Temporal and vertical distribution of ciliophoran communities in the benthos of a small eutrophic loch with particular reference to the redox profile

SUMMARY. The ciliate communities occurring at three benthic sites in a small eutrophic loch have heen investigated over a 2-year period. Two characteristics of the community were studied in detail, the pattern of vertical distribution within the sediment and the temporal distribution of ciliates occurring in the surface sediment. The relationships between ciliate distributions and the environmental factors recorded were analysed by multiple regression. Significant relationships were revealed between vertical distribution of ciliates and the sediment redox (Eh) profile, the larger ciliate communities being associated with regions of higher potential. Other factors such as sediment density, organic matter, temperature and daylength, combined with other indicators of benthic metabolism (sulphide ion activity (Es^2?), pH, oxygen flux) were selected in the regression analysis as accounting for much of the variation in the depth distribution of ciliates. In analysing the temporal distribution of ciliates in the surface sediment, numbers were inversely related to Eh, Es^2? and oxygen flux, a result of the upwards migration of reducing conditions and greater microbial activity in the sediment surface during the summer. Daylength, temperature, organic carbon and benthic chlorophyll-a were also selected as accounting for much of the variation in ciliate number. It is proposed that the large increases in number and biomass of surface-sediment cilates in the summer months resulted from an intolerance of reducing conditions developing immediately beneath the surface and the increased productivity of the benthos as a whole during this period. Methods are also described for the construction, calibration and operation of electrodes used in measuring Eh, Es^2? and oxygen flux in the freshwater benthos. Data recorded for these three variables revealed similar seasonal patterns at each site in each of two consecutive years.     

Estimation of production and respiration rates by the ciliated protozoa community in an experimental ricefield

Estimates of production and respiration rates by a field community of ciliates were made in an experimental ricefield located in the province of Reggio Emilia (Northern Italy) from June to September 13, 1983. Particular attention was given to ciliate communities inhabiting both the water column and the sediment. Production in the sediment was higher than in the water column during the first period of rice cultivation (June–July); in the second period (August–September) production was higher in the water column. A similar trend was recorded for respiration rates. During the entire period, production was estimated at 471 KJ m^-2, while energy losses due to respiration accounted for 178 KJ m^-2. The net production efficiency (K₂) of the total ciliate community was 72.5%. Results obtained are discussed and compared with published data on ciliated Protozoa in other ecosystems.     

Colonization dynamics of ciliate morphotypes modified by shifting sandy sediments

Sandy stream-bed sediments colonized by a diverse ciliate community are subject to various disturbance regimes. In microcosms, we investigated the effect of sediment shifting on the colonization dynamics of 3 ciliate morphotypes differing in morphology, behavior and feeding strategy. The dynamics of the ciliate morphotypes inhabiting sediment pore water and overlying water were observed at 3 sediment shifting frequencies: (1) stable sediments, (2) periodically shifting sediments such as migrating ripples, and (3) continuously shifting sediments as occurring during scour events of the uppermost sediment. Sediment shifting significantly affected the abundance and growth rate of the ciliate morphotypes. The free-swimming filter feeder Dexiostoma campylum was vulnerable to washout by sediment shifting since significantly higher numbers occurred in the overlying water than in pore water. Abundance of D. campylum only increased in pore water of stable sediments. On the contrary, the vagile grasper feeder Chilodonella uncinata and the sessile filter feeder Vorticella convallaria had positive growth rates and successfully colonized sediments that shifted periodically and continuously. Thus, the spatio-temporal pattern of sediment dynamics acts as an essential factor of impact on the structure, distribution and function of ciliate communities in sand-bed streams.     

Annual Changes of Abundance and Biomass of Planktonic Ciliates in the Gdańsk Basin,Southern Baltic

Seasonal changes in the species composition, abundance and biomass of planktonic ciliates were determined every 2–3 weeks at two sites of 30 m depth and one location of 105 m depth in the southwestern Gdańsk Basin between January 1987 and January 1988. A total of 40 ciliate taxa were observed during this period. Autotrophic Mesodinium rubrum dominated ciliate abundance and biomass: maximal values of 50 · 10⁻¹ ind. ^1-1 and 65 μg C 1⁻¹ were recorded. The annual mean biomass of M. rubrum comprised 6 to 9% of the annual mean phytoplankton biomass. The highest abundances and biomasses of heterotrophic ciliates were noted at all stations in the spring and summer in the euphotic zone with maximum values of 28 · 10³ ind. 1⁻¹ and 23 μg C 1⁻¹. Three ciliates assemblages were distinguished in the epipelagic layer: large and medium-size non-predatory ciliates, achieving peak abundance in spring and autumn; small-size microphagous ciliates and epibiotic ciliates which were abundant in summer, and large-size predacious ciliates dominating in spring. Below 60 m, a separate deep-water ciliate community composed of Prorodon-like ciliates and Metacystis spp. was found. The ciliate biomass in the 60–105 m layer was similar to the ciliate biomass in the euphotic zone. The heterotrophic ciliate community contributed 10 to 13% to the annual mean zooplankton biomass. The potential annual production of M. rubrum comprised 6 to 9% of the total primary production. Carbon demand of non-predatory ciliates, calculated on the basis of their potential production, was estimated to be equivalent to 12–15% of the gross primary production.     

Seasonal succession of ciliates in lake constance

We found a recurrent seasonal pattern in abundance and composition of planktonic ciliates in Lake Constance, FRG, over a three-year period. Abundance peaks occurred in early spring and summer/autumn, while ciliate numbers were low in late spring (clear-water phase) and winter. Prostomatida and Oligotrichida dominated in early spring. They responded immediately to the phytoplankton spring bloom, while Haptorida, Peritrichida, and large Scuticociliatida (Histiobalantium) were delayed by 1 to 2 weeks. The spring community broke down at the onset of the clear-water phase.Pelagohalteria viridis containing symbiontic algae appeared shortly after this event. A highly diverse community was recorded in summer/autumn. Peritrichida, small Oligotrichida, and large Scuticociliatida reached their maxima during this season. Small Scuticociliatida were rare throughout the year and contributed moderately to total ciliate numbers only during the cold season. The observed seasonal sequence of pelagic ciliates in Lake Constance is discussed in relation to simultaneously collected data on potential food organisms and grazers.     

Effects of Seasonality and Dispersal on the Ciliate Community Inhabiting Bromeliad Phytotelmata in Riparian Vegetation of a Large Tropical River

This study evaluated the influence of rainfall amount on the abundance, species richness, and species occurrence and abundance distribution of the ciliate community associated with the bromeliad Aechmea distichantha. The plants were collected from a rock wall of about 10‐km long at the left bank of Paraná River. We assessed the effects of both spatial and temporal variables on the community attributes, as well as whether plants geographically closer have a similar abundance distribution and species composition. The ciliate community was substantially distinct between both hydrological periods, with greater values of species richness and abundance in the rainy period. No spatial structuring (differences in the species occurrence and abundance distribution among strata) or geographical similarity (similarity in ciliate species composition among the plants) was found. Multiple regression analysis showed a positive relationship only between the ciliate abundances and water volumes for both periods. Although few of the formulated predictions were confirmed, our study provides valuable information on the ecological aspects of the ciliate community inhabiting bromeliad phytotelmata.     

E-mail: J.Laybourn-Parry@nottingham.ac.ukAnnual plankton dynamics in an Antarctic saline lake

1. The plankton dynamics of Ace Lake, a saline, meromictic basin in the Vestfold Hills, eastern Antarctica was studied between December 1995 and February 1997. 2. The lake supported two distinct plankton communities; an aerobic microbial community in the upper oxygenated mixolimnion and an anaerobic microbial community in the lower anoxic monimolimnion. 3. Phytoplankton development was limited by nitrogen availability. Soluble reactive phosphorus was never limiting. Chlorophyll a concentrations in the mixolimnion ranged between 0.3 and 4.4 μg L^??1 during the study period and a deep chlorophyll maximum persisted throughout the year below the chemo/oxycline. 4. Bacterioplankton abundance showed considerable seasonal variation related to light and substrate availability. Autotrophic bacterial abundance ranged between 0.02 and 8.94 × 10⁸ L^??1 and heterotrophic bacterial abundance between 1.26 and 72.8 × 10⁸ L^??1 throughout the water column. 5. The mixolimnion phytoplankton was dominated by phytoflagellates, in particular Pyramimonas gelidicola. P. gelidicola remained active for most of the year by virtue of its mixotrophic behaviour. Photosynthetic dinoflagellates occurred during the austral summer, but the entire population encysted for the winter. 6. Two communities of heterotrophic flagellates were apparent; a community living in the upper monimolimnion and a community living in the aerobic mixolimnion. Both exhibited different seasonal dynamics. 7. The ciliate community was dominated by the autotroph Mesodinium rubrum. The abundance of M. rubrum peaked in summer. A proportion of the population encysted during winter. Only one other ciliate, Euplotes sp., occurred regularly. 8. Two species of Metazoa occurred in the mixolimnion; a calanoid copepod (Paralabidocera antarctica) and a rotifer (Notholca sp.). However, there was no evidence of grazing pressure on the microbial community. In common with most other Antarctic lakes, Ace Lake appears to be driven by ‘bottom-up’ forces.     

Seasonal change in a saline temporary lake (Fuente de Piedra,southern Spain)

Fuente de Piedra saline lake is located in an endorheic basin in the south of Spain. This lake is very shallow (0.5 m max. depth during 1987–88) and relatively large (± 1350 ha). It is a temporary playa lake, showing irregular cycles, with frequent seasonal drought and a high degree of unpredictability. The lake was sampled monthly during a relatively rainy year (1987–88, 10.5 months permanence). The result of combined analyses for environmental variables (salinity, temperature and soluble inorganic forms of nitrogen and phosphorus), variables related to biological activity (chlorophyll a, sediment organic matter and redox potential) and the direct analysis of the planktonic community, shows the existence of two periods of dominance by autotrophs. The first occurs during winter, exhibits a progressively higher surface to volume ratio for phytoplankton and is followed in the spring by high zooplankton densities (Moina salina, Fabrea salina) and very low phytoplankton densities, suggesting the existence of a period with a detritus-based food web. The summer period coincides with a community better adapted to high salinities that is dominated by Dunaliella salina, D. viridis, diatoms and the ciliate Fabrea salina, and associated with high ammonium concentrations. A new period of organic matter accumulation could be facilitated, in the last moments before the lake dries, by a progressive decrease in zooplankton abundance.     

Seasonal and spatial distribution of ciliates in the sandy hyporheic zone of a lowland stream

The seasonal and spatial distribution of abundance and biomass as well as the taxonomic composition of ciliates inhabiting the sandy hyporheic zone of a lowland stream were studied. The mean abundances varied between 0 and 895 cells ml⁻¹ sediment, and the mean ciliate biomass ranged between 0 and 5.3 μg C ml⁻¹ sediment. Ciliate numbers and biomasses were greatest at the sediment surface and declined significantly with increasing sample depth. Abundance and biomass varied seasonally, with maximum values in late autumn and early winter and minimum values in early summer. The community was dominated by small representatives of the Hymenostomatia and Peritrichia. Ciliate community composition changed with depth from a very diverse community at the sediment surface to a less diverse one at greater sediment depths. Ciliate abundance and biomass were two orders of magnitude lower in the channel water than in the hyporheic zone. Although representatives of all sediment taxa could also be found in the channel water, the greatest concentrations of Peritrichia and Suctoria were in the hyporheic zone. The species of the sandy Ladberger Mühlenbach sediment were ubiquitous; there was no single ciliate fauna that proved to be typical for this kind of freshwater biotope.     

Ciliate communities in shallow groundwater: seasonal and spatial characteristics

1. Ciliated protozoans (Phylum Ciliophora) were collected from five sites in a shallow groundwater system in southern Ontario, Canada over a 13‐month period: one at the spring source, two along the channel banks, and two in the stream channel. Ciliates and environmental data were collected from surface water and at five depths into the sediment, located at 20, 40, 60, 80 and 100 cm. 2. Species richness was high (170 ciliate species belonging to 89 genera were identified) and variable, both spatially and temporally. Highest species richness (86) occurred between 20 and 60 cm, and typically decreased below 60 cm. 3. Ciliate densities were also seasonally and spatially variable. Densities peaked in March between 40 cm (as high as 69 900 cells L⁻¹) and 60 cm, and again in May and June at 80 and 100 cm. Densities were lowest in winter. The surface‐water ciliate community had a different species composition and lower population densities. 4. At all depths, small (<50 μm) bacterivorous ciliates typically dominated, but omnivorous and predatory species were also present (combined, up to 30% of the average density). 5. Several ciliate genera, traditionally considered planktonic, occurred at low densities from 40 cm down to 100 cm. 6. Ordination analysis indicated that the main factors influencing the shallow groundwater ciliate communities were depth and temperature. 7. Dissolved oxygen also appeared to influence these communities in that they typically comprised genera that preferred either low‐oxygen or anaerobic conditions.     

Contrasting dynamics of ciliate communities in sandy and silty sediments of an estuarine intertidal flat

During a 1-year study of the ciliate faunas of a silty and a sandy site on an intertidal flat in the Westerschelde estuary, a total number of 107 taxa were recorded belonging to at least 52 genera and 15 orders. Our results suggest that physical properties of the sediment were more important in regulating ciliate abundance, diversity and community composition than food availability, predation, temperature or oxygen concentration. Ciliate abundance and diversity were positively related to sediment grain size and the ciliate community of silty sediments was found to be a subset of that of sandy sediments. At the sandy site, where the sediment composition was stable, seasonal changes in the ciliate community were related to changes in food availability and/or temperature. At both the sandy and silty sites, a clear vertical gradient in the ciliate community was observed that appeared to be linked to gradients in food availability and oxygen concentration. These vertical gradients in ciliate community composition, however, were less steep than the measured oxygen gradients, probably due to the presence of oxic microniches in the anoxic zone.     

The Feeding Ecology of Actinophrys sol (Sarcodina: Heliozoa) in Chesapeake Bay

The occurrence of Actinophrys sol, a planktonic heliozoan, in Chesapeake Bay was monitored over a four-year period (1988–1991). Actinophrys sol was widely-distributed throughout Chesapeake Bay and could exceed densities of 5,000 cells liter ^?1. It was most abundant during the warmer months. Feeding experiments were conducted with field populations of heliozoa using 1-μm fluorescent microspheres to label ciliate prey. Two ciliates, a small Strobilidium sp. (30 μ in diameter) and a Pleuronema sp. (45 μ length), were the primary ciliate-prey items in the water column when the experiments were conducted, although a wide range of ciliate taxa was ingested. Two other ciliates not present in situ, a Cyclidium sp. (20 μ length) and a Uronema sp. (40 μ length), were also labeled and added at various concentrations to field populations of plankton containing A. sol. Heliozoan ingestion rates on in situ prey at concentrations of 30 Strohilidium and one Pleuronema ml^?1 were 0.2 to 0.3 prey heliozoan^?1 hour^?1. Ingestion rates increased to a maximum of 1.2 prey heliozoan ^?1 hour^?1 with additions of 100 Uronema ml^?1. A mean clearance rate of 0.15 ml heliozoan^?1 day^?1 did not change with increasing prey abundance. The abundance and distribution of A. sol suggests that these sarcodines may exert strong grazing pressure on the planktonic ciliate populations of Chesapeake Bay at certain times of the year, and may be important in shaping the ciliate community composition and distribution.     

Identification of Intracellular Bacteria in the Ciliate Balantidium ctenopharyngodoni (Ciliophora,Litostomatea)

The ciliate Balantidium ctenopharyngodoni is the most prominent protist in the guts of grass carp, where it mainly inhabits the creamy luminal contents of the hindgut. Ciliates are generally colonized by microorganisms via phagotrophic feeding. In order to study the intracellular bacteria in this ciliate, we have successfully established it in in vitro culture. Herein, we investigated and compared the bacterial community structures of cultured and freshly collected B. ctenopharyngodoni. The results showed that these two groups exhibited different bacterial communities. The most abundant bacterial family in freshly collected samples was Enterobacteriaceae, while in cultured samples it was Fusobacteriaceae. In addition, a key intracellular bacterium, Cetobacterium somerae, was identified in the cytoplasm of cultured ciliates using fluorescence in situ hybridization (FISH). This study shows that ciliates can retain the intracellular bacteria acquired in the natural habitat for quite a long time, but the bacterial community structure of ciliates eventually changes after a long period of cultivation.     

土壤纤毛虫群落对退耕还林生态恢复的响应——以侧柏林为例

为了了解土壤纤毛虫群落对退耕还林区生态恢复下土壤环境变化的响应及尝试利用土壤纤毛虫群落特征评价退耕还林生态恢复的效果,于2010年3月至9月采用"非淹没培养皿法"、活体观察法、蛋白银染色法和Foissner计数法对甘肃陇南武都退耕还林区5个不同恢复阶段的样点和1个荒草坡对照样点的土壤纤毛虫群落特征进行了研究,同时测定了p H值、温度、含水量及速效磷、有效钾、铵态氮、有机质和有机碳含量等土壤环境因子并分析了生态恢复条件下土壤纤毛虫群落特征与土壤环境因子的相关性。研究中共鉴定到71种纤毛虫,隶属于3纲、10目、22科、29属。研究发现,不同恢复年限的土样中土壤纤毛虫的物种分布存在明显差异,并随恢复时间的延长,样点间物种相似性减小,群落组成复杂化,物种数、种群密度和物种多样性指数总体均呈增长趋势。优势类群也发生了演替,由恢复初期的肾形目演替到后期的下毛目。相关性分析结果表明,在生态恢复条件下,土壤有机质和铵态氮含量是影响土壤纤毛虫群落结构稳定性的主要因素,不同纤毛虫类群对生态恢复的响应存在差异。冗余分析显示,土壤纤毛虫群落很好地响应了生态恢复过程中土壤环境条件的变化。     

First report of folliculinid ciliates affecting Caribbean scleractinian corals

This is the first report of a ciliate of the genus Halofolliculina infecting hard coral species of six families (Acroporidae, Agaricidae, Astrocoeniidae, Faviidae, Meandrinidae and Poritidae) and milleporids in the Caribbean. Surveys conducted during 2004–2005 in Venezuela, Panama and México confirmed that this ciliate affects up to 25 scleractinian species. The prevalence of this ciliate at the coral community level was variable across sites, being most commonly found at Los Roques, Venezuela, and at Bocas del Toro, Panama (prevalence 0.2–2.5%), but rarely observed in the Mexican Caribbean. Ciliates were more prevalent within populations of acroporids (Acropora palmata, Acropora cervicornis and Acropora prolifera) in Los Roques. Recent observations also corroborate the presence of these ciliates in Curacao and Puerto Rico. Our observations indicate that ciliates affecting corals have a wider distribution than previously thought, and are no longer exclusively found in the Indo-Pacific and Red Sea.     

Oxygen sensing drives predictable migrations in a microbial community

Oxygen sensing is widely practised by aerobic organisms ranging from bacteria to vertebrates, and a dominant oxygen-sensing mechanism may persist among all aerobes. We traced population migrations of 10 species of the larger aerobic ciliated protozoa living in lake sediment, and in the 15 m water column of Esthwaite Water in the English Lake District (UK). In so doing, we discovered that the character and dynamics of the lake sediment and water column were remarkably predictable in performance over a continuous period of almost 2 years. Increasing warming of the lake sediment, coupled with low oxygen tension, resulted in the emergence of aerobic ciliates out of the sediment and their migration into the water column. And with the annual collapse of thermal stratification in the water column, the whole annual cycle was repeated. In an unusual discovery, we found that particular ciliate species seemed to be 'linked' to other (functionally different) ciliate species partners via the ambient oxygen tension. The favoured hypothesis is that all ciliate species in a particular body-size range seek out a particular, preferred oxygen tension. If that is the case, the 'cement' providing the cohesion of the ciliate community might actually be the preferred oxygen tension. The principal aim of our study is to clarify the microbial migration itself, not the response of the different ciliate species to oxygen gradients once they have established themselves in the water column. The latter happens once the organisms have migrated out of the sediment together, driven by the ambient oxygen tension.     

Major changes in trophic dynamics in large, deep sub-alpine Lake Maggiore from 1940s to 2002: a high resolution comparative palaeo-neolimnological study

1. We describe the changes in trophic dynamics in Lake Maggiore from c. 1943 to 2002 using subfossil cladoceran data from a high resolution sediment record, long‐term contemporary data series and historical information. During this period the lake went through a eutrophication phase until 1980 followed by oligotrophication. 2. During the eutrophication period a major increase occurred in the abundance of Chydorus sphaericus, the proportion of planktonic cladocerans and total abundance of cladocerans in the sediment. Since 1980 the abundance declined again and subfossil Eubosmina mucro length and contemporary Daphnia body length increased, most probably as a result of higher abundance of invertebrate predators. 3. Changes in the fish stock composition caused by the introduction of exotic fish during the pre‐eutrophication period and a complete ban on fishing because of Dichloro‐diphenil‐ethanes (DDTs) pollution of the lake (during oligotrophication) could also be detected in the community assemblage and size structure of the sediment zooplankton. 4. We found good correspondence between trophic changes inferred from cladoceran subfossils (community composition, size and predation pressure) and contemporary data, suggesting that sediment samples can be used to infer past development in trophic dynamics, including predation by fish and pelagic invertebrates in lakes with scarce neolimnological data. 5. Furthermore, by combining palaeolimnological cladoceran data rarely obtained from contemporary samples (e.g. benthic and plant‐associated cladocerans, mucro length of bosminids) with contemporary data of organisms poorly represented in the sediment record (e.g. remains of Bythotrephes and fishes) a more complete understanding of changes in trophic dynamics was obtained. 6. The detection in the sediments of meteorological events whose effects on zooplankton had been recorded in the long‐term studies also provided evidence that eutrophication tends to override climate signals. 7. We conclude that a combined palaeo‐neolimnological approach can be a powerful tool for elucidating past changes in the trophic dynamics of lakes and the interaction with climate induced changes, not least when high resolution sediment records are available.     

Fluctuation of the zooplankton community in Lake Biwa during the 20th century: a paleolimnological analysis

Detailed zooplankton records from a 26-cm sediment core with a time resolution of approximately 3–10 years were obtained from Lake Biwa, Japan, to examine the historical variations in the zooplankton community during the 20th century. In the sediments, selected zooplankton remains have fluctuated over the years. Daphnia – large zooplankton herbivores – did not occur from 1900 to 1920, and formed a very minor component of the zooplankton community in the following 30 years, while Bosmina – small zooplankton herbivores – were common during this period. In the mid-1960s, however, when eutrophication was noticeable in this lake, Daphnia numbers increased dramatically and became the dominant zooplankton thereafter. In contrast, Difflugia brevicolla and D. biwae, two amoeboid protozoans that live in connection with the lake bottom environment, occurred abundantly until the late 1950s, but gradually decreased after the mid-1960s. In particular, D. biwae, a species peculiar to this lake, was not found in sediment dated after 1980, suggesting its extinction. These results indicate that the zooplankton community structure changed greatly in the 1960s, and suggest that the eutrophication occurring at this time altered the relative strength of top-down and bottom-up forces on the zooplankton community in Lake Biwa.     

Pelagic Ciliates in a Large Mesotrophic Lake: Seasonal Succession and Taxon‐Specific Bacterivory in Lake Constance

The taxonomic composition of the ciliate assemblage and their taxon‐specific bacterial grazing rates in Lake Constance were investigated over the course of one year. Bacterial grazing rates were measured using natural fluorescently labelled bacteria (FLB) and compared to bacterial production. Small species such as Balanion planctonicum/Urotricha furcata and Rimostrombidium spp./Halteria sp. were the most numerous ciliates on the annual average. Larger ciliates such as Rimostrombidium lacustris and Limnostrombidium spp. contributed significantly to total ciliate biomass, but were relatively unimportant as bacterial grazers. Per capita ingestion rates ranged from 0–194 bacteria ciliate⁻¹ h⁻¹ and changed seasonally up to a hundredfold within a given taxon. Approximately 1% of the bacterial production were removed by the ciliate community on the annual average. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Seasonality of planktonic ciliated protozoa in 20 subtropical Florida lakes of varying trophic state

The planktonic ciliate populations of 20 Florida lakes ranging from oligotrophic to hypereutrophic were examined monthly for one year. Oligotrophic lakes displayed abundance peaks during fall mixis and biomass peaks in late winter and fall. Mesotrophic systems exhibited a spring-fall bimodality in ciliate abundance with a biomass maxima occurring during fall. Eutrophic/hypereutrophic lakes had pronounced abundance and biomass maxima during summer, with the large ciliates Plagiopyla nasuta and Paramecium trichium often contributing heavily to the midsummer biomass peak. Members of the Oligotrichida numerically dominated abundance and biomass peaks in oligotrophic lakes while the Scuticociliatida dominated the communities of higher trophic states. Total ciliate abundance and biomass were strongly correlated with chlorophyll a concentrations as were various ciliate taxonomic groups. The relationship between ciliate seasonal distribution in these subtropical lakes with lake thermal regimes and trophic state is discussed.