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1.
Persaud A. D. Dillon P. J. Molot L. A. Hargan K. E. 《Aquatic Sciences - Research Across Boundaries》2012,74(1):203-212
Animal body size is a driving force behind trophic interactions within biological communities, yet few studies have explored
relationships between body size and trophic position (based on δ15N) at a broad-scale in freshwater lakes. Therefore, our goals were to (1) determine whether body size is a good predictor
of trophic position for multiple pelagic zooplankton taxa and fish communities, and (2) examine how body size-trophic position
relationships at the community level compare to species level for fish. Zooplankton and fish were collected from 12 and 7
lakes, respectively, located in the Kawarthas, southern Ontario, Canada. The results indicated that for zooplankton, significant
positive but different relationships were found between body size and trophic position for cladocerans, in general, and Daphnia, but not Holopedium. For fish, at the lake community level six out of seven relationships were positive and significant, but again, different
among lakes. In contrast, at the species level only three of eight species-specific relationships were significant. Furthermore,
for two widespread species, Perca flavescens and Micropterus dolomieu, significant differences were found between community- and lake-specific species relationships. Our community-level models
and most species-level models provide evidence that trophic interactions in freshwater lakes are size-based. These results
demonstrate that general species models should be applied with caution when using body size to predict trophic position. Additionally,
the predictive power of some relationships found here is questionable since, albeit significant, their strengths are generally
low. Together, our results suggest that body size may have limited use in predicting trophic position of some biota in temperate
freshwater lakes. 相似文献
2.
Trophic cascade hypotheses predict that fish will affect the structure and biomass of pelagic plankton communities. In order to investigate trophic cascade effects from fish down to phytoplankton, whole-lake studies were performed in five hypertrophic (mean total phosphorus (TP) concentrations higher than 1000 mg m−3) shallow lakes located in the Pampa Plain. The main climatic characteristic of this region is the alternation between periods of drought and flood, with corresponding changes of lake depth and conductivity of lake water. All lakes were studied from April to December 2000. Samples were taken of their physical and chemical characteristics and biotic communities, focusing on the zooplankton community. Fish were manipulated in four lakes (Capurro, Longinotti, Vedia 1, Vedia 2), while the fifth (Lake Vedia 3) was left undisturbed as a reference system. High abundance of planktivorous minnows (Jenynsia multidentata and Cheirodon interruptus) dominated the fish community in the reference lake. In the manipulated lakes, fish stocks were largely reduced in late autumn (May). During winter, Capurro, Longinotti and Vedia 1 were stocked with a visual planktivore, the pampean silverside (Odontesthes bonariensis, Atherinidae). Fish stocking was 24, 33 and 19 kg ha−1, respectively. In contrast, no fish were stocked in Lake Vedia 2. Following fish removal, large Daphnia appeared in these lakes and grazed intensively on the phytoplankton. In contrast, no Daphnia were found in the reference lake (Vedia 3). The stocking of O. bonariensis in lakes Capurro, Longinotti and Vedia 1 led to a decrease in the percentage of large cladocerans and a rise in the phytoplankton biomass:TP ratio. Moreover, the lakes mentioned were stocked with different quantities of silversides over different periods of time. These differences were reflected temporarily in the plankton dynamics, affecting mainly larger sized zooplankton. Nevertheless, the presence of Daphnia was short lived in the lake where fish had been removed and no O. bonariensis were stocked. Competition for resources and recruitment of remaining fish probably caused a collapse in the zooplankton biomass. Our results support the idea that fish predation on zooplankton and its effect on phytoplankton is very intense in small pampean lakes. Fish removal was short lived, however. This could be because in small pampean lakes fish recolonization is favored, and minnows are highly prolific. Moreover, if manipulation of the trophic structure of lakes is undertaken in the pampean region, high nutrient loading from the watershed, climate and hydrology should also be taken into account. 相似文献
3.
Crustacean zooplankton distribution patterns and their biomass as related to trophic indicators of 29 shallow subtropical lakes 总被引：3，自引：0，他引：3
A comparative limnological study was carried out to present a snapshot of crustacean zooplankton communities and their relations to environmental factors to test whether there is a consistent relationship between crustacean biomass and trophic indicators among lake groups with similar trophic conditions. The study lakes showed a wide range of trophic status, with total phosphorus (TP) ranging from 0.008 to 1.448 mg L−1, and chlorophyll a from 0.7 to 146.1 μg L−1, respectively. About 38 species of Crustacea were found, of which Cladocera were represented by 25 taxa (20 genera), and Copepoda by 13 taxa (11 genera). The most common and dominant species were Bosmina coregoni, Moina micrura, Diaphanosoma brachyurum, Cyclops vicinus, Thermocyclops taihokuensis, Mesocyclops notius and Sinocalanus dorrii. Daphnia was rare in abundance. Canonical correspondence analysis showed that except for four species (D. hyalina, S. dorrii, C. vicinus and M. micrura), almost all the dominant species had the same preference for environmental factors. Temperature, predatory cyclopoids and planktivorous fishes seem to be the key factors determining species distribution. TP was a relatively better trophic indicator than chlorophyll a to predict crustacean biomass. Within the three groups of lakes, however, there was no consistent relationship between crustacean biomass and trophic indicators. The possible reason might be that top-down and bottom-up control on crustaceans vary with lake trophic state. The lack of significant negative correlation between crustacean biomass and chlorophyll a suggests that there was little control of phytoplankton biomass by macrozooplankton in these shallow subtropical lakes. 相似文献
4.
Wen Zhao Yuanyi Zhao Qiaohan Wang Mianping Zheng Peng Zhang Zhihui He 《洁净——土壤、空气、水》2010,38(10):960-968
The seasonal variations in biomass, abundance, and species composition of plankton in relation to hydrography were studied in saline lake Namuka Co, northern Tibet, China. The sampling was carried out at approximately monthly intervals from June 2001 to July 2002. The salinity ranged from 5.5 to 26 g/L. The mean annual air and water temperature showed a clear seasonal pattern, which was approximately 4.4 and 7.4°C, respectively, with the lowest water temperature in winter (from December to March, −1°C) and the highest in June and July (18°C). The results showed that 36 taxa of phytoplankton and 16 taxa of zooplankton were identified. Both the biomass and abundance of total phytoplankton were lower in the winter and peaked once or twice during the summer and spring in the early August (8.23 mg/L and 158.2 × 106 ind./L). The seasonal variation in total zooplankton biomass and abundance was characterized by lower values in both winter and early spring, and one maximum (90.5 mg/L and 935 ind. L−1) occurred in the late summer. Major phytoplankton species were Gloeothece linearis, Oscillatoria tenuis, Gloeocapsa punctata, Ctenocladus circinnatus, Ulothrix sp., and Spirogyra sp. And major zooplankton species included Vorticella campanula, Brachionus plicatilis, Daphniopsis tibetana, Cletocamptus dertersi, Arctodiaptomus stewartianus. The production of D. tibetana was 420.3 g m3 a−1. The total number of plankton species has a significant negative correlation with the salinity. 相似文献
5.
Anke Schwarzenberger Sofie D’Hondt Wim Vyverman Eric von Elert 《Aquatic Sciences - Research Across Boundaries》2013,75(3):433-445
Lakes are well known for having a pattern of seasonal succession of phytoplankton and zooplankton. The succession of different taxa of phytoplankton results in a succession of zooplankton taxa, and within the genus Daphnia, into a succession of different genotypes (clones). One cause for this succession of Daphnia clones might be the production of digestive protease inhibitors by cyanobacteria, which usually bloom in summer. Here we report seasonal changes in the frequency and the abundance of Daphnia magna haplotypes in a eutrophic lake, which developed a chymotrypsin-inhibitor-producing cyanobacterial bloom in May. These seasonal changes were not related to changes of biotic and abiotic lake parameters. However, a very high content of chymotrypsin inhibitors was observed in May (but not in other months). This was assumed to have exerted a strong punctual selection pressure on the Daphnia population and on the direct targets of the protease inhibitors, i.e. the digestive chymotrypsins of Daphnia. Actually, D. magna from before and during the cyanobacterial bloom showed a different protease pattern on activity stained SDS-PAGE in comparison to clones from the month after the bloom. However, no difference in tolerance, measured as IC50 values, to inhibition by natural lake seston from May was found between the clones from before and after the bloom. Thus, the hypothesis that a seasonal adaptation of D. magna subpopulations from either April/May or June might have occurred could not be proven. This suggests that the Daphnia population investigated here is locally adapted to cyanobacterial protease inhibitors. 相似文献
6.
Patterns of zooplankton–phytoplankton interactions in subtropical lakes of the Southern Hemisphere may deviate from those established for north-temperate lakes. We tested the responses of phytoplankton growth to different community structures of zooplankton and nutrient enrichment in a subtropical Australian reservoir for the prediction of potential outcomes of lake biomanipulation. Two zooplankton communities were created in lake enclosures over 4 weeks: a rotifer-dominated community developed in the presence of planktivorous fish (Hypseleotris spp.) and a Ceriodaphnia-dominated community developed in the absence of fish. Biomass gradients of both communities were established in 20 L containers and several separate containers received no additions (controls) or were enriched with nitrogen and/or phosphorus. The growth rate of total phytoplankton significantly increased in response to nutrient enrichment, indicating nutrient limitation. Most phytoplankton taxa were not markedly affected by grazing of either zooplankton community. However, both communities had significant stimulatory effects on the growth of inedible chlorophytes. The ability of zooplankton grazing to negatively affect phytoplankton growth during the summer was counteracted regardless of zooplankton community structure, possibly by nutrients regenerated by zooplankton. We hypothesise that in the subtropical system studied, changes in food web nutrient recycling may be more important for the outcome of biomanipulation than grazing impacts. 相似文献
7.
Tadesse Dejenie Steven A.J. Declerck Tsehaye AsmelashSarah Risch Joachim Mergeay Tom De BieLuc De Meester 《Limnologica》2012,42(2):137-143
A field survey of zooplankton communities was carried out in 32 recently established tropical semi-arid reservoirs in the highlands of Northern Ethiopia with the aim to identify to what extent environmental factors determine species composition of the cladoceran community in such isolated and young reservoirs. To address seasonal variation, the survey was carried out both at the beginning and the end of the dry season. A total of 15 species of cladocerans were identified. Daphnia was the most abundant cladoceran genus, and was present in all reservoirs. Using presence-absence data, no association between cladoceran community composition and geographic distance was found. RDA results indicate that the set of environmental variables that explained cladoceran community composition differed among seasons. Depth, altitude and fish biomass showed a significant association with cladoceran community composition during the wet season, whereas variation in cladoceran community structure was associated with phytoplankton biomass in the dry season. The relative abundance of Daphnia was much higher in the pelagic than in the littoral zone of our study systems. Two key groups of pelagic filter-feeding cladocerans, Diaphanosoma and Daphnia, showed a clear pattern, in which one or the other tended to strongly dominate the community. In addition, we observed a negative association between dominance of Daphnia in the zooplankton community and dominance of cyanobacteria in the phytoplankton community. 相似文献
8.
放养鲢（Hypophthalmichthys molitrix）、鳙（Aristichthys mobilis）控制富营养化湖泊蓝藻水华暴发是当前最有效的手段之一.为评估富营养化初期湖泊鲢、鳙控藻的生态效果,2016年在洱海红山湾开展原位围栏鲢、鳙控藻实验,对围栏内外的浮游生物群落结构及水环境因子的变化进行对比分析,同时测定了围栏内鲢、鳙的生长及摄食节律.结果表明：围栏内鲢、鳙呈现匀速生长,围栏生存环境适宜.根据Egger''s模型估算鲢、鳙的日摄食量分别为24.96%和18.18%,鲢的日粮高于鳙;滤食率结果表明,鲢对浮游植物的摄食率高于鳙（分别为3.01和2.19 L/（g·h）,而鳙对浮游动物的滤食率高于鲢（分别为18.61和13.54 L/（g·h））.研究期间,围栏内外水体理化因子无显著差异;但围栏内外微囊藻生物量差异明显,并且在7月达到生物量峰值（围栏内为1.7 mg/L,围栏外为2.4 mg/L）.鲢、鳙对浮游植物的优势种类——微囊藻和隐藻有明显的削减效果,6-8月逐渐上升并在8月达到最高（64%）;当浮游植物优势种由微囊藻替换为硅藻门和绿藻门的种类时,鲢、鳙的削减效率不明显（10-11月为负值）.此外,鲢、鳙放养显著降低了浮游甲壳动物的总生物量和枝角类生物量.因此,结合实验结果得出,鲢具有更高的控藻能力,尤其对微囊藻水华,但同时具备了较高对浮游甲壳动物的削减能力,需要进一步分析富营养化初期湖泊——洱海中实施非经典生物操纵的适宜性. 相似文献
9.
云贵高原湖泊夏季浮游植物组成及多样性 总被引：2，自引：2，他引：0
浮游植物是水生生态系统中重要的初级生产者,对维持水生态系统的平衡起着十分重要的作用.根据2008年云贵高原湖泊丰水期浮游植物调查数据,系统地分析了云贵高原13个湖泊中浮游植物的种群密度、生物量、组成及其多样性.云贵高原13个湖泊中共鉴定出浮游植物7门109种(绿藻52种、蓝藻23种、硅藻20种、其他14种).13个湖泊浮游植物Shannon-Wiener指数在0.5-2.2之间,其值大小与单个环境因子无显著相关.相关分析发现浮游植物总量与总氮、总磷、CODMn、硝态氮含量显著正相关,物种丰富度与总氮、总磷(0.1mg/L范围内)、CODMn含量亦显著正相关.另外,研究也发现各湖泊间浮游植物组成的相似性与各湖泊间营养状态差异显著负相关.由此可见,湖泊的营养状态不仅影响浮游植物的总量、组成以及物种丰富度,而且也影响各湖泊物种组成的相似性. 相似文献
10.
Simone Jaqueline Cardoso Fábio RolandSimoni Maria Loverde-Oliveira Vera Lúcia de Moraes Huszar 《Limnologica》2012,42(3):235-241
During the high water season, the flooding reduces environmental heterogeneity in aquatic ecosystems of the Pantanal wetland. When the water level recedes, lakes and channels are formed as individual systems. Therefore, we expected the spatial heterogeneity during the low water phase resulting in changes on biological communities leading to high phytoplankton abundance, biomass and diversity within and between habitats. To test this hypothesis, we analyzed eight freshwater systems (five oxbow lakes, two channels, and the river) during the low water period. Phytoplankton biomass, abundance, diversity (alpha, beta, gamma) and diversity metrics as richness (species per sample), Shannon diversity (H′) and evenness were measured in all systems along with nutrient concentrations, zooplankton and bacteria abundances. We found 97 species as gamma diversity. The alpha diversity was unexpectedly low in comparison to most other South American floodplain systems (38 species in river, 24 in channels and 29 in lakes). Also, the systems are relatively similar in composition (beta diversity, 28%). Connectivity differences between systems highlighted differences in phytoplankton abundance and biomass (fresh weight) ranging from 1428 ind mL−1 (river) to 3710 ind mL−1 (lakes) and from 0.71 mg L−1 (river) to 2.9 mg L−1 (lakes), respectively. However, our results did not indicate significant differences in phytoplankton species richness between the systems during the low water. Our main conclusions are that local factors may be responsible for changes on phytoplankton community and the time of isolation during the low water phase was not sufficient to promote changes in phytoplankton diversity between the habitats. 相似文献
11.
Koenraad Muylaert Steven Declerck Jeroen Van Wichelen Luc De Meester Wim Vyverman 《Limnologica》2006,36(2):69-78
Phytoplankton and zooplankton were monitored during 2 years in four eutrophic shallow lakes (two turbid and two clear water) from two wetland reserves in Belgium. In each wetland, phytoplankton biomass was significantly higher in the turbid lake than in the clear water lake. Although total macrozooplankton biomass and the contribution of daphnids to total zooplankton biomass was comparable in the clear water and the turbid lakes, the grazing pressure of macrozooplankton on phytoplankton as estimated from zooplankton to phytoplankton biomass ratios was higher in the clear water lakes. Estimated grazing by daphnids in the clear water lakes was always high in spring. In summer, however, daphnid biomass was low or daphnids were even absent during prolonged periods. During those periods phytoplankton was probably controlled by smaller macrozooplankton or by submerged macrophytes through nutrient competition, allelopathic effects or increased sedimentation rates in the macrophyte vegetation. 相似文献
12.
An outdoor experiment testing the effect of water flea (Daphnia longispina) and zebra mussels (Dreissena polymorpha) on physical and chemical water parameters and chlorophyll concentration changes was carried out in 12 containers filled with 150 l of unfiltered water from a lowland reservoir. During the 11 weeks of the experiment, the following physical, chemical and biological measurements were recorded: temperature (°C), oxygen concentration (mg dm−3), pH, conductivity (S cm−1), concentration of phosphate phosphorus (PO4-P) and ammonia nitrogen (NH4-N) (g dm−3), total nitrogen (TN) and total phosphorus (TP) (g dm−3), phytoplankton community structure and chlorophyll a concentration (g dm−3). The amount of ammonia ions was the highest in the treatment with zooplankton, while phosphate ions reached the highest values in treatments with zebra mussels. The results confirmed the ability of Daphnia to increase the NH4:PO4 ratio, whereas excretion from zebra mussels resulted in a decrease in both the N:P ratio (ranging from 9 to 13) and the NH4:PO4 ratio in water. In both treatments containing zebra mussels, P-rich water enabled sudden growth of Chlorophyta, resulting in blooms of Hydrodictyon reticulatum after 3–4 weeks of the experiment. Such phenomena were not observed in the control and Daphnia treatments. Our results indicate that zebra mussels, in contrast to Daphnia, may increase the symptoms of water eutrophication and contribute to blooms of expansive phytoplankton species. 相似文献
13.
《Limnologica》2021
Ecological restoration of eutrophic lakes using aquatic macrophytes is an important and practical technology. Here, we investigated the response of phytoplankton and zooplankton to a large-scale 2015-built aquatic macrophyte enclosure (AME, 200,000 m2) screened of by a PVC net in Baima Lake, a eutrophic lake, from spring to autumn of 2019. AME significantly improved water quality by increasing water transparency, and reducing total nitrogen, total phosphorus, and chlorophyll-a content during the growing season. AME significantly decreased phytoplankton abundance and biomass and marginally increased zooplankton abundance and biomass. Phytoplankton and zooplankton communities were closely related to environmental factors, such as water temperature, conductivity, total phosphorus, chemical oxygen demand, and chlorophyll-a inside and outside the AME. The zooplankton:phytoplankton biomass ratio inside was slightly higher than outside the AME. Zooplankton and phytoplankton biomass were significantly positively correlated inside and outside the AME, as were chlorophyll-a and total phosphorus. We found phosphorus to be a key factor limiting primary productivity in Baima Lake, and that bottom-up effects were the main driver to control phytoplankton in the AME. Using aquatic macrophytes to reduce nutrient loads is an effective way to manage eutrophication in Baima Lake. 相似文献
14.
热带浅水湖泊后生浮游动物群落结构对生态修复的响应 总被引：5，自引：4，他引：1
热带浅水湖泊后生浮游动物群落以轮虫和小型枝角类为主,往往缺乏大型浮游动物,其影响因子还存在争议,因此通过减少鱼类,提高大型后生浮游动物密度,从而增强对浮游植物的下行控制、修复热带富营养化湖泊的方法受到质疑.暨大南湖位于广州暨南大学校园内,是热带富营养化浅水湖泊,于2014年1—2月实施以鱼类去除和水生植被重建为主的生态系统修复工程,以期改善水质.通过对南湖修复前后水质、后生浮游动物以及修复后鱼类群落的调查分析,研究了后生浮游动物群落对修复的响应.结果表明:与修复前相比,总氮、总磷和叶绿素a浓度显著降低,透明度显著上升.枝角类丰度和生物量显著增加,修复后初期出现较高密度的大型枝角类蚤状溞(Daphnia pulex),桡足类丰度和生物量没有显著变化,轮虫丰度下降而生物量上升;后生浮游动物体长和生物多样性显著增加.随着鱼类密度的增加,蚤状溞丰度快速降低,后期鱼类减少后蚤状溞丰度又有所升高.因此,本研究显示鱼类是控制热带浅水湖泊大型浮游动物种群的主要因素,由于控制鱼类密度以维持较高大型浮游动物密度较为困难,因此单纯生物操纵在热带浅水湖泊修复中难以取得显著效果. 相似文献
15.
Lake Hayq, a highland lake in Ethiopia, was stocked with Tilapia fish (Oreochromis niloticus) in late 1970s, offering an opportunity to study the effect of fish predation in a natural lake. Since 1930s, some limnological surveys have been done sporadically documenting a change in zooplankton composition including the disappearance of cladocerans, hypothesizing the stocked planktivorous fish could be a cause. Nevertheless, no detailed research was conducted to identify potential effects of fish stocking predominantly due to its remote location. The article presents data about zooplankton composition, abundance and biomass done between October 2007 and January 2009 on short-time intervals including the underlying limnological variables. The zooplankton community was depauperate comprising two copepods, three cladocerans, and six rotifers taxa, as typical for tropical lakes. Total mean standing biomass of all crustacean zooplankton was 237 mg dry mass m−3, which gave Lake Hayq an intermediate position when compared with other tropical lakes. Of copepods, Thermocyclops ethiopiensis was almost an exclusive species, and its temporal variation was influenced by food supply and water temperature. We refute the hypothesis that Tilapia was the cause for the seasonal disappearance of cladocerans, and attribute it to the adverse effect of episodic mixing. Nevertheless, the planktivorous fish probably plays a key role in structuring the cladocerans in particular the large-sized Daphnia magna. In January 2008, we observed a massive planktivorous fish mortality that triggered high algal biomass, which was later grazed by large-sized D. magna demonstrating the trophic cascade hypothesis in a natural ecosystem. 相似文献
16.
高山湖泊对于全球气候变化及人类影响是一个极为敏感的参照系统.九寨沟国家级自然保护区长海作为一个独特的高山湖泊,研究其浮游植物群落结构及其与环境的关系,评估其水质现状及影响因素,有着重要的意义.本文于2014年7月对长海浮游植物群落结构进行了研究.全湖共布设12个采样点,并在中心采样点进行了垂直分层采样.本次调查共发现浮游植物6门38属63种,平均丰度为6.98×10~5cells/L,平均生物量为0.31 mg/L.浮游植物的水平分布差异不大;在垂直分布上,浮游植物的丰度从表层0.5 m至水下50 m呈现先增加后减少的趋势,在20 m水深处达到最大.长海浮游植物的优势种是长海小环藻(Cyclotella changhai)和飞燕角甲藻(Ceratium hirundinella),长海小环藻数量较多,飞燕角甲藻生物量较大.长海浮游植物多样性指数较低,综合各类水质评价方法,可以得出九寨沟长海处于贫-中营养状态. 相似文献
17.
放养河蚌,提高水体透明度以促进沉水植物生长,是湖泊生态修复中的常用手段之一.而小型杂食性鱼类鳑鲏依赖河蚌繁殖,河蚌放养可能会促进鳑鲏种群的发展;而鳑鲏与河蚌交互作用对水生态系统的影响仍研究较少.于2018年11 12月通过原位受控实验,设置对照组、河蚌组、鳑鲏组和河蚌+鳑鲏组,研究了鳑鲏(大鳍鱊Acheilognathus macropterus)与河蚌(背角无齿蚌Sinanodonta woodiana)对水质、浮游生物和底栖生物的影响.结果表明:鳑鲏显著增加了上覆水总氮、总磷、悬浮质和叶绿素a(Chl.a)浓度;但并未显著影响无机悬浮质的浓度,说明鳑鲏对沉积物的扰动作用较弱.此外,鳑鲏显著增加了浮游植物生物量和蓝藻的比例.浮游动物总生物量并未受鳑鲏的影响,但显著增加了浮游动物的丰度,其中以轮虫为主.鳑鲏组的底栖动物总丰度(主要为水丝蚓)显著高于对照组,说明鳑鲏对水丝蚓的摄食压力较低.鳑鲏与河蚌交互作用对总磷、Chl.a、浮游植物和浮游动物丰度具有显著影响:具体表现为河蚌虽然抵消了部分鳑鲏对水质(如氮、磷和悬浮质浓度,以及Chl.a浓度和浮游植物生物量等)的负面影响,但其对浮游动物和水丝蚓生物量的影响不显著.在湖泊生态修复和管理中,需要关注和重视鳑鲏等此类小型杂食性鱼类对水生态系统可能产生的负面影响,通过物理(网簖等)或生物(放养肉食性鱼类)等方式将其控制在较低密度水平,从而降低这些鱼类对水质、浮游生物和底栖生物群落可能产生的负面影响,维持生态修复效果的长效与稳定运行. 相似文献
18.
鲫(Carassius auratus)是我国各类淡水水体的优势鱼类之一.作为底栖杂食性鱼类,一方面,鲫可以通过排泄和扰动沉积物影响湖泊营养和光照水平,通过"上行效应"促进浮游植物生长;另一方面,鲫也可以捕食浮游动物,通过"下行控制"影响藻类生长以及营养盐循环.对于浅水湖泊,两种途径对于生态系统影响的相对重要性仍有待研究.本研究设计了一个两因素户外中宇宙实验,通过在沉积物表面添加隔网的方式,比较两种情况下(能、否接触沉积物),鲫对水体浊度、营养盐和浮游生物生物量的影响.实验在16个大型钢化玻璃桶(400 L)中进行,持续36 d(2019年8月6日—9月11日).研究结果表明:1)在能接触沉积物的条件下,鲫显著促进了沉积物再悬浮,表现为水体的总悬浮物(TSS)和无机悬浮物(ISS)浓度大幅升高;水体的光衰减系数(Kd)增加,总氮(TN)和总磷(TP)浓度明显升高; 2)在不能接触沉积物的条件下,鲫对水体悬浮物(TSS和ISS)浓度和Kd的影响不明显,但是显著降低了水体TN和TP浓度; 3)在两种情况下,鲫对浮游植物叶绿素a浓度以及浮游动物生物量的影响均不显著.本研究表明鲫只有在能够接触沉积物的条件下,才会显著提高水体浊度和营养水平.因此,在缺乏沉水植被的浅水湖泊中,鲫扰动沉积物产生的"上行效应"可能是其对生态系统产生负面影响的主要途径. 相似文献
19.
Seasonal variations in the biomass (Chl a) and primary production (14C-method) of phytoplankton were studied during 12 months of 2005 in the three Ethiopian Rift Valley Lakes (ERVL) Ziway, Awassa and Chamo. Chl a showed an average value of 40, 20, and 30 mg m−3 for the three lakes, respectively. Integrated areal primary production for the total phytoplankton (g C m−2 d−1) varied 2-fold in the three lakes but on different levels, from 0.67–1.8 in L. Ziway, 1.8–4.6 in L. Awassa, and 1.0–2.6 in L. Chamo. The overall photosynthetic efficiency of utilizing photosynthetically active radiation by the phytoplankton on molar basis (mmol C mol of photons−1) resulted in an average value of 1.4 for L. Ziway, 3.5 for L. Awassa and 1.6 for L. Chamo. Among the different factors regulating phytoplankton primary productivity, light penetration and nutrients were the most important in the three lakes. The seasonal variations of incident radiation (most values between 5 and 7 E m−2 h−1) and water temperature (most values between 22 and 24 °C) were small and unlikely to result in the marked differences in phytoplankton primary production. Although relative increase in nutrient concentrations occurred following the rainy periods, the major algal nutrients were either consistently low (nitrate and/or silicate) or high (phosphate and/or ammonium) and remained within a narrow range for most of the study period in all the three lakes. Consequently, phytoplankton biomass and primary production seem to be maintained more by nutrient regeneration or turnover (facilitated by high temperature) than by allochthonous nutrient input. This would be coupled with wind-induced mixing that would play an important role in determining hydrographic characteristics (water column structure) and the associated redistribution of nutrients and phytoplankton, the availability of light and subsequently the spatial (vertical) and temporal patterns of phytoplankton production in these three ERVL. Phytoplankton production (PP) is regarded as a good predictor of fish yield in lakes and seasonal measurements of PP is a prerequisite for good such estimates. 相似文献