Vertical structure and photosynthetic activity of Lake Shira phytoplankton

This study was conducted to analyse vertical dynamics of phytoplankton distribution in Shira Lake during the summer stratification regime. From late June to September phytoplankton in Shira Lake were stratified with the maximum in the lower part of the thermocline, at a depth of 8–12 m, with a chlorophyll concentration up to 23 g and biomass up to 5 mg l^–1. Maxima of chlorophyll and biomass of cyanobacteria and green algae were in different layers. From June to September a major part of chlorophyll a was in green algae, while under ice – in cyanobacteria. The variable fluorescence proves high photosynthetic activity of algae in the depth assemblage. Epifluorescent analysis disclosed that additional light-harvesting pigments were better developed in cells from the depth maximum. The maximum of gross primary production calculated from fluorescence corresponded to the depth maximum of phytoplankton. Primary production over a season was 2.7 gO₂ m^–2. Formation mechanisms of the depth maximum of phytoplankton are discussed in this paper.     

Effect of winter conditions on distributions of anoxic phototrophic bacteria in two meromictic lakes in Siberia,Russia

The year-to-year variations of vertical distribution and biomass of anoxic phototrophic bacteria were studied during ice periods 2003–2005 and 2007–2008 in meromictic lakes Shira and Shunet (Southern Siberia, Russian Federation). The bacterial layers in chemocline of both lakes were sampled with a thin-layer hydraulic multi-syringe sampler. In winter, biomass of purple sulphur bacteria varied considerably depending on the amount of light penetrating into the chemocline through the ice and snow cover. In relatively weakly stratified, brackish Shira Lake, the depth of chemocline varied between winters, so that light intensity for purple sulphur bacteria inhabiting this zone differed. In Shira Lake, increased transparency of mixolimnion in winter, high chemocline position and absence of snow resulted in light intensity and biomass of purple sulphur bacteria exceeding the summer values in the chemocline of the lake. We could monitor snow cover at the lake surface using remote sensing and therefore estimate dynamics and amount of light under ice and its availability for phototrophic organisms. In Shunet Lake, the light intensities in the chemocline and biomasses of purple sulphur bacteria were always lower in winter than in summer, but the biomasses of green sulphur bacteria were similar.     

Vertical stratification of physical,chemical and biological components in two saline lakes Shira and Shunet (South Siberia,Russia)

A feature of meromictic lakes is that several physicochemical and biological gradients affect the vertical distribution of different organisms. The vertical stratification of physical, chemical and biological components in saline, fishless meromictic lakes Shira and Shunet (Siberia, Russia) is quite different mainly because both mean depth and maximum depth of lakes differ as well as their salinity levels differ. The chemocline of the Lake Shira, as in many meromictic lakes, is inhabited by bacterial community consisting of purple sulphur and heterotrophic bacteria. As the depth of the chemocline is variable, the bacterial community does not attain high densities. The mixolimnion in Lake Shira, which is thermally stratified in summer, also creates different habitat for various species. The distribution of phytoplankton is non-uniform with its biomass peak in the metalimnion. The distribution of zooplankton is also heterogeneous with rotifers and juvenile copepods inhabiting the warmer epilimnion and older copepods found in the cold but oxic hypolimnion. The amphipod Gammarus lacustris which can be assigned to the higher trophic link in the fishless lake’s ecosystem, such as Lake Shira, is also distributed non-uniformly, with its peak density generally observed in the thermocline region. The chemocline in Lake Shunet is located at the depth of 5 m, and unlike in Lake Shira, due to a sharp salinity gradient between the mixolimnion and monimolimnion, this depth is very stable. The mixolimnion in Lake Shunet is relatively shallow and the chemocline is inhabited by (1) an extremely dense bacterial community; (2) a population of Cryptomonas sp.; and (3) ciliate community comprising several species. As the mixolimnion of Lake Shunet is not thermally stratified for long period, the phytoplankton and zooplankton populations are not vertically stratified. The gammarids, however, tend to concentrate in a narrow layer located 1–2 m above the chemocline. We believe that in addition to vertical inhomogeneities of both physicochemical parameters, biological and physical factors also play a role in maintaining these inhomogeneities. We conclude that the stratified distributions of the major food web components will have several implications for ecosystem structure and dynamics. Trophic interactions as well as mass and energy flows can be significantly impacted by such heterogeneous distributions. Species spatially separated even by relatively short distances, say a few centimetres will not directly compete. Importantly, we demonstrate that not only bacteria, phytoflagellates and ciliate tend to concentrate in thin layers but also larger-sized species such Gammarus (amphipods) can also under certain environmental conditions have stratified distribution with maxima in relatively thin layer. As the vertical structure of the lake ecosystem is rather complex in such stratified lakes as ours, the strategy of research, including sampling techniques, should consider potentially variable and non-homogeneous distributions.     

The vertical distribution and abundance of <Emphasis Type="Italic">Gammarus lacustris</Emphasis> in the pelagic zone of the meromictic lakes Shira and Shunet (Khakassia,Russia)

The vertical distribution and abundance of Gammarus lacustris in the pelagic zone of two fishless meromictic lakes, L. Shira and L. Shunet, in Southern Siberia (Russia), was studied with the underwater video recording system and using vertical hauls. In both lakes, during summer stratification, Gammarus was distributed non-homogenously, with a stable peak in the metalimnion. The average depth of Gammarus population in the pelagic zone was significantly correlated with the depth of the thermocline. Gammarus abundances obtained using vertical plankton hauls with net were quite comparable with those obtained from video records. The peak abundance of Gammarus in the pelagic zone of the lakes observed with underwater video amounted up to 400 individuals m⁻², while the peak animal densities in the metalimnion reached 50 ind. m⁻³. The data are compared with previously published abundances of Gammarus in the littoral of Lake Shira. Both littoral and pelagic can be equally important habitats for amphipods in meromictic lakes. The absence of fish in the pelagic zone, high oxygen concentration, low water temperature, increased seston concentration, elevated water density in the metalimnion and the anoxic hypolimnion can be the most probable combination of factors that are responsible for the peak of Gammarus in the metalimnion of these lakes.     

The influence of macrophytes on a phytoplankton community in experimental conditions

The impact of submerged macrophytes or their extracts on planktonic algae was studied under experimental conditions. Live Ceratophyllum demersum L., its extract, and extracts of four other plant species induced modifications in the phytoplankton dominance structure. These modifications were: a decline in the number of Oscillatoria limnetica Lemm., which was the most numerous cyanobacterian species, and a decline in biomass and percentage contribution of all cyanobacteria to total algal biomass. This was accompanied by an increase in biomass and percentage contribution of green algae, especially Chlorella sp. and Chlamydomonas sp. Also, there was an increase in biomass and percentage contribution of nanoplankton (under 50 µm) to total phytoplankton biomass.The isolation of planktonic algae from direct influence of C. demersum by means of dialysis membranes caused an increase in number, biomass and percentage contribution of cyanobacteria. Release of organic compounds of over 3000 daltons by macrophytes apparently contributed to a decline of cyanobacteria by changing the phytoplankton dominance structure.     

A metabarcoding comparison of windward and leeward airborne algal diversity across the Ko‘olau mountain range on the island of O'ahu,Hawai‘i1

Airborne algae from sites on the windward (n = 3) and leeward (n = 3) sides of the Ko‘olau Mountain range of O‘ahu, Hawai‘i, were sampled for a 16 d period during January and February 2015 using passive collection devices and were characterized using Illumina MiSeq sequencing of the universal plastid amplicon marker. Amplicons were assigned to 3,023 operational taxonomic units (OTUs), which included 1,189 cyanobacteria, 1,009 heterotrophic bacteria, and 304 Eukaryota (of which 284 were algae and land plants). Analyses demonstrated substantially more OTUs at windward than leeward O‘ahu sites during the sampling period. Removal of nonalgal OTUs revealed a greater number of algal reads recovered from windward (839,853) than leeward sites (355,387), with the majority of these being cyanobacteria. The 1,234 total algal OTUs included cyanobacteria, diatoms, cryptophytes, brown algae, chlorophyte green algae, and charophyte green algae. A total of 208 algal OTUs were identified from leeward side samplers (including OTUs in common among samplers) and 1,995 algal OTUs were identified from windward samplers. Barcoding analyses of the most abundant algal OTUs indicated that very few were shared between the windward and leeward sides of the Ko‘olau Mountains, highlighting the localized scale at which these airborne algae communities differ. Back trajectories of air masses arriving on O‘ahu during the sampling period were calculated using the NOAA HY‐SPLIT model and suggested that the sampling period was composed of three large‐scale meteorological events, indicating a diversity of potential sources of airborne algae outside of the Hawaiian Islands.     

Cryptophytes of Lake Shira (Khakassia,Russia): explosive growth during breakdown of meromixis

Hydrobiologia - We conducted a monitoring study on the dynamics of the abundance, biomass, and vertical distribution of the cryptophyte population in meromictic saline Lake Shira (90.11&nbsp;E,...     

Numerical modeling of vertical stratification of Lake Shira in summer

A one-dimensional numerical model and a two-dimensional numerical model of the hydrodynamic and thermal structure of Lake Shira during summer have been developed, with several original physical and numerical features. These models are well suited to simulate the formation and dynamics of vertical stratification and provide a basis for an ecological water-quality model of the lake. They allow for the quantification of the vertical mixing processes that govern not only the thermal structure but also the nutrient exchange, and more generally, the exchange of dissolved and particulate matter between different parts of the lake. The outcome of the calculations has been compared with the field data on vertical temperature and salinity distributions in Lake Shira. Lake Shira is meromictic and exhibits very stable annual stratification. The stratification is so stable because of the high salinity of the water. If the water in Lake Shira were fresh and other parameters (depth, volume, and meteorology) were the same, as now, the lake would be mixed in autumn. Using the newly developed models and using common meteorological parameters, we conclude that Lake Shira will remain stratified in autumn as long as the average salinity is higher than 3‰.     

In situ study of relative electron transport rates in the marine macroalga <Emphasis Type="Italic">Fucus vesiculosus</Emphasis> in the Baltic Sea at different depths and times of year

The brown alga Fucus vesiculous is one of the few marine species in the Baltic Sea. Fucus vesiculosus shows high morphological and physiological variability as a response to its environmental conditions. The salinity in the Baltic Sea is 4–5 psu, compared to 35 psu in the Atlantic. Photosynthesis of algae is usually measured after collection and transportation to constant culture conditions. However, in this study, relative photosynthetic electron transport rates, calculated from chlorophyll a fluorescence parameters were compared in algae collected from 1 and 4 m depths by SCUBA divers. Measurements of light response curves from the same individuals of F. vesiculosus at different depths and times of the year have, to our knowledge, not been made previously. Measurements were performed on four different occasions during the spring of 2005 (25 February, 3 and 29 April, and 26 May) in the Baltic Sea, using rapid light curves generated with a Diving PAM. In addition, samples were collected for photoinhibition studies in the laboratory. The light response curves obtained in situ at 1 and 4 m depths for F. vesiculosus showed lower values of light saturation with depth. When algae from 1 and 4 m depths were exposed to high irradiances of photosynthetically active radiation (1,400 μmol photons m⁻² s⁻¹), algae from 1 m depth showed a higher degree of photoinhibition in comparison to algae from 4 m depth.     

Experimental study of the impacts of silver carp on plankton communities of eutrophic Villerest reservoir (France)

We examined the impact of five silver carp biomass levels (0, 8, 16, 20, and 32 g m⁻³) on plankton communities and water quality of Villerest eutrophic reservoir (France). We realized the experiments using outdoor mesocosms. The presence of silver carp led to changes in zooplankton and phytoplankton assemblages. High fish biomass strongly reduced cladoceran abundance (through predation). Silver carp inefficiently grazed down particles < 20 μm. More importantly, however, the suppression of herbivorous cladocerans resulted in the increase of small size algae which were relieved from grazing and benefit from high nutrient concentrations. In contrast, in mesocosms without fish, the dominance of cladocerans (mainly Daphnia) controlled small size algae and probably also larger size algae (colonial chlorophytes, cyanobacteria). Thus, the Secchi disc transparency increased markedly. Through cascade effects, the modification of grazers communities led to changes in the utilization patterns of the added nutrients by phytoplankton communities. In high fish biomass treatments, nutrients were more efficiently accumulated into particulate fractions compared with no-fish and low-fish biomass treatments that were characterized by higher dissolved nutrients concentrations. Zooplankton was an essential source of food for silver carp. The productivity of zooplankton sustained a moderate silver carp biomass (up to 16 g m⁻³). In the presence of the highest fish biomass, the productivity of zooplankton was not large enough and silver carps fed on additional phytoplankton. Although mesocosms with high fish biomass were characterized by a slight cyanobacteria development compared with other fish mesocosms, silver carp was not effective in reducing cyanobacteria dominance. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of light quality on sulfide photo-oxidation and growth in an artificial biofilm of the green sulfur bacterium Prosthecochloris aestuarii

We have succeeded in culturing an axenic biofilm of the green sulfur bacterium Prosthecochloris aestuarii strain CE 2404 in an artificial sandy sediment under visible light (400–700 nm). This simulates the conditions of deep submerged sediments. A five-week incubation period, using a 16-hour light / 8-hour dark regime, was applied in the benthic gradient chamber (BGC). The biofilm was located below the oxygen penetration depth of 1.2 mm, namely between 1.5 and 2.5 mm and the biomass peak was at 2.1 mm depth. This is much shallower compared to previously described artificial mats of P. aestuarii, which were grown in the BGC under near infrared (NIR)-rich light. High resolution time courses of photosynthesis were measured as sulfide photo-oxidation rates and studied under visible light and visible light amended with NIR to assess the effect of light quality. Sulfide photo-oxidation rates were rather low under visible light and strongly stimulated at most depths under full light conditions. However, under the latter conditions the rates decelerated after a maximum rate was reached at 8–10 min, apparently due to diffusional limitation of sulfide supply. It was concluded that the top of the mat was not limited by the photon flux density, while the biomass peak and the bottom of the biofilm were severely light limited under the culture conditions. These results support the hypothesis that a biofilm of P. aestuarii can develop in deep submerged sediments, when the oxygen penetration depth is very shallow. Nevertheless, the addition of NIR light strongly enhances the potential of P. aestuarii to grow deeper in the sediment.This revised version was published online in October 2005 with corrections to the Cover Date.     

The vertical microdistribution of cyanobacteria and green algae within desert crusts and the development of the algal crusts

Substantial amounts of algal crusts were collected from five different desert experimental sites aged 42, 34, 17, 8 and 4 years, respectively, at Shapotou (China) and analyzed at a 0.1 mm microscale of depth. It was found that the vertical distribution of cyanobacteria and microalgae in the crusts was distinctly laminated into an inorganic-layer (ca.0.00–0.02 mm, with few algae), an algae-dense-layer (ca.0.02–1.0 mm) and an algae-sparse-layer (ca.1.0–5.0 mm). It was interesting to note that in all crusts Scytonema javanicum Born et Flah (or Nostoc sp., cyanobacterium), Desmococcus olivaceus (Pers ex Ach., green alga) Laundon and Microcoleus vaginatus Gom. (cyanobacterium) dominated at the depth of 0.02–0.05, 0.05–0.1 and 0.1–1.0 mm, respectively, from the surface. Phormidium tenue Gom. (or Lyngbya cryptovaginatus Schk., cyanobacterium) and Navicula cryptocephala Kutz.(or Hantzschia amphioxys (Ehr.) Grun. and N. cryptocephala together, diatom) dominated at the depth of 1.0–3.0 and 3.5–4.0 mm, respectively, of the crusts from the 42 and 34 year old sites. It was apparent that in more developed crusts there were more green algae and the niches of Nostoc sp., Chlorella vulgaris Beij., M. vaginatus, N. cryptocephala and fungi were nearer to the surface. If lichens and mosses accounted for less than 41.5% of the crust surface, algal biovolume was bigger when the crust was older, but the opposite was true when the cryptogams other than algae covered more than 70%. In addition to detailed species composition and biovolume, analyses of soil physicochemical properties, micromorphologies and mineral components were also performed. It was found that the concentration of organic matter and nutrients, electric conductivity, silt, clay, secondary minerals were higher and there were more micro-beddings in the older crusts than the less developed ones. Possible mechanisms for the algal vertical microdistribtion at different stages and the impact of soil topography on crust development are discussed. It is concluded that biomethods (such as fine species distribution and biovolume) were more precise than mineralogical approaches in judging algal crust development and thus could be a better means to measure the potentiality of algal crusts in desert amelioration.     

Contrasting effects of the cyanobacterium Microcystis aeruginosa on the growth and physiology of two green algae,Oocystis marsonii and Scenedesmus obliquus,revealed by flow cytometry

相似文献   

The effect of chemicals released by Gammarus lacustris on the depth distribution of Arctodiaptomus salinus in laboratory conditions

The effect of treatment water containing chemicals released by Gammarus lacustris or crushed/injured Arctodiaptomus salinus induced changes in vertical distribution of Arctodiaptomus in laboratory conditions. With food concentration in the medium corresponding to the maximum of algae concentration in Shira lake, A. salinus in an experimental vessel was situated higher than in the control. Average population depth of A. salinus decreased as the inoculation density of G. lacustris increased.     

Algal biofilms on tree bark to monitor airborne pollutants

Algae are used in biomonitoring systems to detect water or soil pollution. So it is conceivable to establish a biomonitoring system for the detection of airborne pollutants (ozone and particulate matter (PM-10)) in urban habitats by algae. Autotrophic biofilms are widely present, cover nearly every exposed surface, especially tree bark and consist of a large variety of species of algae, cyanobacteria and fungi. To explore the diversity of green algae at different air pollution monitoring sites we choose trees with different structures of bark at three locations in and near Leipzig. We compared the measured levels of air pollution with the algal species and communities present. The sites differed in the quality and amount of airborne pollutants, among which we concentrated on ozone and particulate matter (PM-10). The collection sites were Leipzig-Centre, Leipzig-West and a forest area east of Leipzig (Collmberg). Autotrophic biofilms were collected, algae cultures established and taxonomic and morphological studies were carried out with light microscopy. Green algae were present on tree bark at all sites and forty-eight different algal species and cyanobacteria were isolated. Preliminary results suggested a correlation between pollutants and occurrence of some specific algal species and the specific algal assemblages at a given site. It is concluded that this could provide the basis for a biomonitoring system involving aero-terrestrial algae for the detection of airborne pollutants. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Precipitation patterns, dissolved organic matter and changes in the plankton assemblage in Lake Escondido (Patagonia, Argentina)

Global warming affects the hydrological cycle by increasing the frequency and intensity of extreme rainfall events and dry spells. These changes potentially affect the quantity and quality of dissolved organic matter (DOM) input into lakes. In this study, we investigated if changes in precipitation over a 3-year period correspond to changes in DOM and whether these changes affect light attenuation and plankton community composition. We sampled Lake Escondido, a shallow, oligotrophic Andean lake, nine times, analyzing coloured DOM and plankton community composition. During the study period, we observed that variations in the precipitation regime correlated with DOM parameters (water colour and molecular weight), and this, in turn, affected the plankton composition. Chlorophyll a concentrations of both phytoplanktonic fractions (less than and greater than 2 μm) were related to water colour and TDP. We observed in the small fraction (<2 μm) an increase in phycocyanin-rich cells during periods of high water colour. Larger phytoplanktonic cells (>2 μm) presented two biomass peaks corresponding to increases of the cyanophyte Chroococcus planctonicus and of the haptophyte Chrysochromulina parva. As precipitation decreased, the lake became more transparent, favouring C. planctonicus and mixotrophic oligotrich ciliates with endosymbiotic Chlorella. In the context of global climate change, our results highlight the potential impact of changes in precipitation patterns and, consequently, in DOM quality on the plankton community.     

The fast and slow kinetics of chlorophyll a fluorescence induction in plants, algae and cyanobacteria: a viewpoint

The light-induced/dark-reversible changes in the chlorophyll (Chl) a fluorescence of photosynthetic cells and membranes in the μs-to-several min time window (fluorescence induction, FI; or Kautsky transient) reflect quantum yield changes (quenching/de-quenching) as well as changes in the number of Chls a in photosystem II (PS II; state transitions). Both relate to excitation trapping in PS II and the ensuing photosynthetic electron transport (PSET), and to secondary PSET effects, such as ion translocation across thylakoid membranes and filling or depletion of post-PS II and post-PS I pools of metabolites. In addition, high actinic light doses may depress Chl a fluorescence irreversibly (photoinhibitory lowering; q(I)). FI has been studied quite extensively in plants an algae (less so in cyanobacteria) as it affords a low resolution panoramic view of the photosynthesis process. Total FI comprises two transients, a fast initial (OPS; for Origin, Peak, Steady state) and a second slower transient (SMT; for Steady state, Maximum, Terminal state), whose details are characteristically different in eukaryotic (plants and algae) and prokaryotic (cyanobacteria) oxygenic photosynthetic organisms. In the former, maximal fluorescence output occurs at peak P, with peak M lying much lower or being absent, in which case the PSMT phases are replaced by a monotonous PT fluorescence decay. In contrast, in phycobilisome (PBS)-containing cyanobacteria maximal fluorescence occurs at M which lies much higher than peak P. It will be argued that this difference is caused by a fluorescence lowering trend (state 1 → 2 transition) that dominates the FI pattern of plants and algae, and correspondingly by a fluorescence increasing trend (state 2 → 1 transition) that dominates the FI of PBS-containing cyanobacteria. Characteristically, however, the FI pattern of the PBS-minus cyanobacterium Acaryochloris marina resembles the FI patterns of algae and plants and not of the PBS-containing cyanobacteria.     

An assessment of the influence of recruitment from the sediment on the development of planktonic populations of cyanobacteria in a temperate mesotrophic lake

1. A number of planktonic cyanobacteria species form resting stages that survive in the sediments of lakes. The significance of this life history strategy to the ecology of new planktonic populations was investigated in Esthwaite Water, a mesotrophic lake in the English Lake District.
2. A simple trapping technique was used to quantify vertical movements of five species of buoyant gas-vacuolate cyanobacteria from close to the sediments, along a depth transect.
3. 'Recruitment' from the sediments was found to be widespread amongst the cyanobacteria species associated with the summer phytoplankton community.
4. Estimates of the vertical upward fluxes of cyanobacteria based upon trap catches could not account for observed increases in the planktonic populations suggesting that 'recruitment' was not a significant source of biomass.
5. Vertical upward movements of Anabaena solitaria were recorded prior to this species becoming established in the plankton suggesting that benthic populations might be a source of cells for initial pelagic growth of populations of this species.
6. Low numbers of vegetative filaments of Anabaena flos-aquae , Aphanizomenon flos-aquae and Oscillatoria agardhii were observed in the plankton through the winter. These small overwintering populations appeared to be the primary source of inocula for the large summer populations of these species.