Population dynamics of the freshwater dinoflagellate Ceratium hirundinella in the largest shallow lake of Central Europe, Lake Balaton, Hungary

SUMMARY.

• 1 Horizontal distribution, long-term (1933–82) and short-term (day-to-day) changes in abundance, vertical stratification and circadian rhythm of the freshwater dinoflagellate Ceratium hirtmdinella were studied in Lake Balaton, the largest shallow lake of Central Europe.
• 2 The lowest abundance was consistently found in those areas of the lake which had the strongest currents.
• 3 The density of C. hirundinella seemed to be, at least in those parts of the lake above the level of fertility considered oligotrophic, insensitive to changes in trophic conditions; only its relative contribution to total biomass decreased with increased enrichment.
• 4 During the day the bulk of the population stayed at a level in which the light intensity was between 126 and 440 μE m^-2 s^-1 PAR.

     

Macrozooplankton and the persistence of the deep chlorophyll maximum in a stratified lake

相似文献   

Vertical and seasonal distribution of picoplankton and functional nitrogen genes in a high‐altitude warm‐monomictic tropical lake

相似文献   

The impacts of changing nutrient load and climate on a deep,eutrophic, monomictic lake

相似文献   

A bioenergetic assessment of the influence of stocking practices on rainbow trout (Oncorhynchus mykiss) growth and consumption in a New Zealand lake

Summary

• 1 To investigate the carrying capacity and factors affecting growth of rainbow trout in Lake Rotoiti, we employed a bioenergetics model to assess the influence of stocking rates, timing of releases and prey abundance on growth and prey consumption. We hypothesised that stocking rates and prey abundance would affect growth and prey consumption by influencing per‐capita prey availability, and that the environmental conditions encountered by fish at the time of stocking would affect growth and consumption.
• 2 Prey consumption of stocked rainbow trout was calculated with the Wisconsin bioenergetics model. We calculated growth trajectories of released trout based on data from stocked trout that were released in spring and autumn from 1993 to 2009 and then re‐captured by anglers. Diet, prey energy density, body mass lost during spawning and lake temperature were measured locally.
• 3 Stocking timing had no effect on return rates to anglers or length or weight of caught fish. Although trout released in autumn were smaller than those released in spring, autumn‐released trout grew at a faster rate and had similar lengths and weights to spring cohorts after 2 years of growth in the lake. Modelled consumption parameters were negatively correlated with trout population size, suggesting that stocking rates (347–809 fish ha^?1 year^?1) caused density‐dependent effects on growth. Although common smelt (Retropinna retropinna) accounted for 85% of total prey consumption, no significant relationship was found between prey consumption by individual trout and adult smelt abundance, possibly because trout are targeting smaller smelt that our abundance estimate did not account for.
• 4 Releasing trout in autumn appears to be advantageous for growth, possibly because (i) temperature is more suitable for growth in autumn–winter than in spring–summer and (ii) prey for small trout is abundant in autumn. Mild winter conditions appear to enhance overwinter survival and growth of rainbow trout in warm‐temperate lakes compared to higher latitudes. This implies that moderately productive warm‐temperate lake ecosystems are highly suitable for trout growth in winter, but less so in summer, when lake stratification and high nutrient levels may create conditions suitable for algal blooms and hypolimnetic deoxygenation. High growth rates of trout in warm‐temperate lakes can therefore be supported by timing releases to coincide with favourable winter conditions.

     

Temperature,growth and seasonal succession of phytoplankton in Lake Baikal,Siberia

• 1 Growth rates of two dominant Lake Baikal phytoplankton, the winter diatom Aulacoseira baicalensis and the summer cyanobacterium Synechocystis limnetica, were measured in the laboratory under varied temperature and light regimes to determine the potential role of these abiotic factors in seasonal species succession in the lake.
• 2 Aulacoseira baicalensis grew best at low temperature and not at all above 8 °C. Its maximum instantaneous growth rate was 0.15 d^‐1 recorded at 2–3 °C. Cells grew faster as temperature decreased, apparently in contrast to conventional Q₁₀‐based temperature‐growth relationships.
• 3 The picoplankter Synechocystis limnetica did not grow at 2–3 or 5–6 °C, but grew at a rate of 0.24 d^‐1 at the highest incubation temperature of 17 °C. Maximum growth rate was 0.35 d^‐1 at 8 °C.
• 4 Saturation irradiances (I_k) for growth of Aulacoseira baicalensis and Synechocystis limnetica were near pre‐acclimation values of 40 µmol m^‐2 s^‐1. At temperatures conducive to growth, both phytoplankters grew at all irradiances tested, except for A. baicalensis which would not grow at values above 300 µmol m^‐2 s^‐1 at 8 °C.
• 5 We conclude that temperature is a major driving force for the seasonal succession of species in Lake Baikal. Other factors, including vertical mixing of the water column and grazing by zooplankton, may also play important roles.

     

Wind‐driven thermocline movements affect the colonisation and growth of Achnanthidium minutissimum,a ubiquitous benthic diatom in lakes

相似文献   

The limnology of Lac ďIfni (High Atlas Mountains, Morocco), an unusually productive mountain lake

• 1 Lac ?Ifni (surface area 30 ha, z_max 60 m, altitude 2300 m) lies in a catchment comprised of Precambrian igneous rocks in the High Atlas Mountains of Morocco. Previously described as a typical ohgotrophic lake, it was also reported to have a warm layer at the base of the hypolimnion which was ascribed to phreatic water supply and drainage.
• 2 Visits to the lake made in May/June and September 1990 showed strong thermal stratification but no hypolimnial warm layer. Drainage from the lake is subterranean, through a natural rubble dam, and the water level dropped by at least 7m through the summer. The flushing rate is about 0.6 year^?1.
• 3 The upper part of the metalimnion and the lower epilimnion were strongly supersaturated with oxygen in June, and there was a pH gradient from 7 to 10.5 between the hypolimnion and the epilimnion. These features were less marked in September when planktonic gross primary productivity was estimated to be about 145mgCm^?2 h^?1. In September the hypolimnion was 38% saturated with oxygen; the areal hypolimnetic oxygen deficit between June and September was 0.073mg O₂ cm^?2 day^?1. Total dissolved phosphate concentrations were 7–14 μgl^?1.
• 4 The open water faunal assemblage consisted of Brachionus calyciflorus and Filinia lotigiseta (Rotifera), Cyclops abyssorum (Copepoda), and stunted Salmo trutta (Pisces). Trout diets were comprised principally of adult copepods and copepodites, which showed diurnal vertical migration, and of algal material apparently scraped from rock surfaces. The dry biomass density of Cyclops was at least 2gm^?2 in June and at least 4.1 gm ^?2 in September.
• 5 Tubifex tubifex (Oligochaeta) dominated the benthos below depths of 40m. Mean dry biomass density was 2.8gm^?2, but ranged from 0.6–8.1 gm^?2 between samples. About 50% of the lake bottom is below 40m depth.
• 6 The persistent oxygen supersaruration of the euphoric zone, the field estimate of primary productivity, the hypolimnetic oxygen deficit, the biomass of zooplankton and the benthic biomass together indicate that Lac ?Ifni is an unusually productive mountain lake. This high level of productivity may be sustained by nutrient addition through contamination by dust originating outside the catchment, aided by efficient nutrient recycling in the euphoric zone.

     

Vertical distribution and diel migration of flagellated phytoplankton in a small humic lake

The vertical distributions and migrations are described of the most abundant flagellated phytoplankton species from the summer community of a small forest lake in southern Finland. The lake showed a steep and stable thermal stratification with a shallow oxygenated epilimnion. Horizontal variation of phytoplankton distribution within the lake was tested on two scales and found to be statistically significant only in the case of Mallomonas reginae. The vertical distribution of flagellated phytoplankton was assessed by reference to the distribution of a non-motile, neutrally buoyant species Ankyra judayi. Statistically significant, active vertical positioning was demonstrated for all the flagellates examined with the exception of Spiniferomonas bourrellyi. Diel vertical migrations were apparent for all species showing active positioning and the pattern of an evening descent and a morning ascent was ubiquitous. The extent and timing of diel migrations varied between species. The most extensive migrations were by Cryptomonas marssonii which crossed a temperature gradient of 14 °C and penetrated far into the anoxic hypolimnion. Several categories of competitive advantage can be gained by species undertaking such diel vertical migrations.     

Lake Michigan's suitability for bigheaded carp: The importance of diet flexibility and subsurface habitat

相似文献   

Interannual variability of algal populations and their influence on lake metabolism

• 1 An input-output phosphorus budget is given for Windermere and its two basins based on data available for the late 1980s. The annual areal total phosphorus loading for the whole lake was 1.04 g P m^-2 yr^-1 and for the North and South Basins were 1.08 and 1.70 g P m^-2 yr^-1, respectively. For the whole lake and its South Basin the values were similar to the upper range of critical loads calculated according to the equation of Vollenweider (1976) for the transition between oligotrophy and eutrophy while that for the North Basin (1.08 g P m^-2 yr^-1) was within this range of critical loadings but towards its lower end.
• 2 Changes in the quality of summer phytoplankton are described for Windermere, particularly its South Basin, between 1978 and 1989 in relation to the utilization of nitrate-nitrogen (NO³-N) in the epilimnion, deoxygenarion of the hypolimnion and the ratio of epilimnetic volume to hypolimnetic volume, E_v/H_v The two basins of Windermere with values of E_v/H_v of 0.79 (South Basin) and 0.50 (North Basin) have contrasting conditions of summer deoxygenarion. The shallower South Basin shows marked interannual variability in the development of hypolimnetic anoxia. Years with large hypolimnetic anoxia during autumn are correlated with the production during summer of large populations of the poorly grazed blue-green alga Oscillatoria bourrellyi and exhaustion of NO₃-N in the upper layers. During years when anoxia does not develop the summer phytoplankton consists of small easily grazed algae or larger ones subject to parasitic epidemics. The deeper North Basin never becomes anoxic even though it can contain similar sized populations of O. bourrellyi to the South Basin.
• 3 A possible explanation of the between basin and, for the South Basin, between year variation of utilization of NO₃-N and level of hypolimnetic deoxygenarion is that algal quality can determine lake metabolism dependent upon lake or basin morphology. Poorly grazed large forms such as O. bourrellyi act as sinks for NO₃-N. On sedimentation such populations act as a ‘short circuit’ mechanism descending into deeper layers in sufficient quantities to cause anoxia. Other species subject to crustacean or microbial grazing are mineralized in the epilimnion with little sedimentation to the deeper waters. Subsequent recycling of nitrogen as NH₄-N takes place in the upper layers or thermocline which is more readily taken up by subsequent production. The influence of such ‘short circuit’ mechanisms is reduced in deep lakes and exacerbated in shallow ones.
• 4 The success of species such as O. bourrellyi is dependent upon a sufficient inoculum, an adequate supply of nutrients and the depth of intermittent mixing. The importance of these factors in regulating presence and timing of summer populations is illustrated and discussed.

     

Interaction effects of zooplankton and CO2 on phytoplankton communities and the deep chlorophyll maximum

相似文献   

Regional and hierarchical perspectives of thermal regimes in subarctic, Alaskan lakes

1. We examined 60 clear, stained and glacial lakes in Alaska to quantify the relative importance of climate setting, morphometry, transparency, and lake typology influences on various thermal characteristics including duration of growing season, water temperature, mixing depth (MD) and heat content. We used analysis of variance (ANOVA ) to test for differences in thermal characteristics in association with lake type and employed simple and multiple regression techniques to determine functional relationships between variables. 2. Latitude accounted for 60% of the total variance in length of growing season. Although the date of maximum heat content was consistent among lake types, stained lakes had longer growing seasons compared with clear and glacially turbid lakes. 3. Maximum water temperatures were approximately 3 °C higher in stained lakes and 3 °C lower in glacial lakes compared with clear lakes. Mean water column temperature was significantly lower in glacial lakes (5.9 °C) compared with clear lakes (7.4 °C), but there was no statistical difference between clear and stained lakes (7.2 °C) or between stained and glacial lakes. Maximum surface temperatures were positively related (r²=0.51) to colour (humic stain), but negatively related (r²=0.40) to inorganic turbidity (glacial silt). 4. Only about half of the lakes in our data set underwent summer stratification. None of the glacial lakes developed a distinct thermocline, but stained lakes had shallower MDs (mean 8 m) than clear lakes (mean 12 m). Thus, the MD to total depth ratio for glacial lakes was unity compared with mean values of 0.66 for clear lakes and 0.34 for stained lakes. Fetch explained a significant fraction (51%) of the total variance in MD. Considering all lakes, MD was inversely related to transparency (Secchi depth). In contrast, considering only stratified clear and stained lakes, MD was positively related to Secchi depth (SD), the fraction of the total variance explained was 23%. The sign of the slope was dependent on the mixture of lake types. 5. Despite significant (ANOVA ) differences in water temperatures, growing season, and MDs among the three lake types, there were no statistical differences in the summer heat budget associated with lake type. In addition, heat budgets were poorly correlated with lake area, depth and volume. In contrast, mean water column temperature was strongly and inversely related (r²=0.77) to mean depth. 6. Potential explanations for the similarity in summer heat budget among lake types and weak correlation with morphometry were attributed to different patterns in vertical heat distribution associated with lake typology (colour and turbidity) differences. 7. Multiple linear regression including climatic (latitude and altitude), morphometric, and lake typology (colour and turbidity) factors demonstrated a hierarchical (climate–morphometry–typology) regulation of growing season characteristics, water temperatures, stratification and heat retention. A regional and hierarchical framework for lake thermal characteristics adds to our understanding of potential responses to climatic change and may be important for regional management objectives for fisheries.     

Diel, episodic and seasonal changes in pH and concentrations of inorganic carbon in a productive lake

• 1 Two pH electrodes and a thermistor were used to record conditions in the surface of Esthwaite Water every 15 min over a 12-month period. Combined with approximately weekly measurements of alkalinity they allowed inorganic carbon speciation to be calculated.
• 2 Large changes in pH from 7.1 to nearly 10.3, and hence in concentrations of inorganic carbon species, were measured over a year. Carbon speciation and pH varied on a diel, episodic and seasonal basis. Diel variation of up to pH 1.8 was recorded, although typical daily variation was between 0.03 and 1.06 (5 and 95 percentiles). Daily change in concentration of inorganic carbon varied between 4 and 63 mmol m^-3 (5 and 95 percentiles).
• 3 During lake stratification, episodes of high pH, typically of 1–2 weeks' duration were interspersed with episodes of lower pH. These changes appeared to relate to the weather: e.g. low wind velocity, high pressure, low rainfall and high sunshine hours correlated with periods of high pH.
• 4 Seasonal progression of carbon depletion generally followed stratification and the development of high phytoplankton biomass. When the lake was isothermal, the phytoplankton biomass caused relatively small amounts of carbon depletion.
• 5 During autumn, winter and spring, the lake had concentrations of CO₂* (free CO₂) up to 0.12 mol m^-3 which is nearly seven times the calculated atmospheric equilibrium concentration so the lake will accordingly be losing carbon to the atmosphere. In contrast, during periods of elevated pH the concentration of CO₂* was reduced close to zero and the lake will take up atmospheric CO₂. The rates of transfer between water and the atmosphere were estimated using a chemical equilibrium model with three boundary layer thicknesses. The calculations show that over a year the lake loses CO₂ to the atmosphere with the current mean atmospheric level of 360 μmol mol^-1, at between 0.28 and 2.80 mol m^-2 yr^-1. During elevated pH, rates of CO₂-influx increased up to nearly tenfold as a result of chemical-enhancement by parallel flux of HCO^-₃. Input of CO₂* to the lake from the catchment is suggested to be the main source of the carbon lost to the atmosphere.
• 6 The turnover time for CO₂ between the air and water was calculated to be 1 year for the gross influx and 3.3 years for the net flux. These values are less than the average water residence time of 0.25 years, which indicates that over a year inflow from streams is a more important source of inorganic carbon than the atmosphere.
• 7 Influx of CO₂ from the atmosphere was calculated to be roughly equivalent to between 1 and 4% of the rates of production in the water during mid-summer indicating that this source of inorganic carbon is not a major one in this lake.
• 8 Influx of CO₂ from the hypolimnion was estimated on one occasion to be 6.9 10^-9 mol m^-2 s^-1 using transfer values based on mass eddy-diffusion. These rates are equivalent to 23% of the rate of influx of CO₂ from the atmosphere on this occasion which suggests that the hypolimnion is probably a small source of inorganic carbon to the epilimnion. The exception appears to be during windy episodes when pH is depressed. Calculations based on depth-profiles of CO₂* and HCO^-₃ suggest that the measured changes in pH can be accounted for by entrainment of hypolimnetic water into the epilimnion.
• 9 The solubility product for calcite was exceeded by up to about sixfold which, although insufficient to allow homogeneous precipitation, may have allowed heterogeneous precipitation around algal particles.

     

Primary and Bacterial Production in Two Dimictic Indiana Lakes

The relationship between primary and bacterial production in two dimictic Indiana lakes with different primary productivities was examined during the summer stratification period in 1982. Primary production rates were calculated from rates of H¹⁴CO₃⁻ incorporation by natural samples, and bacterial production was calculated from rates of [³H-methyl]thymidine incorporation by natural samples. Both vertical and seasonal distributions of bacterial production in the more productive lake (Little Crooked Lake) were strongly influenced by primary production. A lag of about 2 weeks between a burst in primary production and the subsequent response in bacterial production was observed. The vertical distribution of bacterial production in the water column of the less productive lake (Crooked Lake) was determined by the vertical distribution of primary production, but no clear relationship between seasonal maxima of primary and bacterial production in this lake was observed. High rates of bacterial production in Crooked Lake during May indicate the importance of allochthonous carbon washed in by spring rains. Bacterial production accounted for 30.6 and 31.8% of total (primary plus bacterial) production in Crooked Lake and Little Crooked Lake, respectively, from April through October. High rates of bacterial production during late September and October were observed in both lakes. Calculation of the fraction of bacterial production supported by phytoplankton excretion implies an important role for other mechanisms of supplying carbon, such as phytoplankton autolysis. Several factors affecting the calculation of bacterial production from the thymidine incorporation rates in these lakes were examined.     

Stay cool: habitat selection of a cyclopoid copepod in a north temperate oligotrophic lake

1. We studied the vertical distributions of Cyclops cf. sibiricus in Lake Toya, a north temperate oligotrophic lake. During the winter circulation period, their distribution was vertically homogeneous both day and night. During the summer stratification period, C. cf. sibiricus stayed below the thermocline. Diel vertical migration (DVM) was pronounced in advanced developmental stages, although the upper limit of the migration became deeper as the thermocline gradually descended. This seasonal change was observed throughout the 4‐year study period, implying that thermal structure is the primary determinant of C. cf. sibiricus distribution. 2. In a field experiment, C. cf. sibiricus incubated in the summer epilimnion, which most of the population never experience, developed faster and grew better than in their original habitat. We consider that trans‐thermocline DVM would not have evolved because of possible disadvantages such as the cost of migration offset the benefit observed in the field experiment. The rapid temperature change at the thermocline may act as a swimming‐cost estimator for the copepod. 3. Low food availability in deep water during the summer stratification period seemed to determine the lower limit of C. cf. sibiricus distribution, and the copepod minimised the risks of predation by fish via DVM. These results suggest that C. cf. sibiricus modified their distribution seasonally to obtain maximum benefit in terms of individual fitness.     

Homogenisation of water and sediment bacterial communities in a shallow lake (lake Balihe,China)

1. Planktonic and benthic bacterial communities hold central roles in the functioning of freshwater ecosystems and mediate key ecosystem services such as primary production and nutrient remineralisation. Although it is clear that such communities vary in composition both within and between lakes, the environmental factors and processes shaping the diversity and composition of freshwater bacteria are still not fully understood.
2. In order to assess seasonal and spatial variability in lake bacterial communities and identify environmental factors underpinning biogeographical patterns, we performed a large-scale sampling campaign with paired water and sediment sample collection at 18 locations during four seasons in Lake Balihe, a subtropical shallow fish-farming lake in mid-eastern China.
3. Pelagic and benthic bacterial communities were distinctly different in terms of diversity, taxonomic composition and community structure, with Actinobacteria, Bacteroidetes, Cyanobacteria and Alphaproteobacteria dominating lake water, and Acidobacteria, Bacteroidetes, Chloroflexi, Gammaproteobacteria and Deltaproteobacteria dominating sediment. Nevertheless, these two communities had stronger spatial concordance and overlap in taxa during spring and autumn seasons. Together, the main drivers of both the spatial and temporal variations in Lake Balihe bacterial communities were identified as water temperature, turbidity, nitrogen and phosphorus availability, and thermal stratification controlled by wind-mixing and activity of the dense farmed fish populations. Notably, populations affiliated with Firmicutes, known to be abundant in fish gut microbiome, were especially abundant in the summer season and locations where high fish biomass was found, suggesting a potential link between fish gut microbiome and the pelagic bacterial communities.
4. Our findings demonstrated seasonal homogenisation of pelagic and benthic bacterial communities linked to marked shifts in a set of seasonally-driven environmental variables including water temperature and nutrient availability.

     

Interannual variations in atmospheric forcing determine trajectories of hypolimnetic soluble reactive phosphorus supply in a eutrophic lake

相似文献   

Plant community structure determines primary productivity in shallow,eutrophic lakes

相似文献