Small Shallow Water Research Articles

Development of a 60-year high-resolution water body evaporation dataset in China

Evaporation from water bodies (Ew) is a critical component of the global water cycle. However, existing evaporation products that include Ew often suffer from drawbacks such as coarse resolution, short time span, and high uncertainty. This study developed a 60-year (1960–2019) high-resolution (0.05º×0.05º) evaporation dataset for small shallow water bodies in China based on the Penman model. Two key factors affecting the accuracy of the Penman model were considered: the uncertainty of the empirical wind function and changes in heat storage in the water body. Specifically, we used large-size (20 or 100 m2) pan evaporation (Epan) observations from 21 sites as a benchmark to correct the wind function of the Penman model. A data-driven model was then developed to map the spatial distribution of the wind function coefficients across China. The corrected wind function significantly improved the accuracy of Epan estimates compared to the original wind function, with the Kling-Gupta efficiency (KGE) increased by 0.05∼0.10. To model the effect of heat storage changes on evaporation, an equilibrium temperature method was used. We also introduced an area-dependent scaling factor into the wind function to account for the effect of water body's size on Ew estimation. The reliability of the Ew algorithm was tested on two lakes using eddy-covariance flux observations, and simulations showed good agreement with observations. The Epan (20 m2 pan) dataset and its two components calculated from the radiative and aerodynamic terms of the Penman model can be accessed at https://osf.io/qd28m/. Users can utilize the two Epan components and the area-dependent scaling factor to estimate evaporation for water bodies of varying sizes. However, caution is needed when applying this dataset to deep water bodies, as it is designed for shallow water bodies.

Exploring surface water as a transmission medium of avian influenza viruses – systematic infection studies in mallards

ABSTRACT Mallards (Anas platyrhynchos) are an abundant anseriform migratory wild bird species worldwide and an important reservoir for the maintenance of low pathogenicity (LP) avian influenza viruses (AIV). They have also been implicated in the spread of high pathogenicity (HP) AIV after spill-over events from HPAIV-infected poultry. The spread of HPAIV within wild water bird populations may lead to viral contamination of natural habitats. The role of small shallow water bodies as a transmission medium of AIV among mallards is investigated here in three experimental settings. (i) Delayed onset but rapid progression of infection seeded by two mallards inoculated with either LP or HP AIV to each eight sentinel mallards was observed in groups with access to a small 100 L water pool. In contrast, groups with a bell drinker as the sole source of drinking water showed a rapid onset but lengthened course of infection. (ii) HPAIV infection also set off when virus was dispersed in the water pool; titres as low as 102 TCID50 L−1 (translating to 0.1 TCID50 mL−1) proved to be sufficient. (iii) Substantial loads of viral RNA (and infectivity) were also found on the surface of the birds’ breast plumage. “Unloading” of virus infectivity from contaminated plumage into water bodies may be an efficient mechanism of virus spread by infected mallards. However, transposure of HPAIV via the plumage of an uninfected mallard failed. We conclude, surface water in small shallow water bodies may play an important role as a mediator of AIV infection of aquatic wild birds.

Chara lipkinii (Charales, Charophyceae): a new dioecious Mediterranean species under risk of extinction in the wild and some implications for the taxonomy of the genus Chara

A new species, Chara lipkinii, was described based on specimens from the Mediterranean, Israel. Dioecy, 10-13 branchlets in a whorl, complete tylacanthous to isostichous displostichous axial cortex with very short solitary spine cells, hardly visible diplostephanous bistipulate short obtuse stipulodes, frequently appearing as haplostephanous, in combination with completely ecorticate branchlets without cortex initials and with 1-3, mainly two nodes with unilateral bract cells distinguish it from species of Chara described to date. Its morphological traits, which are most important in the infrageneric taxonomy described by Wood, point towards its placement in the subsection Chara, rather than its distant clustering with both Chara and Grovesia. The oospore surface of C. lipkinii showed no features allowing identification based on oospore morphology only, but could be useful to distinguish it from some species. According to our analyses, the genetic affinity of species based on rbcL and ITS1 mostly does not support infrageneric division of the genus Chara based on morphological traits. Chara lipkinii is a freshwater and brackish water species, growing in small shallow inland water bodies and streams in the Eastern Mediterranean, i.e., in one of the most threatened water bodies of the region. The species faces a very high risk of extinction in the wild. It has disappeared from all previously discovered localities, which no longer support charophyte populations. The gradual decline and disappearance of living plants from one recently discovered locality of C. lipkinii were observed as a result of heavy sediment accumulation and eutrophication. Urgent action to restore the habitat needs to be taken.

AN INTERNAL WAVE GENERATION METHOD FOR THE NON-HYDROSTATIC MODEL SWASH

Numerical wave propagation models are commonly used as engineering tools for the study of wave transformation in coastal areas. In order to simulate waves in the nearshore zone correctly, the generation and absorption of waves at the boundaries of the models need to be modelled accurately. In numerical models, incident waves are usually generated by prescribing their horizontal velocity component at the boundary of the computational domain over the vertical direction. Additionally, in order to absorb and to prevent re-reflections in front of the numerical wave generator, a weakly reflective wave generation boundary condition is applied in which the total velocity signal is a superposition of the incident velocity signal and a velocity signal of the reflected waves. However, this method is based on the assumption that the reflected waves are small amplitude shallow water waves propagating perpendicular to the boundary of the computational domain and hence this method is weakly reflective for directional and dispersive waves. Within the present study, an internal wave generation method combined with sponge layers is applied in the non-hydrostatic model SWASH, in order to more accurately generate waves and avoid re-reflections at the boundaries.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/5M3aU03XJvI

The ecological preferences of Eurytemora affinis (Poppe, 1880) in the water bodies of Kazakhstan (Central Asia) and some notes about Eurytemora caspica Sukhikh & Alekseev, 2013

Abstract The purpose of this work is to analyse the influence of external factors on quantitative variables of Eurytemora affinis in water bodies of Kazakhstan. In 1997-2018, more than 150 water bodies located in various regions of the country were surveyed. The results obtained and analysis of the published literature showed that E. affinis primarily inhabits small shallow water bodies of Central and Eastern Kazakhstan. Populations from the North-Eastern Caspian Sea, originally identified as “Eurytemora affinis”, could be attributed to the recently described species Eurytemora caspica. In the water bodies examined, E. affinis was found at water temperatures from 12 to 25°C and at salinities from 0.2 to 7.1 g/dm3. The highest abundance of Eurytemora was recorded at 21-22°C and a salinity of 1.0-3.0 g/dm3. The optimum temperature range in the water bodies examined in an extreme continental climate is higher than the values given for E. affinis in water bodies in a moderately temperate climate. The optimal TDS [Total Dissolved Solids] value (1.0-3.0 g/dm3) has shifted towards more truly fresh waters than was stated for E. affinis collected from the sea (6.2-8.2), and this was confirmed in experiments (from 3.0-10.0 to 10.0-15.0). In the majority of the examined water bodies of Kazakhstan, males dominated the Eurytemora populations. Male dominance in E. affinis populations might be due to the adverse effect of elevated temperature on the lifespan of females, and it was also connected with the level of toxic pollution of the water bodies. It seems that E. affinis endures a relatively high content of heavy metals, but it does not inhabit water bodies with very high toxic pollution. The revealed features of E. affinis’ biology in Kazakhstan water bodies might be associated with both the heterogeneity of its populations from different parts of the range, and the existence of a complex of closely related species that at present is collectively named “Eurytemora affinis”.

Sloshing in Regular Polygonal Basins—Frequencies, Modes, and Tileability

Abstract The classical theory of small amplitude shallow water waves is applied to regular polygonal basins. The natural frequencies of the basins are related to the eigenvalues of the Helmholtz equation. Exact solutions are presented for triangular, square, and circular basins while pentagonal, hexagonal, and octagonal basins are solved, for the first time, by an efficient Ritz method. The first five eigenvalues of each basin are tabulated and the corresponding mode shapes are discussed. Tileability conditions are presented. Some modes (eigenmodes) can be tiled into larger domains.

APPLICATION OF RAMAN SPECTROSCOPY IN COMPARISON BETWEEN CRYPTIC MICROBIALITES OF RECENT MARINE CAVES AND TRIASSIC PATCH REEFS

ABSTRACTMicrobialites are common carbonate structures in cryptic niches of marine environments throughout geological time. In this research we compare the microbialites of small bioconstructions (biostalactites) of modern submarine caves of Sicily with those developed in small crypts of Carnian patch reefs of the Dolomite Mountains (Heiligkreuz Formation, Alpe di Specie) using Raman spectroscopy, a method that allows in situ determination of the organic content of microbial components. This methodology partly solves the uncertainty of geomicrobiological studies that use bulk measurements (i.e., biomarker analyses), which make it difficult to associate mineral precipitates with a specific microbial process. In the modern marine caves, the complex biotic relationships among skeletal organisms (mainly serpulids) and microbial communities produced biostalactites in which microbially induced biomineralization is the consequence of autotrophic and chemoheterotrophic bacterial activities. Sulfate-reducing bacteria, fed by metazoan organic matter, flourish in millimetric oxygen-depleted cavities of the skeletal framework, and induce autochthonous micrite deposition and early stabilization of the biostalactites. Similar processes have been interpreted to induce the deposition of the microbialites in the Upper Triassic patch reefs of the Dolomites. These small shallow water reefs, made up mainly of scleractinian corals, sponges and red algae, hold a skeletal framework rich in millimeter- to centimeter-size cavities, ideal cryptic niches for growth of microbial communities. Specific sulfate-reducing bacteria biomarkers are first identified using bulk measurements obtained by solvent extraction. The subsequent in situ characterization of organic compounds through micro-Raman spectroscopy indicates the same biogeochemical signatures of the microbialites within the cryptic cavities of the biostalactites of modern marine caves as those inside the skeletal framework of Carnian patch reefs. These data, showing the same processes in Triassic and modern cryptic microenvironments, is evidence that the microbially mediated precipitation in confined environments is a process independent of geological time that further investigation may be able to test.

Sulfidic Anion Concentrations on Early Earth for Surficial Origins-of-Life Chemistry

A key challenge in origin-of-life studies is understanding the environmental conditions on early Earth under which abiogenesis occurred. While some constraints do exist (e.g., zircon evidence for surface liquid water), relatively few constraints exist on the abundances of trace chemical species, which are relevant to assessing the plausibility and guiding the development of postulated prebiotic chemical pathways which depend on these species. In this work, we combine literature photochemistry models with simple equilibrium chemistry calculations to place constraints on the plausible range of concentrations of sulfidic anions (HS−, HSO3−, SO32−) available in surficial aquatic reservoirs on early Earth due to outgassing of SO2 and H2S and their dissolution into small shallow surface water reservoirs like lakes. We find that this mechanism could have supplied prebiotically relevant levels of SO2-derived anions, but not H2S-derived anions. Radiative transfer modeling suggests UV light would have remained abundant on the planet surface for all but the largest volcanic explosions. We apply our results to the case study of the proposed prebiotic reaction network of Patel et al. (2015) and discuss the implications for improving its prebiotic plausibility. In general, epochs of moderately high volcanism could have been especially conducive to cyanosulfidic prebiotic chemistry. Our work can be similarly applied to assess and improve the prebiotic plausibility of other postulated surficial prebiotic chemistries that are sensitive to sulfidic anions, and our methods adapted to study other atmospherically derived trace species.

A framework to simulate small shallow inland water bodies in semi-arid regions

In this study, a framework for simulating the flow field and heat transfer processes in small shallow inland water bodies has been developed. As the dynamics and thermal structure of these water bodies are crucial in studying the quality of stored water , and in assessing the heat fluxes from their surfaces as well, the heat transfer and temperature simulations were modeled. The proposed model is able to simulate the full 3-D water flow and heat transfer in the water body by applying complex and time varying boundary conditions. In this model, the continuity, momentum and temperature equations together with the turbulence equations, which comprise the buoyancy effect, have been solved. This model is built on the Reynolds Averaged Navier Stokes (RANS) equations with the widely used Boussinesq approach to solve the turbulence issues of the flow field. Micrometeorological data were obtained from an Automatic Weather Station (AWS) installed on the site and combined with field bathymetric measurements for the model. In the framework developed, a simple, applicable and generalizable approach is proposed for preparing the geometry of small shallow water bodies using coarsely measured bathymetry. All parts of the framework are based on open-source tools, which is essential for developing countries.

A new tool for the assessment of severe anthropogenic eutrophication in small shallow water bodies

Unlike in deep stratified lakes, the assessment of eutrophication in shallow aquatic systems (i.e., wetlands, marshes, ponds) should be based on the interaction between water and sediment. The availability of P to primary producers is naturally higher in shallow systems, because the sediment plays an active part via adsorption, precipitation and release processes. Thus, many wetlands in protected areas are naturally eutrophic and have a high trophic status due to intrinsic features and thus, display a high concentration of total-P in the water without necessarily implying pollution or poor quality. We have provided a diagnostic tool based on the chemical equilibrium of dissolved reactive P (operationally-defined as o-P) between water and sediment that distinguish anthropogenic eutrophication from a background of natural eutrophy. When the P-binding capacity of the sediment becomes saturated, the o-P concentration increases in the water as long as both the biological uptake and the sediment adsorption are unable to cope with the rate of P-release from the sediment under a long-term P load (or severe anthropogenic eutrophication). In such conditions, we have found that the ratio of total-P/particulate-P exceeds 2.0 in the water, and have used this threshold to validate this tool in other sets of wetlands.

Opportunities for aquaculture in the ethnic Garo community of northern Bangladesh

Abstract The adoption of aquaculture in small shallow ponds, ditches and rice fields by the Garo households of northern Bangladesh has been limited. However, the results from the present study suggest that there is considerable potential for the development of small-scale aquaculture in the Garo community. The Delphi method identified a number of factors that would contribute to the development of aquaculture in the Garo community, including favourable water resources, economic profitability, suitable climatic conditions, access to inputs and the availability of labour. Survey results imply that small-scale aquaculture could bring wider benefits to the Garo community in terms of livelihood opportunities, food security, poverty alleviation, socioeconomic development and environmental sustainability. Despite potential benefits, the present study identified various social, economic, technical, environmental and institutional constraints for small shallow water aquaculture in the Garo community. We suggest that technical and financial assistance as well as institutional and organisational support are needed for the development of aquaculture in the Garo community.

Influence of Combinations of Pesticides and Fertilizers on Aquatic Productivity

We have examined the effects of environmentally realistic concentrations of widely used pesticides and fertilizers for rice paddy in Western Ghats regions of India on chlorophyll and zooplankton production using a laboratory mesocosm. Malathion (100 μg·L-1), Cypermethrin (25 μg·L-1), Nitrate-nitrogen (8 mg·L-1) and Phosphate-phosphorus (8 mg·L-1) in different combinations such as pesticide-pesticide and pesticide-fertilizer were tested in fully factorial manner for a period of 42 days. Study revealed that, chlorophyll production was supported by addition of fertilizers, while combinations of fertilizers with either one or two pesticides reduce the zooplankton density and diversity rendering chlorophyll concentration more than control groups. This could indicate the reason for eutrophication of ponds located in agro-ecosystems. Single application of combinations of pesticides (in spite of presence of fertilizers) even at low concentrations can produce severe negative effects on several taxonomic groups zooplankton living in small shallow water.

Control of invasive American bullfrog Lithobates catesbeianus in small shallow water bodies

Setting up cost-efficient control programs for alien invasive species requires the development of adequate removal methods in combination with insights in population size and dynamics. American bullfrog Lithobates catesbeianus is an alien invasive species, which is suspected to cause substantial ecological damage around the globe. However, control of bullfrog populations is difficult, as no conclusive management measures have yet been determined. We investigated how double fyke nets could contribute to bullfrog management by assessing the tadpole population size in 10 permanent small shallow water bodies. Two population size estimate methods were applied, being the catch–depletion and mark–recapture method. Catchability of bullfrog tadpoles proved to be very consistent over ponds and methods, with one catch per unit of effort (one double fyke net for 24 h) retaining on average 6 % of the tadpole population. Population density varied considerably among ponds, ranging from 950 to 120,804 larger tadpole individuals/ha. Using these insights in developing a cost-efficient eradication program for the species, we projected the number of catch efforts needed to reduce tadpole numbers to a threshold that more than likely affects final bullfrog population size. Predictions indicated that for the specified thresholds the use of eight double fyke nets at a time is most cost-efficient in high abundance populations, while using five double fyke nets seems most suitable in low abundance populations. What the exact threshold number of remaining tadpole individuals should be is uncertain, but forecasts demonstrate that only half of the budget would be needed when aiming at a drop to fewer than 100 remaining tadpoles than when a decrease to fewer than 10 remaining tadpoles is pursued. Given the fairly limited cost of bullfrog management with double fyke nets, however, it may be worthwhile to fully reduce the tadpole population.

Heterophylly of Didiplis diandra (Nutt. ex A.DC.) Wood (Lythraceae) and a Key to Some Rooted Shallow Water and Shoreline Herbs of the Mid-Atlantic Piedmont

Didiplis diandra is a small shoreline aquatic plant scattered throughout eastern North America. In the Atlantic coast states from Virginia to Georgia it has been confused with other species that grow in similar habitats. Leaves of D. diandra are heterophyllous, submersed leaves average 15.4 mm long while emersed leaves average 6.3 mm long. A taxonomic key is presented to aid in identification of small shallow water and shoreline aquatic plants including members of the genera Callitriche, Crassula, Elatine and Ludwigia.

Determination of chlorophyll content of small water bodies (kettle holes) using hyperspectral airborne data

This study presents an approach for chlorophyll content determination of small shallow water bodies (kettle holes) from hyperspectral airborne ROSIS and HyMap data (acquired on 15 May and 29 July 2008 respectively). Investigated field and airborne spectra for almost all kettle holes do not correspond to each other due to differences in ground sampling distance. Field spectra were collected from the height of 30–35cm (i.e. area of 0.01–0.015m2). Airborne pixels of ROSIS and HyMap imageries cover an area of 4m2 and 16m2 respectively and their spectra are highly influenced by algae or bottom properties of the kettle holes. Analysis of airborne spectra revealed that chlorophyll absorption near 677nm is the same for both datasets. In order to enhance absorption properties, both airborne hyperspectral datasets were normalized by the continuum removal approach. Linear regression algorithms for ROSIS and HyMap datasets were derived using normalized average chlorophyll absorption spectra for each kettle hole. Overall accuracy of biomass mapping for ROSIS data was 71%, and for HyMap 64%. Biomass mapping results showed that, depending on the type of kettle hole, algae distribution, the ‘packaging effect’ and bottom reflection lead to miscalculations of the chlorophyll content using hyperspectral airborne data.

Dynamic model of Lake Chozas (León, NW Spain)—Decrease in eco-exergy from clear to turbid phase due to introduction of exotic crayfish

We developed a dynamic model of the phosphorus cycle in Lake Chozas, a small shallow water body in León (NW Spain). The calibrated model simulated seasonal dynamics of phosphorus concentrations in major components of the lake's ecological network before and after 1997, the year when an invasive allochthonous crustacean, the Louisiana red swamp crayfish ( Procambarus clarkii), was introduced into the lake. The shift from clean to turbid phase, due to grazing by crayfish on submerged vegetation, caused a gradual decrease in eco-exergy, reflecting an increase in entropy, related to breakdown of ecosystem internal equilibria. This case study verifies the hypothesis of Marchi et al. (2010) that, after an initial relatively stable state, the allochthonous species may cause an increase in entropy indicating perturbation of the ecosystem.

Seasonal steady-state budgets of nutrients and stoichiometric calculations in an Eastern Mediterranean lagoon (Papas Lagoon-Greece)

The Papas Lagoon is an enclosed, small shallow water body in western Greece. The lagoon is naturally affected by eutrophication phenomena, but occasionally during the summer season, dystrophic crises occur, related to the decomposition of large beds of macroalgae. Physicochemical data collected monthly, from June 1998 to September 1999, were compiled and coupled with historical meteorological data, in order to construct seasonal water, salt and nutrients budgets using a single box single layer LOICZ model. Nutrients and other hydrochemical parameters exhibit great spatial and temporal variations. The non-conservative dissolved inorganic phosphorus flux (ΔDIP) is always positive, thus indicating that the system acts as a net source of DIP for the adjacent coastal waters. Higher values were estimated uring summer and autumn, probably due to organic matter mineralisation and release of DIP from surficial sediments in the reduced environment. In contrast to the ΔDIP, the non-conservative balance of dissolved inorganic nitrogen (ΔDIN) is negative for most of the year, except for the summer, indicating the dominance of DIN removal processes in the Papas Lagoon. The Ulva growth and decomposition processes seem likely to be of essential importance for the evaluation of the non-conservative DIN fluxes. During the investigated period the amount of organic carbon respired and mineralized is greater than that produced by gross photosynthesis and the Papas Lagoon is a net heterotrophic system. Losses of DIN via denitrification appear to dominate over its inputs through nitrogen fixation throughout the year.

Abundance and ingestion rate of the sea hare, <i>Dolabella auricularia</i> (Lightfoot, 1786) in a shallow embayment (eastern Mactan Is., Cebu central Philippines)

The hypothesis that the sea hare, Dolabella auricularia (Gastropoda: Aplysiidae) is capable of regulating the biomass of the dominant macroalga, Cladophora sp. and thus restructure the algal assemblage in a small shallow water embayment eastern Mactan Is., central Philippines was explored. A mark and recapture technique was employed to quantify the overall population of Dolabella in the area. A feeding experiment was also conducted to determine if algal type (food preference among the green alga, Cladophora sp., the brown alga, Sargassum cristaefolium and the seagrass Cymodocea rotundata), time of day (daytime vs nighttime) and size (small vs large specimens) could significantly affect the feeding rate of D. auricularia. The estimated population of D. auricularia ranged from 4,163 – 14,288 individuals. Assuming only 2 hectares of the 15-hectare embayment are inhabited by the sea hare, the population density would ranged from 2-7 individuals/10 m. The ingestion rate by food type showed the following order of preference: Cladophora sp. > C. rotundata > S. cristaefolium. Time of day did not significantly affect overall ingestion rate of the sea hare. However, smaller individuals ( 100 g) whether it is during the day or night. The daily ration of D. auricularia for the green alga, Cladophora is about 47 g FW *Corresponding author’s email address: dydt_up@yahoo.com The Philippine Scientist, Volume 42 (2005) 68 for sea hare 100 g. Considering the population size of the Dolabella and its ingestion rate with particular preference for Cladophora, it can be deduced that the D. auricularia population should be an important structuring force in regulating the growth of Cladophora in the shallow embayment.

Diurnal temperature fluctuations in an artificial small shallow water body

For aquatic biological processes, diurnal and annual cycles of water temperature are very important to plants as well as to animals and microbes living in the water. An existing one-dimensional model has been extended to simulate the temperature profile within a small water body. A year-round outdoor experiment has been conducted to estimate the model input parameters and to verify the model. Both model simulations and measurements show a strong temperature stratification in the water during daytime. Throughout the night, however, a well-mixed layer starting at the water surface develops. Because the water body is relatively small, it appears that the sediment heat flux has a strong effect on the behaviour of the water temperature throughout the seasons. In spring, the water temperature remains relatively low due to the cold surrounding soil, while in autumn the opposite occurs due to the relatively warm soil. It appears that, in small water bodies, the total amount of incoming long wave radiation is sensitive to the sky view factor. In our experiments, the intensity of precipitation also appears to have a small effect on the stratification of the water temperature.

Non-predatory mortality indices of cladoceran zooplankton in the pelagial and littoral of a shallow meso-eutrophic lake

391 The role of topical factors, such as depth, bottom type, and the presence of water vegetation, in the functioning of plankton populations in relatively small shallow water bodies is not clear. In addition, the effect of macrophytes on plankton may be not only topical, but also metabolic (see, e.g., review [1]). The influence of macrophytes on littoral zooplankton may be studied with the use of the recently developed method of direct determination of the mortality in crustacean plankton unrelated to predation [2‐5]. The mortality due to aging, starvation, diseases, parasites, and negative physical and chemical factors is evaluated on the basis of calculation of dead individuals in samples stained with a special dye (e.g., [6]) and measurements of the sedimentation rate of dead bodies with the use of sedimentation traps. It was shown [3, 7] that the relative number of dead zooplankters is proportional to the specific mortality and, hence, is a reliable quantitative index. In this work, we measured the percentage of dead individuals in the populations of the dominant zooplankton species (Cladocera) in three biotopes of a freshwater lake—the pelagial biotope and two littoral biotopes, grown with bul rush and bare (the macrophyte-free littoral)—to determine the possible topical difference in the mortality. The work was performed in July of 2006 in the meso-eutrophic Lake Obsterno belonging to the Perebrodskaya group of lakes (northwestern Belarus). The lake area is 990 ha, the average depth is 5.3 m, and the maximum depth is 12 m. Reed and bul rush are the predominant species among littoral emergent plants. The main sediment type in the lake littoral is sand. For a detailed description of the lake morphometry, see [8, 9]. Samples of zooplankton were collected at 11 a.m. and 7 p.m. on July 25 and 26 using Apstein’s plankton net (the area of the inlet hole was 0.05 m 2 ; the mesh size was 70 µ m). In the pelagials and bul rush littorals, the net was towed from the bottom to the surface (4‐0 and 1‐ 0 m, respectively); the horizontal tow in the macrophyte-free littoral was performed over the space of 4 m; two samples were collected in each biotope (the replications and all the necessary characteristics were determined separately for each sample). The depth of sampling stations was 5.5 m in the pelagial and 1.3 m in the