Crustacean zooplankton community structure in temporary and permanent grassland ponds

Lentic community structure varies across a size gradient of ponds and lakes with physical factors, such as pond drying, and biotic factors, such as fish predation, determining the species assemblage. We studied the effects of pond drying and fish absence on crustacean zooplankton across a gradient of pond sizes in a Texas grassland. We determined the species compositions and size distributions of crustacean zooplankton in 20 temporary and 18 permanent ponds in April after March rains had refilled the ponds. The surface areas of temporary and permanent ponds ranged from <0.01 to 0.21 ha and 0.04 to 13.8 ha, respectively, and temporary ponds were significantly smaller, on average, than permanent ponds. Fish were absent from all temporary ponds and present in all permanent ponds. We detected a difference in the zooplankton species assemblages of the temporary and permanent ponds. Out of 14 total zooplankton taxa that occurred in eight or more ponds, seven taxa were significantly more prevalent in temporary ponds and four taxa were significantly more prevalent in permanent ponds. The sizes of zooplankton in the temporary fishless ponds were greater than those in the permanent ponds with fish present. We concluded that pond size mediated susceptibility to pond drying, and pond drying determined the presence and absence of fish and their secondary trophic-level effect on zooplankton community structure. Handling editor: Steven Declerck     

Ciliate populations in temporary freshwater ponds: seasonal dynamics and influential factors

SUMMARY 1. The ciliate populations of two temporary ponds in southern Ontario were studied throughout their aquatic phases in 2001. Pond I (～1 ha) held water for 98 days, whereas Pond II (～0.25 ha) held water for 34 days. Populations were assessed both within the ponds themselves and within a series of enclosures in which invertebrate predator pressure was manipulated. 2. In the natural pond water, total ciliate abundance in Pond II rose rapidly from day 1 increasing two orders of magnitude by day 7. In contrast, total abundance in Pond I began at the same level as in Pond II but increased much more slowly, reached a plateau of around 500 individuals L^?1, and increased again late in the hydroperiod. 3. Despite being only 500 m apart, the two ponds were fairly dissimilar in terms of their species richness and species composition. Pond I contained 50 species compared with 70 species for Pond II, with only 24 species shared. Additional species occurred within the enclosures raising the total species richness to 145 species; 88 from Pond I, 104 from Pond II, with 47 species (30%) in common. Pond II contained more mid‐sized ciliates (50–200 μm), whereas Pond I was dominated by smaller ciliates, especially in mid‐May and early June. In Pond I, cumulative species richness throughout the hydroperiod was highest in the predator addition enclosures (65 ± 4 species), followed by the partial‐predator exclusion enclosures (50 ± 4). Lowest species richness was found in the control enclosures (39 ± 2) and in the pondwater controls (39 ± 0). Differences between the ciliates in the natural pond water and the enclosures appeared to be related to a greater concentration of phytoplankton within the enclosures (perhaps resulting from extensive growth of duckweed, Lemna, outside), and higher densities of zooplankters in the pond. 4. The physicochemical environment influenced species richness, total abundance and the number of rare species (27 in Pond II versus 13 in Pond I). Variation in ciliate abundance in Pond I could be explained by the number of days after filling (39%) and enclosure treatment (23%). These two parameters also explained 72% of the variation in species richness in Pond I (46 and 26%, respectively). Sixty‐five per cent of the variation in abundance in Pond II could be explained by the measured parameters: number of days after filling 27%, pH 19%, and nitrate levels 12%. Fifty‐two per cent of the variation in species richness was explained by the environmental parameters, of which pH was the most influential. Species succession was a strong feature of both ponds and its relationship to environmental variables and the presence of other organisms is discussed. 5. Addition of invertebrate predators resulted in higher abundance and higher species richness for a limited time period in one of the ponds – suggesting that differences in foodweb dynamics may influence ciliate community composition.     

Relating fish kills to upwellings and wind patterns in the Salton Sea

Awareness of pond conservation value is growing all over Europe. Ponds are recognized as important ecosystems supporting large numbers of species and several rare and threatened aquatic plants, macroinvertebrates and amphibians. Notwithstanding ponds, particularly temporary ones, are still neglected in Italy. There are some gaps in our understanding of the macrophyte ecology and the conservation value of Mediterranean small still waters. Therefore, this study investigated the macrophyte communities and physico-chemical characteristics of 8 permanent and 13 temporary ponds along the Tyrrhenian coast near Rome, with the aim to relate the distribution of aquatic plants to environmental variables, and to define the botanical conservation value of ponds. Throughout the study period (Spring 2002), Principal Component Analysis performed on abiotic variables clearly discriminated temporary ponds, smaller and more eutrophic, from permanent ponds, larger and with higher pH and oxygen concentration. A total of 73 macrophyte taxa were collected in the study ponds. Temporary waters hosted a smaller number of plant species than permanent ones. Besides hydroperiod length, the environmental factors related to plant richness were maximum depth, surface area, dissolved oxygen and nitrogen concentration in the water. Moreover, the Non-metric Multidimensional Scaling showed a high dissimilarity in the taxonomic composition of aquatic plants between temporary and permanent ponds. The former contained more annual fast-growing species (Callitriche sp. pl. and Ranunculus sp. pl.), while in the latter species with long life-cycles (i.e. Potamogeton sp. pl.) were more abundant. Our results highlighted that temporary and permanent ponds in central Italy have different macrophyte assemblages, with aquatic species (including some of conservation interest at regional scale) exclusively found in each pond type. This suggested that both type of ponds could give an irreplaceable contribution to the conservation of aquatic plant diversity of these freshwater ecosystems. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: R. Céréghino, J. Biggs, B. Oertli & S. Declerck The ecology of European ponds: defining the characteristics of a neglected freshwater habitat     

Spatiotemporal allozyme variation in the damselfly, Lestes viridis (Odonata: Zygoptera): gene flow among permanent and temporary ponds

Several insect species seem to persist not only in permanent but also in temporary ponds where they face particularly harsh conditions and frequent extinctions. Under such conditions, gene flow may prevent local adaptation to temporary ponds and may promote phenotypic plasticity, or maintain apparent population persistence. The few empirical studies on insects suggest the latter mechanism, but no studies so far quantified gene flow including both pond types. We investigated the effects of pond type and temporal variation on population genetic differentiation and gene flow in the damselfly Lestes viridis in northern Belgium. We report a survey of two allozyme loci (Gpi, Pgm) with polyacrylamide gel electrophoresis in 14 populations from permanent and temporary ponds, and compared these results with similar data from the same permanent populations one year before. The data suggested that neither pond-drying regime, nor temporal variation have a substantial effect on population genetic structuring and did not provide evidence for stable population differentiation in L. viridis in northern Belgium. Gene flow estimates were high within permanent and temporary ponds, and between pond types. Our data are consistent with a source-sink metapopulation system where temporary ponds act as sinks in dry years, and are quickly recolonized after local population extinction. This may create a pattern of apparent population persistence of this species in permanent and temporary ponds without clear local adaptation.     

Regional enrichment of predacious water beetles in temporary ponds at opposite east–west ends of the Palearctic

Regional and local species richness of temporary pond dytiscid water beetles were compared among three regions within the Palearctic: (1) Sweden in north west Europe, (2) Primorye and (3) Sakhalin Island in the Russian Far East. Both local and regional species richness were highest in Sweden and lowest in Sakhalin. Regional species richness was calculated from literature and collecting data for each region and for nested parts of regions. Local species richness was estimated from standardized net samples from fourteen or fifteen ponds in each region. Two different rarefaction techniques applied to the net-sample data confirmed the observed interregional differences in species richness. Partial least square regression showed that pond area, depth and temperature affected local species richness positively in each region, whereas increasing shade and drought frequency had negative effects. Residuals from the regression analysis were positive in Sweden, negative in Sakhalin, and near zero in Primorye ponds. Consequently, the local species richness was related positively to regional species richness also when compensated for differences in the local pond environment. This was verified when pond species richness of each region was correlated with principal component scores representing a combination of pond area, depth and temperature. The species' distributions among ponds displayed significantly nested patterns in Sweden and Sakhalin. However, species were significantly sorted along the pond area gradient only in Sweden. It is concluded that the observed interregional differences in local species richness are best explained by the accompanying gradient in regional species richness, lending support to the hypothesis of regional enrichment. Selected historical and ecological explanations for the observed differences in regional species richness are discussed.     

Effect of the filling season on aquatic plants in Mediterranean temporary ponds

Aims Pond environmental conditions may differ among years with regards to the season in which ponds begin to fill. We experimentally evaluated how seedling emergence, plant growth and phenology differed among years in which filling occurred in winter, autumn or spring.Methods We collected sediments from a natural temporary pond and located them in aquariums. They were placed in a climatic chamber that simulated annual variation in field environmental temperatures and light conditions. Aquariums were assigned to one of three treatments, which differed in the date on which they were filled with water (autumn, winter and spring). We counted the number of seedlings of different species emerged and recorded data about the presence of flowers, seeds or spores every week. The experiment was finished in June, when we harvested the plants and estimated their biomass.Important findings In most species, seedling emergences were primarily related to time after filling, and thus synchronized their life cycles with the unpredictably timed wet phase of the ponds. Autumn filling resulted in the highest numbers of seeds/spores. However, winter filling promoted plant growth the most. In the spring filling treatment, more terrestrial plant seedlings emerged and fewer seeds/spores were produced. When ponds are flooded earlier, plants may produce a higher number of propagules. However, in years when inundation is delayed to spring and hydroperiods are short, seedling emergence deplete the seed bank and there is little to no seed production, while terrestrial monocots are able to colonize pond basin.     

Leaching from vegetation of soluble polyphenolic compounds,and their abundance in temporary ponds in the Doñana National Park (SW Spain)

The origin of allochthonous soluble polyphenols in the water of the temporary ponds of Doñana National Park during flood and heavy rainfall was examined. Soil and litter samples were found to leach large quantities of polyphenolic compounds. The concentration of these compounds showed a significant correlation with the organic content of the soil samples, but indicated no correlation with the litter samples. Rain simulation tests proved that fresh vegetation leached soluble polyphenolic compounds. Mediterranean scrub (Cystaceae) from dry poor-nutrient soils yielded the highest concentration (being furthest away from the ponds), whereas wetland (Ericaceae) and littoral vegetation (Juncaceae and Cyperaceae) rated second and third, respectively. The potential of the surrounding vegetation to leach high concentrations of polyphenolic compounds suggests that this is the main source of the rapid polyphenolic enrichment of these ponds during periods of heavy rain.     

The conservation value of English urban ponds in terms of their rotifer fauna

The rotifer assemblages of 26 urban ponds have been compared with the preliminary English national classification of small water bodies. It was found that similar TWINSPAN indicator species occurred in both classifications and that the urban ponds were classified appropriately as permanent, lowland sites, with intermediate conductivity. The factors responsible for shaping these urban rotifer assemblages were associated with cadmium (p < 0.01), lead (p < 0.01), zinc (p < 0.05), phosphate (p < 0.05), pH (p < 0.01) and macrophyte richness (p < 0.01). The conservation value of these sites (in terms of species richness) was found to be similar to relatively undamaged sites upon comparable geology, indeed mean values were higher from urban sites. The size of the buffer zone around the pond was highly correlated with species richness (p < 0.01) and negatively correlated with lead (p < 0.05) and phosphate (p < 0.05). It is suggested that conservation management may be better targeted if more attention is paid to the maintenance and enhancement of the buffer zone.     

Life syndrome of the bryophyte communities as an adaptative pattern in the Mediterranean temporary ponds of Italy

An ecological and biological investigation on the bryophyte communities of the Mediterranean temporary ponds was carried out in Italy. Here, the occurrence of a rich set of liverworts is very significant, as several species of Riccia characterize the communities from a physiognomical, ecological and syntaxonomical point of view. The moss component is represented only by acrocarpous mosses, e.g. Archidium alternifolium and Pleuridium acuminatum which play an important phytosociological role. In this study, the bryophyte communities are used to identify a pattern, corresponding to a “functional type” which reflects the correlated response of the bryophyte communities toward the prevalent ecological parameters of the habitat. The individuated functional type assembles life strategy, life form, lifespan, spore size, dispersal strategy, reproduction effort, independently from the taxonomical relationship of the species characterizing the communities. It represents an adaptative pattern of coevolved characters, adopted by the bryophyte communities for the habitat establishment and re-establishment following the seasonal water fluctuations typical of the investigated habitat.     

Filling ephemeral ponds affects development and phenotypic expression in Ambystoma talpoideum

相似文献   

Changes in sediment phosphate composition of seasonal ponds during filling

Most ponds from the Doñana National Park are shallow temporary freshwater bodies on eolian sands. The total phosphate concentration and the fractional P-composition of the sediments from two small ponds were studied before and inmediately after they were filled (autumn, 1996). Total phosphorus concentration was measured in 2 different size fractions: 2–0.1 mm (coarse) and <0.1 mm (fine). In both ponds, the total phosphorus concentration of the fine sediment increased by 20% at the beginning of the filling period, whereas 5 weeks later it did not increase further. The percentage of organic matter of the fine sediment was relatively high (between 13–18%) and did not change significantly during filling. The concentration of sediment total iron and Fe(OOH) increased significantly in both ponds during filling. The sequential P fractionation of the fine sediment included, besides the determination of two inorganic fractions (Ca-bound P and Fe-bound P), an organic-P fraction extracted with acid, another extracted with alkali, two organic-P fractios from the Ca-EDTA/dithionite and the Na₂-EDTA extracts which contained high concentrations of humic substances. The pond sediments were rich in organic P compounds as the sum of all organic-P fractions ranged between 267 and 320 g g^-1 (68% and 79% of the sum of all fractions). Significant changes (P<0.01) in the fractional P-composition of sediments were found after filling. Acid soluble organic phosphate increased about 30% in both ponds. Iron-bound phosphate increased significantly (about 40%) only in the pond where a higher concentration of Fe(OOH) was measured after filling. An adsorption experiment was carried out for each sediment to simulate P input during filling. Both the iron-bound phosphate and Ca-bound P increased significantly (P<0.01) suggesting that these two fractions were involved in the P-adsorption during the laboratory experiment.     

The chemistry of surface water in prairie ponds

Water analyses from 80 small prairie ponds, 0.17 to 89.8 hectares, in Manitoba and Saskatchewan between 1967 to 1972 exhibited two basic ionic dominance patterns HCO₃ > SO₄ > Cl and SO₄ > HCO₃ > Cl. The order of SO₄ and Cl were reversed in 40 percent of the bicarbonate ponds below 500 µmhos/cm. At salinities above 12,000 µmhos/cm, Cl exceeds SO₄ in several wetlands. Temporary wetlands were characterised by Ca > K > Mg > Na / HCO₃ > Cl > SO₄, semi-permanent ponds Mg > Ca > Na > K / SO₄ > HCO₃ > Cl while the permanent pond structure was Ca > Mg > Na > K / HCO₃ > SO₄ > Cl.Conductivities of the wetlands studied ranged from 47 to 23,000 µmhos / cm.Seasonal changes in salinity varied within and between pond types as well as from year to year. The average salinity increase within season in temporary ponds was 67 percent, 63 percent in semi-permanent ponds and 20 percent for permanent ponds. These changes were affected by evaporation, transpiration, see-page and precipitation patterns. Ionic dominance patterns did not change within a season although Mg, K and HCO₃ increased at higher rates than Ca, Na, CI and SO₄.Temporary wetlands are slightly acidic, averaging pH 6.8 while semi-permanent and permanent ponds were alkaline, pH range 7.1 to 9.2. No stratification of pH with depth and minimal diurnal variation was recorded.At two study areas, Bradwell and St. Denis fhe following ranges (micrograms/litre) were recorded: 3 to 630 PO₄-P, 10 to 650 NO₃-N, 5 to 630 TDFe, 1 to 13 TDCu and 1 to 27 TDZn. Colour was 5 to 190 Hazen units at St. Denis and 10 to 110 for Bradwell.Two herbicides, 2,4-D and 2,4,5-T were detected at levels of 4 to 111 and 1.4 to 13.5 micrograms/litre, respectively, from 15 ponds at St. Denis.     

Integrating detection probabilities in species distribution models of amphibians breeding in Mediterranean temporary ponds

Aim The imperfect detection of species may lead to erroneous conclusions about species–environment relationships. Accuracy in species detection usually requires temporal replication at sampling sites, a time‐consuming and costly monitoring scheme. Here, we applied a lower‐cost alternative based on a double‐sampling approach to incorporate the reliability of species detection into regression‐based species distribution modelling. Location Doñana National Park (south‐western Spain). Methods Using species‐specific monthly detection probabilities, we estimated the detection reliability as the probability of having detected the species given the species‐specific survey time. Such reliability estimates were used to account explicitly for data uncertainty by weighting each absence. We illustrated how this novel framework can be used to evaluate four competing hypotheses as to what constitutes primary environmental control of amphibian distribution: breeding habitat, aestivating habitat, spatial distribution of surrounding habitats and/or major ecosystems zonation. The study was conducted on six pond‐breeding amphibian species during a 4‐year period. Results Non‐detections should not be considered equivalent to real absences, as their reliability varied considerably. The occurrence of Hyla meridionalis and Triturus pygmaeus was related to a particular major ecosystem of the study area, where suitable habitat for these species seemed to be widely available. Characteristics of the breeding habitat (area and hydroperiod) were of high importance for the occurrence of Pelobates cultripes and Pleurodeles waltl. Terrestrial characteristics were the most important predictors of the occurrence of Discoglossus galganoi and Lissotriton boscai, along with spatial distribution of breeding habitats for the last species. Main conclusions We did not find a single best supported hypothesis valid for all species, which stresses the importance of multiscale and multifactor approaches. More importantly, this study shows that estimating the reliability of non‐detection records, an exercise that had been previously seen as a naïve goal in species distribution modelling, is feasible and could be promoted in future studies, at least in comparable systems.     

Life history comparisons of Daphnia obtusa from temporary ponds, cultured with a low-quality food

Temporary pond Daphnia flourish on relatively poor-quality food, suggesting adaptation to stringent temporary pond conditions. We conducted laboratory life history experiments on populations of Daphnia obtusa from a shaded woodland temporary pond (short hydroperiod, dystrophic) and an open farmland temporary pond (long hydroperiod, eutrophic), and compared a suite of physical/chemical conditions in the ponds to evaluate habitat conditions. We hypothesized that the shaded woodland pond population would be more fit in terms of life history variables for individuals (age and size at first reproduction, mean brood size, mean number of neonates) and populations (generation time, net reproductive rate R ₀, and intrinsic reproductive rate r) given a standard, low-quality food (trout chow and yeast). Life history traits of woodland pond animals were mixed, relative to farm pond animals, and consistent with bet-hedging for an unpredictable habitat. Values of life history traits rivaled or exceeded those of other studies using phytoplankton as food, and were influenced by the pond water used for our study. Life histories clearly differ among local and regional temporary pond Daphnia obtusa populations, and should be valuable for examining the relative influences of local selection and metapopulation dynamics on population structure.     

九龙江河口区养虾塘沉积物-水界面营养盐交换通量特征

通过对九龙江河口区陆基养虾塘水样和沉积物样品采集分析及结合室内模拟实验,探讨了虾塘在不同养殖阶段沉积物-水界面营养盐通量时间变化特征及其主要影响因素。虾塘沉积物向上覆水体释放NO_x~--N(NO_2~--N和NO_3~--N)、NH_4~+-N和PO_4~(3-)-P能力均呈现随养殖时间推移而降低的特征。沉积物在养殖中期和后期分别呈现对上覆水体NO_x~--N和PO_4~(3-)-P的吸收现象,但总体表现为释放(平均通量分别为(1.87±1.15)、(1.58±0.52)mg m~(-2)h~(-1)和(1.22±0.62)mg m~(-2)h~(-1))。沉积物-水界面溶解无机氮交换以NH_4~+-N为主(沉积物平均释放通量为(46.18±13.82)mg m~(-2)h~(-1))。沉积物间隙水与上覆水间的营养盐浓度差(梯度)及温度对上述交换通量的时间动态特征具有重要调控作用。研究结果表明养殖初期或中期沉积物较高的无机氮(尤其是NO_2~--N和NH_4~+-N)释放是养殖塘水质恶化的一个极具潜力的污染内源,可能会对虾的健康生长产生负面效应,控制沉积物无机氮释放是养虾塘养殖初期和中期重要的日常管理活动之一。     

刺参养殖池塘水体中浮游病毒的丰度

运用荧光显微技术,于2007年3～11月,对大连市附近4个地区的刺参养殖池塘及相应的海域进行了浮游病毒丰度的监测和分析,对刺参养殖池塘生态系统的浮游病毒丰度在时间、空间分布上的变化进行了探讨。荧光显微观察结果显示,刺参养殖池塘浮游病毒在时间和空间分布上均存在极显著差异（P〈0.01）,8月中旬平均丰度达到峰值,为2.54&#215;10^10个/L,7月下旬浮游病毒的平均丰度最低,为1.43&#215;10^9个/L。复州湾海域的浮游病毒丰度显著高于其他地区,该地区浮游病毒丰度平均达到1.17&#215;10^10个/L,夏家河子地区浮游病毒丰度最低,平均为3.89&#215;10^9个/L。同一刺参养殖池塘中部区域的浮游病毒丰度高于进水和排水口。刺参养殖池塘水体中浮游病毒丰度与养殖池塘所处的海区位置、养殖池塘的密度密切相关。     

Multispecies coexistence of branchiopods (Anostraca,Notostraca & Spinicaudata) in temporary ponds of Chaouia plain (western Morocco): sympatry or syntopy between usually allopatric species

The study of the structure of communities of Crustacean branchiopods Anostraca, Notostraca and Spinicaudata of temporary ponds in Morocco revealed the existence of a geographical area with a particularly diversified number of species. Over a few hectares, 11 species, among the 18 known in Morocco, are present. While most of them are usually allopatric and belong to distinct associations, indicative of particular ecological and climatic conditions, they can coexist in Chaouia plain, either in adjoining ponds (sympatric species) or in the same pond (syntopic species). In one pond we could find up to 10 phyllopods: 6 Anostraca, 2 Notostraca and 2 Spinicaudata.This faunistic diversity may result from abiotic features (the location of the ponds at the boundary of two climatic areas) and from a heterogeneous geological substratum, creating a patchwork of temporary ponds with various mesologic conditions.Secondarily, this diversity may result from different life history characteristics of each coexisting species. As all species hatch synchronically, coexistence is only possible if their growth rates and life span are different. This implies that horizontal and vertical distribution, and exploitation of food supplies in the habitat differ for each ecophase of the syntopic species (spatial and trophic exclusion).     

土壤动物群落空间格局和构建机制研究进展

群落空间格局和构建机制一直是生态学研究的核心内容。在生物多样性严重丧失的背景下, 揭示群落空间格局及其构建机制, 有助于深刻理解生物多样性丧失的原因, 更有助于应对生物多样性保护等重大生态环境问题。然而, 陆地生态系统的研究多集中于地上生物群落, 对地下生态系统, 尤其是土壤动物空间格局和构建机制的研究尚不充分。事实上, 土壤动物多样性是全球生物多样性的关键组成之一, 是地下生态系统结构和功能维持的重要部分。对土壤动物空间格局和构建机制的研究, 能明确不同空间尺度条件下土壤动物多样性的维持机制。土壤动物群落常在多种空间尺度形成复杂的空间分布格局, 因此, 本文首先介绍了不同空间尺度主要土壤动物群落的空间自相关性特征, 阐述了土壤动物群落斑块和孔隙镶嵌分布的复杂空间格局。继而阐明这种空间格局主要受生物间作用、环境过滤和随机扩散的调控, 并说明这三个过程对土壤动物群落的调控能力和作用方式。作者提出, 这三个过程仍是今后土壤动物群落空间格局和构建机制研究的重点内容, 需要进一步加强以土壤动物为研究对象的群落构建理论的验证和发展。我国土壤动物群落空间格局和构建机制起步较晚, 希望本文能够促进我国土壤动物生态学相关领域的研究。     

寡盐水鱼池藻菌土腥异味化合物研究

通过利用固相微萃取-气质联用色谱测定天津市寡盐水养鱼池中浮游藻类和放线菌的次生代谢产物——土腥异味化合物（土臭味素和二甲基异莰醇）浓度,感官评价养殖鱼土腥异味程度,同时测定浮游藻类和放线菌生物量,探讨鱼池中土臭味素和二甲基异莰醇浓度、浮游藻类和放线菌生物量以及养殖鱼异味之间的相互关系。结果表明,寡盐水养鱼池水体中普遍存在土臭味素和二甲基异莰醇,其中二甲基异莰醇是鱼池中的主要异味物质,浓度0．33—5302．70ng&#183;L^-1,土臭味素浓度相对较低,0．29～12．10ng&#183;L^-1。养鱼池中共测到6门94属的浮游藻类,生物量0．07～186．48mg&#183;L^-1,以蓝藻Cyanophyta、裸藻Euglenophyta等种类为主。放线菌共测到3个属,总生物量0．01&#215;10^4-1．50&#215;10^4个&#183;L^-1,以链霉菌属Streptomyces为主。巨颤藻Oscillatoria princeps和放线菌是天津地区寡盐水养鱼池中能够产生二甲基异莰的主要产源。水体异味和鱼肉发生异味不同步。