Ephemeral saline lakes on the Canadian prairies: their classification and management for emergent macrophyte growth

At two ephemeral saline lakes in Saskatchewan, changes in the physical and chemical features of water and sediments at various basin positions were monitored during a wet-dry cycle in 1978 and 1979. Water salinity fluctuated widely in response to changes in water volume and mass of solute in the water. When basins were dry, the soluble salt content of sediments 0–10 cm deep was higher than sediments 50–60 cm deep and sediments in the lake centre were more saline than at the shoreline. Upon reflooding, there was a large immediate decrease in sediment salinity at the 0–10 cm depth, such that this layer was less saline than sediments 50–60 cm deep. Sediments in the lake centre remained more saline than at the shoreline.Classification of lake salinity is necessary to assess the potential of a lake for emergent production. The large variances in ephemeral lake salinity due to water volume changes indicate that classification should be based upon the water volume-salinity cycle of these lakes rather than the salinity of any single water or sediment sample. Water management efforts to lower salinities, to improve these wetlands for emergent growth, should be aimed at reducing the salinity regime of the littoral zone. Flushing, dilution and drying and reflooding techniques are discussed as methods to decrease salinity.     

Distribution and abundance of littoral benthic fauna in Canadian prairie saline lakes

The littoral benthos of 18 lakes in Alberta and Saskatchewan ranging in salinity from 3 to 126 (g1^–1 TDS) were investigated twice, in the spring and in the summer of 1986. Multiple Ekman dredge samples were taken at water depths of about 0.5, 1.0 and 2 metres in each transect. Two to three transects were used in each lake according to its estimated limnological diversity for a total of 114 stations. A total of 76 species was present varying from 29–31 species in the three lakes of lowest salinity (means of 3.1–5.55) to only 2 species in lakes exceeding 100. Species richness decreased rapidly in salinities greater than 15.Biomass maximum mean of 10.91 g m^–2 dry weight (maximum 63.0 g m^–2) occurred in culturally eutrophic Humboldt Lake (3.1) but one third as great in other low salinity lakes. However, biomass again increased to about 4.5 gm^–2 in two lakes of 15 As the salinity increased still further biomass declined steadily until a minimum of 0.0212 g m^–2 was recorded in most saline Aroma Lake (mean 119). Summer biomass (11 lakes) was greater than spring biomass (4 lakes) because some groups such as amphipods, corixids and ostracods became more abundant in summer. Wet weight biomass averaged 15.8 of dry weight biomass.Seasonality (spring or summer), sediment texture and organic matter content, water depth, pH, salinity (TDS) and the presence of aquatic plants ( plant cover) were considered in the matrix involving species dry weight biomass at each of 117 stations. TWINSPAN classification of the samples yielded a dendrogram with 18 indicator species. Successive dichotomies divided these indicator species into four main lake groups based on salinity, i.e., Group I: 3–10 (Gammarus, Glyptotendipes I, Chironomus cf. plumosus), Group II: 10–38%. (Hyalella, Enallagma,Bezzia), Group III: 38–63 (Hygrotus salinarius, Cricotopus ornatus), Group IV: >63 (Dolichopodidae, Ephydra hians). Each of these main groups was subdivided into smaller groups of lakes based on factors such as pH, seasonality (spring or summer species dominance), organic matter and plant cover. Depth of samples played no apparent role.     

Anostraca,Cladocera and Copepoda of Spanish saline lakes

A study of 102 samples from almost all salt water bodies in Spain has allowed the preparation of a comprehensive list of anostracans, cladocerans and copepods living in such extreme environments. Among the 26 species recorded, 9 are halobionts, but 17 can exist in less saline waters. Of the halobionts, several are widely distributed throughout arid areas around the Mediterranean (Arctodiaptomus salinus, Cletocamptus retrogressus, Branchinectella media, Branchinella spinosa, Daphnia mediterranea, Moina salina); Branchinecta orientalis ( = B. cervantesi) only appears in Guadiana watershed and toward the east of Hungary, and the Alona belonging to the A. elegans complex is a Spanish endemic. In the second group are many typically freshwater species which also appear occasionally in saline waters, and colonizers of wetlands in steppes, characteristically adapted to a wide range of salinity; one of the formers, Diaphanosoma cf. mongolianum, deserves closer study. The Spanish halobiontic fauna seems to be very old judging by the existence of some isolated species, e.g. B. orientalis may be a Tertiary relic. Persistence through time could have resulted from the continuous aridity of some Iberian localities during the Pleistocene and the ecological constancy of wetlands maintained by regional groundwater discharges.     

Chinese and Mongolian saline lakes: a limnological overview

More than half of China's lakes are saline (viz. have salinities > 3 g L⁻¹). Most salt lakes are in northwestern China (Tibet, Qinghai, Sinkiang, Inner Mongolia). Most Mongolian salt lakes are in the west of that country. Tectonic movements have been of the greatest importance in lake origins, but aeolian activity and deflation have also played a role. Many salt lakes in Qinghai-Tibet lie at altitudes > 4 000 m.a.s.l.; Aiding Hu (Sinkiang) lies at −154 m.a.s.l. Again, many lakes are large in area and deep. Small, shallow lakes are also common. Dimictic thermal patterns prevail in deep lakes, polymictic patterns in shallow ones. The highest salinity recorded is 555 g L⁻¹. The salinity of Qinghai Lake, the largest Chinese salt lake, is 14 g L⁻¹, but mean lake salinity on the northern Tibetan plateau is about an order of magnitude greater. Lop Nor has a salinity of ∼ 5 g L⁻¹. Dominant ions are Na and Cl; Mg, Ca, SO₄ and HCO₃ + CO₃ are important in certain lakes. Most major ions originate by weathering and leaching from rocks. pH values are generally high (often > 9.0). There are no bird or fish species confined to salt lakes, though many are associated with lakes of low or moderate salinity. Artemia occurs widely inland and in coastal salt pans, but is the only major macroinvertebrate of highly saline lakes. In lakes of only low to moderate salinity, invertebrate communities comprise widespread halotolerant freshwater forms and halophiles, some regionally endemic. Submerged and emergent macrophytes occur in lakes of low salinity, but phytoplankton species are more halotolerant. Ctenocladus circinatus, a green alga, is known from a Tibetan salt lake with a salinity of 200 g L⁻¹. There is a dearth of basic limnological information on Chinese and Mongolian salt lakes. More work in particular is needed on a variety of geographically widespread lakes to (a) document seasonal physico-chemical events, and (b) compile comprehensive biological inventories of taxa present. Chinese salt lakes are significant sites for palaeoclimatic research, for conservation purposes, and for the resolution of several important biological questions (especially of an ecological and biogeographical sort). They also have important economic values. Unfortunately, the natural existence of many appears to be threatened by decreased inflows, largely the result of human impact on catchments.     

Climate-related differences in the dominance of submerged macrophytes in shallow lakes

It has been suggested that shallow lakes in warm climates have a higher probability of being turbid, rather than macrophyte dominated, compared with lakes in cooler climates, but little field evidence exists to evaluate this hypothesis. We analyzed data from 782 lake years in different climate zones in North America, South America, and Europe. We tested if systematic differences exist in the relationship between the abundance of submerged macrophytes and environmental factors such as lake depth and nutrient levels. In the pooled dataset the proportion of lakes with substantial submerged macrophyte coverage (> 30% of the lake area) decreased in a sigmoidal way with increasing total phosphorus (TP) concentration, falling most steeply between 0.05 and 0.2 mg L⁻¹. Substantial submerged macrophyte coverage was also rare in lakes with total nitrogen (TN) concentrations above 1–2 mg L⁻¹, except for lakes with very low TP concentrations where macrophytes remain abundant until higher TN concentrations. The deviance reduction of logistic regression models predicting macrophyte coverage from nutrients and water depth was generally low, and notably lowest in tropical and subtropical regions (Brazil, Uruguay, and Florida), suggesting that macrophyte coverage was strongly influenced by other factors. The maximum TP concentration allowing substantial submerged macrophyte coverage was clearly higher in cold regions with more frost days. This is in agreement with other studies which found a large influence of ice cover duration on shallow lakes' ecology through partial fish kills that may improve light conditions for submerged macrophytes by cascading effects on periphyton and phytoplankton. Our findings suggest that, in regions where climatic warming is projected to lead to fewer frost days, macrophyte cover will decrease unless the nutrient levels are lowered.     

Chinese saline lakes

China has many saline lakes. Most occur in the west and north-east. Four main regions can be distinguished: Qinghai-Tibet Plateau, North western, North-central and Eastern. All types of chemical composition occur, but some regionalization of types is found. The Palaeolimnology of many saline lakes in China has been investigated, and a variety of dating techniques indicate ages between the Quaternary and the Recent. Organisms studied include Artemia, Dunaliella salina and some halophilic bacteria. The important role of organisms in many processes of geochemical and geological interest is stressed. Geoecology, as a combination of geology, mineral deposition and ecology, is a subject worth greater attention.     

Distribution patterns of ostracods in iberian saline lakes. Influence of ecological factors

A limnological survey of the Iberian mesosaline and hypersaline lakes allowed study of biogeographical and ecological aspects of their ostracod populations. Eucypris aragonica Brehm & Margalef; Eucypris mareotica (Fischer) and Heterocypris barbara inermis (Gauthier) are the only species found in waters with salinities between 10 and 100. Each species tends to be restricted to one of the three large Iberian Tertiary depressions: E. aragonica in the Ebro River basin; E. mareotica in the Guadalquivir River basin (South Spain) and H. barbara inermis in the tableland of La Mancha (Central Spain). Both E. mareotica and H. barbara inermis are distributed in inland waters of regions around the Mediterranean Sea, while E. aragonica is only known from Spain. Historical factors have been traditionally used to account for the distribution of several crustacean species and recent faunas have been seen as the remnat of those inhabiting Tertiary Depressions around ancient Mediterranean Sea.Ecological factors, mainly ion composition, account for their observed distribution pattern in Spanish lakes. E. mareotica typically inhabits high chloride waters while H. barbara inermis prefers lakes with high sulphate. E. aragonica seems to be restricted to chloride waters with a high sulphate content and very irregular (or aperiodic) hydrological regimes. Presence of parthenogenetic populations and waterfowl exchange between different saline-lake areas in the Iberian Peninsula facilitate ostracod dispersion.     

Effects of retrogressive permafrost thaw slumping on sediment chemistry and submerged macrophytes in Arctic tundra lakes

1. Global warming is predicted to cause changes in permafrost cover and stability in the Arctic. Zones of high ion concentration in regions of ice‐rich permafrost are a reservoir of chemicals that can potentially be transferred to fresh waters during thawing. Consequently, input of enriched runoff from the thaw and sediment and vegetation from the landscape could alter lakes by affecting their geochemistry and biological production. 2. Three undisturbed lakes and five lakes disturbed by retrogressive permafrost thaw slumps were sampled during late summer of 2006 to assess the potential effects of thermokarst shoreline slumping on water and sediment chemistry, the underwater light regime, and benthic macrophyte biomass and community structure. 3. Undisturbed lakes had sediments rich in organic material and selected micronutrients, while disturbed lakes had sediments richer in calcium, magnesium and strontium, greater transparency of the water column, and a well‐developed submerged macrophyte community. 4. It is postulated that enriched runoff chemistry may alter nutrient availability at the sediment–water interface and also the degradation of organic material, thus affecting lake transparency and submerged macrophytes. The results suggest that retrogressive permafrost slumping can significantly affect food webs in arctic tundra lakes through an increase in macrophyte biomass and development of a more complex benthic habitat.     

Salinity tolerance of three ostracode species (Crustacea:Ostracoda) of Iberian saline lakes

Laboratory experiments and field data were used to determine salinity tolerance limits of three ostracode species (Prionocypris aragonica, Eucypris mareotica and Heterocypris barbara) from Iberian saline lakes. Salinity tolerance appeared related to ionic composition and temperature. Implications for ostracode ecology and geographical distribution are evaluated.     

An assessment of the importance of emergent and floating-leaved macrophytes to trophic status in the Loosdrecht lakes (The Netherlands)

The potential importance of the six major emergent and floating-leaved macrophyte species in recycling of sediment phosphorus in the Loosdrecht lakes was studied. Representative plant samples were collected at the time of maximum biomass, and analysed for biomass and carbon, nitrogen and phosphorus contents. Species cover was determined by aerial photography.Total cover in the seven lakes studied ranged between 2 and 26 percent. For the four main species, biomass per unit area increased with lake trophic status. Consistent differences in C, N and P contents per unit biomass were not observed. Although cover values were small, significant amounts of C, N and P were contained in the macrophytes when compared with maximum sestonic content.Potential P loads from macrophyte decay were calculated. In Lake Loosdrecht, the P load represented 15 percent of current external P inputs. The potential importance of macrophyte decay to P recycling in the other lakes is greater.Decay of macrophyte species at the end of the growing season appears to affect autumnal nutrient and chlorophyll a levels in the water column of some lakes. The re-establishment of submerged species following lake restoration may increase the importance of this pathway in the lakes.     

Biological and ecological features of saline lakes in northern Tibet,China

In May and July 2001, the biological and ecological features of 22 salt lakes in northern Tibet , China, were investigated.Their salinity ranged from 1 to 390 g l^–1. One hundred and thirty two samples were collected. Ninty five taxa of phytoplankton and 42 taxa of zooplankton were recorded. The dominant cation was sodium, with magnesium generally sub-dominant; CO₃^2– was the dominant anion in low salinity, chloride was the dominant anion with increasing salinity. Major species were Gloeothece linearis, Oscillatoria tenuis, Chroococcus minutus (blue-green algae); Navicula spp, Cymbella pusilla, Diatoma elongatum(diatoms); Dunaliella salina, Chlorella vulgarisand Ulothrix tenerrima (green algae). Major zooplankton included: Vorticella campanula, Epistylis daphniae (Protista); Keratella quadrata, Brachionus plicatilis (Rotifera); Artemiaspp. (Anostraca); Daphniopsis tibetana (Cladocera); Cletocamptus dertersiand Cyclops vicinus (Copepoda). Ten species were recorded in hypersaline waters; apart from those metioned above, they included CyclidiumsppLitonotus fasciola, Euplotes terricola, Strombilidium viride, Brachionus variabilis, Colurella adriatica, Keratella cochlearis, Colurella adriatica, and Cyclops sp. Seven taxa of benthic macroinvertebrates are recorded, represented by Cyprissp. (Ostracoda), Gammarus sp. (Amphipoda), Radixsp. and Hippeutis sp. (Mollusca); chiroonomids Tendipus group salinarius (Diptera), Nematoda, Trochophora and Ephrdra sp. At present, there are fishes only in Bangong Co., and no fishes recorded in other salt lakes. The total number of plankton species has a significantly negative correlation with the salinity, and decreased with increasing altitude, but not significant.     

Plankton community and the relationship with the environment in saline lakes of Onon-Torey plain,Northeastern Mongolia

The plankton community of sixteen saline lakes located on Onon-Torey plain (Northeastern Mongolia) during the filling phase and the raising of the water level was investigated in July 2011. Thirty-five taxa of phytoplankton and thirty-one species of zooplankton were found. For phytoplankton, blue-green algae (Merismopedia elegans, Anabaenopsis elenkinii, Arthrospora fusiformis, Spirulina major, Lyngbya sp., Oscillatoria sp.) and green algae (Monoraphidium minutum, Tetrastrum komarekii, Ankyra ocellata, Oocystis sp.) were dominant. For zooplankton, Filinia longiseta, Brachionus plicatilis, B. variabilis, Hexarthra mira (Rotifera), Daphnia magna, Moina brachiata, M. mongolica (Cladocera), Arctodiaptomus bacillifer, Mixodiaptomus incrassatus, Metadiaptomus asiaticus (Copepoda) dominated. Mineralization, active hydrogen ratio, dissolved oxygen and water temperature were the main factors influencing the diversity, structure and distribution of plankton organisms in the steppe lakes during low water level. The RDA analysis for phytoplankton and zooplankton from different lakes was carried out for selected two groups which included lakes and a subset related species. The first group is of oligohaline and mesohaline lakes in which mostly green algae, rotifers and copepods inhabit. The second group is of mesohaline and polyhaline lakes with mainly blue-green algae, some crustaceans and rotifers inhabiting. High abundance and biomass of Spirulina major, Oscillatoria sp. and Brachionus variabilis were observed in lakes with high mineralization, pH and temperature.     

Microbial decomposition of freshwater macrophytes in the littoral zone of lakes

The decomposition of several lake macrophytes was investigated under field conditions. Data on weight and phosphorus loss, numbers of microbial decomposers and their activity were obtained.Experiments were conducted in the littoral of two lakes with different levels of macrophyte development.Weight loss during 40–60 days of decomposition for fast-decomposing plants was 60–95% and after 365-day of incubation, Potamogeton perfoliatus L. lost nearly 100% of its initial weight. Slow-decomposing plants lost 20–50% of their initial weight after 40–60 days of incubation, and Phragmites australis (Cav.) Trin. ex Steud. lost 84% of its initial weight after 365 days.Total phosphorus content in plants did not decrease at the first stages of decomposition.The number of microbial decomposers utilizing both labile and resistant substrates increased 2–6 times during the first 5–25 days period. During this period the community was morphologically diverse and biochemically active (high level of microbial respiration). It coincided with the highest weight loss. After that period, the number of microorganisms utilizing labile substrates, as well as the rate of decomposition decreased.The part of macrophyte organic matter entering the biological cycle in two lakes made up 3.5% and 26% of phytoplankton primary production. Bacterial production on decomposing macrophytes was calculated at 4% and 51% of bacterioplankton production, respectively, in both lakes.     

Bird abundance and species richness on Florida lakes: influence of trophic status,lake morphology,and aquatic macrophytes

Data from 46 Florida lakes were used to examine relationships between bird abundance (numbers and biomass) and species richness, and lake trophic status, lake morphology and aquatic macrophyte abundance. Average annual bird numbers ranged from 7 to 800 birds km^–2 and bird biomass ranged from 1 to 465 kg km^–2. Total species richness ranged from 1 to 30 species per lake. Annual average bird numbers and biomass were positively correlated to lake trophic status as assessed by total phosphorus (r = 0.61), total nitrogen (r = 0.60) and chlorophyll a (r = 0.56) concentrations. Species richness was positively correlated to lake area (r = 0.86) and trophic status (r = 0.64 for total phosphorus concentrations). The percentage of the total annual phosphorus load contributed to 14 Florida lakes by bird populations was low averaging 2.4%. Bird populations using Florida lakes, therefore, do not significantly impact the trophic status of the lakes under natural situations, but lake trophic status is a major factor influencing bird abundance and species richness on lakes. Bird abundance and species richness were not significantly correlated to other lake morphology or aquatic macrophyte parameters after the effects of lake area and trophic status were accounted for using stepwise multiple regression. The lack of significant relations between annual average bird abundance and species richness and macrophyte abundance seems to be related to changes in bird species composition. Bird abundance and species richness remain relatively stable as macrophyte abundance increases, but birds that use open-water habitats (e.g., double-crested cormorant, Phalacrocorax auritus) are replaced by species that use macrophyte communities (e.g., ring-necked duck, Aythya collaris).     

Nitrogen in the Pyrenean lakes (Spain)

Lakes in the Pyrenees show a broad variability in nitrogen content and in the distribution of its different oxidation forms, which has no direct relation with any single physiographical, chemical or trophic feature of the lakes. Concentration of bound nitrogen in rain is low compared with other European mountains, but the annual load lies in the middle range. Seasonal and local variation in the composition of rainwater mainly depends on the geographical origin of the storms. Catchment and in-lake processes introduce further variability: NH₄ ⁺, which is at similar concentration to NO₃ ^- in the rain, is quickly oxidized or adsorbed in the catchment; aquatic macrophytes can either reduce mean NO₃ ^- concentration in lake water (Ranunculo-Potametum) or greatly increase it in sediment pore water (Isoetes); NO₂ ^- depends on pH; decomposition of particulate nitrogen in sediments changes with depth; lakes act as traps for dissolved inorganic nitrogen; changes in dissolved organic nitrogen suggest high microbial activities even in cold waters; melting period introduces most of the seasonal variability. Institute of High-Mountain Research, University of Barcelona     

Hyperthermal effluent Effects on heleoplanktonic Cladocera and the influence of submerged macrophytes

In July and August, 1974, measurements were made of the standing crops of Cladocera in the littoral zone of Par Pond (Savannah River Plant, Aiken, South Carolina, U.S.A.), which receives hyperthermal effluent from a nuclear reactor. Crops of Ceriodaphnia spp. and Diaphanosoma brachyurum were greater in the heated than in the ambient area, while Bosmina longirostris maintained higher standing crops in the ambient area than in the area receiving hyperthermal effluent. In August, 1974, exclosures were placed in the effluent-affected area to test the hypothesis that the high density of rooted aquatic macrophytes in the effluent-affected area influences the standing crop of these Cladocera. The effects of changes in reactor effluent temperature were also determined in the exclosure experiments. The results of the exclosure study support two generalizations: 1) the presence of dense rooted vegetation allows higher standing crops of Ceriodaphnia spp. and D. brachyurum; and 2) lower temperatures than those usually found at the heated station would favor B. longirostris standing crops, while the higher effluent temperatures favor Ceriodaphnia spp. and D. brachyurum.     

Primary production in three lakes of differing salinity in Victoria,Australia

Lakes Purrembete, Bullenmerri and Gnotuk are relatively deep lakes with salinities of 0.4, 8 and 58 respectively. From Carbon-14 experiments conducted monthly over a year annual primary production was 96.2, 182.1 and 90.1 gCm^-2. These values correlate well with chlorophyll-a in Purrumbete and Bullenmerri, but not in Gnotuk. There is considerable dark fixation in both the saline lakes.     

Viruses in the plankton of freshwater and saline Antarctic lakes

1. Virus‐like particle (VLP) abundances in nine freshwater to saline lakes in the Vestfold Hills, Eastern Antarctica (68° S) were determined in December 1999. In the ultra‐oligotrophic to oligotrophic freshwater lakes, VLP abundances ranged from 1.01 to 3.28 × 10⁶ mL^–1 in the top 6 m of the water column. In the saline lakes the range was between 6.76 and 36.5 × 10⁶ mL^–1. The lowest value was found in meromictic Ace Lake and the highest value in hypersaline Lake Williams. Virus to bacteria ratios (VBR) were lowest in the freshwater lakes and highest in the saline lakes, with a maximum of 23.4 in the former and 50.3 in the latter. 2. A range of morphologies among VLP was observed, including phages with short (Podoviridae) and long tails, icosahedric viruses of up to 300 nm and star‐like particles of about 80 nm diameter. 3. In these microbially dominated ecosystems there was no correlation between VLP and either bacterial numbers or chlorophyll a. There was a significant correlation between VLP abundances and dissolved organic carbon concentration (r=0.845, P < 0.01). 4. The data suggested that viruses probably attack a spectrum of bacteria and protozoan species. Virus‐like particle numbers in the freshwater lakes were lower than values reported for lower latitude systems. Those in the saline lakes were comparable with abundances reported from other Antarctic lakes, and were higher than most values published for lower latitude lakes and many marine systems. Across the salinity spectrum from freshwater through brackish to hypersaline, VLP concentrations increased roughly in relation to increasing trophy. 5. Given that Antarctic lakes have a plankton almost entirely made up of bacteria and protists, and that VLP abundances are high, it is likely that viruses play a pivotal role in carbon cycling in these extreme ecosystems.     

Effects of aquatic macrophytes on water quality and phytoplankton communities in shallow lakes

We investigated aquatic macrophytes, water quality, and phytoplankton biomass and species composition in three shallow lakes with different levels of vegetation cover and nutrient concentration in Kushiro Moor, during August 2000. Trapa japonica can live in a wide range of nutrient levels. This species forms an environment with a steeper extinction of light, higher concentrations of dissolved organic carbon (DOC), lower concentrations of dissolved oxygen (DO) near the bottom, and lower concentrations of nitrate+nitrite and soluble reactive phosphorus (SRP) than other vegetation types. The pH was much higher in a Polygonum amphibium community, and the DO near the bottom did not decrease compared to a T.japonica community in the summer. The relationship between chlorophyll a and the limiting nutrient (total phosphorus (TP) when total nitrogen (TN):TPis 10 and TN/10 when TN:TP is <10) significantly differed between lakes with and without submerged vegetation. The chlorophyll a concentrations at a given nutrient level were significantly lower in water with submerged macrophytes than in water without them. Correspondence analysis showed that the difference in phytoplankton community structure across sites was largely due to the presence or absence of submerged macrophytes, and the ordination of phytoplankton species in the lakes with submerged macrophytes is best explained by environmental gradients of TN, chlorophyll, pH and SRP.     

A technique for examining microspatial distribution of Cladocera associated with shallow water macrophytes

Cladocera living in close association with shallow water macrophytes were collected from specific locations on plants using a device similar to an aspirator bottle. The proposed technique did not differ significantly from plastic bag or cylindrical tube enclosure techniques in sampling Cladocera living on Chara stems. Shaking the plants followed by collection of the surrounding waters seriously underestimated the abundance of plant associated organisms.The method successfully demonstrated diel changes in the microdistribution of Chydorus brevilabris living on stems of the emergent plant Hydrolea ovata. C. brevilabris was most abundant at the bases of vertical stems at midday and appeared to move up the stems and into the water column at night.