Late Summer Period Research Articles

Night-active Macroheterocera species in traps with synthetic attractants in the Velyka Dobron’ Game Reserve (Ukraine, Transcarpathia)

We allocated some new types of bait traps using different volatile aromatic compounds in the Velyka Dobron’ Game Reserve (Ukraine, Transcarpathian region) where light trap surveys on Macroheterocera were already carried out since 2009. The phenylacetaldehyde-based traps were especially effective for the species of subfamilies Plusiinae and Helio-thinae, while the members of some other subfamilies (Hadeninae, Noctuinae) were more attracted by the isoamyl-alcohol-based traps. The highest attractivity was observed in case of the mixture containing isoamyl-alcohol, acetic acid and red wine. The highest num-ber of species was observed in mid-July, but the peak of individual numbers appeared in early August. Majority of species of this assemblage was formed by bivoltine species connected to herbaceous food plants. The dominant species of this late summer period was Trachea atriplicis (second brood). It was sharply replaced by the monovoltine Allophyes oxyacanthae in September. The bulk of species of this early autumnal period was formed by monovoltine species with woody-shrubby larval food plants. Biogeographical spectrum of the assemblage was dominated by widely distributed Euro-Siberian species combined with significant presence of Mediterranean and Boreo-continental faunal elements. In the ecological spectrum of the assemblage the species connected to forested habitats are well represented but together with the presence of numerous generalist species.

What can Akabane disease teach us about other arboviral diseases.

Viruses of the Simbu serogroup cause lesions to foetuses that are seen at birth and that correlate with the stage of pregnancy at which the dam first contracts the virus. The Simbu serogroup comprises arboviruses known to cause outbreaks of abnormal parturitions in domestic ruminants; these abnormalities include abortion, stillbirth, and congenitally deformed neonates. Simbu serogroup members include: Akabane virus (AKAV), Aino virus, Cache Valley virus, and Schmallenberg virus. Lately, dairy herds calf malformations have been observed in Europe, where there have been reports of clinical manifestations such as diarrhoea, fever, and reduced milk yield in adult lactating cows. The Israeli dairy cattle industry has experienced 2 major episodes of abnormal parturitions that resulted from 2 arboviral Simbu serogroup episodes, which occurred 35 years apart. A wave of apparently newly introduced AKAV was noted from the beginning of January 2012. Investigations carried out throughout the period of late Summer 2011 to early Winter 2012, associated the Israeli AKAV strain with central nervous system manifestations in lactating cows. A lack of clinical/epidemiological 'uniformity' among the AKAV infections was noted during these investigations. Here we describe and discuss the clinical and spatial distribution differences found among the 3 above-mentioned outbreaks. Comparable features in the clinical presentation, spatial distribution, and target‑animal issues relating to Akabane disease are discussed.

ENSO related SST anomalies and relation with surface heat fluxes over south Pacific and Atlantic

The role of surface heat fluxes in Southern Pacific and Atlantic Ocean SST anomalies associated with El Nino Southern Oscillation (ENSO) is studied using observation and ocean reanalysis products. A prominent dipole structure in SST anomaly is found with a positive (negative) anomaly center over south Pacific (65S–45S, 120W–70W) and negative (positive) one over south Atlantic (50S–30S, 30W–0E) during austral summer (DJF) of El Nino (LaNina). During late austral spring-early summer (OND) of El Nino (LaNina), anomalous northerly (southerly) meridional moisture transport and a positive (negative) sea level pressure anomaly induces a suppressed (enhanced) latent heat flux from the ocean surface over south Pacific. This in turn results in a shallower than normal mixed layer depth which further helps in development of the SST anomaly. Mixed layer thins further due to anomalous shortwave radiation during summer and a well developed SST anomaly evolves. The south Atlantic pole exhibits exactly opposite characteristics at the same time. The contribution from the surface heat fluxes to mixed layer temperature change is found to be dominant over the advective processes over both the basins. Net surface heat fluxes anomaly is also found to be maximum during late austral spring-early summer period, with latent heat flux having a major contribution to it. The anomalous latent heat fluxes between atmosphere and ocean surface play important role in the growth of observed summertime SST anomaly. Sea-surface height also shows similar out-of-phase signatures over the two basins and are well correlated with the ENSO related SST anomalies. It is also observed that the magnitude of ENSO related anomalies over the southern ocean are weaker in LaNina years than in El Nino years, suggesting an intensified tropics-high latitude tele-connection during warm phases of ENSO.

Inhibitory effect of polyunsaturated aldehydes (PUAs) on the growth of the toxic benthic dinoflagellate Ostreopsis cf. ovata

Diatoms have been shown to produce and release a wide range of secondary metabolites that mediate interactions between individuals of different species. Among these compounds, different types of fatty acid derived long-chained polyunsaturated aldehydes (PUAs) have been related to multiple functions such as intra- or interspecific signals and adverse effect on the reproduction of marine organisms. Several studies have reported changes on growth, cell membrane permeability, flow cytometric properties and cell morphology in phytoplankton organisms exposed to PUAs, but little information is available on the effect of these compounds on benthic microalgae. Ostreopsis cf. ovata is a toxic benthic dinoflagellate which causes massive blooms along the Mediterranean coasts typically during the late summer period. In this study the effects of three toxic PUAs known to be produced by several algae (2E,4E-decadienal, 2E,4E-octadienal and 2E,4E-heptadienal) on the growth, cytological features and cell morphology of O. cf. ovata were investigated. Our results show a clear decrease of O. cf. ovata growth with longer-chain molecules than with shorter-chain ones, confirmed also by EC50 values calculated at 48h for 2E,4E-decadienal and 2E,4E-octadienal (6.6±1.5, 17.9±2.6μmolL−1 respectively) and at 72h for 2E,4E-heptadienal (18.4±0.7μmolL−1). Moreover, morphological analysis highlighted up to 79% of abnormal forms of O. cf. ovata at the highest concentrations of 2E,4E-decadienal tested (9, 18 and 36μmolL−1), a gradual DNA degradation and an increase of lipid droplets with all tested PUAs. Further studies are needed to better clarify the interactions between diatoms and O. cf. ovata, especially on bloom-forming dynamics.

The Importance of Reedbeds and Riparian Areas for Cetti’s Warbler Cettia cetti throughout its Annual Cycle

This study describes the importance of reedbed and riparian habitats for the annual cycle of Cetti’s warbler Cettia cetti. We examined the seasonal variation in population structure and body condition using a long-term data set (11 years) from bird ringing. Because seasonal variations in the differential use of each wetland type should be influenced by food resources and shelter conditions for roosting, a short term study (1 year) was performed to assess the diet, trophic niche and health condition of Cetti’s warbler, and to examine differences in the abundance of food resources and temperature between the two habitats. Results revealed that reedbeds are very important for Cetti’s warbler, supporting large numbers of (mainly) juvenile females during the late summer and autumn periods. Fecal analysis showed that during late summer predator insects (mostly Coleoptera) were more important for Cetti’s warblers on the reedbed, while Phytophagous insects (Hemiptera) were more important for Cetti’s warblers on the riparian habitat. Stable isotope mixing models from blood and feathers samples corroborated these results and revealed the opportunistic foraging behaviour of Cetti’s warbler. The variation on the δ13C values of juvenile secondary feathers was higher for the reedbed, indicating a wider provenance for birds that move into the reedbed in late summer/early autumn. The δ13C values for the riparian area had a smaller variation suggesting that these birds were less dispersive. Overall, the higher abundance of higher trophic level food resources, and higher minimum temperatures for roosting on the reedbed, makes this habitat particularly attractive for Cetti’s warbler after the breeding season.

Quantifying rapid spatial and temporal variations of CO2 fluxes from small, lowland freshwater ponds

Small ponds comprise a substantial portion of the total area of the Earth’s inland waters. They can be powerful carbon sinks or sources, potentially significant processors of organic carbon. Our understanding of their role is constrained by the absence of information regarding their CO2 fluxes (F CO2) and how these change with wet or dry phases and across distinct pond plant communities. We monitored the F CO2 from 26 neighbouring small ponds over a 2-week drying period in late summer in 2014. The mean F CO2 on day 1 (−641 ± 1490 mg m−2 day−1) represented a net intake across the site. As ponds dried they switched to becoming CO2 sources resulting in a net site emission of CO2 by day 12 (3792 ± 2755 mg m−2 day−1) although flux rates did not vary systematically between plant communities. Significant variability in the F CO2 was observed amongst adjacent ponds on individual sampling days, resulting in marked spatial heterogeneity in CO2 processing. This large degree of temporal and spatial heterogeneity across short time periods and small distances highlights the variability in the F CO2 from temporary systems, making it hard to generalize their role in carbon cycle models.

Assessment of anthropogenic pressures on South European Atlantic bogs (NW Spain) based on hydrochemical data

This study aims to identify the main mechanisms controlling the hydrochemistry of nine Atlantic bogs. The basic hypotheses are (i) the main functional characteristics of these wetlands (e.g. minerotrophic influence) can be traced and accurately quantified by seasonal hydrochemistry monitoring and (ii) influences (oceanity, pollution) of the surrounding environment at different scales can be statistically outlined. The effect of several landscape variables on bog water chemistry was assessed by combining water analysis with the analysis of spatial data via geographical information system (GIS) tools. The results did not show any significant relationship between hydrochemistry and land use/land cover at the watershed scale, but we found a significant relationship between the Zn concentration and the distance to a nearby power station (located outside the watersheds). A similar link was also established with N–NH4 +, in this case most likely related to the farming activities. Our results allowed us to identify the period of late summer to early autumn as the most appropriate for detecting minerotrophic traits in South European Atlantic mires. The study showed that an integrated analysis of hydrochemical data with territorial variables is a useful tool for management purposes in peatlands.

Changes in Susceptibility to Heat During the Summer: A Multicountry Analysis

Few studies have examined the variation in mortality risk associated with heat during the summer. Here, we apply flexible statistical models to investigate the issue by using a large multicountry data set. We collected daily time-series data of temperature and mortality from 305 locations in 9 countries, in the period 1985–2012. We first estimated the heat-mortality relationship in each location with time-varying distributed lag non-linear models, using a bivariate spline to model the exposure-lag-response over lag 0–10. Estimates were then pooled by country through multivariate meta-analysis. Results provide strong evidence of a reduction in risk over the season. Relative risks for the 99th percentile versus the minimum mortality temperature were in the range of 1.15–2.03 in early summer. In late summer, the excess was substantially reduced or abated, with relative risks in the range of 0.97–1.41 and indications of wider comfort ranges and higher minimum mortality temperatures. The attenuation is mainly due to shorter lag periods in late summer. In conclusion, this multicountry analysis suggests a reduction of heat-related mortality risk over the summer, which can be attributed to several factors, such as true acclimatization, adaptive behaviors, or harvesting effects. These findings may have implications on public health policies and climate change health impact projections.

Use of satellite data to identify critical periods for early life survival of northern shrimp in the Gulf of Maine

AbstractThe northern shrimp Pandalus borealis is at its southern limit in the Gulf of Maine (GOM), and recruitment success is higher in years with relatively cool water temperature. However, the mechanisms for the temperature effect are not clear. We used rolling window analysis of daily satellite data to identify critical periods for early life survival of the 1998–2012 northern shrimp year‐classes and to investigate the importance of the phenology of the hatch and bloom. Survival was negatively correlated with sea surface temperature (SST) during a 6‐week period around the time of larval emergence (late winter) and during a 4‐week period in late summer when SST and stratification reached annual maxima. Survival was negatively correlated with chlorophyll‐a concentration (chl‐a) during two 5‐week periods centered approximately a month before the hatch midpoint and around the time of settlement to the benthos. A small‐magnitude winter bloom occurred around the time of the hatch in many years, but our results did not reveal a link between survival and bloom‐hatch phenology. The timing of winter and spring blooms were correlated with SST during the preceding 10 months. A survival model including SST and chl‐a during the critical periods explained 73% of the variance in survival. Summer SST increased significantly during the study period; the other critical variables showed no trend. The rolling windows approach revealed sensitive periods in early life history that may not have otherwise been hypothesized, providing a foundation for research towards a greater understanding of processes affecting recruitment.

Heterogeneity in leaf litter decomposition in a temporary Mediterranean stream during flow fragmentation

In temporary Mediterranean streams, flow fragmentation during summer droughts originates an ephemeral mosaic of terrestrial and aquatic habitat types. The heterogeneity of habitat types implies a particular ecosystem functioning in temporary streams that is still poorly understood. We assessed the initial phases of leaf litter decomposition in selected habitat types: running waters, isolated pools and moist and dry streambed sediments. We used coarse-mesh litter bags containing Populus nigra leaves to examine decomposition rates, microbial biomass, macroinvertebrate abundance and dissolved organic carbon (DOC) release rates in each habitat type over an 11-day period in late summer. We detected faster decomposition rates in aquatic (running waters and isolated pools) than in terrestrial habitats (moist and dry streambed sediments). Under aquatic conditions, decomposition was characterized by intense leaching and early microbial colonization, which swiftly started to decompose litter. Microbial colonization in isolated pools was primarily dominated by bacteria, whereas in running waters fungal biomass predominated. Under terrestrial conditions, leaves were most often affected by abiotic processes that resulted in small mass losses. We found a substantial decrease in DOC release rates in both aquatic habitats within the first days of the study, whereas DOC release rates remained relatively stable in the moist and dry sediments. This suggests that leaves play different roles as a DOC source during and after flow fragmentation. Overall, our results revealed that leaf decomposition is heterogeneous during flow fragmentation, which has implications related to DOC utilization that should be considered in future regional carbon budgets.

Variation in pre-treatment count lead time and its effect on baseline estimates of cage-level sea lice abundance.

Treatment efficacy studies typically use pre-treatment sea lice abundance as the baseline. However, the pre-treatment counting window often varies from the day of treatment to several days before treatment. We assessed the effect of lead time on baseline estimates, using historical data (2010-14) from a sea lice data management programme (Fish-iTrends). Data were aggregated at the cage level for three life stages: (i) chalimus, (ii) pre-adult and adult male and (iii) adult female. Sea lice counts were log-transformed, and mean counts by lead time relative to treatment day were computed and compared separately for each life stage, using linear mixed models. There were 1,658 observations (treatment events) from 56 sites in 5 Bay Management Areas. Our study showed that lead time had a significant effect on the estimated sea lice abundance, which was moderated by season. During the late summer and autumn periods, counting on the day of treatment gave significantly higher values than other days and would be a more appropriate baseline estimate, while during spring and early summer abundance estimates were comparable among counts within 5days of treatment. A season-based lead time window may be most appropriate when estimating baseline sea lice levels.

Correlation between extreme rainfall and insurance claims due to urban flooding – case study Fredrikstad, Norway

During the last decades an increase in extreme rainfall has led to more urban flooding. This study is based on insurance claims of damages caused by heavy rain during 2006-2012 in Fredrikstad, Norway. Data are analysed using Principal Component Analysis. The purpose has been to find characteristics of extreme rainfall and its influence on the extent of urban flooding. The number of claims seems to be peaked in the late summer period. Furthermore, the precipitation depth the week before an extreme rainfall seems to have significantly influence for the pay out from insurers, and thus the changing in runoff factor due to soil wetness is of importance. Compared to 25-year frequency rainfall with 30 min duration, relatively less intensive, but more stable and long-lasting rain seems to lead to more claims. Experiences from previous events may help to determine the level of flood risk when extreme rainfall is forecasted.

Correlation between extreme rainfall and insurance claims due to urban flooding – case study Fredrikstad, Norway

During the last decades an increase in extreme rainfall has led to more urban flooding. This study is based on insurance claims of damages caused by heavy rain during 2006-2012 in Fredrikstad, Norway. Data are analysed using Principal Component Analysis. The purpose has been to find characteristics of extreme rainfall and its influence on the extent of urban flooding. The number of claims seems to be peaked in the late summer period. Furthermore, the precipitation depth the week before an extreme rainfall seems to have significantly influence for the pay out from insurers, and thus the changing in runoff factor due to soil wetness is of importance. Compared to 25-year frequency rainfall with 30 min duration, relatively less intensive, but more stable and long-lasting rain seems to lead to more claims. Experiences from previous events may help to determine the level of flood risk when extreme rainfall is forecasted.

Rapid increase of observed DIC and pCO2 in the surface waters of the North Sea in the 2001-2011 decade ascribed to climate change superimposed by biological processes

The CO2 system in the North Sea over the 2001-2011 decade was investigated using four comprehensive basin-wide datasets covering the late summer periods of 2001, 2005, 2008 and 2011. We find that rises in surface water DIC and pCO2 exceeded concurrent rises in atmospheric pCO2, which we attribute primarily to biological activity in late summer. After accounting for this biological signal, the observed ocean acidification occurs at a rate that is consistent with concurrent atmospheric and open ocean CO2 increases over the 2001-2011 decade. Nevertheless, we do find a consistent reduction in CO2 undersaturation in the NNS and an increase in CO2 supersaturation in the SNS. We propose that the synergistic effects of increasing atmospheric pCO2 and subsequent decrease in seawater buffering capacity, together with rising sea surface temperatures in the future oceans, may reduce the strength of the North Sea as a CO2 sink. Such a reduction would diminish the efficiency of this region as a continental shelf pump with respect to uptake of CO2 by the sea. Ultimately this would constitute a positive feedback mechanism, i.e. enhancing the airborne fraction of anthropogenic CO2 and thus the net rate of increase of atmospheric pCO2 and subsequent global climate change.

Downward particle flux and carbon export in the Beaufort Sea, Arctic Ocean; the role of zooplankton

Abstract. As part of the international, multidisciplinary project Malina, downward particle fluxes were investigated by means of a drifting multi-sediment trap mooring deployed at three sites in the Canadian Beaufort Sea in late summer 2009. Mooring deployments lasted between 28 and 50 h and targeted the shelf-break and the slope along the Beaufort-Mackenzie continental margin, as well as the edge between the Mackenzie Shelf and the Amundsen Gulf. Besides analyses of C and N, the collected material was investigated for pigments, phyto- and microzooplankton, faecal pellets and swimmers. The measured fluxes were relatively low, in the range of 11–54 mg m−2 d−1 for the total mass, 1–15 mg C m−2 d−1 for organic carbon and 0.2–2.5 mg N m−2 d−1 for nitrogen. Comparison with a long-term trap data set from the same sampling area showed that the short-term measurements were at the lower end of the high variability characterizing a rather high flux regime during the study period. The sinking material consisted of aggregates and particles that were characterized by the presence of hetero- and autotrophic microzooplankters and diatoms and by the corresponding pigment signatures. Faecal pellets contribution to sinking carbon flux was important, especially at depths below 100 m, where they represented up to 25 % of the total carbon flux. The vertical distribution of different morphotypes of pellets showed a marked pattern with cylindrical faeces (produced by calanoid copepods) present mainly within the euphotic zone, whereas elliptical pellets (produced mainly by smaller copepods) were more abundant at mesopelagic depths. These features, together with the density of matter within the pellets, highlighted the role of the zooplankton community in the transformation of carbon issued from the primary production and the transition of that carbon from the productive surface zone to the Arctic Ocean's interior. Our data indicate that sinking carbon flux in this late summer period is primarily the result of a heterotrophic-driven ecosystem.

Observations and environmental implications of variability in the vertical turbulent mixing in Lake Simcoe

Abstract A field study was conducted in Lake Simcoe to examine variations in turbulent mixing rates for a 40-day period in late summer of 2011. High sampling frequency records of water currents and temperature profiles were acquired using an acoustic Doppler current profiler (ADCP) and a chain of fast-response temperature loggers respectively. The acquired data were processed to quantify the relative strengths of the stratification in relation to the velocity shear, expressed by the dimensionless gradient Richardson number ( Ri g ). We then used the calculated Ri g as a proxy to estimate vertical turbulent eddy diffusivity ( K z ) in the stratified water column of the lake. K z exhibited large spatial and temporal variability with frequent high values in the epilimnion ( K z ~ 10 − 5 –10 − 4 m 2 s − 1 ), and relatively low values in the metalimnion ( K z ~ 10 − 7 –10 − 6 m 2 s − 1 ) and the hypolimnion ( K z ~ 10 − 6 –10 − 5 m 2 s − 1 ). We correlated the K z variability with the environmental forcing through the Lake number ( L N ), which expresses the relative strengths of the stratification to the wind forcing. Analysis of the environmental implications of K z variability suggested that vertical turbulent transport of dissolved oxygen was 10% of the total oxygen depleted in the hypolimnion for the observation period. We concluded that at least some of the observed year-to-year variability of hypolimnetic oxygen depletion could be due to the variation in turbulent transport of dissolved oxygen across the thermocline.

The importance of natural habitats to Brazilian free-tailed bats in intensive agricultural landscapes in the Winter Garden region of Texas, United States

The conversion of natural lands to agriculture is a leading cause of the worldwide loss of biodiversity. In particular, cropland monocultures alter insect abundance and diversity compared to adjacent natural habitats. While agricultural lands can provide large numbers of insect pests as prey items to predators such as bats, insect pest population size vary greatly throughout growing seasons. This study assesses the importance of land use and corn earworm moth availability as spatial and temporal drivers of bat activity. We quantified spatial variation in land use patterns at fifteen sites located within the Winter Garden region in south central Texas and used bat detectors and insect pheromone traps to monitor nightly bat activity and corn earworm moth abundance across the landscape and throughout most of the year. Our temporal analyses show that bat activity was positively correlated with moth abundance, but only early in the growing season when moth abundance is at its peak. The key result from this study is a positive relationship between bat activity and natural habitat cover during late summer months, corresponding to periods of low moth abundance and a peak in bat activity. During the late summer period, bats were more active at sites containing a larger percentage of natural habitats than those containing a larger percentage of agricultural land. Our results strongly suggest that intensive agricultural practices create systems providing bats with inconsistent resource supply, but the persistence of natural habitats provides consistency in food supply though time. Taken together, these findings illustrate the importance of protecting and restoring natural habitats for the conservation for bats and the pest-suppression services they provide in agricultural ecosystems.

Differences in carbon uptake and water use between a managed and an unmanaged beech forest in central Germany

Net atmospheric carbon dioxide exchange, total evapotranspiration and net primary production of two neighbouring beech (Fagus sylvatica L.) forests in central Germany differing in site management were measured using the eddy covariance technique and biometric methods. The unmanaged site was an old-growth forest with admixtures of ash (Fraxinus excelsior L.) and sycamore (Acer pseudoplatanus L.) trees whereas the managed site was a regularly thinned, even-aged (about 130years old), pure beech stand. Average carbon fluxes measured over seven years did not differ significantly between the two forests. Evapotranspiration was slightly higher (and consequently water use efficiency lower) at the unmanaged site. The maximum rates as well as the interannual variability of both net ecosystem exchange and net primary production were considerably larger at the managed, even-aged stand. The lowest annual carbon sequestration rates were observed in years with high fruit production in beech combined with cold and dry spells during leaf development which affected the carbon balance of the managed forest more than that of the unmanaged forest. In contrast, an extraordinarily dry period in late summer 2003 caused a stronger reduction in net carbon uptake in the old-growth forest which can probably be attributed to the contribution of ash to the ecosystem fluxes. Ash has a different phenology which made it more susceptible to the late summer drought. The relative importance of tree and structural (age, size) diversity, leaf area index and regenerative growth as well as the temporal frame and extent of single weather extremes for the forest–atmosphere exchange is discussed and it is concluded that site management and forest structure needs to be included in soil–vegetation–atmosphere-transfer models as it can often override effects of land use or plant functional type.

Mixtures of clovers with plantain and chicory improve lamb production performance compared to a ryegrass–white clover sward in the late spring and early summer period

AbstractA research programme was undertaken over two consecutive years with the purpose of studying the effect of herb–clover swards on lamb production performance year‐round. The focus of this study was on two consecutive late spring and early summer periods (2011, 2012). In each year, three sward treatments were compared on grazed paddocks with 40 lambs ha−1: (i) grass–clover mixture (perennial ryegrass [Lolium perenne L.] and white clover [Trifolium repens]); (ii) plantain–clover mixture (plantain [Plantago lanceolata], white clover and red clover [Trifolium pratense]); and (iii) chicory–plantain–clover mixture (plantain, chicory [Cichorium intybus L.] and white and red clovers). Lambs were weighed at 2‐week intervals, and carcass weights and GR tissue depth measurements were obtained at slaughter. In both years, lambs on treatments (ii) and (iii) had greater (P < 0·05) final live weight, liveweight gain, carcass weight, dressing‐out percentage and GR tissue depth measurements, and lower feed conversion ratio compared to lambs on treatment (i). Lamb production was similar in treatments (ii) and (iii) (P > 0·05) in each year. Therefore, during the late spring and early summer period, herb–clover mixture swards were found to be a superior option to perennial ryegrass–white clover for finishing lambs.

Functional phytoplankton distribution in hypertrophic systems across water body size

Distribution of algae was studied in a series of water bodies ranging from 10−2 to ~109 m2 in the lowland region of the Carpathian basin in a late summer period. It has been demonstrated that lake size has pronounced impact on the morphological and chemical properties of the water bodies, and acting through these variables it shapes the distribution of the various algal groups in the water bodies of different sizes. Changes of the relative abundance of the various algal groups along the spatial scale showed four apparently distinct patterns. We found increasing relative abundance of heterocytic cyanobacteria, dinoflagellates and those taxa which have no capability of active locomotion and are characterised by high sinking rate in the large water bodies. The flagellated algae (Chlamydomonas spp., euglenophytes, Synura spp.) and the tichoplanktonic elements were characteristic for small-sized water bodies. Most of the chrysophytes and several other flagellated taxa showed hump-shaped distribution along the size scale of water bodies. The group of large colonial flagellated chlorophytes, non-heterocytic filamentous cyanobacteria and filamentous chlorophytes occasionally occurred in high relative abundance both in small and large-sized water bodies. Our findings suggest that water body size has pronounced impact on the composition of algal assemblages.