Life cycle phenology, secondary production, and trophic guilds of caddisfly species in a lake-outlet stream of Patagonia

Lake-outlets are transitional areas recognized as highly productive ecosystems in terms of density and biomass of aquatic insects. Life cycle, secondary production, trophic guilds and environmental constraints of caddisfly assemblages were investigated on a natural lake-outlet stream (Nant y Fall) in Patagonia, Argentina. We investigated the site monthly from May 2007 to April 2008 by recording environmental data and sampling caddis larvae using a Surber sampler at riffle areas (n = 36). Mastigoptila longicornuta, Smicridea annulicornis, Smicridea frequens, Brachysetodes quadrifidus and Parasericostoma ovale displayed well synchronized univoltine life cycles, while Neoatopsyche brevispina, Neopsilochorema tricarinatum, showed an asynchronous development pattern, although most of them had an extended recruitment, similar to those reported for non lake-outlet streams in the area. Annual secondary production per species varied from 8.22 (B. quadrifidus) to 3568.83 mg m⁻² y⁻¹ (P. ovale), with overall caddisfly production amounting to 4.8 g m⁻² y⁻¹. Shredder/collector-filterer ratio was 3.3/1 suggesting that the system was detrital based. Redundancy analysis indicated that seasonally dynamic variables such as discharge, benthic particulate organic matter and temperature were the main predictors of seasonal caddisfly assemblage variation. We propose that the variety of food resources and the significant spatial heterogeneity at lake-outlet streams contribute to sustain a rich caddisfly community.     

Life history, growth and production of Theodoxus fluviatilis in Lake Esrom, Denmark

A population of Theodoxus fluviatilis L in the littoral zone of Lake Esrom was investigated from November 1977 to February 1979. The population was sampled every month in the winter period and twice during the rest of the year. Biomass was estimated as ash-free dry weight (AFDW) of the organic matter both of the soft parts of the animal and the shell itself. The relation between AFDW (c) and shell length (l) was log c=2.9509×log (l)−1.7120. The population comprised more than 1 year-class, which could be separated by shell length, by a narrow band on the shells and the growth of algae on the shell. The life cycle lasted years. The oldest animals had a shell length of 7.0-7.5 mm. A few individuals who were estimated to be years had a shell length up to 8.6 mm. Population density varied between 575 and 2115 individuals m⁻² on the stony substratum. The average was 1160 individuals m⁻². Mortality was low during the summer period. In winter many animals died due to the effect of ice and stormy weather on the stony substratum. Growth of the animals was estimated from the shell length. Maximum growth was observed from May to August with no growth during the winter. Egg capsules were found on the stones all year round. New capsules were found from late May to the middle of November. Most freshly laid capsules were observed in May-June and August-September. Capsules from the late summer hatched in spring and capsules laid in the spring hatched in August-September. The average annual net production for the whole population was estimated by three methods. The Allen curve method gave 1.895 AFDW m⁻², the growth-increment method gave 1.784 mg AFDW m⁻² and the Hynes method 2.284 mg AFDW m⁻². Corresponding estimated P/B ratios were 1.29, 1.30 and 1.57. Annual net-production of the four investigated year-classes was 16 mg AFDW m⁻² year⁻¹ for 1975, 224 mg AFDW m⁻² year⁻¹ for 1976, 1.258 mg AFDW m⁻² year⁻¹ for 1977 and 287 mg AFDW m⁻² year⁻¹ for 1978. P/B ratios for the three oldest year-classes were, respectively, 0.32, 0.50 and 1.67. A comparison with other investigations on gastropod life cycles, reproduction and P/B ratios is made and differences discussed. Variations are correlated to temperature, and food quality and quantity.     

Life cycle of Agapetus fuscipes (Trichoptera, Glossosomatidae) in a first-order upland stream in central Germany

The number of immature stages and the seasonal patterns of development are basic life history features of a stream dwelling species and knowledge about these important components are essential for understanding its adaptations to its dynamic environment. The life cycle of Agapetus fuscipes (Trichoptera, Glossosomatidae), one of the dominant scrapers in the upper and middle reaches of the Breitenbach, a first-order upland stream in central Germany, was analysed. The pronotum length and the relationship between pronotum length, larval biomass and case length showed seven distinct larval instars, contrary to earlier findings from the Breitenbach. In addition to a few trichopteran species from other functional feeding groups, A. fuscipes is the only scraping caddis fly reported to have more than five larval instars. The moult increments of pronotum length and larval biomass were distinctly lower than in glossosomatid species with five larval instars. A. fuscipes is clearly univoltine in the Breitenbach. First-instar larvae were found from July to the beginning of December, and second-instar larvae from July to January. At the beginning of December the population consisted of the instars I to V, and development did not cease during winter. The sixth-instar larvae occurred mostly in January, and the seventh-instar larvae were never present before January. The prepupae and pupae occurred in April. The last pupae were found at the beginning of September, although most of the emergence took place in June and July. At least five different immature stages with different ecological demands were present at any time throughout the year. The ecological advantage having two additional larval instars compared to other glossosomatid species may be to compensate for the high rate of mouthpart wear that occurs while the larvae feed on the rough Bunter Sandstone substratum. A further advantage may be to spread the risk of high mortality under unfavourable environmental conditions.     

Long-term differences in annual litter production between alien (Sonneratia apetala) and native (Kandelia obovata) mangrove species in Futian,Shenzhen, China

Annual litter production in alien (Sonneratia apetala) and native (Kandelia obovata) mangrove forests in Shenzhen, China were compared from 1999 to 2010. S. apetala had significantly higher litter production than K. obovata, with mean annual total litter of 18.1 t ha⁻¹ yr⁻¹ and 15.2 t ha⁻¹ yr⁻¹, respectively. The higher litter production in S. apetala forest indicates higher productivity and consequently more nutrient supply to the estuarine ecosystems but may be more invasive due to positive plant-soil feedbacks and nutrient availability to this alien species. Two peaks were recorded in S. apetala (May and October), while only one peak was observed in K. obovata, in early spring (March and April). Leaf and reproductive materials were the main contributors to litter production (>80%) in both forests. These results suggest that the ecological function of S. apetala and its invasive potential can be better understood based on a long-term litter fall analysis.     

Rotifer abundance, biomass, and secondary production after the recovery of hydrologic connectivity between a river and two marginal lakes (São Paulo, Brazil)

Rotifera density, biomass, and secondary production on two marginal lakes of Paranapanema River were compared after the recovery of hydrologic connectivity with the river (São Paulo State, Brazil). Daily samplings were performed in limnetic zone of both lakes during the rainy season immediately after lateral inflow of water and, in the dry period, six months after hydrologic connectivity recovery. In order to identify the factors that affect rotifer population dynamics, lake water level, volume, depth, temperature, transparency, dissolved oxygen, pH, alkalinity, conductivity, suspended solids, nutrients, and chlorophyll-a were determined. Variations of water physical and chemical factors that affect rotifer population were related to the lake-river degree of connection and to water level rising after drought. The water lateral inflow from the river resulted in an increase in lake water volume, depth, and transparency and a decrease in water pH, alkalinity, and suspended solids. The lake with the wider river connection, more frequent biota exchange, and larger amount of particulate and dissolved materials was richer and more diverse, while rotifer density, biomass, and productivity were lower in both periods studied. Density, biomass, and secondary production were higher in the lake with the smaller river connection and the higher physical and chemical stability. Our results show that the connectivity affects the limnological stability, associated to seasonality. Stable conditions, caused by low connectivity in dry periods, were related with high density, biomass and secondary production. Conversely, instability conditions in rainy periods were associated to elevated richness and diversity values, caused by exchange biota due to higher connectivity.     

Life history and temporal distribution of Orchestia sp. cf. cavimana (Amphipoda, Talitridae) on a lake shore in central Italy

The life history of the amphipod Orchestia sp. cf. cavimana (Heller, 1865) was studied throughout the course of a year with monthly samplings and the use of pitfall traps along the shores of Lake Albano in central Italy. The data thus obtained showed two peaks in abundance (the first in June and the second in October) and a minimum capture frequency in February. Egg-bearing females were recorded in spring and late summer, whilst recruitment occurred from spring to autumn, with maximum in June and October. The data collected also indicated the presence of a positive correlation between the abundance of talitrids and both temperature and sediment moisture. Morphological analysis enabled the identification of four different cohorts (with a lifespan of the species of approximately 12–15 months) all four of which remained distinguishable throughout the course of the year. It, moreover, enabled sex determination in individuals of 5 or more millimetres. The subsequent distribution indicated that, when significant, the sex ratio was female biased and that maximum size was greater in males. In particular, maximum sizes were recorded in spring for both males and females and were of 17.5 and 13.0 mm, respectively. Furthermore, the total body length recorded for egg-bearing females was positively correlated with the number of eggs in their brood pouch.     

Assessment of overland flow variation and blue water production in a farmed semi-arid water harvesting catchment

Upgrading agriculture in semi-arid areas and ensuring its sustainability require an optimal management of rainfall partition between blue and green waters in the farmed water harvesting catchment. The main objective of this study is to analyze the influence of heterogeneous land use on the spatial and temporal variation of rainfall partitioning and blue water production within a typical farmed catchment located in north-eastern Tunisia. The catchment has an area of 2.6 km² and comprises at its outlet a dam, which retains the runoff water in a reservoir. Overland flow and soil water balance components were monitored during two cropping seasons (2000/2001 and 2001/2002) on a network of eleven plots of 2 m² each with different land use and soil characteristics. The hydrological balances of both the catchment and reservoir have been monitored since 1994.Observed data showed a very large temporal and spatial variability of overland flow within the catchment reflecting the great importance of total rainfall as well as land use. During the 2001/2002 season the results showed a large variation of the number of observed runoff events, from 27 to 39, and of the annual overland flow depths, from 8 mm (under vineyard on calcaric cambisols) up to 43 mm (under shrubs-pasture on haplic regosols), between the plots. The annual runoff amounts were moderate; they always corresponded to less than 15% of the annual rainfall amount whatever the observation scale. It was also observed that changes in land use in years with similar rainfall could lead to significant differences in blue water flow. An attempt for predicting the overland flow by the general linear regression approach showed an r² of 31%, the predictors used are the class of soil infiltration capacity, the initial moisture saturation ratio of the soil surface layer and the total rainfall amounts.These experimental results indicate that the variation in land use in a semi-arid catchment is a main factor of variation in soil surface conditions and explain the major role played by the former on hydrological behavior of the upstream area and on rainfall partition between overland flow and infiltration. Therefore, to predict the water harvesting capacities in terms of blue water production of a farmed catchment in semi-arid areas it seems essential to consider precisely its land use and its temporal evolution related to management practices.     

Life history traits of the grass shrimp Palaemonetes antennarius (Decapoda, Palaemonidae) in the delta of the Neretva River, Croatia

The life history of the freshwater shrimp Palaemonetes antennarius (H. Milne Edwards, 1837) was investigated from April 1993 to November 2002 at 13 sites in the delta of the Neretva River, Croatia. The sex ratio (males vs. females) was in favour of females throughout the study year . The breeding period lasts from April to August with a peak of 75% of the ovigerous female in June. The maximum number of eggs carried by ovigerous females was 73, and there was a positive significant linear correlation between fecundity (number of early embryonic stage eggs per female) and female body size (carapace length) (R²=0.698, p<0.01). The breeding period was longer in limnocrenes and lakes with oligohaline-limnic water than in other habitat types because the water is more rapidly warmed in spring and cooled more slowly in autumn in these habitats. Larvae were present from June to October, with a peak reaching 19.4% of the total population in June. The shrimps follow a synchronic univoltine life cycle with a short egg-laying period and a new summer generation. Their larvae, apparently having no ecological flexibility, did not appear in any environment with high oscillations of salinity.     

武汉东湖铜锈环棱螺的种群动态及次级生产力

1999年6月至2000年5月对武汉东湖铜锈环棱螺的种群生态学进行了周年研究.铜锈环棱螺年均密度和生物量分别为92.2ind./m2和142.83g/m2,密度和生物量的高峰分别出现在6月(157ind./m2)和11月(20578g/m2);东湖铜锈环棱螺为一年一代,其一年中种群含有5个年龄组,其中1998年龄组占绝对优势.利用瞬时增长率法计算东湖铜锈环棱螺的周年生产量带壳湿重为91.56g/m2,去壳干重为5.32g/m2,P/B系数为0.64.同时研究了铜锈环棱螺的生产力动态变化,其生产量累积多数季节均有发生,且以1998年龄组占优.     

太湖流域上游西苕溪源头溪流中毛竹、石栎和山胡椒落叶分解比较

比较了毛竹、石栎和山胡椒叶片的理化属性,采用粗网叶袋法研究了三种落叶在太湖流域上游西苕溪中的分解过程,探讨了毛竹叶成为溪流优势外来能源后对溪流生态过程和底栖动物群落结构的影响.三种落叶的氮、磷含量及叶片厚度都存在显著差异,毛竹叶的氮含量(30.23 g/kg)远高于石栎(20.98 g/kg)和山胡椒(9.69 g/kg),其中毛竹叶的分解速率最快(k=0.00592 d-1),山胡椒(0.00297 d-1)和石栎叶(0.00212 d-1)较慢.三种落叶叶袋间的大型底栖无脊椎动物包括各取食功能团的多度和生物量无显著差异,而4次采样间的差异很显著.大型底栖动物的取食功能团中,撕食者的数量比例最高(40.3%),生物量比例为41.6%,是落叶分解的重要功能类群.撕食者中,利用阔叶筑巢的鳞石蛾Lepi-dostoma数量最多,占全部底栖动物的14%,是该溪流中主要的撕食者类群.因此,由于毛竹叶具有氮、磷含量较高、叶形较窄,以及两年进行一次换叶的特点,当毛竹叶替代其他阔叶秋季落叶的树种成为源头溪流优势外来能源后,可能会改变源头溪流中的氮磷含量、溪流外来能源的量和滞留时间以及底栖动物群落结构.     

Abundance distribution and seasonal variations of Calanus sinicus (Copepoda: Calanoida) in the northwest continental shelf of South China Sea

The effect of monsoon, coastal current and temperature on the distribution and seasonal variations of Calanus sinicus abundance were studied. The samples from the northwest continental shelf of South China Sea were collected with 505 μm planktonic nets from July 2006 to October 2007. The abundance of C. sinicus made up 34.28% and 12.34% of all copepods in spring and summer, respectively. The distribution of C. sinicus varied seasonally and regionally. The distribution of C. sinicus ranged between east inshore and offshore waters from the Leizhou Peninsula to Hainan Island, with a mean of 23.00 (±77.78) ind. m⁻³ in spring. In summer it had a mean of 13.74 (±45.10) ind. m⁻³ occurring only in the east inshore waters from Leizhou Peninsula to Hainan Island. C. sinicus was not abundant during autumn and winter seasons. The surveyed area was divided into three sub-regions based on topographical analysis and water mass, region I (included the east inshore waters of Leizhou Peninsula), region II (included the east inshore waters of Hainan Island) and region III (included the offshore waters from Leizhou Peninsula to Hainan Island). The average abundance of C. sinicus within region I was determined to be 115.63 (±145.93) and 68.12 (±84.00) ind. m⁻³ in spring and summer, respectively, values higher than those of regions II and III. Our findings suggested that C. sinicus was transported from the East China Sea to the northwest continental shelf of South China Sea by the Guangdong Coastal Current, which was driven by the northeast monsoon in spring. The presence of a cold eddy, in addition to coastal upwelling driven by the southwest monsoon, provided suitable survival conditions for C. sinicus in summer. This species disappeared in autumn due to high temperatures (>27 °C) and did not begin to enter into the northwest continental shelf of South China Sea from the East China Sea during the period of investigation in winter. The frequency of C. sinicus was low in region III during the year as a result of the South China Sea Warm Current and pelagic waters with high temperature during the spring and summer months.     

Seasonal distribution of the inorganic carbon system and net ecosystem production in the north eastern shelf of the Gulf of Cádiz (Southwest Iberian Peninsula)

There is scatter information of the inorganic carbon system in the coastal zones and it is important to increment our knowledge and understand the global carbon cycle. We investigated the distribution of inorganic carbon system parameters and its controls in the coastal waters of the north eastern shelf of the Gulf of Cádiz (GoC) during four cruises that took place in June 2006, November 2006, February 2007 and May 2007. The objectives of this study are: (1) to describe the spatio-temporal distribution of inorganic carbon system parameters in waters of the north eastern shelf of the GoC using four cruises, each undertaken in one of the four seasons, (2) to calculate net ecosystem production (NEP) and (3) to examine factors controlling these distributions. The distribution of inorganic carbon system parameters in the north eastern shelf of the Gulf of Cádiz showed temporal and spatial variability. River input, mixing, primary production, respiration, CO₂ air-sea exchange, and remineralization were factors that controlled such distributions. The coastal zone of the GoC is autotrophic on an annual scale at a rate of 1.0 mmol m⁻² d⁻¹. Further measurements are needed it to improve the NEP calculation and to evaluated to intra-annual variability.     

Distribution patterns and habitat characterization of Simuliidae (Insecta: Diptera) in a low-order sandstone stream (Weidlingbach, Lower Austria)

A total of 1504 larval and 31 pupal Simuliidae were caught from March 2000 to February 2001 at the Weidlingbach, a fourth order tributary of the Danube near Vienna, Austria, using a modified box sampler (sampling area = 2116 cm²) at 12 sampling stations from source to mouth. From the six species collected, Prosimulium tomosvaryi (Enderlein) and two species of the Simulium ornatum-group (S. trifasciatum Curtis and S. ornatum Meigen) accounted for 97.5% of the total. Based on head width, instars 1–7 were collected in the S. ornatum-group and instars 2–7 in P. tomosvaryi; from two of the remaining species [Simulium (Nevermannia) cryophilum (Rubzov) and S. (N.) vernum Macquart], only pupae were sampled. The S. ornatum-group was most abundant on coarse substrates (median = 55.9 mm) exposed to high water velocity (median = 55.9 cm/s; range = 9–83 cm/s); the latter was also true for P. tomosvaryi although it favoured smaller sediment grain sizes (median = 32.4 mm). Species richness and population density increased from source to mouth. At sampling sites near the source Simuliidae were completely lacking. In headwaters only P. tomosvaryi was present, whereas the S. ornatum-group and Simulium (Simulium) argyreatum Meigen was collected exclusively near the mouth.     

Diet and feeding strategies of round goby,Neogobius melanostomus (Pallas, 1814) from the invasion front in the Danube River tributaries (Bulgaria): ontogenetic shift and seasonal variation

The round goby Neogobius melanostomus is one of the most successful Ponto-Caspian fish invaders, established in a variety of aquatic ecosystems throughout Europe and North America. Diet and feeding strategies of N. melanostomus from three recently invaded tributaries of the Lower Danube River (Bulgaria) were investigated. Research design is based on monthly examination of the round goby diet and macroinvertebrate density. The results show that the round goby consume a wide range of different organisms – 76 taxa in total (identified to family, genus or species level). The most common prey taxa in all three rivers were Chironomidae (Orthocladius/Cricotopus spp., Tanytarsini g. sp.), Trichoptera larvae (Psychomyiidae g. sp., Hydropsyche spp.) and Ephemeroptera nymphs (Baetis spp.). Only in one of the rivers, a predominant feeding on crustaceans (Gammarus spp.) was observed. The taxonomical composition of consumed invertebrates suggests that the round goby prefers the ecological group of “sprawling/walking” insect larvae associated to coarse substratum. Feeding activity was observed throughout the whole year, even during low-temperature months. Three seasonal and four size-depended shifts in the species’ diet were determined. Generalization feeding tactics predominated in all three rivers. Specialization was rare and specific for each tributary, where a few individuals consumed invertebrates from fine substratum and/or submerged vegetation. Possible relationships between the spread of N. melanostomus and the recent invasion of the Asian clam (Corbicula fluminea) in the Bulgarian Danube tributaries were discussed. Generalisation and feeding plasticity contribute to the round goby’s establishment success in the Danube tributaries and might facilitate its further upstream spread.     

Autecology of Limnomysis benedeni Czerniavsky, 1882 (Crustacea: Mysida) in Lake Constance, Southwestern Germany

The Ponto-Caspian mysid Limnomysis benedeni was first recorded in Lake Constance in summer 2006, and a stable population developed at the site of discovery. Although this mysid is common in the Rhine and Danube rivers, little is known about its ecology and impact in systems of invasion. We investigated the autecology of L. benedeni in habitat-choice and food experiments. In the habitat-choice experiments, highly structured habitats, i.e., stones covered with zebra mussels (Dreissena polymorpha), macrophytes, and especially stonewort, were strongly preferred. In food experiments, L. benedeni fed mostly on food sources with a small particle size, e.g., biofilm on leaf litter, biodeposited material of zebra mussels, epilithon, and phytoplankton. We also compared the L. benedeni population data from Lake Constance with that from rivers. In Lake Constance, female L. benedeni were nearly 30% larger and carried more than three times more eggs in spring (9.4±0.6 mm and 28.4±5.7 eggs) than in summer (6.7±0.8 mm and 8.7±2.9 eggs). The mysids present in spring might be the generation that over-wintered; in summer, this generation was probably replaced by a new generation of smaller individuals. The large brood size and the detritivorous feeding strategy might allow L. benedeni to colonize Lake Constance rapidly.     

Isolation of 12 microsatellite markers following a pyrosequencing procedure and cross-priming in two invasive cryptic species, Alexandrium catenella (group IV) and A. tamarense (group III) (Dinophyceae)

Alexandrium catenella (group IV) and Alexandrium tamarense (group III) (Dinophyceae) are two cryptic invasive phytoplankton species belonging to the A. tamarense species complex. Their worldwide spread is favored by the human activities, transportation and climate change. In order to describe their diversity in the Mediterranean Sea and understand their settlements and maintenances in this area, new microsatellite markers were developed based on Thau lagoon (France) samples of A. catenella and A. tamarense strains. In this study twelve new microsatellite markers are proposed. Five of these microsatellite markers show amplifications on A. tamarense and ten on A. catenella. Three of these 12 microsatellite markers allowed amplifications on both cryptic species. Finally, the haplotypic diversity ranged from 0.000 to 0.791 and 0.000 to 0.942 for A. catenella and A. tamarense respectively.     

Seasonal and spatial variation in lipid and triacylglycerol levels in juvenile chinook salmon (Oncorhynchus tshawytscha) from the Bridge River, British Columbia

Triacylglycerols (TAGs) are the primary form of energy storage in fish, but little work has been done on the dynamics of TAG storage and use in relation to environmental conditions. We sampled age-0 chinook salmon (Oncorhynchus tshawytscha) in two reaches of a regulated river in British Columbia, Canada that had different discharge regimes. During the summer, fish from the reach with high freshet flows grew more slowly and had lower TAG levels than those from the reach with lower and more stable flows. In addition, smaller individuals had lower TAG levels than larger ones. We suggest that in the reach with higher flows fish were unable to obtain sufficient surplus energy for somatic growth and lipid storage. In the fall, when flows were lower, TAG storage increased and the proportion of total lipids that were TAGs were similar for both small and large fish. The allocation of energy to TAG stores was likely a strategy to ensure individuals had sufficient energy for overwintering. Our results suggest that individual-based variation in TAG levels may be sensitive to environmental factors and can be used as a measure of fish condition and performance, but more work is needed to fully understand lipid dynamics in seasonally and spatially variable rearing environments.     

Harmful algal blooms (HABs) in Daya Bay, China: An in situ study of primary production and environmental impacts

A month-long investigation of phytoplankton biomass and primary production (PP) was carried out during a harmful algal bloom (HAB) in Daya Bay, China, in 2003. During the bloom, the phytoplankton community was dominated by Scrippsiella trochoidea and Chattonella marina. The phytoplankton biomass (Chl a) and PP reached peak levels of 519.21 mg m⁻³ and 734.0 mgC m⁻³ h⁻¹, respectively. Micro-phytoplankton was the key contributor to Chl a and PP in a cage-culture area and in the adjacent HAB-affected waters, with percentages of up to 82.91% and 84.94%, respectively. The HAB had complicated relationships with hydrological and meteorological factors in Daya Bay. However, the water around the cage-culture area always showed statistically greater phytoplankton biomass and nutrient loadings than in adjacent waters, suggesting that this was the “trigger area” of the bloom. The spatial and temporal distribution of diverse HABs in Daya Bay, their ecological characteristics, and their environmental impacts are also discussed in this paper.     

Urban environments as habitats for rare aquatic species: The case of leeches (Euhirudinea, Clitellata) in Warsaw freshwaters

Reduced biological diversity in freshwater habitats situated in urban areas has been discussed in numerous studies. Certain municipal areas, however, can help save animal diversity of freshwater invertebrates. In the present study animals were collected or observed alive in 13 freshwater environments localized in Warsaw - the second largest city of Central Europe - in a densely populated, urban building complex close to the city, and also in suburban areas. Leech assemblages in all the environments under observation were numerically dominated by a few common species, but on the whole 19 species were collected or observed. The populations of six rare leech species inhabit both flowing and standing waters in Warsaw. Five of these species are on the Polish Red List of Species and one is strictly protected. The shallow Lake Powsinkowskie is the richest freshwater environment in the studied area in terms of species richness and rarity and also one of the richest lakes in Poland. Taxonomic diversity in the environments under study seems not to be directly related to the size of the water body or the level of degradation but rather to the habitat complexity, especially the diversity of the bottom in littoral zone. Certain freshwater habitats located inside this great urban complex still create good conditions for rare, highly specialized species.