Influence of Dry Season and Food Quality and Quantity on Behavior and Feeding Strategy of Propithecus verreauxi in Kirindy, Madagascar

According to optimal foraging theory, herbivores can base food choice mainly on the quality or the quantity of food, or both. Among herbivorous primates, folivorous lemurs living in the highly seasonal environment of Madagascar have to cope with the shortage of high-quality food during the dry season, at least in deciduous forests. We studied (Verreaux's sifaka) in Kirindy, western Madagascar, to understand the influence of dry season and food quality and quantity on behavioral patterns and feeding strategy (qualitative vs. quantitative dietary choice) of a folivorous lemur in a deciduous forest. We followed 7 groups (4 groups/period; 3 individuals/group/month) during 4 periods of the year (wet season: February–March; early/middle/late dry season: May–June; July–September; October–November). We collected samples of plants eaten and examined behavioral and feeding patterns, considering food quality (macronutrients, proteins/fibers ratio, and tannins) and abundance. We found 1) a significant reduction of home range, core area, and daily path length from the wet to the dry season, possibly related to dietary change and 2) a daily period of inactivity in the dry season for energy conservation. Regarding the feeding strategy, Kirindy sifakas showed 1) high variation and selection in choosing food items and 2) a dietary choice based mainly on quality: Kirindy sifakas fed on plant species/families independently from their abundance and tannins represented a feeding deterrent during the dry season. Overall, behavioral and dietary adaptations allow Kirindy sifakas to overcome the shortage of high-quality food in the lean period.     

Fruit Availability and Peccary Frugivory in an Isolated Atlantic Forest Fragment: Effects on Peccary Ranging Behavior and Habitat Use

The goal of this study was to examine seasonal frugivory by two sympatric peccary species ( Tayassu pecari and T. tajacu ) in a small (2178 ha), Atlantic Forest fragment on the inland plateau region of São Paulo State, Brazil. Fruit availability was determined with systematic ground surveys conducted over a 5-yr period. Examining fruit availability trends for dry and wet seasons, we found that species diversity was greater in the wet season, but the total number and dry mass of fruits were higher in the dry season. Fruit abundance in the dry season was due to one palm, 'jeriva' ( Syagrus romanzoffiana ), which could be considered a keystone species at Caetetus Ecological Station as it also supported a diverse array of mammals, birds, reptiles, and insects. White-lipped peccaries were the only ungulates that ate palmito fruits ( Euterpe edulis ) at Caetetus. They consumed ripe and unripe fruits and predated the seeds by chewing the pulp and seed. This occurred primarily during the dry season and was associated with a seasonal range shift and a preference for palmito habitat by the white-lipped peccaries. The dominance of fruits in peccary diets (80% fruit items in scat) has management implications for other plateau forest fragments. Forest fragments with diminished fruit abundance or diversity, or lacking key species such as S. romanzoffiana or E. edulis , will not support the energetic requirements of the characteristically large and highly mobile white-lipped peccary populations.     

Bacteria and viruses in the water column of tropical freshwater reservoirs

In tropical freshwater reservoirs of Sri Lanka, which are linked in an aquatic network, bacterial abundance and production as well as virus abundance, frequency of viral infection and virus production were investigated together with a set of nutrient species (Kjeldahl-N, NO3-N, total P, soluble P, PO4-P). At two characteristic seasons (wet season, dry season), samples were taken from two types of reservoirs (new upland impoundment and ancient, shallow lowland reservoir), each during 4 days at various depths of the entire water columns. Kjeldahl-N and total P were greatly elevated in the wind-mixed water body of the shallow impoundment during the dry season, whereas the deeper reservoir type exhibited no obvious seasonality. In SYBR green trade mark -stained samples, bacterial abundance showed no seasonal pattern in either reservoir type. Bacterial secondary production, however, was significantly elevated in the entire water column of the shallow impoundment under wind-mixed conditions in the dry season. Highest abundance of virus particles and elevated frequency of bacteria containing mature phages were also observed in the shallow reservoir during the dry season indicating favourable conditions for virus propagation. Data from this aquatic network show that most virus parameters, such as abundance or frequency of visibly infected cells, were positively linked to bacterial abundance and production, but also to organic nitrogen or some phosphorus species. We calculated that between 13.2% and 46.1% of the bacterial standing stocks would be subjected to virus-mediated mortality. Estimates of bacteriophage production revealed that from 10 x 10(9) up to 98 x 10(9) phages were produced per litre and day. Bacteria and viruses in the studied tropical freshwater system appear to be linked to various environmental conditions and may affect processes at the ecosystem scale.     

Seasonal and diel variations in the activity of canopy insect herbivores differ between deciduous and evergreen plant species in a tropical dry forest

This study evaluated whether herbivorous insects can be expected to have particular adaptations to withstand the harsh dry season in tropical dry forests (TDFs). We specifically investigated a possible escape in space, with herbivorous insects moving to the few evergreen trees that occur in this ecosystem; and escape in time, with herbivores presenting an increased nocturnal rather than diurnal activity during the dry season. We determined the variation in the free-feeding herbivorous insects (sap-sucking and leaf chewing) between seasons (beginning and middle of both rainy and dry seasons), plant phenological groups (deciduous and evergreen trees) and diel period (diurnal and nocturnal) in a Brazilian TDF. We sampled a total of 5827 insect herbivores in 72 flight-interception traps. Contrary to our expectations, we found a greater herbivore diversity during the dry season, with low species overlap among seasons. In the dry season, evergreen trees supported greater richness and abundance of herbivores as compared to deciduous trees. Insects were also more active at night during the dry season, but no diel differences in insect abundance were detected during the rainy season. These results indicate that the strategies used by insect herbivores to withstand the severe climatic conditions of TDFs during the dry season include both small-scale escape in space and time, with evergreen trees playing a key role in maintaining resident insect herbivore populations in TDFs. Relatively more nocturnal activity during the dry season may be related to the avoidance of harsh climatic conditions during the day. We suggest that the few evergreen tree species occurring in the TDF landscape should be especially targeted for protection in this threatened ecosystem, given their importance for insect conservation.     

Domestic Water Use in Rural Semiarid Africa: A Case Study of Katarko Village in Northeastern Nigeria

Katarko village in the Sahel region of northeastern Nigeria relies entirely on natural sources of water such as rainfall and ground water. Thelatter is potentially the only constant source of water. This study is based on primary data collected in Katarko during a period of 8 months in 1996. Analysis indicates that per capita daily water consumption is higher (44.9 l) in the rainy season than in the dry season (26.1 l). The proportion of households who useless than 150 l per day, the minimum daily requirement recommended by the World Health Organization (Dieterich & Henderson, 1963) increases from 29% during the rainy season to 67% during the dry season. Most households prefer to use water of poor quality that is to be found closer to their homes to traveling long distances to or spending extra time at the water sources to obtain good quality water. Poor water quality, appalling sanitation, and unhygienic water-handling practices, particularly during the dry season, contribute to the high incidence of diarrhea in the village.     

A mechanistic explanation for global patterns of liana abundance and distribution

One of the main goals in ecology is determining the mechanisms that control the abundance and distribution of organisms. Using data from 69 tropical forests worldwide, I demonstrate that liana (woody vine) abundance is correlated negatively with mean annual precipitation and positively with seasonality, a pattern precisely the opposite of most other plant types. I propose a general mechanistic hypothesis integrating both ecological and ecophysiological approaches to explain this pattern. Specifically, the deep root and efficient vascular systems of lianas enable them to suffer less water stress during seasonal droughts while many competitors are dormant, giving lianas a competitive advantage during the dry season. Testing this hypothesis in central Panama, I found that lianas grew approximately seven times more in height than did trees during the dry season but only twice as much during the wet season. Over time, this dry season advantage may allow lianas to increase in abundance in seasonal forests. In aseasonal wet forests, however, lianas gain no such advantage because competing plants are rarely limited by water. I extend this theory to account for the local, within-forest increase in liana abundance in response to disturbance as well as the conspicuous decrease in liana abundance at high latitudes.     

Leaf flushing phenology and herbivory in a tropical dry deciduous forest,southern India

Patterns of leaf-flushing phenology of trees in relation to insect herbivore damage were studied at two sites in a seasonal tropical dry forest in Mudumalai, southern India, from April 1988 to August 1990. At both sites the trees began to flush leaves during the dry season, reaching a peak leaf-flushing phase before the onset of rains. Herbivorous insects emerged with the rains and attained a peak biomass during the wet months. Trees that flushed leaves later in the season suffered significantly higher damage by insects compared to those that flushed early or in synchrony during the peak flushing phase. Species whose leaves were endowed with physical defenses such as waxes suffered less damage than those not possessing such defenses. There was a positive association between the abundance of a species and leaf damage levels. These observations indicate that herbivory may have played a major role in moulding leaf flushing phenology in trees of the seasonal tropics.     

Scales of spatiotemporal variability in macroinvertebrate abundance and diversity in monsoonal streams: detecting environmental change

1. We quantified spatial and temporal variability in benthic macroinvertebrate species richness, diversity and abundance in six unpolluted streams in monsoonal Hong Kong at different scales using a nested sampling design. The spatial scales were regions, stream sites and stream sections within sites; temporal scales were years (1997–99), seasons (dry versus wet seasons) and days within seasons. 2. Spatiotemporal variability in total abundance and species richness was greater during the wet season, especially at small scales, and tended to obscure site‐ and region‐scale differences, which were more conspicuous during the dry season. Total abundance and richness were greater in the dry season, reflecting the effects of spate‐induced disturbance during the wet season. Species diversity showed little variation at the seasonal scale, but variability at the site scale was apparent during both seasons. 3. Despite marked variations in monsoonal rainfall, inter‐year differences in macroinvertebrate richness and abundance at the site scale during the wet season were minor. Inter‐year differences were only evident during the dry season when streams were at base flow and biotic interactions may structure assemblages. 4. Small‐scale patchiness within riffles was the dominant spatial scale of variation in macroinvertebrate richness, total abundance and densities of common species, although site or region was important for some species. The proportion of total variance contributed by small‐scale spatial variability increased during the dry season, whereas temporal variability associated with days was greater during the wet season. 5. The observed patterns of spatiotemporal variation have implications for detection of environmental change or biomonitoring using macroinvertebrate indicators in streams in monsoonal regions. Sampling should be confined to the dry season or, in cases where more resources are available, make use of data from both dry and wet seasons. Sampling in more than one dry season is required to avoid the potentially confounding effects of inter‐year variation, although variability at that scale was relatively small.     

垂叶榕榕小蜂群落及种间互作网络季节动态

群落中的物种相互作用构成了复杂的生态网络。有关物种的数量和组成的季节性动态变化已有较多的研究, 但是对于生态网络的动态变化知之甚少。揭示生态网络的动态变化对于理解群落的稳定性以及群落的动态变化过程和机理具有重要意义。本研究以垂叶榕(Ficus benjamina)榕小蜂群落为研究对象, 分别在西双版纳的干季和雨季采集了榕小蜂的种类和数量信息。比较了两个季节榕小蜂群落的动态变化以及共存网络的参数(例如网路直径、连接数、嵌套性和群落矩阵温度)变化。结果显示: 雨季榕果内传粉榕小蜂Eupristina koningsbergeri所占比例高于干季, 传粉榕小蜂的种群数量也高于干季, 而在干季非传粉榕小蜂的种类增加(干季15种小蜂, 雨季14种)。从榕树-传粉榕小蜂互利共生系统的适合度来看, 干季非传粉小蜂的增加对传粉榕小蜂和榕树的适合度是不利的。在干季, 共存网络物种间的连接数(干季0.95, 雨季0.47)多于雨季, 群落矩阵温度(干季23.24, 雨季2.64)也显著高于雨季。表明干季榕小蜂群落组成及种间关系较雨季更为复杂而多样, 高的矩阵温度暗示群落受到的干扰更大。     

Seasonal decline of the tomato leafminer,Tuta absoluta,in the shifting landscape of a vegetable‐growing area

Insect pest populations exhibit seasonal dynamics in response to changes in resource availability or other environmental factors such as climatic conditions, natural enemies, and intra‐ or interspecific competition. Understanding such dynamics is critical for developing effective integrated pest management strategies. The objective of the present study was to identify factors driving the seasonal decline of the tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), in the shifting landscape of a vegetable‐growing area in Senegal. A set of 42 tomato fields was monitored for the number of T. absoluta adults caught in pheromone traps and for the incidence of larvae, during 5 months from June to November 2016 in the Niayes area (Senegal). The surface of solanaceous host crops, climatic conditions, and abundance of natural enemies were also monitored. A drastic decline in T. absoluta abundance was observed during the rainy season. The decrease in resource availability, especially tomato crops, in the surrounding landscape of monitored fields was the main factor affecting the population dynamics during the rainy season. However, alternative host crops such as eggplant and Ethiopian eggplant, can provide ‘reservoirs’ for residual populations of the pest. For applied purpose, it would be interesting to focus the management efforts on residual populations during the rainy season, to make more difficult the reconstitution of populations during the dry season.     

Seasonal variation in patch use in a tropical African environment

We used giving-up densities (GUD) to study patch use decisions of small granivorous passerines throughout the year. We measured GUDs continuously in four sites for a period of 9–10 months per year during 2004 and 2005 in a savannah area in Jos, central Nigeria. The study thus covered a period from the middle of the dry season, through the wet season to the beginning of the next dry season in each year. We placed experimental food patches in both open areas and in cover to investigate possible effects of predation risk and thermal hazard on the foraging behavior of the birds. We found a difference in GUDs between the microhabitats, with a consistently lower GUD in cover throughout the year and for the two years. During both years GUDs followed a pattern coinciding with the seasonal change in local seed availability. An initial decline in GUDs late in the dry season was followed by a steady increase during and after the rains. A similar trend in GUDs observed for both years supports the conclusion that GUDs measure the feeding birds' assessment of environmental quality, possibly in combination with other factors changing predictably during the year. We conclude that food abundance may act with other environmental and ecological factors to affect foraging decisions throughout the year.     

北部湾近岸海域浮游动物群落结构特征及季节变化

2017年3月(枯水期)、7月(丰水期)和10月(平水期)分别对北部湾近岸海域44个站位的浮游动物进行了调查。结果共检出浮游动物251种和浮游幼体24类,其中枯水期138种(类),丰水期134种(类),平水期191种(类),分属河口低盐、近岸暖温、近岸暖水和外海暖水4个生态类群。优势种9种,其中枯水期以原生动物占绝对优势,丰水期以枝角类、桡足类和浮游幼体类占优势,平水期以十足类和浮游幼体类占优势。浮游动物丰度年均值为789.95个/m~3,呈现出枯水期(1540.19个/m~3)明显高于平水期(457.58个/m~3)和丰水期(372.08个/m~3)的季节变化特征;浮游动物生物量年均值为252.40 mg/m~3,生物量的季节变化与丰度变化不一致,平水期生物量(385.01 mg/m~3)明显高于枯水期(221.41 mg/m~3)和丰水期(150.78 mg/m~3)。多样性指数平水期最高(3.16),丰水期(2.35)次之,枯水期(2.22)最低。枯水期和丰水期北部湾近岸海域浮游动物生物量和丰度水平分布特征基本呈现自河口近岸海域向外海递增的趋势,平水期浮游动物生物量与丰度的空间分布较为均匀。浮游动物的种类组成结构以及优势种的演替对浮游动物的生物量和丰度季节变化有着重要的决定作用。径流导致的悬浮物、营养盐等的变化可能是决定北部湾近岸海域浮游动物生物量和丰度空间分布的主要因素。研究还表明与其他海湾相比,北部湾近岸海域浮游动物群落结构趋于小型化,需加大关注。     

Effect of Seasonality on the Behavior of an Insectivorous Primate, Tarsius spectrum

The distribution and quality of food resources is generally recognized as the preeminent factor explaining much interspecific and intraspecific variation in the behavior of nonhuman primates. Primates that live in seasonal environments often show predictable responses to fluctuating resources. In order to compensate for the reduction in resource availability, primates variously switch to alternative, poorer quality food sources, increase the amount of time they spend foraging, or increase their daily path length. Some primate species reduce their group size or maximize the group dispersion. I address whether spectral tarsiers (Tarsius spectrum), which are insectivores, modify their behavior in the same ways as frugivores and folivores in response to seasonal or scarce resources. My results indicate that wild spectral tarsiers modify their activity budget in response to seasonal resources. Specifically, during periods of low resource availability, spectral tarsier males and females spent more time traveling and foraging compared to their activity budget during the wet season. Males and females not only increased the amount of time they spent foraging during times of low resource abundance but also modified their foraging behavior. During the wet season, when resource abundance was high, they consumed Orthoptera and Lepidoptera with greater frequency than during the dry season. During the dry season, when resource abundance was low, spectral tarsiers still ate numerous Orthoptera and Lepidoptera, but they also increased consumption of Coleoptera and Hymenoptera. Spectral tarsiers were also more likely to be involved in territorial disputes during the dry season than during the wet season. Intragroup encounters decreased in frequency in the dry season versus the frequency of encounters during the wet season.     

Comparative analysis of population characteristics of the brown planthopper,Nilaparvata lugens stål,between wet and dry rice cropping seasons in West Java,Indonesia

Population dynamics of the brown planthopper (BPH),Nilaparvata lugens Stål, were investigated in paddy fields in the coastal lowland of West Java, Indonesia, where rice is cultivated twice a year, in the wet and dry cropping seasons. Distinct differences in the basic features of population dynamics were detected between the two rice cropping seasons: (1) In the wet season, BPH populations multiplied rapidly in the period from initial to peak generation, reaching quite often the destructive level despite the low density of initial immigrants. However, in the dry season, the population growth rate and the peak population density were much lower than those in the wet season. The abundance of natural enemies such as arthropod predators played a major role in determining such a difference in seasonal population development. (2) The density at the peak generation or the occurrence of outbreaks in each field was predictable in the wet season with fairly high accuracy on the basis of the density at the initial or previous seasonal generations. In the dry season, however, the rate of population growth and the peak population density widely varied among the fields depending on the water status in each field. (3) Density-dependent processes to regulate the population density were detected in both cropping seasons. In the wet season, the regulatory processes were only detected in such high densities as cause the considerable deterioration of host plants, which suggested that the processes were largely attributable to intra-specific competition. In the dry season, however, the regulatory processes operated at a much lower density in the earlier stages of the crops. The results of an analysis of adult longevity or residence period suggested that the density-dependent dispersal of macropterous adults played an important role in stabilizing the population fluctuation among the fields in the early dry season.     

Ovarian activity of Sokoto red goats using abattoir specimens

Ovarian activity of Sokoto red goats was studied for 12 months using 141 pairs of ovaries obtained from a Zaria abattoir. Ovarian activity occurred throughout the year but higher activity was observed during the rainy (June to September) and dry (January to March) seasons. The higher ovarian activity during the rainy season is perhaps due to the availability of pasture during this time, while the higher activity during the dry season might be related to the goat's ability to convert leaves and dry forage that are mostly available during this season into useful nutrients. Temperature increase, particularly during the dry season, might be a factor for higher ovarian activity during the same period.     

Ants climb plants because they cannot swim: ant presence on flowers during the flood season reduces the frequency of floral visitors

1. Seasonal changes in environments may not only affect habitat connectivity but may also affect its use by species and their interactions. Thus, during the flood season, ants are forced to develop survival strategies such as vertical plant migration.
2. According to this, it has been hypothesized that the presence of ants may directly affect plant-pollinator interactions.
3. Thus, we asked the following questions: (i) Are floral visitors of Hyptis brevipes expelled due to ant presence on inflorescences during the flood period? (ii) Is the ant effect mediated by the abundance of ants foraging on inflorescences? And, (iii) Does flower abundance predict the abundance of floral visits and ants?
4. We experimentally sampled 59 H. brevipes plants with and without ants during the flooded season, and observed no differences in flower abundance between ant treatments.
5. The probability of detaining floral visitors on H. brevipes increased with ant abundance and exceeded 50% possible repellency, but the probability of visitor deterrence was not related to flower abundance. Furthermore, the abundance of flowers did not predict the number of ants on H. brevipes individuals or the frequency of floral visits.
6. Consequently, ant repelling effects are pronounced when there are more ants foraging on plants. However, the ant repelling effect can be mitigated when plants flourish all year-round and exhibit higher concentrations of flowers in the dry months. Additionally, the different sexual functions of plants may present specific responses due to the explosive pollination mechanism associated with ant effects.

     

Phylogenetic and functional underdispersion in Neotropical phyllostomid bat communities

Habitat conversion creates a mosaic of land cover types, which affect the spatial distribution, diversity, and abundance of resources. We used abundance, functional, and phylogenetic information to determine if Neotropical bat communities exhibited phylogenetic or functional overdispersion or underdispersion in response to habitat conversion. Overdispersion suggests the operation of intraclade competition, niche partitioning, limiting similarity, or character displacement, whereas underdispersion indicates the operation of interclade competition, abiotic filtering, or biotic filtering. We expected (1) biotic filtering in landscapes with extensive forest loss to result in underdispersion; (2) niche partitioning in heterogeneous landscapes with intermediate forest loss to result in overdispersion; and (3) intraclade competition during times of low resource abundance (i.e., dry season) to increase, resulting in overdispersion. Most bat communities exhibited phylogenetic or functional underdispersion; none exhibited overdispersion. Expectations were not met: underdispersion did not increase with forest loss, heterogeneous landscapes did not induce overdispersion, and no evidence supported the contention that intraclade competition changed with season. Empirical responses were season‐specific, likely because resource availability may affect relationships between forest cover and underdispersion and between biodiversity and underdispersion. During the dry season, only high diversity sites exhibited underdispersion (i.e., functional or phylogenetic redundancy), whereas underdispersion occurred in low, intermediate, or high diversity communities during the wet season; we suggest that this difference likely arises due to changes in resource abundance. Communities with high diversity and redundancy occupied heterogeneous sites during the dry season, but communities with high redundancy were restricted to large forest reserves during the wet season.     

Phenology of Ficus variegata in a seasonal wet tropical forest at Cape Tribulation, Australia

Abstract. We studied the phenology of 198 mature trees of the dioecious fig Ficus variegata Blume (Moraceae) in a seasonally wet tropical rain forest at Cape Tribulation, Australia, from March 1988 to February 1993. Leaf production was highly seasonal and correlated with rainfall. Trees were annually deciduous, with a pronounced leaf drop and a pulse of new growth during the August-September drought. At the population level, figs were produced continually throughout the study but there were pronounced annual cycles in fig abundance. Figs were least abundant during the early dry period (June-September) and most abundant from the late dry season (October-November) through the wet season (December-April). The annual peak in reproduction actually reflected two staggered peaks arising from gender differences in fig phenology. In this dioecious species, female and male trees initiated their maximal fig crops at different times and flowering was to some extent synchronized within sexes. Fig production in the female (seed-producing) trees was typically confined to the wet season. Male (wasp-producing) trees were less synchronized than female trees but reached a peak level of fig production in the months prior to the onset of female fig production. Male trees were also more likely to produce figs continually. Asynchrony among male fig crops during the dry season could maintain the pollinator population under adverse conditions through within- and among-tree wasp transfers.     

Distribution and abundance of magpie geese,Anseranas semipalmata,in the Alligator Rivers Region,Northern Territory

Aerial surveys from 1981 to 1984 were used to identify monthly changes in the abundance of magpie geese on Jive floodplains in the Alligator Rivers Region of the monsoonal Northern Territory, and ground surveys were conducted during the same period on one of the plains to provide more detailed distributional information. The aerial surveys showed that the Magela floodplain was inhabited by few geese during the wet season (November-March), but that numbers then increased to an estimated average peak of 80 000 in the late dry season. The Nourlangie floodplain and Boggy Plain (a large backswamp of the South Alligator floodplain) exhibited a similar pattern, except that the peaks occurred 2–3 months before the end of the dry season and comprised many more geese (an estimated average of 350 000 birds). In contrast, geese were uncommon on the East Alligator floodplain except during the wet season, and densities and numbers were lower than on the three previous plains. The Cooper floodplain was occupied intermittently, and numbers and densities were always relatively low. Geese appeared to return from their breeding localities to the floodplains of the Alligator Rivers Region progressively during the dry season, concentrating first on the extensive Eleocharis swamps of the Nourlangie floodplain and then waiting out the remainder of the dry on the substantial permanent waters of the Magela floodplain and other nearby wetlands. Ground surveys on the Magela floodplain suggested that geese were highly mobile, apparently seeking suitable nesting habitat in the late wet season, and then a sequence of feeding areas during the dry season. Aerial surveys underestimated densities; on the basis of ground surveys, average peak numbers on the Magela plain were calculated to be 500 000. We estimate that the Alligator Rivers Region supported an average of about 1.6 million geese in the dry season, but very many fewer during the wet season.     

纳帕海高原湿地浮游病毒丰度及与环境因子相关性研究

目的利用EFM技术对纳帕海湿地不同季节7个水样样品中的浮游病毒丰度开展了调查,并对影响浮游病毒丰度的环境因子进行了相关性分析。方法元素检测,叶绿素a检测,荧光显微镜检测浮游细菌及浮游病毒的丰度。结果从生态分布上来看旱季和雨季浮游病毒丰度的平均值分别为3.63×10~6/mL和3.71×10~7/mL,浮游病毒丰度季节性变化不显著。从对影响浮游病毒丰度的环境因子相关性分析来看,旱季浮游病毒与Chl-a具有弱负相关性(r=0.49,P0.05);而雨季浮游病毒丰度与Chl-a具有显著正相关性(r=0.37,P0.05),表明雨季纳帕海湿地浮游病毒丰度受Chl-a含量的影响较大。旱季浮游病毒丰度与温度显著负相关,虽然在雨季浮游病毒丰度与温度也呈负相关,但并不显著;在雨季,水体pH变化较明显,而浮游病毒丰度与水体pH呈显著负相关,表明湿地的来水主要在雨季,而离子组成变化大。虽然在雨季和旱季,从多点采样的平均值来看浮游病毒丰度并无明显差异,但从一些局部的采样点来看,雨季的浮游病毒丰度显著高于旱季,说明在纳帕海区域浮游病毒的分布并不平均,因采样点环境的不同会产生明显的区别。结论对纳帕海高原湿地浮游病毒生态分布的调查,是对该地域生态学研究的补充,使得这一独特地理环境的微生物研究更加系统化。