An approach to analyzing environmental drivers to shape spatial variations in body-size structure of biofilm-dwelling protozoa during an annual cycle in marine ecosystems

As an inherent trait, body-size structure has been used to summarize functional features of a community instead of taxonomic resolutions due to the high redundancy for bioassessment. In this study, the multivariate approaches were used to determine the environmental drivers to the spatial variation in body-size structure based on an annual dataset of biofilm-dwelling protozoa. Samples were monthly collected at four stations within a gradient of pollution in coastal waters of the Yellow Sea, northern China during a 1-year cycle. The second-stage (2STAGE) clustering and ordination analyses demonstrated that the annual patterns were significantly different among four sampling stations. Mantel analysis showed the spatial variations in body-size structures of the protozoa were significantly correlated with the water quality status along the pollution gradient. Best matching analysis revealed that the potential environmental drivers to shape the spatial difference in body-size structure may be pH, chemical oxygen demand (COD) and nutrients (e.g., soluble phosphates, ammonia and nitrates). It is suggested that the multivariate approaches used may determine the environmental drivers to shape the spatial variations in body-size structure of biofilm-dwelling protozoa in marine ecosystems.     

Body-size spectra of biofilm-dwelling protozoa and their seasonal shift in coastal ecosystems

Community-based assessment of protozoa is usually performed at a taxon-dependent resolution. As an inherent ‘taxon-free’ trait, however, body-size spectrum has proved to be a highly informative indicator to summarize the functional structure of a community in both community research and monitoring programs in aquatic ecosystems. To demonstrate the relationships between the taxon-free resolution of protozoan communities and water conditions, the body-size spectra of biofilm-dwelling protozoa and their seasonal shift and environmental drivers were explored based on an annual dataset collected monthly from coastal waters of the Yellow Sea, northern China. Body sizes were calculated in equivalent spherical diameter (ESD). Among a total of 8 body-size ranks, S2 (19–27 μm), S3 (28–36 μm), S4 (37–50 μm) and S5 (53–71 μm) were the top four levels in frequency of occurrence, while rank S1 (13–17 μm), S2 and S4 were the dominant levels in abundance. These dominants showed a clear seasonal succession: S2/S4 (spring) → S2/S4 (summer) → S4 (autumn) → S2 (winter) in frequency of occurrence; S1 (spring) → S4 (summer) → S2 (autumn) → S1 (winter) in abundance. Bootstrapped average analysis showed a clear seasonal shift in body-size spectra of the protozoa during a 1-year cycle, and the best-matching analysis demonstrated that the temporal variations in frequency of occurrence and abundance were significantly correlated with water temperature, pH, dissolved oxygen (DO), alone or in combination with chemical oxygen demand (COD) and nutrients. Thus, the body-size spectra of biofilm-dwelling protozoa were seasonally shaped and might be used as a time and cost efficient bioindicator of water quality in marine ecosystems.     

Insights into discriminating water quality status using new biodiversity measures based on a trait hierarchy of body-size units

Biofilm-dwelling protozoa have successfully used as a feasible bioindicator for bioassessment of water quality status in marine ecosystems. Based on a dataset of biofilm-dwelling protozoa in coastal waters of the Yellow Sea, we demonstrated a spatial variation in body-size spectrum of protozoan communities along a gradient of increasing environmental pollution. Two biodiversity indices, as a new indicator of water quality, were proposed, first being body-size diversity (Δ′) logistically corresponded to taxonomic diversity index but with a trait hierarchy of body-size units based on Euclidean distance resemblance, and the second a modified body-size diversity index (Δ′_m) with a modified hierarchy based on the trait matrix. The values of both indices Δ′ and Δ′_m were found to be significantly correlated with the changes of environmental variables, especially the nutrients. Furthermore, the body-size diversity (Δ′_mrk) at body-size-rank-1 (“genus-level”) resolution might be used as a potential surrogate of those at “species-level” resolution. Thus, we suggest that the ecological parameters based on body-size spectrum may be used as potential bioindicator of water quality status, and that the body-size rank sufficiency might be an effective time-efficient protocol for monitoring programs by identifying taxa to “genus-level” body-size rank.     

An approach to analysis of functional redundancy in protozoan communities for bioassessment in marine ecosystems

It is necessary to detect how much ecological redundancy or response units (RUs) exist in communities for reducing the “signal-to-noise” ratios of the observed full species data in community-based ecological research and monitoring programs. To reveal the functional redundancy in ciliated protozoan communities in marine ecosystems for both ecological research and monitoring programs, a multivariate approach (peeling procedure) was used to identify the response units to the environmental changes using a dataset of biofilm-dwelling ciliates from coastal waters of the Yellow Sea, northern China. From the full 141-species dataset, three subsets with sufficient information of the whole community (correlation coefficient >0.75) were identified as response units (RUs 1–3) at three levels of functional redundancy, which comprised 20, 26 and 27 species, respectively. These response units appeared to be interchangeable between functional equivalents on both spatial and temporal scales. In terms of relative abundance, RU1, which predominated the ciliate communities over 1-year period, and RU2, which occurred only in warm seasons (except winter) with a peak in summer, presented a decreasing trend, while RU3, which distributed all four seasons with two peaks in summer and autumn, increased with the increase of pollution level. Furthermore, high proportions of bacterivores were found in RU1 during warm seasons and represented an increase trend, while high relative abundances of algivores occurred in RUs 2 and 3 appeared to be decreasing along the pollution gradient. These results demonstrated that the ciliated protozoan assemblages have high functional redundancy in response to environmental changes in marine ecosystems.     

An approach to analysis of colonization dynamics in community functioning of protozoa for bioassessment of marine pollution

Biological trait analysis is a powerful tool to summarize the spatial/temporal patterns of community functioning and ecosystem process at taxon-free resolutions. To identify the optimal colonization period with high homogeneity in functional patterns of protozoa for bioassessment, 1-month baseline colonization survey was conducted in coastal waters of the Yellow Sea. A fuzzy-coding functional trait system was used to summarize the functional structure of protozoan communities during the colonization process. The functional patterns showed a low homogeneity during the early stage (3–7 days), followed by a stable stage (10–14 days) with high homogeneity, and the last stage (21–28 days) with high heterogeneity. The functional richness showed a low variability, while the functional evenness and divergence generally showed a decreasing trend during the whole colonization process. Furthermore, the functional dispersion and RaoQ indices generally leveled off only during the stable stage. These results suggest that it is necessary to determine the optimal exposure time period with high homogeneity of community functioning for bioassessment using protozoan colonization in marine ecosystems.     

Identifying functional species pool of planktonic protozoa for discriminating water quality status in marine ecosystems

It is cost-effective protocol to identify a functional species pool for marine bioassessment by removing redundant species from a raw dataset. The feasibility of functional species pool for discriminating water quality status was studied based on a dataset of 120 samples of ciliated protozoa. From the full 60-species dataset of the whole ciliate communities, a 35-species subset was identified as a functional species pool, the species number, abundance and biodiversity indices of which were significantly correlated with those of the full species dataset. The spatial pattern of the subset was significantly related to the changes in nutrients soluble reactive phosphates (SRP), nitrate/nitrite nitrogen (NO₃-N/NO₂-N) and ammonium nitrogen (NH₄-N). Four indices of the taxonomic diversity (Δ), taxonomic distinctness (Δ*), average in taxonomic distinctness (Δ⁺) and the variation in taxonomic distinctness (Λ⁺) based on this small species pool were significantly correlated with the changes of nutrients NO₃-N and/or (NH₄-N). The paired indices Δ⁺ and Λ⁺ showed a clear decreasing trend of departure from the expected taxonomic pattern. These findings suggest that the 35-species functional species subset may be used as a feasible functional surrogate of ciliated protozoan assemblages for community-based bioassessment in marine ecosystems.     

Can annual cyclicity of protozoan communities reflect water quality status in coastal ecosystems?

With many advantages, many ecological parameters of protozoan communities have been successfully used as a useful bioindicator for bioassessment of water quality in Chinese marine waters. However, as regard the response of the annual cyclicity of protozoan communities to seasonal environmental stress, a further investigation was needed. In this study, the cyclicity of annual variations in community patterns of biofilm-dwelling protozoa was studied based on an annual dataset. Samples were monthly collected, using glass slide method, at four stations, within a pollution gradient, in coastal waters of the Yellow Sea, northern China during a 1-year period. The cyclicity patterns of the microbiota represented a significant spatial variation among four stations. The low value of cyclicity coefficients occurred in heavily polluted area, while the high values were in less stressed areas. Correlation analysis showed that the cyclicity measure was significantly related to environmental variables ammonia, transparency and dissolved oxygen. Thus, it is suggested that the annual cyclicity of protozoan communities may be used as a potential bioindicator of bioassessment in marine ecosystems.     

Hierarchical structure of stream ecosystems: consequences for bioassessment

It has long been recognized that communities and their ecosystems are structured at several, nested spatial scales. But identifying the appropriate scale(s) to collect, analyse and interpret data to answer specific questions about ecosystems has been a vexing problem for ecologists. We collected observations of the benthic invertebrate community and its environment in 10 primarily agricultural tributary streams of the Thames River in southwestern Ontario, Canada. Within each stream we sampled two reaches, in each reach we sampled three riffles, and in each riffle we took three kick samples of invertebrates and characterized the substrate environment. We also characterized the habitat at each of the 20 reaches (10 streams × 2 reaches/stream). Most of the variability in the stream invertebrate community structure (as described with taxonomic richness and the biotic index of tolerance, as well as by the Bray-Curtis distance of the community composition from the mean at a spatial scale) was at larger spatial scales of among streams and between riffles. Much of the substrate and habitat variation was also at the larger spatial scales, as were correlations between the biota and the environment of the benthic invertebrate community. We concluded that for the purposes of bioassessment, characterization of one reach per stream is sufficient, at least in this context, for describing a stream and evaluating its health. Handling editor: R. Norris     

Seasonal variations in colonization dynamics of periphytic protozoa in coastal waters of the Yellow Sea,northern China

The colonization features of periphytic protozoa have proved to be a useful tool for indicating water quality status in aquatic ecosystems. In order to reveal the seasonal variations in colonization dynamics of the protozoa, a 1-year baseline survey was carried out in coastal waters of the Yellow Sea, northern China. Using glass slides as artificial substrates, a total of 240 slides were collected at a depth of 1 m in four seasons after colonization periods of 3, 7, 10, 14, 21, and 28 days. A total of 122 ciliate species were identified with 21 dominant species. The colonization dynamics of the protozoa were well fitted to the MacArthur-Wilson and logistic models in all four seasons (P < 0.05). However, the equilibrium species numbers (S_eq), colonization rates (G), and the time to 90% S_eq (T_90%) represented a clear seasonal variability: (1) more or less similar levels in spring and autumn (S_eq = 29/23; G = 0.301/0.296; T_90%=7.650/7.779); (2) with a significant difference in summer and winter (S_eq = 32/121; G = 0.708/0.005; T_90% = 3.252/479.705). Multivariate approaches demonstrated that the exposure time for the species composition and community structure of the protozoa to an equilibrium period were 10–14 days in spring and autumn, but less and more time periods were needed in summer and winter, respectively. Based on the results, we suggest that the colonization dynamics of periphytic protozoa were different within four seasons, and an optimal sampling strategy for monitoring surveys should be modified during different seasons in marine ecosystems.     

A multi-agency comparison of aquatic macroinvertebrate-based stream bioassessment methodologies

Sharing ecological data can increase the amount of information available to state and federal agencies to manage water resources. Because state agencies in the US use different methods to assess biological water quality, the quality and comparability of data must be understood before data can be shared. The documentation of data quality objectives and performance characteristics has been recommended as a way to compare biological data collected using different methods. To address this issue, five state agencies conducted a pilot study on methods comparability and performance characteristics of their methods and assessments (i.e. precision and sensitivity) at two streams located in the coastal plain of the southeastern US. Taxa richness and North Carolina Biotic Index (NCBI) results were not directly comparable among agencies using different sample processing, collection, and analysis methods, although these results often produced similar site rankings. Comparison of performance characteristics across methods suggested that assessment information could be shared among some agencies despite differences in methods and metric results.     

An approach to analyzing spatial patterns in annual dynamics of planktonic ciliate communities and their environmental drivers in marine ecosystems

The environmental drivers to shape the spatial patterns in annual dynamics of the planktonic ciliate communities were studied based on an annual dataset from a bay, northern Yellow Sea. Samples were biweekly collected at five stations with different environmental condition status during a 1-year period. The second-stage-analysis-based multivariate approaches were used to reveal the internal dynamics in annual patterns of the ciliate assemblages. Results showed that: (a) there was a clear spatial variability in annual dynamics among five stations; (b) the dominant species represented different succession dynamics among four samples stations during the 1-year cycle; and (c) the spatial variations in annual patterns of the ciliates were significantly correlated with nutrients, alone or in combination with salinity and dissolve oxygen (DO). Thus, it is suggested that the nutrients may be the main drivers to shape the spatial patterns in annual dynamics of planktonic ciliate communities in marine ecosystems.     

The role of biofilms and protozoa in Legionella pathogenesis: implications for drinking water

Current models to study Legionella pathogenesis include the use of primary macrophages and monocyte cell lines, various free-living protozoan species and murine models of pneumonia. However, there are very few studies of Legionella spp. pathogenesis aimed at associating the role of biofilm colonization and parasitization of biofilm microbiota and release of virulent bacterial cell/vacuoles in drinking water distribution systems. Moreover, the implications of these environmental niches for drinking water exposure to pathogenic legionellae are poorly understood. This review summarizes the known mechanisms of Legionella spp. proliferation within Acanthamoeba and mammalian cells and advocates the use of the amoeba model to study Legionella pathogenicity because of their close association with Legionella spp. in the aquatic environment. The putative role of biofilms and amoebae in the proliferation, development and dissemination of potentially pathogenic Legionella spp. is also discussed. Elucidating the mechanisms of Legionella pathogenicity development in our drinking water systems will aid in elimination strategies and procedural designs for drinking water systems and in controlling exposure to Legionella spp. and similar pathogens.     

Development of a RIVPACS-type predictive model for bioassessment of wadeable streams in Wyoming

RIVPACS models produce a community-level measure of biological condition known as O/E, which is derived from a comparison of the observed (O) biota with those expected (E) to occur in the absence of anthropogenic stress. We used benthic macroinvertebrate and environmental data collected at 925 stream monitoring stations, from 1993 to 2001, to develop, validate, and apply a RIVPACS model to assess the biological condition of wadeable streams in Wyoming. From this dataset, 296 samples were identified as reference, 157 of which were used to calibrate the model, 46 to validate it, and 93 to examine temporal variability in reference site O/E-values. We used cluster analyses to group the model development reference sites into biologically similar classes of streams and multiple discriminant function analysis to determine which environmental variables best discriminated among reference groups. A suite of 14 categorical and continuous environmental variables best discriminated among 15 reference groups and explained a large proportion of the natural variability in biota within the reference dataset. Eleven of the predictor variables were derived from GIS. As expected, mean O/E-values for reference sites used in model development and validation were near unity and statistically similar. Temporal variability in O/E-values for reference sites was low. Test site values ranged from 0 to 1.45 (mean = 0.73). The model was accurate in both space and time and precise enough (S.D. of O/E-values for calibration data = 0.17) to detect modest alteration in biota associated with anthropogenic stressors. Our model was comparable in performance to other RIVPACS models developed in the United States and can produce effective assessments of biological condition over a broad, ecologically diverse region. We also provide convincing evidence that RIVPACS models can be developed primarily with GIS-based predictor variables. This framework not only simplifies the extraction of predictor variable information while potentially reducing expenditures of time and money in the collection of predictor variable information, but opens the door for development and/or application of RIVPACS models in regions where there is a paucity of local-scale, abiotic information.     

Use of marker pigments and functional groups for assessing the status of phytoplankton assemblages in lakes

Phytoplankton is a key biological quality element for the establishment of the Water Framework Directive (WFD) ecological status in reservoirs and lakes. In freshwaters, inverted microscope examination is the traditional standard method for estimating phytoplankton and assessing taxonomic composition. Based on the enumeration of algal units and measurements for biovolume calculation, this technique is cumbersome and time-consuming. In large monitoring programmes, such as the application of the WFD in lakes and reservoirs, chemotaxonomy (HPLC pigment analysis and CHEMTAX treatment) is ideally suited as an alternative method because it allows the rapid processing of large numbers of samples from numerous locations and depths, thereby providing ideal temporal and spatial resolution. The low taxonomical detail obtained by HPLC and CHEMTAX (phytoplankton classes or phyla) can easily be overcome by a rapid inverted microscope screening with identification of the dominant species. Combining HPLC and microscopy provides a useful method for monitoring phytoplankton assemblages, which can be used to implement the WFD with respect to phytoplankton. Here, we present the application of a method combining marker pigments and microscopy to phytoplankton samples from 12 Belgian reservoirs. This method substantially reduced the workload and enabled us to assess the status of the phytoplankton assemblage in these lakes. The method complies with the WFD, as it takes into account taxonomic composition, assesses abundance and biomass of the phytoplankton taxa, and easily detects blooms. Additionally, a set of templates of probability of occurrence of phytoplankton functional groups at the maximal ecological potential for reservoirs from the Central/Baltic region is presented, based on reference conditions defined for natural lakes from other regions.     

New ocean,new needs: Application of pteropod shell dissolution as a biological indicator for marine resource management

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Use of macroinvertebrate-based multimetric indices for water quality evaluation in Spanish Mediterranean rivers: an intercalibration approach with the IBMWP index

For the European Parliament and Commission to implement the Water Framework Directive (WFD), the water-quality indices that are currently used in Europe need to be compared and calibrated. This will facilitate the comparative assessment of ecological status throughout the European Union. According to the WFD, biologic indices should respond consistently to human impacts, using multimetric approaches and water-quality classification boundaries adjusted to a common set of normative definitions. The European Commission has started an intercalibration exercise to review biologic indices and harmonize class boundaries. We used data from rivers in Spain to compare the IBMWP (Iberian Biological Monitoring Working Party) index, which is commonly used by water authorities in Spain and by several research centers, with the Intercalibration Common Multimetric Index (ICM-Star), which was used as a standard in the intercalibration exercise. We also used data from Spanish rivers to compare the multimetric indices ICM-7 (based on quantitative data) and ICM-9 (based on qualitative data) with the IBMWP. ICM-7 and ICM-9 were proposed by the Mediterranean Geographical Intercalibration Group (Med-GIG). Additionally, we evaluated two new multimetric indices, developed specifically for macroinvertebrate communities inhabiting Mediterranean river systems. One of these is based on quantitative data (ICM-10), while the other is based on qualitative data (ICM-11a). The results show that the IBMWP index responds well to the stressor gradient present in our data, and correlates well with ICM-Star. Moreover, the IBMWP quality class boundaries were consistent with the intercalibration requirements of the WFD. However, multimetric indices showed a more linear relation with the stressor gradient in our data, and less variation in reference values. In addition, they may provide more statistical power for detecting potential environmental impacts. Multimetric indices produced similar results for quantitative and qualitative data. Thus, ICM-10 (also named IMMi-T) and ICM-11a (also named IMMi-L) indices could be used to meet European Commission requirements for assessing the water quality in Spanish Mediterranean rivers. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: Joel Trexler     

Use of response surface methodology for optimizing process parameters for high inulinase production by the marine yeast <Emphasis Type="Italic">Cryptococcus aureus</Emphasis> G7a in solid-state fermentation and hydrolysis of inulin

The optimization of process parameters for high inulinase production by the marine yeast strain Cryptococcus aureus G7a in solid-state fermentation (SSF) was carried out using central composite design (CCD), one of the response surface methodologies (RSMs). We found that moisture, inoculation size, the amount ratio of wheat bran to rice husk, temperature and pH had great influence on inulinase production by strain G7a. Therefore, the CCD was used to evaluate the influence of the five factors on the inulinase production by strain G7a. Then, five levels of the five factors above were further optimized using the CCD. Finally, the optimal parameters obtained with the RSM were the initial moisture 61.5%, inoculum 2.75%, the amount ratio of wheat bran to rice husk 0.42, temperature 29 °C, pH 5.5. Under the optimized conditions, 420.9 U g⁻¹ of dry substrate of inulinase activity was reached in the solid-state fermentation culture of strain G7a within 120 h whereas the predicted maximum inulinase activity of 436.2 U g⁻¹ of inulinase activity of 436.2 U g⁻¹ of dry weight was derived from the RSM regression. This is the highest inulinase activity produced by the yeast strain reported so far. A large amount of monosaccharides and oligosaccharides were detected after inulin hydrolysis by the crude inulinase.