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.     

Distributions and Biomass of Benthic Ciliates,Foraminifera and Amoeboid Protists in Marine,Brackish, and Freshwater Sediments

The quantitative importance of ciliates, foraminifers, and amoebae was investigated in marine, brackish, and freshwater sediments from 15 littoral stations. Total protozoan communities were usually dominated by ciliates in term of abundance, while amoebae often dominated in terms of biomass. Applying the biomass‐metabolic rate equation, ciliates, amoebae, and foraminifera were estimated to contribute 66% of the total abundance and 33% of the biomass, but up to 55% of the combined metabolic rate to the micro‐ and meiobenthos in the 15 sediments. Statistical analyses using ciliate data demonstrated: (1) species composition and community structures represented significant differences between freshwater and marine/brackish sediments, and subsequently between temperate and arctic sampling sites; (2) the occurrence of dominant ciliates and their allocation to feeding types indicated that herbivory was the most common feeding strategy in these sediments; (3) multivariate analyses showed all of the tested environmental factors (temperature, salinity, silt/clay, carbon, nitrogen, and chlorophyll a) to be important to varying degrees, but especially the combination of salinity, temperature, and silt/clay. Multiple factor effects or comprehensive influences might be important in regulating the distribution of protozoa in sediments. The importance of protozoa in sediment systems and the potential ecological significance of cysts are discussed.     

Analysis of the community structure of planktonic ciliated protozoa relative to trophic state in Florida lakes

The planktonic ciliate populations of 30 Florida lakes constituting a broad trophic gradient were examined to determine the response of protozoan community structure to increasing eutrophication. Both ciliate abundance and biomass were strongly related to lake trophic state. Comparison of the Florida data base with a comparable north temperate lake group indicated that subtropical lakes generally possess higher ciliate abundance and biomass at a given trophic state than temperate lakes. However the equations derived for each data base were not significantly different. Community diversity and species richness increased with increasing lake productivity. Highly acidic lakes displayed significantly reduced diversity and numbers of species when contrasted with nonacidic oligotrophic lakes. Small-bodied (< 30 um) ciliates dominated all lakes but were proportionally less important in oligotrophic lakes. Presence-absence data produced three assemblages: an ubiquitous association of primarily small ciliate taxa, a group of large ciliates mainly restricted to eutrophic-hypereutrophic lakes, and a very large ciliate,Stentor niger, which dominated the protozoan communities of acidic oligotrophic lakes.     

Carbon flow dynamics in the pelagic community of the Sau Reservoir (Catalonia,NE Spain)

Changes in the pelagic community structure and activity along the longitudinal axis of the eutrophic Sau Reservoir (Catalonia, NE Spain) were studied between 1996 and 1999. Samples were taken from several transects from river to dam, measuring dissolved organic carbon (DOC), bacterial abundance and production, chlorophyll a concentration, heterotrophic nanoflagelate (HNF) and ciliate abundances and their grazing rates, and zooplankton density. The role of microbial and classical food chains (i.e., based directly on phytoplankon) were compared in the Sau Reservoir by analysing river-to-dam gradients in biomass and carbon and their temporal changes. The detritic metabolic pathway was more important near to the inflow, due to high allochthonous organic matter loads allowing the rapid development of the microbial food web. Protozoans (HNF and ciliates) consumed most of the bacterial production (i.e., >50%) in the reservoir. As opposed to the systems of lower trophic status ciliate carbon biomass and bacterivory contributions were larger than those of the HNF. We estimated species-specific ciliate growing rates on bacteria and distinguished several periods with high importance of distinct ciliate communities.     

Unimodal patterns of microbial communities with eutrophication in Mediterranean shallow lakes

The role of the microbial communities in the classical planktonic food web and its response to eutrophication in shallow lakes is still contradictory. Mediterranean shallow lakes with different eutrophication levels were sampled to study the influence of eutrophication on the microbial food web (MFW) and their contribution to the planktonic food web. Percentage of ciliate biomass in the metazooplankton (MZP) showed a U-shaped trend with eutrophication, with maximum at both ends of the chlorophyll-a (Chla) gradient. The MZP to phytoplankton ratio demonstrated a unimodal pattern with minimum values at the two ends of the Chla gradient and maximum values in the Chla range 5-10 μg l^?1. In contrast, the MFW to phytoplankton ratio reached its minimum in the central part of the Chla gradient and maximum values at the extremes of the gradient. These patterns support the hypothesis that the relative importance of bacteria and ciliates is lowest in mesotrophic shallow lakes, and highest in oligotrophic and hypereutrophic systems. These results stress the importance of protozoan in the trophic web, and indicate it is essential to include this group, especially ciliates, when quantifying zooplankton in warm shallow lakes.     

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.     

The annual cycle of planktonic ciliates in nearshore waters at Signy Island, Antarctica

The abundance and biomass of marine planktonic ciliates in BorgeBay, Signy Island, were determined at monthly intervals betweenApril 1990 and June 1991. At least 24 different ciliate taxawere recorded from samples preserved in Lugol's iodine, includingthe tintinnids Codonellopsis balechi, Cymalocylis convallaria,Laackmaniella naviculaefera and Salpingella sp., and the aloricatetaxa Didinium sp. and Mesodinium rubrum. Ciliate abundance andbiomass exhibited a clear seasonal cycle with high values duringthe austral summer and low values in the austral winter. Abundanceranged from 0.3 10³l^–1 in September to 2.3 10³l^–1in January, while biomass ranged from 0.5 µg C l^–1in October to 12.6 µg C l^–1 in December. Small ciliatesdominated abundance throughout the year, and biomass duringwinter. Larger ciliates contributed most to biomass during summer.Aloricate ciliates were common throughout the year, while tintinnidscontributed substantially to abundance and biomass only duringsummer. Salpingella sp. was the commonest tintinnid, but C.convallariacontributed most to tintinnid biomass. The seasonal patternof ciliate abundance and biomass matched that of chlorophylla concentration and bacterial biomass, suggesting tight trophiccoupling between ciliates and other components of the pelagicmicrobial community. ¹Present address: Scott Polar Research Institute, Universityof Cambridge, Lensfield Road, Cambridge CB2 1ER, UK     

A comparative study on planktonic ciliates in two shallow mesotrophic lakes (China): species composition, distribution and quantitative importance

The species richness and seasonal development of planktonic ciliates were studied and compared in two shallow mesotrophic lakes, one covered with dense submerged macrophytes, the other macrophyte poor. Considerable differences in ciliate species composition, dominant taxa, abundance and biomass were observed. Ciliates were much more species rich in the macrophyte-rich lake, while they were more abundant numerically in the macrophyte-poor lake. Altogether, 96 species, included in 53 genera, 14 orders were identified. Among them, 80 species (included in 45 genera, 14 orders) observed from the macrophyte-rich lake, against 49 species (36 genera, 12 orders) were from the macrophyte-poor lake. In the macrophyte-rich lake, the mean abundance and biomass were 13.5 cells ml^-1 and 547.10 g l^-1 f.w.; abundance and biomass were higher in spring and winter; naked oligotrichs dominated total ciliate abundance and Peritrichida dominated the biomass. In the macrophyte-poor lake, ciliate mean abundance and biomass were 35.5 cells ml^-1 and 953.39 g l^-1 f.w.; abundances peaked in autumn; Scuticociliates dominated the abundance and Tintinnids dominated the biomass. Possible causes for the observed differences are discussed.     

2007年10月南海北部浮游纤毛虫的丰度和生物量

报道2007年10月南海北部海域(21°25.47′N 17°24.95′N,109°28.86′E 113°13.01′E)纤毛虫丰度和生物量的水平分布及砂壳纤毛虫的种丰富度。包括了13个断面的82个站位,Rosette采水器采水,水深低于15 m的站位采0,5 m和10 m;小于30 m站位,采0,10 m和底层;大于30 m的站位,采0,10,30 m和底层。纤毛虫丰度为0 5757 ind./L,平均(848±776)ind./L。无壳纤毛虫占绝对优势,其丰度占纤毛虫总丰度的比例平均为(91.9±9)%;纤毛虫生物量为0 12.09μg C/L,平均是(1.2±1.54)μg C/L,无壳纤毛虫的生物量平均为(0.94±1.27)μg C/L,占纤毛虫总生物量的78.6%。共发现砂壳纤毛虫16个属,49种,拟铃虫最多,具有一定的季节性。纤毛虫水体(40 m到表层)丰度为6.4×1069.1×107ind./m2,平均是(3.6×106±1.4×106)ind./m2;水体生物量3.6 195.8 mg C/m2,平均(48.1±33.7)mg C/m2。纤毛虫多分布于近岸浅水区(高温低盐,高Chl a),最大丰度要高于我国其他海区,不是Chl a最高的地方纤毛虫的丰度也最大,纤毛虫丰度最大时Chl a偏低。     

The distribution of ciliates on Ecology Glacier (King George Island, Antarctica): relationships between species assemblages and environmental parameters

Ciliates are important consumers of pico- and nano-sized producers, are nutrient regenerators, and are an important food source for metazoans. To date, ecological research on ciliates has focused on marine ecosystems rather than on glacier habitats. This paper presents the first major study on ciliates from the Ecology Glacier (South Shetland Islands, Antarctica). The objective of the study was to investigate the structure and spatial distribution of ciliate communities and to identify the environmental factors determining the structure of the assemblages. Microbial communities were collected from three habitats: surface snow, cryoconite holes, and glacier streams. Sampling was carried out every 3–4 days from January 17 to February 24, 2012. A total of 18 ciliate taxa were identified. The species richness, abundance, and biomass of protozoa differed significantly between the stations studied with the lowest numbers in streams on the glacier surface and the highest numbers in cryoconite holes. The RDA performed to specify the direct relationships between the abundance of ciliate taxa and environmental variables showed obvious differences between studied habitats. The analysis showed that all variables together explained 62.4 % of total variance. However, variables that significantly explained the variance in ciliate communities in cryoconite holes, snow, and surface streams were temperature, conductivity, and total nitrogen. Further research is required to explain the impact of biotic factors influencing the presence of ciliates, including the abundance of bacteria, microalgae, and small Metazoa.     

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 campaigns between March and December 2006. Total ciliate and dinoflagellate abundance mirrored the seasonal progression of phytoplankton, peaking with 5.8 × 10⁴ cells l⁻¹ in April at an average chlorophyll a concentration of 10 μg l⁻¹. Dinoflagellates were more abundant than ciliates, dominated by small athecates. Among ciliates, aloricate oligotrichs dominated the assemblage. A large fraction (>60%) of ciliates 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 μg C l⁻¹ highest in conjunction with the phytoplankton spring bloom in April. Growth experiments revealed similar specific growth rates for heterotrophic ciliates 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 Kongsfjorden and need to be taken into account when discussing the fate of phytoplankton and biogeochemical cycling in Arctic marine ecosystems.     

Size dependence of composition, photosynthesis and growth in the colony-forming freshwater ciliate, Ophrydium versatile

1. Ophrydium versatile is a symbiotic ciliate which forms gelatinous colonies up to several centimetres in diameter in transparent temperate lakes. The ciliates are evenly spaced at the colony surface and constitute a small proportion of the surface area (7%) and volume (3.1%) of the colony, but a large proportion of organic carbon (74%) and nitrogen content (82%) (exemplified for 1 cm³ colonies). The majority of the colony volume is formed by the jelly. The biomass proportion of ciliates scales inversely with colony size, following the decline of surface area to colony volume. The largest colonies found in Danish lakes in early summer contain almost 1 million ciliates, and assuming they derive from a single ciliate undergoing exponential division, they need twenty generations and, presumably, almost a year to reach maximum size. 2. The ciliates contain numerous symbiotic zoochlorellae that constitute about 10% of ciliate volume and more than half of the carbon content. Zoochlorellae dominate oxygen metabolism of the assemblage, resulting in low light compensation points, a large diel photosynthetic surplus, and a marked dependence on light for sustained growth and ciliate metabolism. Estimated gross photosynthesis (7ng C ciliate^?1 day^?1) of Ophnrydium from shallow, clear waters in June greatly exceeded the estimated carbon contained in filtered bacteria and small algae (1.9ng C cilicate^?1 day^?1). Nitrogen and phosphorus content of the prey, however, may provide the main nutrient source consistent with the correspondence between mass-specific rates of nutrient uptake and measured relative growth rates (average 0.067 day^?1, generation time 10 days). 3. The large Ophrydium colonies require increased allocation of photosynthetic carbohydrates with increasing colony size to maintain the jelly. The large colonies tend to become gas-filled, floating, mechanically destroyed and their ciliate inhabitants abandon them as swarmers. Colony formation, however, should offer protection against predators which may be more important for the natural abundance than the costs of growing in a colony.     

土壤纤毛虫群落对退牧还草生态恢复的响应——以玛曲县为例

为研究退牧还草对土壤纤毛虫群落特征的影响、退牧还草后土壤环境变化以及如何利用原生动物纤毛虫群落特征来评价退还效果的可行性,于2015年5月至2016年3月在甘肃省甘南藏族自治州玛曲县选取3个不同恢复年限的草地样点和1个未经过退牧还草对照样点,采用"非淹没培养皿法"、活体观察法和培养直接计数法对土壤纤毛虫的物种数和密度进行测定,同时测定了土壤温度、pH值、含水量、土壤孔隙度、速效钾、速效氮、速效磷、全氮、全钾、全磷和有机质含量,并分析了在生态逐渐恢复条件下,土壤纤毛虫群落特征与土壤环境因子间的相关性。研究共鉴定到纤毛虫95种,隶属9纲15目21科28属。研究发现,退牧还草样地与未退牧还草样地的土壤纤毛虫的物种分布存在明显差异:退牧还草后的3个样点间的物种相似性减小,群落组成复杂化,纤毛虫丰度、丰富度指数、均匀度指数和物种多样性指数增高。相关性分析结果表明,退牧还草后,对纤毛虫群落结构稳定性影响最主要的是土壤有机质、含水量和土壤全氮、全磷和全钾的含量,不同恢复年限样点的土壤纤毛虫群落组成差异较大。土壤纤毛虫群落对退牧还草生态恢复过程中土壤环境条件的变化有较好的响应。     

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.     

Distribution of planktonic ciliates in highly coloured subtropical lakes: comparison with clearwater ciliate communities and the contribution of myxotrophic taxa to total autotrophic biomass

SUMMARY 1. The planktonic ciliate communities of eleven organically coloured north and central Florida lakes representing a variety of trophic conditions were examined during 1979–80. The total abundance and biomass of ciliates were not significantly different from comparable clearwater lakes and only minor taxonomic replacements were noted at the order level.
2. Timing of population peaks of oligotrophic lakes was dissimilar to clearwater lakes of the same trophic state, but seasonality in meso-trophic and eutrophic lakes resembled patterns described for comparable clearwater lakes.
3. Various ciliate components were strongly correlated with chlorophyll a concentrations, but only moderately correlated to dominant phytoplankton groups. No significant correlations were found between ciliate components and bacterial abundance.
4. Myxotrophic taxa numerically dominated oligotrophic systems, particularly during midsummer, and accounted for a large percentage of the total ciliate biomass. Estimates of the ciliate contribution to total autotrophic biomass indicate that these zoochlorellae-bearing protozoa may account for much of the autotrophic biomass during midsummer periods in coloured lakes, and thus may lead to an overestimation of phytoplankton standing crops available to zooplankton grazers if chlorophyll a is used as a surrogate measure of algal biomass.     

Impacts of environmental scenarios on chlorophyll-a in the management of shallow, eutrophic lakes following biomanipulation: An application of a numerical model

Accurate prediction of species changes in lake ecosystems following biomanipulation measures is of paramount importance in view of water quality management. The temporal variation of phytoplankton biomass as chlorophyll-a and transparency as Secchi depth measurements are studied in the Lake Bleiswijkse Zoom, The Netherlands, with a comprehensive structural dynamic model. In the formulation of the biological model, phytoplankton as several species, zooplankton, detritus, planktivores and benthivores, and piscivores are considered to be major contributing state variables for the model. The primary goal of this paper is to describe the possible impacts of several environmental scenarios on chlorophyll-a biomass qualitatively as it would help lake and environmental managers and relevant authorities elucidate the processes of eutrophication and biomanipulation in a broad way. Some of the scenarios that have been studied by this model are: (1) The effect of fixed stoichiometry in terms of internal nitrogen and phosphorus that are tied up within algal cells; (2) the effects of external phosphorus limitation; (3) light limitation and external nitrogen limitation on algal growth; (4) probable consequences that have taken place within the chlorophyll-a biomass due to change in biomasses of various aquatic organisms; and (5) possible changes of chlorophyll-a biomass due to higher temperatures caused by global warming.     

Stratification and dynamics of microbial loop communities in Lake Fryxell, Antarctica

1. Lake Fryxell, situated in the McMurdo Dry Valleys, Antarctica, offers the opportunity to study microbial loop processes in the absence of crustacean zooplankton and other higher organisms. This is the first study of Lake Fryxell to provide detailed temporal and vertical variations of microbial loop organisms.
2. Protozoan communities are concentrated around the chemocline (9–10 m) in Lake Fryxell. Phototrophic nanoflagellates (PNAN), heterotrophic nanoflagellates (HNAN) and ciliates formed deep maxima of 14 580, 694 and 58 cells mL−1 respectively. Although abundance and biomass at the chemocline was high, diversity of protozoa was low, Plagiocampa accounting for> 80% of the total ciliate biomass.
3. In the mixolimnion (4.5–8 m), protozoa were less abundant, but more diverse, with 24 ciliate morphotypes being identified within this region of the water column. Inter-annual variability of protozoan biomass and abundance was greater in the mixolimnion than at the chemocline due to more variable nutrient and prey concentrations.
4. Physicochemical gradients in Lake Fryxell were very stable because the perennial ice cover reduced wind driven currents. As a consequence, ciliate species occurred in distinct depth strata, Monodinium being most abundant directly beneath the ice cover, Askenasia having maximum abundance at 8 m and Plagiocampa dominating ciliate biomass at the chemocline. The lack of vertical mixing reduced seasonal successions of PNAN and ciliate species. Three cryptophyte species dominated the PNAN community at all times (>79% of total biomass).     

Drift-ice and under-ice water communities in the Gulf of Bothnia (Baltic Sea)

The algal, protozoan and metazoan communities within different drift-ice types (newly formed, pancake and rafted ice) and in under-ice water were studied in the Gulf of Bothnia in March 2006. In ice, diatoms together with unidentified flagellates dominated the algal biomass (226 ± 154 μg ww l⁻¹) and rotifers the metazoan and protozoan biomass (32 ± 25 μg ww l⁻¹). The under-ice water communities were dominated by flagellates and ciliates, which resulted in lower biomasses (97 ± 25 and 21 ± 14 μg ww l⁻¹, respectively). The under-ice water and newly formed ice separated from all other samples to their own cluster in hierarchical cluster analysis. The most important discriminating factors, according to discriminant analysis, were chlorophyll-a, phosphate and silicate. The under-ice water/newly formed ice cluster was characterized by high nutrient and low chlorophyll-a values, while the opposite held true for the ice cluster. Increasing trends in chlorophyll-a concentration and biomass were observed with increasing ice thickness. Within the thick ice columns (>40 cm), the highest chlorophyll-a concentrations (6.6–22.2 μg l⁻¹) were in the bottom layers indicating photoacclimation of the sympagic community. The ice algal biomass showed additional peaks in the centric diatom-dominated surface layers coinciding with the highest photosynthetic efficiencies [0.019–0.032 μg C (μg Chl-a ⁻¹ h⁻¹) (μE m⁻² s⁻¹)⁻¹] and maximum photosynthetic capacities [0.43-1.29 μg C (μg Chl-a ⁻¹ h⁻¹)]. Rafting and snow-ice formation, determined from thin sections and stable oxygen isotopic composition, strongly influenced the physical, chemical and biological properties of the ice. Snow-ice formation provided the surface layers with nutrients and possibly habitable space, which seemed to have favored centric diatoms in our study.     

Trophic-functional patterns of biofilm-dwelling ciliates at different water depths in coastal waters of the Yellow Sea,northern China

Vertical variations in trophic-functional patterns of biofilm-dwelling ciliates were studied in coastal waters of the Yellow Sea, northern China. A total of 50 species were identified and assigned to four trophic-functional groups (TFgrs): algivores (A), bacterivorous (B), non-selective (N) and raptors (R). The trophic-functional structures of the ciliate communities showed significant variability among different water depths: (1) with increasing water depth, relative species numbers and relative abundances of groups A and R decreased sharply whereas those of groups B and N increased gradually; (2) in terms of the frequency of occurrences, group A dominated at depths of 1–3.5 m whereas group B dominated at 5 m, while in terms of the probability density function of the trophic-functional spectrum, group A was the highest contributor at 1 m and group B was highest at the other three depths; (3) distance-based redundancy analyses revealed significant differences in trophic-functional patterns among the four depths, except between 2 and 3.5 m (P > 0.05); and (4) the trophic-functional trait diversity increased from 1 to 3.5 m and decreased sharply at 5 m. Our results suggest that the biofilm-dwelling ciliates maintain a stable trophic-functional pattern and high biodiversity at depths of 1–3.5 m.     

Phytoplankton biomass and chlorophyll-a in some shallow lakes in central Europe

Based on 388 parallel data of phytoplankton biomass and chlorophyll-a of two shallow lakes and two ponds, the following results were obtained:

1. Relative chlorophyll-a content of phytoplankton biomass varied between 0.08–1.88%; chlorophyll-a concentration showed great differences among lakes.
2. Significant correlations (r = 0.68–0.92) were established between phytoplankton biomass and chlorophyll-a concentration. The regression in the artificial ponds was non-linear.
3. In parallel with the increase of average cell volume, a decrease in relative chlorophyll-a content was observed. A significant correlation (r = + 0.83) between the two variables was found. Relative chlorophyll-a content of phytoplankton is a log-function of average cell volume.