A mathematical model of the interactions in the mixed culture of invertebrates and algae in the “producer–consumer” aquatic biotic cycle

This paper presents a mathematical model of interactions between two herbivorous invertebrates (ciliate Paramecium caudatum and rotifer Brachionus plicatilis) and two planktonic algae (Chlorella vulgaris and Scenedesmus quadricauda) spatially segregated in two compartments of a chemostat–type experimental microcosm system. The model mimics a producer–consumer aquatic biotic cycle, describing the dynamics of the mixed culture of ciliates and rotifers, as consumer compartment, feeding on the mixed algal culture, as producer compartment, under N-limiting conditions. We experimentally found that metabolites of the alga Scenedesmus produce an adverse effect on the reproduction of ciliate Paramecium. Taking this effect into account improved the behavior of the model, the results of which came into qualitative agreement with the experimental results. Both our experimental and modeling approaches demonstrated that, even in conditions of a spatially–segregated producer-consumer biotic cycle, species coexistence is impossible either in the mixed algal culture or in the mixed invertebrate culture. Scenedesmus excluded Chlorella, whereas Brachionus excluded Paramecium.     

Dynamics of the reversible transition of Vibrio cholerae into the uncultivable state in the presence of organic and inorganic microcosmic components

The dynamics of the transition of V. cholerae into the uncultivable state in distilled, river and tap water, containing organic and inorganic components added, was studied. As additives, potassium nitrate, potassium phosphate, magnesium sulfate, ammonium chloride, lysine, alpha-ketoglutarate, succinic acid, catalase were used. The study of the influence of biotic factors on transition into the uncultivable state was carried out in the presence of one-celled green algae Scenedesmus quadricauda or infusoria Paramecium caudatum. The linear dependence of speed of transition into the uncultivable form on the concentration of cells was noted. The composition of the microcosmic medium was also found to have some influence on the speed of transition into the uncultivable form and on the reversibility of this process. The presence of organic substances, such as peptone solution or destroyed cells of phyto- and zooplankton, in the microcosmic medium prolonged the time of transition into the uncultivable form and produced a positive effect on the capacity of the population to reversion. In respect of live biotic components, no such dependence was found. Inorganic additives prolonged the time of transition into the uncultivable state, but did not promote reversion.     

Comparing the invasibility of experimental "reefs" with field observations of natural reefs and artificial structures

Natural systems are increasingly being modified by the addition of artificial habitats which may facilitate invasion. Where invaders are able to disperse from artificial habitats, their impact may spread to surrounding natural communities and therefore it is important to investigate potential factors that reduce or enhance invasibility. We surveyed the distribution of non-indigenous and native invertebrates and algae between artificial habitats and natural reefs in a marine subtidal system. We also deployed sandstone plates as experimental 'reefs' and manipulated the orientation, starting assemblage and degree of shading. Invertebrates (non-indigenous and native) appeared to be responding to similar environmental factors (e.g. orientation) and occupied most space on artificial structures and to a lesser extent reef walls. Non-indigenous invertebrates are less successful than native invertebrates on horizontal reefs despite functional similarities. Manipulative experiments revealed that even when non-indigenous invertebrates invade vertical "reefs", they are unlikely to gain a foothold and never exceed covers of native invertebrates (regardless of space availability). Community ecology suggests that invertebrates will dominate reef walls and algae horizontal reefs due to functional differences, however our surveys revealed that native algae dominate both vertical and horizontal reefs in shallow estuarine systems. Few non-indigenous algae were sampled in the study, however where invasive algal species are present in a system, they may present a threat to reef communities. Our findings suggest that non-indigenous species are less successful at occupying space on reef compared to artificial structures, and manipulations of biotic and abiotic conditions (primarily orientation and to a lesser extent biotic resistance) on experimental "reefs" explained a large portion of this variation, however they could not fully explain the magnitude of differences.     

Lysozyme-antilysozyme interactions in protozoa-bacteria communities (a model Tetrahymena-Escherichia community)]

Lysozyme and antilysozyme activities present in a wide range of microorganisms determine the so-called lysozyme-antilysozyme system of hydrobionts, which greatly contribute to the formation of aquatic biocenoses. However, the mechanism of the functioning of this system in natural freshwater communities remains obscure. The experimental investigation of lysozyme-antilysozyme interactions in a model Tetrahymena--Escherichia community showed that the antilysozyme activity of Escherichia coli leads to incomplete phagocytosis, thus enhancing bacterial survival in a mixed culture with infusoria. The selection and reproduction of bacterial cells resistant to grazing by infusoria determine the character of host-parasite interactions and allow bacteria to survive. It was demonstrated that the antilysozyme activity of microorganisms, which is responsible for bacterial persistency in natural biocenoses, is involved in the maintenance of protozoa-bacteria communities in bodies of water.     

Distribution of lead and cadmium in trophic levels of some marine organisms

The concentrations of lead and cadmium in two species of algae, two species of invertebrates, and one species of fish (from Fehmern Baltic Sea) were determined using atomic absorption spectrophotometry. The concentrations of these metals at the producer level (algae) were always higher than at the consumer level. Also, among the consumers there was an obvious difference according to feeding habits, in such a way that they could be ranked according to their high content of lead and cadmium as follows: filter feeder (detritous feeder), plankton feeder. In addition, distribution of lead and cadmium varied within the individual producer (Fucus vesiculosus) in such a way that the holdfast exhibited the highest concentration followed by the apcial tip and the branches of the first dichotomy was the lowest. This alga reflects clear selectivity in absorbing more lead than cadmium.     

Investigation of Lysozyme–Antilysozyme Interactions in a Model Tetrahymena–EscherichiaCommunity

Lysozyme and antilysozyme activities present in a wide range of microorganisms determine the so-called lysozyme–antilysozyme system of hydrobionts, which greatly contribute to the formation of aquatic biocenoses. However, the mechanism of the functioning of this system in natural freshwater communities remains obscure. The experimental investigation of lysozyme–antilysozyme interactions in a model Tetrahymena–Escherichiacommunity showed that the antilysozyme activity of Escherichia colileads to incomplete phagocytosis, thus enhancing bacterial survival in a mixed culture with infusoria. The selection and reproduction of bacterial cells resistant to grazing by infusoria determine the character of host–parasite interactions and allow bacteria to survive. It was demonstrated that the antilysozyme activity of microorganisms, which is responsible for bacterial persistency in natural biocenoses, is involved in the maintenance of protozoa–bacteria communities in bodies of water.     

Coal mine drainage effects on a lotic ecosystem in Northwest Colorado,U.S.A.

An aquatic biological survey was conducted in 1979–1980 to determine the effects of drainage from an active coal strip-mine on Trout Creek, in northwest Colorado, U.S.A. Sampling was conducted over four seasons at four stations for periphyton, benthic invertebrates and fish. Periphyton in Trout Creek changed in the relative abundance of algae divisions in no apparent relation to mining. Diatoms were the predominant division at all sites. Golden-brown algae were abundant in spring at the stations upstream and adjacent to the mine. Blue-green algae were relatively important at stations upstream and downstream of the mine in winter. Benthic invertebrates exhibited a progressive increase in density, biomass and number of taxa from the upstream station to the downstream station. Shannon-Wiener diversity index for bethic invertebrates decreased slightly downstream of mine drainage but remained indicative of a clean water community. Aquatic insects (especially Trichoptera) were the predominant invertebrates at all stations. Analysis of functional groups of benthic invertebrates revealed increased importance of collector species at the lower sites while shredders were most important upstream of the mine. Unlike the invertebrates, fish exhibited slightly lower biomass at the station adjacent to the mine. The decrease was due to fewer salmonids. However, salmonid density and biomass increased substantially at the station just downstream of the mine. Non-game species (suckers and minnows) increased in numbers downstream and were most abundant at the lowest station. This coal strip-mine had little discernable adverse effects on the periphyton and invertebrates of Trout Creek. Fish populations did not appear to be significantly affected by the mine. Apparently, the presence of settling ponds and a buffer zone of unmined land between the mine and the stream helped to minimize adverse effects.     

Effect of blue-green alga (Cyanobacteria) and their exometabolites on formation of resting forms and variability of Yersinia pseudotuberculosis

Research, carried out with the use of bacteriological methods and polymerase chain reaction, revealed that the transformation of Y. pseudotuberculosis, associated with blue-green algae Anabaena variabilis, into resting (noncultivable) forms took shorter time than in soil extract containing no algae. The exometabolites of "old" cultures of these algae sharply accelerated the formation of resting Y. pseudotuberculosis forms. The influence of the algae and the products of their metabolism was manifested far more intensively at 22 degrees C than at 4 degrees C. After passage through infusoria resting Y. pseudotuberculosis forms, preserved in the mucous covering of cyanobacteria, partially reverted into vegetative forms, capable of growing on solid culture media. The revertants essentially differed from the initial vegetative forms by having lower enzymatic activity, agglutinability and cytopathogenicity, as well as by the loss of plasmid p45. The probable role of blue-green algae, widely spread in soils and water reservoirs, in the processes of reversible transformation of Y. pseudotuberculosis vegetative and resting forms, closely connected with seasonal changes of temperature conditions.     

Invertebrate drift,discharge, and sediment relations in a southern Appalachian headwater stream

Drifting invertebrates and suspended sediments were collected at monthly intervals from June 1977 to May 1978. The numbers and biomass of drifting organisms reflected the seasonal cycles of aquatic insects. Some aquatic organisms showed behavioral drift either during a sample day or during some portion of their life cycle. Parapsyche cardis Ross and Diplectrona modesta Banks (Trichoptera: Hydropsychidae) dispersed as first instar larvae; few later instars of these two net-spinning caddisflies drifted. The drift of nymphal Peltoperla maria Needham et Smith (Plecoptera: Peltoperlidae) was apparently related more to detritus transport than to benthic densities or discharge alone. Power law relations between the magnitude of daily invertebrate drift and discharge or sediment variables are demonstrated for some taxa in Hugh White Creek. The general level of stream invertebrate drift appears to be related to detritus transport, and drift during storms is also related to detritus transport. During storms, terrestrial invertebrate drift was related to rainfall intensity, canopy washing, and channel expansion. Drift density of aquatic invertebrates in Hugh White Creek was within the range of previously reported values for other streams, but the estimate of yearly export (aquatic invertebrates = 134 g · y^?1; terrestrial invertebrates = 23 g · y^?1) is lower reflecting the smaller size of Hugh White Creek in comparison with those other streams.     

Mechanisms of microalgae selection during the assembly of a planktonic community

We attempt to ascertain the selection mechanisms that affect algal species’ abilities to thrive in a given environment, and how the variability of the response is reflected in the community structure (total biomass, diversity) and also in community function (photosynthesis and respiration). For that, we formed algal communities, assembling eight species of freshwater cosmopolite algae with distinct morphologies (Cosmarium contractum, Cryptomonas ovata, Euglena gracilis, Limnothrix redekei, Monoraphidium contortum, Pediastrum tetras, Planktothrix agardhii and Scenedesmus acutus) and performed four treatments combining low and high nutrient concentrations (N and P) in the culture media and a presence or absence of herbivores (a mixture of Daphnia magna, Keratella cochlearis and Brachionus calicyflorus). Competition between pairs of algae was also studied, and the viability of the species as inocula after a senescence period. The presence of herbivores (predation) and nutrient concentration (competition) are the mechanisms affecting (individually or synergistically) microalgae assemblages, originating different alternative states from the same pool of species. However, the effect of these mechanisms may vary, depending on algal properties such as size, growth rate and viability as an inoculum. The presence of herbivores and oligotrophic conditions reduce the primary producer biomass but increase diversity due to relaxation of competition and increase the uncertainty of final states. The variations in the community structure directly reflect on community function, affecting primary production and respiration.     

Use of infusoria Paramecium caudatum for the evaluation of the toxicity of antigens of different causative quarantine agents

The results of the evaluation of the toxicity of bacterial antigens obtained from the causative agents of plaque, glanders, melioidosis, cholera on infusoria of the species P. caudatum, as well as on cell lines L-929, CHO K-1 and peritoneal macrophages of BALB/c mice, are presented. As revealed in this study, the method of toxicity determination on infusoria is similar in its sensitivity to the methods of testing on. CHO K-1 and L-929 cells, but the former is simpler, more available and permits the determination of toxic doses producing disturbances in the vital activity of the infusoria, but not leading to their death.     

尼日利亚热带雨林池塘中茄氏旗鳉的食性

本文逐月研究了尼日利亚Mfangmfangpond中茄氏旗鳉全年的食性。其食谱按优势多寡出现的次序分别是陆生无脊椎动物、大型植物、水生无脊椎动物、小型甲壳动物、沙粒和藻类。我们将膜翅目、鞘翅目和双翅目昆虫作为其食性的次级项,而全年都出现的有机体碎屑作为初级项。雄鱼较雌鱼捕食了更多的陆生无脊椎动物。茄氏旗在雨季有16项食物组成,但旱季只有7项。就相对重要性而言,陆生和水生无脊椎动物在旱季更大,而大型植物碎屑、小型甲壳动物、沙粒和藻类则在雨季更大。成鱼较幼鱼更多地以外源性无脊椎动物为食。雌鱼较雄鱼有更强的觅食能力;同样,成鱼较幼鱼的觅食能力强得多.     

6种微藻对氯霉素和硫酸新霉素敏感性研究

目的:探讨3种真眼点藻(点状魏氏藻(Visderia punctata)、波氏真眼点藻(Eustigmatos polyphem)、魏氏真眼点藻(Eustigmatos vischeri))和3种绿藻(栅藻(Scnedesmus sp.)、斜生栅藻(Scenedesmus obliqulis)、爪哇栅藻(Scenedesmus jaoaensis))对2种抗生素的敏感性.方法:采用藻液细胞计数法和藻细胞固体平板培养法研究了氯霉素和硫酸新霉素对6种微藻生长的影响.结果:液体培养,3种绿藻对氯霉素敏感性均高于硫酸新霉素,10μg·mL-1氯霉素即可明显抑制3种绿藻的生长(P＜0.05),而硫酸新霉素在浓度为200 μg·mL-1时才显示出明显抑制作用:3种真眼点藻对2种抗生素都不敏感.固体培养,除波氏真眼点藻外,其它5种微藻对氯霉素的致死浓度均为50μg·mL-1;波氏真眼点藻、栅藻、斜生栅藻和爪哇栅藻对硫酸新霉素的致死浓度分别为100 μg·mL-1、200μg· mL-1、50μg·mL-1和50μg·mL-1.结论:氯霉素可作为选育6种微藻抗性突变株的筛选剂.     

淀山湖周丛动物群落的初步研究

作者于1991年11月至1992年11月对淀山湖水生植物上周丛动物进行了初步研究。共观察到84种周丛动物,以原生动物(38.10%)和轮虫(22.62%)占多数。按个体大小,分为小型周丛动物群落和大型周丛动物群落两种群落类型。小型周丛动物群落的优势种为似钟虫、角突臂尾轮虫等,个体数量受周丛原生动物支配,一年中有两次高峰(3-4月份和11月份),生物量在3月份最大,主要受周丛轮虫控制。大型周丛动物群落的优势种为线虫和螺类,一年只有一次数量高峰(6-8月),生物量中螺类占绝对优势(96.4%)。周丛动物在不同水生植物上的分布数量不同,沉水植物中以金鱼藻最多,大茨藻最少;并且叶上的数量明显高于茎上。漂浮植物上一般多于沉水植物,且根部最多,茎、叶相近。水生植物上周丛动物多为广布种,特有种罕见,主要出现于小型周丛动物群落中。       

萼花臂尾轮虫培养滤液对铜绿微囊藻、斜生栅藻和小球藻群体形成及生长的影响

为探索浮游动物和藻类之间可能存在的信息传递,研究了萼花臂尾轮虫培养滤液对铜绿微囊藻、斜生栅藻和小球藻的生长及群体形成的影响.把萼花臂尾轮虫按1000个·L^-1的初始密度置于小球藻中培养24h后,用孔径0.15μm的微孔滤膜抽滤,得到轮虫培养滤液,此滤液中含有轮虫在生活过程中释放的一些信息化学物质.将轮虫培养滤液以20%的比例分别加入纯培养的铜绿微囊藻、斜生栅藻和小球藻中,进行为期7d的试验.结果表明,萼花臂尾轮虫培养滤液能显著地促进斜生栅藻的群体形成,而对铜绿微囊藻和小球藻在群体形成方面没有显著作用.另外,该滤液能显著提高小球藻种群的增长,对铜绿微囊藻和斜生栅藻的生长无明显影响.3种藻类对萼花臂尾轮虫的潜在牧食采取了不同的生态策略:斜生栅藻形成群体,增大摄食阻力,从而降低被摄食的风险;小球藻通过提高增长率来抵消被取食的损失;铜绿微囊藻是通过其它方式来降低被牧食(例如毒素).这些方式分别是这些藻类维持种群规模的反牧食防御策略之一.     

Axenic culture of <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> using antibiotics

The rotifer Brachionus plicatilis culture is composed of complex microcosms including bacteria, protozoans, algae, and fungi. Previous studies reported methods to establish axenic rotifer cultures, but further refinement of these techniques is needed, for molecular biological research which requires pure culture to isolate nucleic acids from rotifers only. In order to render rotifer culture axenic, we tested five antibiotics: ampicillin (Amp), chloramphenicol (Cp), kanamycin (Km), nalidixic acid (Na), and streptomycin (Sm) at 30–100 μg/ml. Except for Cp, which reduces rotifer reproduction, all other antibiotics at the tested concentrations did not affect rotifer reproduction or show any toxic effects. A rotifer disinfection method was finally established by treating the resting eggs with 0.25% (w/v) sodium hypochlorite (NaOCl) for 3 min, washing with sterilized sea water, and then exposing the neonates to an Amp, Km, Na, and Sm mixture. Using four nutrient media, we confirmed that this protocol renders the rotifer culture bacterial and fungus free. The axenic rotifer culture generated here is useful not only for genetic analysis of Brachionus plicatilis, but for studying the rotifer life cycle without bacterial influence.     

Variability in characteristics of production and macromolecule content within microalgae cells during growth period

Variability in primary production and destruction during growth of an experimental population of Scenedesmus quadricauda has been determined. Accumulation of proteins, total lipids, and carbohydrates in algae cells was depending on phases of an algae population lifecycle.     

Structural and trophic characteristics of protozoan plankton in a subarctic Lake (Northern Karelia)

The seasonal dynamics of ciliate abundance has been studied in Lake Krivoye (the White Sea coast). A high species diversity of ciliates and their maximal biomass in the plankton are observed in the early spring in spite of low water temperatures (5–7°C). In spring, infusoria comprise 90% of the zooplankton biomass; i.e., infusoria as primary consumers are the main consumers of algal and microzooplankton production and the major carriers of energy to the next trophic level. During this period, a significant portion of planktonic infusoria biomass is constituted by the species containing zoochlorella. The high biomass of symbiotic algae (25% of the total biomass of planktonic algae) in a spring cilioplankton testifies to the important role that algosymbionts play in the primary production in some parts of the year.     

Experimental separation of effects of consumers on sessile prey in the low zone of a rocky shore in the Bay of Panama: direct and indirect consequences of food web complexity

The effects of predation by a diverse assemblage of consumers on community structure of sessile prey was evaluated in the low rocky intertidal zone at Taboguilla Island in the Bay of Panama. Four functional groups of consumers were defined: (1) large fishes, (2) small fishes and crabs, (3) herbivorous molluscs, and (4) predaceous gastropods, (l) and (2) included fast-moving consumers and (3) and (4) included slow-moving consumers. Experimental treatments were: no consumers deleted (all groups present), most combinations of deletions of single groups (i.e., one group absent, three present), pairs of groups deleted (two absent, two present), trios of groups deleted (three absent, one present), and the entire consumer assemblage deleted (all groups absent). Changes in abundance (percent cover) of crustose algae, solitary sessile invertebrates, foliose algae, and colonial sessile invertebrates were quantified periodically in 2–4 plots of each treatment from February 1977 to January 1980 after the initiation of the experiment in January 1977.

Space on this shore is normally dominated by crustose algae; foliose algae, solitary sessile invertebrates, and colonial sessile invertebrates are all rare. After deletion of all consumers, ephemeral green algae increased from 0 to nearly 70% cover. Thereafter, a succession of spatial dominants occurred, with peak abundances as follows: the foliose coralline alga Jania spp. by July 1977, the barnacle Balanus inexpectatus by April 1978, and the rock oyster Chama echinata by January 1980. Although no longer occupying primary rock space, Jania persisted as a dominant or co-dominant turf species (with the brown alga Giffordia mitchelliae and/or the hydrozoan Abietinaria sp.) by colonizing shells of sessile animals as they became abundant instead of the rock surface.

Multivariate analysis variance (MANOVA) indicated that the effect of each group was as follows. Molluscan herbivores grazed foliose algae down to the grazer-resistant, but competitively inferior algal crusts, altered the relative abundances of the crusts, and inhibited recruitment of sessile invertebrates. Predaceous gastropods reduced the abundance of solitary sessile animals. Small fishes and crabs, and large fishes reduced the cover of solitary and colonial sessile animals and foliose algae, although they were incapable of grazing the foliose algae down to the rock surface. Many of the effects of each consumer group on prey groups or species were indirect; some effects were positive and some were negative. The variety of these indirect effects was due to both consumer-prey interactions among the consumers, and competitive or commensalistic interactions among the sessile prey. Comparison of the sum of the effects of each of the single consumer groups (i.e., the sum of the effect observed in treatments with one group absent, three present) with the total effects of all consumers (i.e., the effect observed in the treatment with all groups absent) indicates that a “keystone” consumer was not present in this community. Rather, the impacts of the consumer groups were similar but, due to dietary overlap and compensatory changes among the consumers, not readily detected in deletions of single consumer groups. The normally observed dominance of space by crustose algae is thus maintained by persistent, intense predation by a diverse assemblage of consumers on potentially dominant sessile animals and foliose algae. The large difference in structure between this and temperate intertidal communities seems due to differences in degree, not kind of ecological processes which produce the structure.     

两品系萼花臂尾轮虫摄食强度的比较研究

对广州和芜湖两品系萼花臂尾轮虫的摄食强度及其与食物浓度、食物种类和培养时间之间的关系进行了比较研究.结果表明,食物浓度、食物种类和培养时间均对轮虫滤水率和摄食率有显著影响.两品系轮虫滤水率和摄食率均随培养时间的延长而减小;20 h内,两品系轮虫的总滤水率均与食物浓度呈曲线相关,而两品系轮虫总摄食率均与食物浓度呈直线相关.广州和芜湖两品系轮虫均在以小球藻为食物时有较大的滤水率,分别为0.0029±0.0001和0.0039±0.0008ml·ind.^-1·h^-1;广州品系轮虫以小球藻为食物时的摄食率(0.3992×10⁴±0.00850×⁴ cell·ind.-1·h^-1)显著地大于以栅藻为食物时的摄食率(0.170×⁴±0.0370×⁴ cell·ind.^-1·h^-1),而它们均与以混合藻为食物时的摄食率无显著差异;芜湖品系轮虫摄食率不受食物种类影响.轮虫滤水率和摄食率因食物浓度、食物种类和培养时间的不同而在品系间存在着差异.