Ciliate Abundance Research Articles

Compositional differences among planktonic ciliate communities in four subtropical eutrophic lakes in China

Ciliate community composition was investigated in four subtropical eutrophic lakes with cyanobacterial blooms in three seasons during 2009–2010 using the quantitative protargol staining approach. Among the four lakes, Lake Taihu and Chaohu are situated in the mid-lower Yangtze Plain near sea level, and Lake Dianchi and Xingyunhu are located on the Yunnan–Kweichow Plateau. A total of 102 ciliate species, representing 15 orders and 66 genera, were studied. Ciliate communities in Lake Taihu and Chaohu were characterized by abundant algivorous and mixotrophic oligotrichs and prostomatids, while Lake Dianchi and Xingyunhu ciliate communities were primarily characterized by voracious bacterivorous scuticociliates and peritrichids. Cluster analysis based on the transformed square root of ciliate abundance showed that samples from Lake Taihu and Chaohu composed one group whereas samples from Lake Dianchi and Xingyunhu composed another group in each season. Our results indicated that all dominant ciliate species are ubiquitous and that species dominance is regulated by different factors in different subtropical eutrophic lakes.

THERMAL IMPACTS OF A COAL POWER PLANT ON THE PLANKTON IN AN OPEN COASTAL WATER ENVIRONMENT

Over a five-year period, this study examined the overall impact of coal power plant cooling processes on entrained copepods and the local plankton community on the west coast of Korea. Mortality differences between the intake and discharge water of the single most dominant copepod, Acartia hongi, were positively correlated with temperature differences between the two locations. Laboratory tests showed copepod sensitivity to temperature increase, and with very low chlorine concentration applied, thermal stress was the major source of copepod mortality. Chlorophyll a concentration, ciliate abundance, and total copepod abundance at the intake showed no discernable differences from the values at the discharge. Most likely, this was due to rapid mixing of the population in the discharge water with adjacent populations in the macrotidal open coastal water environment.

Benthic ciliate and meiofaunal communities in two contrasting habitats of an intertidal estuarine wetland

Annual variations in benthic meiofaunal and ciliated protozoan communities were investigated using monthly samplings from June 2006 to May 2007 in two habitats characterized by different vegetal coverage in an estuarine intertidal wetland of Qingdao Jiaozhou Bay, China. The sediment composition was stable at each site: sediments densely covered with seagrass (Suaeda glauca) in the lower estuarine site (Station S) were finer, with higher content of organic matter, phaeopigments and water than sediments at the upper estuarine site (Station S-P) which was unvegetated other than for patches of S. glauca and common reed (Phragmites australis). Chlorophyll a exhibited a similar distribution in the two habitats. A total of 14 meiofaunal groups, and 249 species of ciliates belonging to 37 genera, 28 families and 16 orders, were isolated from the two sites. Univariate and multivariate measures of the communities were significantly different between the two habitats. There were higher abundances of ciliates and meiofauna, and a greater diversity of ciliates, at Station S than Station S-P (223 vs. 61 species). Herbivorous ciliates were numerically predominant in ciliate communities at both sites. The representative ciliates at Station S-P belonged to the Cyrtophorida and appeared to be a reduced subset of the assemblage at Station S, which was characterized by members of the Prostomatida, Cyrtophorida, Hypotrichida and Scuticociliatida. More than 96% of the total meiofauna were nematodes, accounting for 93% of the differences in the abundance compositions of the meiofaunal communities between habitats. The average individual weights of nematodes were nearly 3 times greater at Station S than Station S-P, indicating a distinctive species composition at each site. Temperature, salinity and food availability were key factors that regulated the ciliate and meiofaunal community structure. Nematodes were the dominant group in terms of the combined abundance, biomass and benthic metabolism of ciliates and meiofauna. With respect to the dominance of herbivorous ciliates and epistrate-feeder nematodes in seagrass sediment, predator–prey relationships and competition for food resources between nematodes and ciliates are likely to be important factors in controlling the abundances of these groups.

Are ciliated protozoa communities affected by macrophyte species, date of sampling and location in horizontal sub-surface flow constructed wetlands?

The effects of design and operational factors on the dynamics of ciliated protozoa in constructed wetlands (CWs) treating wastewater remain poorly known, although bacterivory by ciliates could have important implications for nutrient cycling in these systems. We conducted a greenhouse experiment with eight wetland mesocosms (1 m2) fed with synthetic wastewater to assess how macrophyte species (Phragmites australis, Phalaris arundinacea, and Typha angustifolia), location within CW (longitudinal, depth), and temporal fluctuations affect ciliate abundance and diversity. Urosoma similis was the most abundant taxon, but Hypotrichidae, Scuticociliates, Drepomonas revoluta, and Acineria uncinata were also abundant. Longitudinal location had the highest impact on ciliate dynamics, with more abundant and diverse communities in the initial section of wetlands. P. australis/T. angustifolia and P. arundinacea had the most and least favorable conditions for ciliates, respectively, but differences among macrophytes were mostly not significant. Ciliate abundance appeared to decline from August to November, most likely because of lower temperature and plant inputs of organic matter and oxygen. Depth had no apparent impact on ciliate dynamics, suggesting that sampling at multiple depths in CW is not necessary to adequately monitor ciliate communities. Overall, our results suggest that macrophytes, location, and date of sampling influenced ciliated dynamics but stress the need for direct manipulative experiments of ciliate abundance, diversity, and composition conducted on a full annual cycle to better understand the impact of ciliates on nutrient cycling in CWs. This is especially true to determine if the associations found in our principal component analysis are robust.

Potential risk of Mesodinium rubrum bloom in the aquaculture area of Dapeng’ao cove, China: diurnal changes in the ciliate community structure in the surface water

Diurnal changes in the structure of the ciliate community in surface waters were studied in the aquaculture area of Dapeng’ao cove, China. Two periods of heavy rainfall occurred during the study period, intensifying water column stratification and influencing the water’s properties. A total of 21 ciliate taxa from 15 genera were identified; the dominant species was Mesodinium rubrum. The maximum abundance of M. rubrum reached 3.92×104 indiv. dm−3, contributing 95.1% (mean value) to the total ciliate abundance. Diurnal changes in M. rubrum abundance were highly variable, the driving force probably being irradiance and food availability. The results suggest that M. rubrum may form blooms in aquaculture areas when there is a suitable physical regime with enriched nutrients, which is potentially harmful to the fish-farming industry.

Live labeling technique reveals contrasting role of crustacean predation on microbial loop in two large shallow lakes

We tested the hypotheses that the ciliate assemblages in moderately eutrophic lake are controlled by the effective crustacean predation, and the high abundances of planktonic ciliates in highly eutrophic and turbid lake are due to insufficient regulation by crustacean zooplankton. A food tracer method coupled with natural assemblage of microciliates labeled with fluorescent microparticles was used to measure the cladoceran and copepod predation rates on planktonic ciliates and to estimate the carbon flow between the ciliate–crustacean trophic links. The results revealed that the microciliates (15–40 μm) were consumed by all dominant cladoceran and copepod species in both the lakes studied, mainly by Chydorus sphaericus and cyclopoid copepods in Lake Vortsjarv, and by Daphnia spp. and Bosmina spp. in Lake Peipsi. The grazing loss in moderately eutrophic Peipsi indicated strong top-down control of ciliates mainly by cladocerans. The extraordinary abundant population of planktonic ciliates having a predominant role in the food web in highly eutrophic and turbid Vortsjarv is explained by the measured low crustacean predation rates on ciliates. The estimated carbon flow from the ciliates to crustaceans suggest that in eutrophic lakes majority of the organic matter channeled via metazooplankton to higher trophic levels may originate from the microbial loop.

Response of a microbial food web to prolonged seasonal hypoxia in a boreal lake

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 14:105-120 (2012) - DOI: https://doi.org/10.3354/ab00379 FEATURE ARTICLE Response of a microbial food web to prolonged seasonal hypoxia in a boreal lake Grażyna Bręk-Laitinen*, Jessica López Bellido, Anne Ojala Department of Environmental Sciences, University of Helsinki, 15140 Lahti, Finland *Email: grazyna.brek@helsinki.fi ABSTRACT: The clearwater boreal Lake Vesijärvi experiences annual periods of hypolimnetic hypoxia with unknown consequences for the microbial food web. We quantified the abundance of heterotrophic bacteria, autotrophic picoplankton (APP), nanoflagellates (NF) and ciliates in Lake Vesijärvi throughout the water column and vegetation season and determined how these varied with changes in environmental conditions, including dissolved oxygen concentrations. The abundance and diversity of ciliates increased significantly throughout the water column with the development of thermal stratification and the onset of hypoxia leading to distinct ciliate communities in the oxic epilimnion and hypoxic hypolimnion. Bacterivorous taxa dominated in the hypoxic zone, while in the epilimnion, bacterivorous, algivorous and predatory taxa feeding on other protozoa were present. Seasonal changes in oxygen and temperature explained nearly 80% of variance in ciliate community composition. Changes in total ciliate numbers correlated with seasonal dynamics of bacteria, but not with the dynamics of NF. In the epilimnion, NF were abundant in early spring and their numbers were positively correlated to numbers of prostomatids and haptorids, but not to APP or bacteria. In the hypolimnion, a significant correlation was found between NF and bacteria, but not NF and ciliates. Significant positive correlations between ciliates and bacteria suggest that concentrations of food resources are important in determining the abundance of ciliates in the plankton. Moreover, we recorded close coupling between seasonal dynamics of bacteria and productivity of phytoplankton, including APP. KEY WORDS: Autotrophic picoplankton · Bacteria · Nanoflagellates · Ciliates · Anoxia · Hypoxia Full text in pdf format Information about this Feature Article NextCite this article as: Bręk-Laitinen G, López Bellido J, Ojala A (2012) Response of a microbial food web to prolonged seasonal hypoxia in a boreal lake. Aquat Biol 14:105-120. https://doi.org/10.3354/ab00379 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 14, No. 2. Online publication date: January 04, 2012 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2012 Inter-Research.

2010年两个航次獐子岛海域浮游纤毛虫丰度和生物量

We investigated the abundance and biomass of planktonic ciliates in the sea around Zhangzi Island,Northern Yellow Sea,in July and August 2010.Ciliates were sampled from surface,middle and bottom depths at nineteen sample stations along three transects(Transect STA,Y1 and Y2).A 1-L water sample was collected at each depth with a 2.5-L Niskin water sampler and fixed in 1% acid Lugol′s iodine solution.The bottles were stored in the dark for up to two months until analyzed.The fixed water samples were left to settle for at least 48 h in plastic bottles and the supernatant was siphoned out until a 150 mL sample was left.The concentrated sample was examined and counted following the Utermhl method.A subsample of 16 mL of the concentrated sample was settled in Utermhl sedimentation chambers and counted using an Olympus IX51 inverted microscope at 100× or 400×.The classification of tintinnids was based on taxonomic literature.The dimensions of the ciliates were measured and the cell volume of each species was estimated using appropriate geometric shapes.Non-loricate ciliates were divided into three size classes by cell volume: NCI(103 to 104 μm3),NCII(104 to 105 μm3) and NCIII(105 μm3).The carbon-to-volume ratio used to calculate biomass was 0.19 pg C/μm3.The plasma of tintinnids was assumed to occupy 30% of the lorica volume.Abundance and biomass of the ciliates cross-water column were calculated as the integral of the abundance and biomass from the bottom to the surface.The results showed that the average abundance of total ciliates in July and August was(5107±4451) ind/L and(7894±7212) ind/L,respectively.The average biomass of total ciliates was(10.17±9.06) μg C/L and(15.24±18.49) μg C/L.Surface ciliate abundance and biomass decreased from coastal to offshore waters in July.Surface ciliate abundance was higher at St.Y1-3 and St.Y2-5 while surface ciliate biomass was higher at St.Y2-5 and St.Y1-1.Ciliate abundance decreased from the surface or subsurface down to the bottom along Transect STA in July,Transect STA and Y1 in August,while it was vertically homogeneous along Transect Y2 in August.The average abundance and biomass of total ciliates cross-water column were higher in coastal waters than in offshore waters in July and were higher at St.Y2-5 and St.Y1-1 in August.A total of 17 and 21 tintinnid species were identified,in July and August respectively.Nearly 50% of species were in the genus Tintinnopsis,and we recorded the species Tintinnopsis corniger Hada,1964 for the first time in Chinese waters.Tintinnids occupied(19.0±21.6)% and(13.0±16.1)% of the total ciliate abundance and(58.2±33.0)% and(42.6±33.2)% of the total biomass in July and August,respectively.Small bio-volume ciliates dominated in total non-loricate ciliate abundance in both July and August.

Horizontal Distribution of Psammonic Ciliates in Two Lakes of Different Trophic Status: Relationship to Physical and Chemical Parameters

Horizontal Distribution of Psammonic Ciliates in Two Lakes of Different Trophic Status: Relationship to Physical and Chemical ParametersThe aims of this study were to identify the taxonomic diversity and abundance of psammonic ciliate communities in mesotrophic and eutrophic lakes (Łęczna-Włodawa Lakeland, eastern Poland). The effect of selected physical and chemical water parameters on ciliates community was also analysed. Psammon samples were collected during three seasons: spring, summer and autumn of 2010. In each lake, in the psammolittoral, samples were collected in the euarenal, higroarenal, and hydroarenal zones. A total of 53 ciliate taxa were recorded. The highest value of the Shannon-Weaver index was recorded in summer in eutrophic lake (2.79). At the same time in mesotrophic lake, a lower value of the index was determined (0.79). The mean numbers of ciliates ranged from 516 ind.cm-3in the eutrophic lake to 191 ind. cm-3in the mesotrophic lake. In eutrophic lake, the highest number of ciliates was recorded in the euarenal (649 ind. cm-3), and the lowest in the higroarenal (425 ind. cm-3). In the mesotrophic lake, the highest average numbers were determined in the higroarenal (235 ind. cm-3), and the lowest in the hydroarenal (155 ind. cm-3). Irrespective of the lake trophy, Hymenostomata (Paramecium sp., Glaucoma sp., Uronema nigricans) occurred in the highest numbers (from 13 to 95%). The results demonstrated that N-NH4, P-PO4and TOC can strongly regulate the abundance and taxonomic composition of ciliates. The strongest correlations between numbers of ciliates and physical and chemical water parameters were observed in the higro- and hydroarenal zones of the eutrophic lake.

Diversity and seasonality in structure of ciliate communities in the Neva Estuary (Baltic Sea)

Diversity and structure of ciliate communities in the Neva Estuary (Baltic Sea) were studied at two near-shore stations from October 2007 to January 2009. Ciliates from 111 taxa were detected, including new records of 24 species for the Baltic Sea. The ciliate taxa were grouped into size-categories and trophic guilds and their species composition, abundance and biomass were monitored in different seasons. Two distinct associations replaced each other during seasonal succession at water temperatures 5–128C. During the warm season (late April–October) ciliate communities were composed essentially of picoand nano-filterers (mostly algivorous) that became less important in the cold season (October–early April). The predator, Monodinium balbiani, and bactivorous peritrichs were characteristic of the warm season, while in the cold season, other predatory (Lacrymaria coronata group) and bactivorous (Cyclidium spp., Aspidisca sp., Chilodonella sp.) ciliates occurred. The most abundant size groups were small ciliates (20–30 mm) and nanociliates (,20 mm). A proportion of large ciliates (.60 mm) increased in the cold season due to the appearance of benthic species in the plankton. Total ciliate abundance and biomass ranged 0.12–10.3 10 ind L and 0.3– 53.3 mg C L, respectively. An unusual winter peak of the ciliate Trithigmostoma sp. was observed (32.8 mg C L) although generally the overall ciliate numbers decreased in the cold season.

Ciliate community structure, diversity and trophic role in offshore sediments from the Yellow Sea

We investigated the community structure, diversity and trophic role of ciliates in the sediments from 48 stations in the Yellow Sea using Ludox density centrifugation and quantitative protargol stain. The ciliate abundance ranged from 1 to 221cellscm−3 and biomass from 0.0001 to 0.47μgCcm−3 in the upper 8cm of the sediments. On average, 77% of ciliate abundance and 81% of biomass were distributed in the 0–2cm sediment layers, while the respective proportions were only about 6% and 3% in the 5–8-cm layers. Among the 198 morphospecies, Prostomatea was the most dominant group accounting for 45% of the total abundance and 58% of the total biomass. Carnivorous ciliates constituted the primary feeding type, occupying about 64% of the total biomass, followed by bacterivores (21%), algivores (12%) and omnivores (3%). The ciliate abundance and biomass in the upper 5cm of sediments were two orders of magnitude higher than those in the upper 10m of the Yellow Sea water column. The estimated ciliate bacterivory and herbivory indicate that ciliate ingestion had little direct influence on bacterial standing stock but possibly had an important impact on diatoms in the sediments from the Yellow Sea.

Long-term (1998–2007) trends on the spatial distribution of heterotrophic ciliates in the East China Sea in summer: effect of the Three Gorges Dam construction

The spatial distribution of heterotrophic ciliates, environmental factors and potential food items (bacteria, Synechococcus spp. and nanoflagellates) were measured in the East China Sea to examine which variables contributed importantly to the long-term distribution of ciliates between 1998 and 2007. In July 1998 and June 2003, heterotrophic ciliates were found to be abundant (1,000–2,000 × 103 cells m−3) in regions where surface salinity 32. After August 2003, shortly after the completion of the Three Gorges Dam, we found no significant areal differences in the abundance of heterotrophic ciliates (HC). However, we found a significantly negative correlation between temperature and HC abundance of surface water after the completion of the dam, suggesting that temperature had a greater influence on HC abundance, once the original saline state had changed. For the long-term trends on the vertical distribution of HC, their abundance was significantly higher in the upper 50 m of the water column than at either 75 or 100 m. Abundance of Synechococcus spp. at these levels varied significantly in regions of surface salinity <32, suggesting that ciliates and picophytoplankton contribute greatly to mediating the transfer of organic matter to higher trophic levels in this marine ecosystem.

Phytoplankton growth and microzooplankton grazing in the continental shelf area of northeastern South China Sea after Typhoon Fengshen

Dilution experiments were used to investigate the phytoplankton growth and microzooplankton grazing in the continental shelf area of northeastern South China Sea during 30 June and 7 July, 2008, occurring about a week after Typhoon Fengshen. We detected negative phytoplankton growth rates (−0.03 to −2.02 d −1) and measured grazing rates of microzooplankton on phytoplankton in size-fractionations of 20–200 μm (1.25±0.44 d −1), 3–20 μm (1.48±0.63 d −1) and <3 μm (1.02±0.42 d −1). Results showed significant correlations between phytoplankton growth and microzooplankton grazing rates, between phytoplankton and ciliate abundance, and between the dominant phytoplankton Thalassionema nitzschioides and the dominant ciliate Helicostomella longa ( p<0.05). Phytoplankton decay, due to nutrient-limited conditions occurring with the fading of upwelling and spreading of freshwater plume after Typhoon Fengshen, may account for negative phytoplankton growth rates in this study. Synergism in the specific size-selective grazing of various species, including ciliates and heterotrophic dinoflagellates, may contribute to similar grazing rate on phytoplankton in different size-fractionations, at the integrated level. Interactions between phytoplankton and microzooplankton, including grazing selectivity, top-down and bottom-up control between phytoplankton and microzooplankton may contribute to these findings. Our results indicate that under conditions of negative phytoplankton growth microzooplankton grazing may reduce energy loss from the epipelagic waters by retrieving energy from the decaying phytoplankton community.

Response of biofilm-dwelling ciliate communities to enrichment with algae

The role of benthic versus planktonic algae in shaping semi-natural ciliate biofilms was studied using miniature flow cells fed by a permanent flow of natural field water from the River Rhine, Germany. Increased food availability for the ciliates was achieved either by supplementation with planktonic algae or by artificial illumination (to stimulate benthic algal growth). Manipulation of both resources significantly increased the total abundance of ciliates and caused significant shifts in the structure of the ciliate community. Supplementation with planktonic algae particularly stimulated suspension-feeding Peritrichia, whereas Choreotrichia were reduced, probably due to indirect effects such as competition or interference. Increased density of benthic algae especially stimulated surface- feeding groups (e.g. Stichotrichia, Nassophorea), causing the establishment of seasonally atypical structures in the ciliate community, as has been observed in late fall. Ciliates generally responded faster to increased resources during the summer, as compared with winter, suggesting that tempera- ture, as well as the availability of resources, has an important role in shaping ciliate biofilms. Our results are among the first that demonstrate the different contributions of planktonic and benthic algae in shaping ciliate biofilms. Furthermore, they accentuate the need for studies with a higher taxonomic resolution when addressing the responses of microbial biofilms to the increased avail - ability of food.

Ciliate distributions and forcing factors in the Amundsen and Bellingshausen Seas (Antarctic)

Data for ciliate abundance, biomass and taxonomic composition, along with relevant biotic and abiotic parameters, were gathered from 9 profiles in the Bellingshausen and Amundsen Seas (Southern Ocean) during late summer and early autumn 2006. A total of 70 species were found, with extrapolations using species accumulation curves suggesting that the true diversity lay between 77 and 90 species. Ciliate abundance and biomass were low, but not unexpectedly so, given the time of year and productivity of the system. Despite the harsh environment, species richness was not less than that found for protists from more temperate habitats, and declined with depth less steeply than abundance and biomass. Ciliate biomass was driven primarily by productivity, with tighter correla- tions between chlorophyll a (chl a) and either abundance or biomass than those seen from other marine systems. Community composition was also driven by productivity, with a principal compo- nents analysis (PCA) on species data showing the first axis strongly correlated with productivity para- meters. Moreover, species abundance distributions (SADs) were most often best matched by the geo- metric distribution, thought to be expected when relatively few parameters determine species distributions. Abundance and diversity were also compared using settled and quantitative protargol stain (QPS) samples. QPS samples had lower mean abundance, higher total species richness and higher taxonomic resolution than did the settled samples. However, per-sample species (or morpho- type) richness was the same in settled and QPS samples.

Species composition and spatial distribution of abundances and biomass of phytoplankton and ciliates during summer stratification in the Gulf of Hammamet (Tunisia)

We studied the distribution of phytoplankton and ciliate communities in relation to environmental factors at 6 stations sampled between 28 and 31 July 2006 during the summer water stratification in the Gulf of Hammamet (Tunisia, eastern Mediterranean Sea). A strong thermocline was established at 30 m, and, on average, the N/P ratio was lower than the Redfield ratio (16), suggesting a potential N limitation. The inshore location was numerically dominated by dinoflagellates (55%) represented essentially by members of the generaProtoperidinium, Gymnodinium, and crypticScrippsiella trochoideaand on the offshore by diatoms (68%). The phytoplankton assemblage was largely dominated by the diatomsThalassionema nitzshioidesandRhizosolenia styliformis, while the ciliate community was numerically dominated by small taxa such asLohmanniella oviformis(6 × 102cells l−1) andUronema marinum(5.50 × 102cells l−1). The total phytoplankton abundance increased from the coastal area (5.26 × 102 ± 4.48 × 102) to the open sea (10.33 ×102 ± 28.06 × 102) and decreased from the surface to the bottom, inversely to the ciliate abundance. Total phytoplankton and abundances showed similar patterns. Total ciliate biomass decreased from the inshore (0.25 ± 0.58) to the offshore (0.06 ± 0.10) areas but increased from the surface to the bottom. The diversity index of both phytoplankton and ciliate communities showed a decrease with a coastal–open sea gradient. The relationships between phytoplankton and ciliates suggest planktonic micro-heterotrophs were implicated in the channelling of matter and energy through the microbial loop in the Gulf of Hammamet.

The effect of anoxia and anaerobia on ciliate community in biological nutrient removal systems using laboratory-scale sequencing batch reactors (SBRs)

Little is known about the effect of anaerobic and anoxic stages on the protozoan community in the activated sludge process and how this subsequently affects performance. Using a laboratory-scale BNR system the effect of different periods of anoxia on both the protozoan community and performance efficiency have been examined. Four SBRs were operated at two cycles per day using a range of combined anoxic/anaerobic periods (0, 60, 120 and 200 min). Effluent quality (TOC, BOD, TP, TN, NH 4–N, NO 3–N and NO 2–N), sludge settleability and ciliate community (species diversity and abundance) were analysed over a periods of up to 24 days of operation. The species richness and total abundance of ciliates were found to decrease with longer anoxic/anaerobic periods. Both, positive and negative significant correlations between the abundance of certain species and the period of anoxia was observed (e.g. Opercularia microdiscum, Epicarchesium granulatum), although other species (i.e. Acineria uncinata, Epistylis sp.) were unaffected by exposure to anoxia. In the laboratory-scale units, the 60 min anoxic/anaerobic period resulted in good process performance (TOC and BOD removal of 97–98% respectively), nitrification (80–90%), denitrification (52%) but poor levels of biological P-removal (12%); with the protozoan community moderately affected but still diverse with high abundances. Increasing the length of anoxia to up to 200 min did not enhance denitrification although P-removal rates increased to between 22 and 33%; however, ciliate species richness and total abundance both decreased and sludge settleability became poorer. The study shows that activated sludge ciliate protozoa display a range of tolerances to anoxia that result in altered ciliate communities depending on the length of combined anoxic/anaerobic periods within the treatment process. It is recommended that anoxic/anaerobic periods should be optimised to sustain the protozoan community while achieving maximum performance and nutrient removal.

Characterization of rumen ciliate community composition in domestic sheep, deer, and cattle, feeding on varying diets, by means of PCR-DGGE and clone libraries

The structure and variability of ciliate protozoal communities in the rumens of domestic New Zealand ruminants feeding on different diets was investigated. The relative abundance of ciliates compared with bacteria was similar across all samples. However, molecular fingerprinting of communities showed ruminant-specific differences in species composition. Community compositions of cattle were significantly influenced by diet. In contrast, diet effects in deer and sheep were weaker than the animal-to-animal variation. Cloning and sequencing of almost-full-length 18S rRNA genes from representative samples revealed that New Zealand ruminants were colonized by at least nine genera of ciliates and allowed the assignment of samples to two distinct community types. Cattle contained A-type communities, with most sequences closely related to those of the genera Polyplastron and Ostracodinium. Deer and sheep (with one exception) harboured B-type communities, with the majority of sequences belonging to the genera Epidinium and Eudiplodinium. It has been suggested that species composition of ciliate communities may impact methane formation in ruminants, with the B-type producing more methane. Therefore, manipulation of ciliate communities may be a means of mitigating methane emissions from grazing sheep and deer in New Zealand.

Microbial processes in a high-latitude fjord (Kongsfjorden, Svalbard): II. Ciliates and dinoflagellates

The composition and ecological role of ciliates and dinoflagellates were investigated at one station in Kongsfjorden, Svalbard, during six consecutive field cam- paigns between March and December 2006. Total ciliate and dinoflagellate abundance mirrored the seasonal progression of phytoplankton, peaking with 5.8 9 10 4 cells l -1 in April at an average chlorophyll a concentration of 10 l gl -1 . Dinoflagellates were more abundant than ciliates, dominated by small athecates. Among ciliates, aloricate oligotrichs dominated the assemblage. A large fraction ((60%) of cil- iates and dinoflagellates contained chloroplasts in spring and summer. The biomass of the purely heterotrophic fraction of the ciliate and dinoflagellate community (protozooplankton) was with 14 l gCl -1 highest in conjunction with the phytoplankton spring bloom in April. Growth experiments revealed similar specific growth rates for heterotrophic cil- iates and dinoflagellates (\0-0.8 d -1 ). Food availability may have controlled the protozooplankton assemblage in winter, while copepods may have exerted a strong control during the post-bloom period. Calculations of the potential grazing rates of the protozooplankton indicated its ability to control or heavily impact the phytoplankton stocks at most times. The results show that ciliates and dinoflagellates were an important component of the pelagic food web in Kongs- fjorden and need to be taken into account when discussing the fate of phytoplankton and biogeochemical cycling in Arctic marine ecosystems.

The influence of emergent and submerged macrophyte beds on ciliate communities in a shallow lake

Abstract Relationships between ciliates and the presence of emergent and submerged vegetation were studied in a shallow lake in eastern Poland. Samples were collected in zones of Phragmites, Typha, Batrachium, Elodea, Stratiotes and from the open water zone. The abundance and biomass of ciliates were significantly higher at sites with structurally most complex plants than in the open water or sparsely vegetated sites. The redundancy analysis indicated that bacterial abundance and total organic carbon were the most influential variables that determine the distribution of ciliates. However, chlorophyll a and Ptot have a lesser influence on the distribution of these microorganisms. Based on differences in macrophyte structure, two groups of habitats with similar patterns of size-related ciliate distribution were distinguished. The first group consisted of three vegetation zones of sparse stem structure and the open water zone, the second group comprised submerged macrophyte species, which were more complex.