Periphytic Diatom Assemblages Research Articles

Role of microhabitats in shaping diversity of periphytic diatom assemblages

Diverse macrovegetation can provide heterogeneous habitats for benthic diatoms. The removal of macrophytes as direct plant control, however, can be considered as a threat, which can even lead to remarkable microhabitat alterations. Lake Tisza (Hungary) has a high nature conservation value, but it is also an important recreation centre, which is why very delicate water management is necessary including vegetation thinning. Here, we studied the importance of microhabitat heterogeneity (emergent, submerged and floating macrophytes) in maintaining diverse periphytic diatom assemblages. We hypothesized that the substrate type has greater influencing role on the composition and diversity of diatoms than the lake heterogeneity related to basins. We also assumed that floating vegetation hosts the most different and least diverse diatom assemblages. Our results mostly proved these hypotheses. Heterogeneous assemblages were formed on the different substrates (support hypothesis), however, the basin level differences were also detected (reject hypothesis). Our results also highlighted, that macrophyte species with lesser morphological complexity hosted the least diverse periphytic assemblages (support hypothesis). However, many unique and red list taxa were found on floating plants (reject hypothesis). These findings emphasize the key role of microhabitat complexity in maintaining diverse and healthy functioning of microbial assemblages in a multi-purpose reservoir.

Changing Water Levels in Lake Superior, MI (USA) Impact Periphytic Diatom Assemblages in the Keweenaw Peninsula

Predicted climate-induced changes in the Great Lakes include increased variability in water levels, which may shift periphyton habitat. Our goal was to determine the impacts of water level changes in Lake Superior on the periphyton community assemblages in the Keweenaw Peninsula with different surface geology. At three sites, we identified periphyton assemblages as a function of depth, determined surface area of periphyton habitat using high resolution bathymetry, and estimated the impact of water level changes in Lake Superior on periphyton habitat. Our results suggest that substrate geology influences periphyton community assemblages in the Keweenaw Peninsula. Using predicted changes in water levels, we found that a decrease in levels of 0.63 m resulted in a loss of available surface area for periphyton habitat by 600 to 3000 m2 per 100 m of shoreline with slopes ranging 2 to 9°. If water levels rise, the surface area of substrate will increase by 150 to 370 m2 per 100 m of shoreline, as the slopes above the lake levels are steeper (8–20°). Since periphyton communities vary per site, changes in the surface area of the substrate will likely result in a shift in species composition, which could alter the structure of aquatic food webs and ecological processes.

Functional and Compositional Responses of Periphyton Mats to Simulated Saltwater Intrusion in the Southern Everglades

Periphyton plays key ecological roles in karstic, freshwater wetlands and is extremely sensitive to environmental change making it a powerful tool to detect saltwater intrusion into these vulnerable and valuable ecosystems. We conducted field mesocosm experiments in the Florida Everglades, USA to test the effects of saltwater intrusion on periphyton metabolism, nutrient content, and diatom species composition, and how these responses differ between mats from a freshwater versus a brackish marsh. Pulsed saltwater intrusion was simulated by dosing treatment chambers monthly with a brine solution for 15 months; control chambers were simultaneously dosed with site water. Periphyton from the freshwater marsh responded to a 1-ppt increase in surface water salinity with reduced productivity and decreased concentrations of total carbon, nitrogen, and phosphorus. These functional responses were accompanied by significant shifts in periphytic diatom assemblages. Periphyton mats at the brackish marsh were more functionally resilient to the saltwater treatment (~ 2 ppt above ambient), but nonetheless experienced significant shifts in diatom composition. These findings suggest that freshwater periphyton is negatively affected by small, short-term increases in salinity and that periphytic diatom assemblages, particularly at the brackish marsh, are a better metric of salinity increases compared with periphyton functional metrics due to functional redundancy. This research provides new and valuable information regarding periphyton dynamics in response to changing water sources in the southern Everglades that will allow us to extend the use of periphyton, and their diatom assemblages, as tools for environmental assessments related to saltwater intrusion.

Evaluating features of periphytic diatom communities as biomonitoring tools in fresh, brackish and marine waters

The aims of this study were to assess the biodiversity of periphytic diatom assemblages in fresh, brackish and marine waterbodies of Korea, and to assess the effect of environmental and anthropogenic factors on parameters such as the quantity and biovolume of lipid bodies and deformations of diatoms as early warning measures of anthropogenic impact. Diatom samples were collected from 31 sites (14 freshwater, 10 brackish and 7 marine), which included less impacted (upstream) and impacted (downstream) sites in each water type. Our results showed higher abundance and biodiversity of periphytic diatoms at the less impacted sites in terms of species richness, Shannon index, cell count and biovolume of the communities than at the impacted sites for freshwater and estuarine sites, but not for marine sites. 84 diatom species were noted in freshwater, 80 in brackish water and 40 in marine waters. In comparison to diatoms of the impacted sites, those of less impacted freshwater, brackish and marine sites had less lipid bodies (also less biovolume) and a lower percentage of teratological frustules, and showed more mobile forms in the community. Principal component analysis (PCA) also showed clear segregation of impacted from less impacted sites by the extent of the presence of lipid bodies (higher both in number and biovolume) and deformities in diatom frustules. Pearson correlation analysis revealed that lipid body induction and deformities were positively correlated with metals (Cd, Co, Cr, Cu, Fe, Pb and Zn) and nutrients (total phosphorus and total nitrogen), whereas they showed negative correlation with salinity, dissolved oxygen, suspended solutes and pH. Life-forms, lipid bodies and deformities in diatoms may be an effective biomonitoring tool for assessing biological effects of pollutants in non-marine aquatic ecosystems in Korea.

Influence of enumeration time periods on detecting community parameters of periphytic diatoms using an artificial substratum in coastal waters

Community parameters of diatoms have been used as useful bioindicators for bioassessment of both lentic and lotic systems. The influence of enumeration time periods on detecting community parameters of periphytic diatom assemblages within different exposure times was studied using an artificial substratum in coastal waters of the Yellow Sea, northern China, during the period May–June 2010. Samples were collected at a depth of 1 m, and were examined with different enumeration time periods. Enumeration time periods represented a significant influence on detecting the community features of periphytic diatoms, although no significant changes occurred in periphytic diatom community structure between two enumeration schemes (within 24 h and 24–48 h). The delayed enumeration (within 24–48 h) may result in the similarity of the communities being reduced 10–29%, and in species numbers decreasing and in abundance increasing with exposure duration, respectively. The diversity (richness, evenness and diversity of species) indices were significantly decreased in almost all samples with >10% standard errors at some exposure times by the delayed enumeration scheme. These results suggest that the delayed enumeration may have resulted in the species richness and individual abundance of periphytic diatoms significantly decreasing and increasing, respectively, and thus significantly affected the analyses of species diversity for assessing water quality in marine ecosystems.

Responses and structural recovery of periphytic diatom communities after short-term disturbance in some rivers (Hanoi, Vietnam)

Field transfer experiments of periphytic diatom assemblages developed on artificial substrates were set up to assess the responses of those communities to environmental disturbances. The glass slides were positioned for colonization at the relatively unpolluted site (Red, in the Red River) and at the heavily polluted site (TL, in the To Lich River) in the beginning of the experiment. After a period of 2 weeks, the colonized glass slides were concomitantly transferred from the unpolluted Red site to the heavily polluted TL site and to the moderate polluted site (NT2, in the Nhue River) and, conversely, from the TL site to the Red site, and then to the NT2 site. The responses and the adapting capacity of periphytic diatom communities to environmental changes were assessed through the cell density, diversity index, species richness, taxonomic composition, and diatom indices after 2 and 4 weeks of transfer periods. For all transfers except for the transfer from the Red to the TL site in which the growth inhibition of diatom cells was found, the diatom density significantly increased until the end of the experiment. Thus, the diatom communities have expressed their pollution tolerance or sensitivities by changing their composition to adapt themselves to environmental changes. Characteristic species of the Red site (Gyrosigma scalproides, Navicula recens) were replaced by Nitzschia palea, Nitzschia umbonata, Aulacoseira granulate typical species of the NT2 site, in the biofilm transferred from the Red site to the NT2 site. The relative abundances of typical diatom species of the Red site proliferated in the biofilm transferred from the TL site to the Red site. The replacement of periphytic diatom communities appeared after the transfer from the second week at the different sites. The slow shift of the species towards the typical species at the TL site could result from the organized structure of diatoms within biofilm before the transfer from the Red site to the TL site. The shifts in values of the Index of Specific Polluosensitivity and Diatom Assemblage Index to organic pollution throughout the experiment indicated the clear sensitivity of these indices to water quality changes.

THE INFLUENCE OF SUBMERGED MACROPHYTES ON SEDIMENTARY DIATOM ASSEMBLAGES(1).

Submerged macrophytes are a central component of lake ecosystems; however, little is known regarding their long-term response to environmental change. We have examined the potential of diatoms as indicators of past macrophyte biomass. We first sampled periphyton to determine whether habitat was a predictor of diatom assemblage. We then sampled 41 lakes in Quebec, Canada, to evaluate whether whole-lake submerged macrophyte biomass (BiomEpiV) influenced surface sediment diatom assemblages. A multivariate regression tree (MRT) was used to construct a semiquantitative model to reconstruct past macrophyte biomass. We determined that periphytic diatom assemblages on macrophytes were significantly different from those on wood and rocks (ANOSIM R = 0.63, P < 0.01). A redundancy analysis (RDA) of the 41-lake data set identified BiomEpiV as a significant (P < 0.05) variable in structuring sedimentary diatom assemblages. The MRT analysis classified the lakes into three groups. These groups were (A) high-macrophyte, nutrient-limited lakes (BiomEpiV ≥525 μg · L(-1) ; total phosphorus [TP] <35 μg · L(-1) ; 23 lakes); (B) low-macrophyte, nutrient-limited lakes (BiomEpiV <525 μg · L(-1) ; TP <35 μg · L(-1) ; 12 lakes); and (C) eutrophic lakes (TP ≥35 μg · L(-1) ; six lakes). A semiquantitative model correctly predicted the MRT group of the lake 71% of the time (P < 0.001). These results suggest that submerged macrophytes have a significant influence on diatom community structure and that sedimentary diatom assemblages can be used to infer past macrophyte abundance.

Planktonic and periphytic diatoms as indicators of stress on great rivers of the United States: Testing water quality and disturbance models

Planktonic and periphytic diatom assemblages were investigated as potential biological indicators of ecological conditions in the Ohio, Missouri and Upper Mississippi rivers. Diatoms were analyzed to determine which of the two assemblage types was most appropriate for monitoring environmental conditions. The comparative effectiveness of diatom data format was similarly evaluated, testing relative and absolute abundance data. Stressor gradients for the rivers were created using principal components analysis for suites of water quality variables, landscape disturbance variables, and combined variables. Diatom-based weighted averaging transfer functions were developed for these integrated stressor gradients using each habitat and data format. Representing the diatoms as relative abundance data provided optimal tracking of environmental stress, and both periphyton and phytoplankton showed potential as indicators of disturbance. These results reinforce the use of relative abundance data, often used for diatom water quality monitoring, over more labor intensive data formats. Diatom-based models were also created to infer water quality measures and to compare measured and diatom-inferred water quality to landscape stressors. In most instances, diatom-inferred water quality data were more strongly related to watershed-based stressors. This investigation supports the value of diatoms in assessing landscape stressors in large rivers as well as the more traditionally applied water quality conditions. The findings further suggest both planktonic and periphytic diatom assemblages may be used as bioindicators of river condition and may provide unique stressor response information.

Recovery of seasonality on periphytic diatom assemblages in urban rivers

Recovery of seasonality on periphytic diatom assemblages in urban rivers

Ecological effects of flow regulation on macroinvertebrate and periphytic diatom assemblages in the Hawkesbury–Nepean River, Australia

AbstractThe effects of flow regulation on macroinvertebrates and periphytic diatoms were examined in the Hawkesbury–Nepean River system in Australia. Regulated sites below eight dams or weirs were compared with unregulated sites above the impoundments and sites on two nearby unregulated streams. The management of the water supply during the study created two types of flow regulation, sites with water supply releases and sites with comparatively small or no releases. The macroinvertebrate communities in three habitats and periphytic diatoms below the storages and weirs differed from the biota at unregulated sites above the weirs and on unregulated systems. The number of macroinvertebrate taxa in riffle and pool‐rock assemblages was significantly lower at regulated sites when compared with unregulated sites and the number of stream edge macroinvertebrate and diatom taxa was unaffected by regulation. Riffle and pool‐rock macroinvertebrate assemblages differed between the two types of regulation. However, periphytic diatom and edge habitat macroinvertebrate assemblages did not differ between the two types of flow regulation. Examination of environmental variables associated with the change in the biota suggested that the principal effect of the management of the water supply system in the Hawkesbury–Nepean River was changed hydrology rather than altered water quality. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Periphytic diatom assemblages in a stream rehabilitated with treated sewage receiving water from a natural stream

Periphytic diatom assemblages in a stream rehabilitated with treated sewage receiving water from a natural stream

Is genus or species identification of periphytic diatoms required to determine the impacts of river regulation

As periphytic diatoms are widely used for biological assessment of rivers, a comparison was made of the use of information at genus or species levels to test the effects of river regulation in eastern Australia. 74 species from 30 genera were recorded from 10 regulated and 13 unregulated sites. The interpretation of the effects of eight dams and weirs on the periphytic diatom assemblages gave broadly similar results whichever taxonomic level was used. The similarity of the efficiency of using data at either taxonomic level is probably related to the fact that the majority of genera have few species. It is suggested that the small number of species within each genus effectively reduces the chances of differing species responses to environmental disturbance negating the response at the genus level.

Diatom Indicators of Stream and Wetland Stressors in a Risk Management Framework

Ecological risk assessment and risk management call for "state-of-the-science" methods and sound scientific assessments of ecosystem health and stressor effects. In this paper recent developments of periphyton indicators of biotic integrity and ecosystem stressors of streams and wetlands are related in a framework of ecological metrics that can be used to quantify risk assessment and risk management options. Many periphyton metrics have been employed in past assessments of water quality and a periphyton indices of biotic integrity has been applied by the state of Kentucky. In addition, the sensitivity of species composition of periphytic diatom assemblages has been shown to respond predictably to ecological stressors so that specific pH, conductivity, and total phosphorus in wetlands and streams can be inferred with weighted average indices. Inference of nutrient conditions by diatom indicators of total phosphorus is shown to have sufficient precision to be a valuable complement to one-time measurement of highly variable total phosphorus in streams. Quantitative indices of sustainability and restorability of ecosystem integrity are proposed, respectively, as the changes in ecological conditions that can occur without significant change in ecological integrity or changes that are necessary to restore ecological integrity.

Lake Water Salinity and Periphytic Diatom Succession in Three Subarctic Lakes, Yukon Territory, Canada

Seasonal changes in water chemistry and periphytic diatom assemblages were monitored for a saline, a subsaline, and freshwater lake in the central Yukon Territory. Athalassic saline lakes, such as these, are believed to be extremely rare in arctic regions. All three study lakes exhibited a gradual shoreline retreat over the season (28 May to 22 August 1992) due to evaporative water loss. As the season progressed, the saline lake exhibited a marked increase in conductivity and salinity, similar to changes observed for inland salt lakes in more southern regions. The seasonal changes in water chemistry were less pronounced in the subsaline and freshwater lakes. The periphytic diatom populations of the saline lake closely tracked changes in the lake's salinity, exhibiting a successional shift from taxa with low salt tolerances (e.g., Nitzschia cf. commutata and N. cf. palea) to those with high salt tolerances (e.g., Amphora acutiuscula) over the study period. Periphytic diatoms in the subsaline and freshwater lakes also exhibited marked successional changes, shifting to almost complete dominance by a single species (Cocconeis placentula and Achnanthes minutissima respectively), but these shifts were not related to lake water salinity alone.Key words: lakes, diatoms, seasonal succession, saline, subarctic, Yukon

Diatom-temperature transfer functions based on the altitudinal zonation of diatom assemblages in Papua New Guinea: a possible tool in the reconstruction of regional palaeoclimatic changes

Indirect and direct gradient ordination techniques were used to study the relationship between present-day benthic and periphytic diatom assemblages and environmental factors along an altitudinal gradient in Papua New Guinea. Both within the screened initial data-set and a narrowly-defined subset of soft-water lakes, shifts in diatom assemblages are clearly related to altitudinal differences. This relation is used to construct transfer functions for inferring altitude (and hence average water temperature) from the diatom records. Calibration by canonical correspondence analysis (CCA) and simple weighted averaging calibration proved to be superior to models using WA with tolerance downweighting and to a simple WA model based on a selection of 52 indicator taxa. From the calibration models and the linear relationship between altitude and epilimnetic water temperature, the average lake water temperature can be predicted with an accuracy of 3.2°C. After further refinement, a transfer function for palaeotemperature based on diatoms would be of potential value for climatic reconstructions in tropical regions.

Multivariate analysis of periphytic and benthic diatom assemblages from Papua New Guinea

The benthic and periphytic diatom flora is studied in 136 fresh waters in Papua New Guinea. DCA ordination and TWINSPAN are used to describe 20 diatom assemblages. Conductivity, water temperature and altitude are the main sources for the variation in the data.

Spatial and Seasonal Variation of Diatom Assemblages Composition in a Partly Polluted River.

Environmental factors affecting the species composition of periphytic diatom assemblages were analyzed in the partly polluted Asa River, in Tokyo, Japan, using principal component analysis, individual differences scaling and direct gradient analysis. The effects of water pollution, seasonal change of temperature, and substrate were detected, among which pollution was the most influential in this river. Substrate had only a little effect. The existence of both direct and indirect effects (through water quality and temperature) was suggested.