space and time. The overall results may potentially explain the sustainability of biodiversity and the spatiotemporal emergence of phytoplankton and zooplankton species under the influence of TPP combined with their physical movement in the subsurface water.     

丹江口水库浮游植物时空动态及影响因素

2007年7月至2008年6月对丹江口水库浮游植物进行了为期一年的调查和分析,共采集到浮游植物8门、60属、110种及变种.种类组成以绿藻门、硅藻门和蓝藻门为主,其中绿藻门占优势,共计46种(42％),其次为硅藻35种(32％).藻类年平均密度为4.17×106 celVL,最高密度为6.10×107 cell/L,最低密度为5.16×103 cell/L.各季节浮游植物优势种差异显著,春季为一种颤藻(Oscillatoria sp.)和尖针杆藻(Synedra acus),夏秋两季为啮蚀隐藻(Cryptomonas erosa),冬季转为倪氏拟多甲藻(Peridiniopsis niei).空间分布上,丹江、汉江库区以及取水口3个区域浮游植物优势种为尖针杆藻,五青入库区则以倪氏拟多甲藻占优势.磷浓度是驱动丹江口水库藻类密度的主要影响因子.根据建库几十年来的对丹江口水库较为全面的4次调查资料,分析了丹江口水库的浮游植物群落演替及变化趋势.自1958年以来,50年间,整个水库浮游植物密度增加了16倍,水库富营养化程度有增加的趋势.种类组成由适应河流的固着型硅藻,经过硅藻-绿藻-蓝藻型逐渐发展为硅藻-甲藻-隐藻-蓝藻型.     

玉米根系分布空间和空间密度分布的数学模型

应用重积分研究了土壤层中散根型和直根型玉米根系的分布空间,同时研究了玉米根系的空间密度分布．     

湖南壶瓶山国家级自然保护区两栖 爬行动物多样性的时空格局

本研究利用2013至2016年湖南壶瓶山国家级自然保护区巡护监测数据,评估壶瓶山保护区两栖爬行动物多样性水平。壶瓶山保护区在8个监测站点布设了25条两栖爬行动物调查样线,进行常规监测,其中,日间样线14条,夜间样线11条,日间样线平均长度4 km,夜间样线平均长度0.75 km。每个月,每条样线平均调查3次。4年共调查到62种两栖爬行动物,占湖南省两栖爬行动物总种数的38.04%。逐月计算各监测站点的alpha多样性指数和整个保护区的beta多样性指数,按季节比较不同站点间物种组成的Hellinger距离。结果显示,保护区不同位置间、不同的监测站点间以及年际间的两栖爬行动物多样性没有显著差异,提示保护区环境具有相对稳定性。但是,个别位于实验区或邻近实验区的站点,物种组成有着剧烈的波动,表明人为活动影响了两栖爬行动物的分布。另外,保护区两栖爬行动物的物种组成与多样性有着显著的季节差异,这与两栖爬行动物的生物学特性有关。以上结果说明,壶瓶山保护区两栖爬行动物的多样性结构具有稳定性和敏感性的特点,可以考虑用作保护区生物多样性水平的监测指标。     

Nutrients and phytoplankton in Lake Peipsi during two periods that differed in water level and temperature

Data for the vegetation periods (May–November) of 1985–2003 were used to collate the nutrient content and biomass of the most important phytoplankton groups in Lake Peipsi (Estonia). Two periods differing in external nutrient load and water level were compared by analysis of variance. The years 1985–1988 were characterized by the highest loads of nitrogen and phosphorus, high water level and cool summers. The years 2000–2003 were distinguished by low or medium water levels and warm summers. The first period showed statistically significantly higher values of total nitrogen (N_tot) and a higher N_tot:P_tot mass ratio. The second period showed a higher content of total phosphorus (P_tot), a higher ratio of dissolved inorganic compounds N to P and higher phytoplankton and cyanobacterial biomasses. Comparison between parts of the lake demonstrated that the differences between the two periods were more evident in the shallower and strongly eutrophic parts, Lake Pihkva and Lake Lämmijärv, than in the largest and deepest part, the moderately eutrophic Lake Peipsi s.s. Temperature and water level acted synergistically and evidently influenced phytoplankton via nutrients, promoting internal loading when the water level was low and the temperature high. The effect of water level was stronger in the shallowest part, Lake Pihkva. The difference in P_tot content between the southern and northern parts was twofold; the N_tot:P_tot mass ratio was significantly lower in the southern parts, and phytoplankton biomass (particularly the biomass of cyanobacteria) was significantly higher for Lake Pihkva and Lake Lämmijärv than for Lake Peipsi s.s.     

赤潮过程浮游植物与营养物质时间变化率研究

利用2000年大亚湾澳头海域赤潮定点连续调查资料及其多年现场调查资料,采用灰色回归模型,综合分析赤潮发生过程水体中浮游植物细胞密度与营养物质(NO3-、NH4+、PO4^3-、SiO3^2-、Fe)的时间变化率关系,分析了叶绿素a含量与浮游植物细胞密度相互关系．结果表明,预测值与实测基值本一致,复相关系数范围在0．51～0．83．当水体叶绿素浓度为5．8μg·dm-3,预示可能发生赤潮,通过采样分析水体叶绿素a含量或利用水色卫星遥感资料反演水体叶绿素浓度,计算浮游植物细胞密度,为赤潮的预测预报提供简便有效的方法．此外．本水域初级生产力由磷控制．     

Spatial trend of Foot and Mouth Disease virus (FMDV) serotypes in cattle and buffaloes, Pakistan

The present study describes the frequency of Foot and Mouth Disease (FMD) virus serotypes (O, A and Asia-1) in major regions (all provinces) of Pakistan using Indirect Sandwich ELISA. Also, spatial distribution of various FMD serotypes and their comparison is discussed. A total of 590 samples (Epithelial tissue) have been analyzed during a period of five years (2005–2009). Out of 590 samples, 180 were found positive, giving an overall confirmation of FMDV about 33.2 %. Of the prevalent serotypes, FMDV ‘O’ serotype caused most outbreaks (20.7 %), followed by serotype A (6.6 %) and serotype Asia-1 (4.6 %) while there was no positive case of type ‘C’. The study clearly showed that the disease was more frequent in the agro-climatic zones than in hilly areas. Based on the data of 590 samples (>50 outbreaks), the overall prevalence of FMDV in cattle and buffaloes in Pakistan was 33.2 %, while in cattle alone, it was 37.1 %, higher than in buffalo (28.7 %). There were eight cases of mixed serotypes infection, indicating the presence of endemic state of disease. Another significant feature was the change over time. In phase-I (2005–2007), there was an overall prevalence of 29.4 %, while the occurrence of the serotype O, A and Asia-1 was 20.4 %, 2.9 % and 4.7 %, respectively. During phase-II (2008-2009), the overall prevalence was 59.21 %, while those of serotype O, A and Asia-1 were 22.4 %, 31.6 % and 4.0 %, respectively. This clearly indicated a shift from serotype O to A, which may help to explain the occurrence of more severe outbreaks, despite vaccination.     

Distribution,pest status and agro-climatic preferences of lepidopteran stem borers of maize in Kenya

Lepidopterous stem borers are the main field insect pests that attack maize, Zea mays L. in tropical Africa. A survey was carried during the long and short rain cropping seasons of 2002 / 2003 across six main agro-climatic zones (ACZs) to determine the spatial distribution of important stem borer species in Kenya. A total of 474 visits were made in the seventy-eight localities conveniently chosen to represent each of the six ACZs. 189,600 stems were checked for infestation, of which 27,799 infested stems were destructively cut and dissected for stem borer larvae identification. An average of 1.4 stem borer larvae were recovered per infested plant. 54.5% of the recovered larvae were identified as Chilo partellus (Swinhoe) (Crambidae), 39.7% as Busseola fusca (Fuller) (Noctuidae), 4.5% as Sesamia calamistis Hampson (Noctuidae) and 0.8% as Chilo orichalcociliellus (Strand) (Crambidae). Minor species present included Eldana saccharina Walker (Pyralidae), Sesamia nonagrioides (Lefebvre) (Noctuidae), Sesamia cretica Lederer (Noctuidae), Sesamia sp. (Noctuidae), Sciomesa piscator Fletcher (Noctuidae), Busseola sp near phaia (Noctuidae), Chilo sp, Ematheudes sp 1 (Pyralidae) and Ematheudes sp 2 (Pyralidae). Farms were grouped into respective ACZs for statistical analysis and subsequent comparison of dominant species. Results indicated that B. fusca was the dominant stem borer species in high potential zones (highland tropics, moist transitional zone and moist midaltitude) while the exotic C. partellus dominated smallholder farms in low potential zones (dry midaltitude, dry transional and lowland tropical zone). Within each ACZs, there was evidence of variation in species proportions between seasons. These spatio-temporal differences in community structure are discussed in terms of agro-climatic biological adaptations.     

大型热带水库-松涛水库枯水期浮游植物群落特征

松涛水库是一个大型热带水库,分为两个主要水域:番加洋和南丰洋,2003年12月对该水库的这两个水域的浮游植物进行采样,共发现7门65种藻类。松涛水库番加洋库区水体的浮游植物总细胞密度为1.08×10⁶cells·L^-1,主要种类组成为蓝藻(Cyanophyta)-绿藻(Chlorophyta)型。松涛水库南丰洋库区水体的浮游植物群落为细胞密度为1.14×10⁶cells·L^-1,主要种类组成为绿藻(Chlorophyta)-硅藻(diatom)型。松涛水库库区水体总体已为避-富营养,其中富营养型浮游植物指示种类有:铜绿微囊藻(Microcystis aeruginosa Kütz.),针状蓝纤维藻(Dactylococcopsis acicularis),镰形纤维藻(Ankistrodesmus falcatus),小环藻(Cyclotella menighiniana),模糊直链藻(Melosira spp.)等。与亚热带和温带的水库比较,处于热带地区的松涛水库浮游植物,在湖泊区微囊藻等适应高温高光强的种类具有更高的细胞密度。松涛水库河流区最主要的优势种是硅藻门的针杆藻。     

Studies on Temporal and Spatial Variations of Phytoplankton in Lake Chaohu

Temporal and spatial variations of the phytoplankton assemblage in Lake Chaohu, a large shallow eutrophic lake in China, were studied from September 2002 to August 2003. A total of 191 phytoplankton species was identified, among which Chlorophytes （101） ranked the first, followed by Cyanophytes （46） and Bacillariophytes （28）. On aver- age over the entire lake, the maximum total algal biomass appeared in June （19.70 mg/L） with a minimum （5.05 mg/ L） in November. In terms of annual mean biomass, cyanobacteria contributed 45.43% to total algal biomass, followed by Chlorophytes （27.14%）, and Bacillariophytes （20.6%）. When nitrate （NOs-N） and ammonium （NH4-N） concentrations dropped in spring, fixing-nitrogen cyanobacterium （Anabaena） developed quickly and ranked the first in terms of biomass in summer. It is likely that dominance of zooplanktivorous fish and small crustacean zooplankton favored the development of the inedible filamentous or colony forming cyanobacteria. The persistent dominance of cyanobacteria throughout all seasons may indicate a new tendency of the response of phytoplankton to eutrophication in Lake Chaohu.     

Distribution and abundance of patas monkeys (Erythrocebus patas) in Laikipia, Kenya, 1979-2004

Patas monkeys may be especially vulnerable to local extinction because they live in relatively small, female-philopatric groups at low densities and are strongly polygynous. We assessed a patas monkey population in Kenya's 9,700 km(2) Laikipia District over 25 years, using data collected in 1979-1981 and 1992-2004. The data were based on intensive observations of three study groups, "on the ground" counts, and surveys of Laikipia residents. In 1979-1981, a minimum of 415 patas monkeys lived in 14-15 groups. By 2000, the best estimate suggested 310-445 patas monkeys living in 13-17 groups over a greater surveyed area, suggesting that patas monkeys in Laikipia may have undergone a slight decline in numbers over time. Their distribution, however, was similar over time. The relative stability of this population has likely been the result of beneficial co-existence with large-scale cattle ranching. Outside Laikipia, substantial habitat alteration from rising human populations has coincided with the near disappearance of patas monkeys where they were previously more numerous. The small population in Laikipia, probably the largest remaining in Kenya, may therefore be critical to the continued existence of patas monkeys in that country and may be dependent on maintenance of large-scale ranches. Such land use provides patas monkeys with water and broad expanses of Acacia drepanolobium woodlands, the habitat to which patas are restricted in Laikipia.     

Interactions of Photobleaching and Inorganic Nutrients in Determining Bacterial Growth on Colored Dissolved Organic Carbon

Abstract Bacteria are key organisms in the processing of dissolved organic carbon (DOC) in aquatic ecosystems. Their growth depends on both organic substrates and inorganic nutrients. The importance of allochthonous DOC, usually highly colored, as bacterial substrate can be modified by photobleaching. In this study, we examined how colored DOC (CDOC) photobleaching, and phosphorus (P) and nitrogen (N) availability, affect bacterial growth. Five experiments were conducted, manipulating nutrients (P and N) and sunlight exposure. In almost every case, nutrient additions had a significant, positive effect on bacterial abundance, production, and growth efficiency. Sunlight exposure (CDOC photobleaching) had a significant, positive effect on bacterial abundance and growth efficiency. We also found a significant, positive interaction between these two factors. Thus, bacterial use of CDOC was accelerated under sunlight exposure and enhanced P and N concentrations. In addition, the accumulation of cells in sunlight treatments was dependent on nutrient availability. More photobleached substrate was converted into bacterial cells in P- and N-enriched treatments. These results suggest nutrient availability may affect the biologically-mediated fate (new biomass vs respiration) of CDOC.     

Spatial and Temporal Ecology of Native and Introduced Fish Larvae in Lower Putah Creek,California

For two years we studied the distribution and abundance of native and introduced fish larvae in Putah Creek (Yolo County, CA), a low elevation regulated stream. We used light traps and conical drift nets to sample the fish larvae at two spatially separated sites from March through July 1997 and at four sites from February through August 1998. Native larvae occurred both earlier in the year and in higher abundance than those of introduced species. Both native larvae and overall numbers of larvae were more abundant at upstream sites in both years. Sampling of larvae appeared to be sensitive to the detection of rare species. Drift nets and light traps collected similar numbers of larvae, but each method tended to select for different taxa. There were significant trends in diel patterns of abundance, with more fish larvae being found during the hours of darkness. We suggest that differences between the sites were due to habitat changes resulting from an upstream dam that has created a refuge of diverse habitat and cool flowing water for native taxa.     

动物生境选择研究中的时空尺度

尺度研究已成为生态学上的一个重要概念和研究热点,但是在动物生境选择的研究中尚未引起足够的重视。动物的生境选择包括多层次的判别和一系列等级序位,在各个尺度和水平上具有不同的特征和机制,受到时空尺度的严格限定。繁殖期的时间限制、社群压力、环境变化、动物生理需求的变化决定了动物生境选择的时间制约性;而生境资源的斑块化分布、功能生境之间的相互作用决定了动物生境选择的空间制约性。研究者对时间和空间尺度的选取与应用会直接影响到生境选择研究结果的科学性和实效性。本文从动物生境选择的时空制约性出发,分析了生境选择研究中时间尺度的重要性,叙述了国内外生境选择研究中常见的研究尺度,强调了多尺度研究和长期生态研究的必要性,尺度的选择应该成为生境选择研究的起点和基础。     

流溪河和潖江河从化段浮游植物群落结构研究

2007年9月至2008年9月对广州流溪河和琶江河从化段浮游植物进行周年调查,分析其种类组成、细胞数量、优势种类组成、种类多样性等群落结构特征及其季节变化。广州流溪河和琶江河从化段浮游植物种类丰富,共鉴定了隶属于90属的218种（包含变种和变型）,其中绿藻为优势种类,共31属92种,占总种类数的42.20%。浮游植物细胞数量的变化范围是5.1～2090×103cell/L之间,平均值为152×103cell/L,最高值出现在春季,最低值出现在夏季。多样性H’指数较高,各站平均值变化范围为1.03～4.22,丰富度的变化范围为1.00～7.83,均匀度变化范围为0.63～0.85。多样性指数的最高值都出现在夏季,最低值出现在冬季。     

Phytoplankton and Nutrients in the River Strymon,Greece

Phytoplankton species composition, biomass, diversity, nutrients and chlorophyll a were studied at monthly intervals from December 1991 to December 1992 in a selected area of the river Strymon. SRP ranged from 53 to 182 μg⁻¹ l⁻¹ and DIN from 265 to 850 μg⁻¹ I⁻¹. Nutrient values do not indicate strong anthropogenic effects. Chlorophyll α ranged from 1.0 to 35.3 μg⁻¹ I⁻¹ and followed the temporal distribution of total phytoplankton biomass. Phytoplankton biomass exhibited maxima in winter – spring and summer (6.8 g m⁻³ in December 1991, 4.8 g m⁻³ in April 1992 and 9.3 g m⁻³ in August 1992) composed mainly of diatoms, chlorphytes, cyanophytes and dinophytes. Nanoplankton was the most important component of phytoplankton biomass (69.5%) revealing increased values in winter and early spring. Phytoplankton diversity ranged from 0.8 to 3.2. The hydrological conditions in the river Strymon seem to be appropriate for the algae to reproduce themselves in the running water and so, to develop as a true potamoplankton. However, significant populations of phytoplankton must have been carried out from the Kerkini reservoir, situated at the north of the sampling station. The phytoplankton species composition and their periodicity in the river resemble those of typical, large, lowland and nutrient – rich rivers of Europe.     

二点叶蝉自然种群的时空动态

选择受密度影响较小的负二项分布K值 ,描述玉米上二点叶蝉自然种群在 3个海拔高度上的空间格局及时序动态。在玉米生育期间 ,二点叶蝉种群即可作聚集分布亦可作均匀分布。 4月中下旬 ,二点叶蝉种群呈均匀分布 (K <0 ) ;5月份 ,呈聚集分布 (K >0 ) ;6月上中旬呈均匀分布 (K <0 ) ;6月下旬至 7月上旬呈聚集分布 (K >0 ) ,表现为扩散→聚集→再扩散→再聚集的总趋势。K值亦表明 ,5月份高海拔聚集强度最高 ,6月下旬至 7月上旬则低海拔的聚集强度最高。根据Taylor的幂函数法和Iwao的M -X回归方程的系数 ,高、中海拔的聚集强度大于低海拔