High Diversity Of Diatoms Research Articles

Preliminary Assessment of Ecological Status of the Siversky Donets River Basin (Ukraine) Based on Phytoplankton Parameters and Its Verification by Other Biological Data

The river basin of Siversky Donets is of great scientific interest since this river runs through a territory with heavy industry (in particular, coal mining, chemical processing and metal industries). Within the basin, rivers of different sizes were explored (small, medium, large and extra-large) that flow through siliceous and calcareous rocks on the same elevation (lowland—below 200 m a.s.l.). Phytoplankton, as one of the Biological Quality Element, was used to perform the assessment of ecological status of the water bodies within the Siversky Donets river basin in 2019. The state monitoring program based on the updated approaches has been implemented in the river basin for the first time. The composition of phytoplankton species in the basin comprised 167 species (168 intraspecies taxa), mainly Bacillariophyta (63%) and Chlorophyta (22%) with the presence of other species (Cyanobacteria, Charophyta, Chrysophyta, Dinophyta and Euglenophyta). High species diversity and divisions amount are a distinctive property of the smaller rivers, while the bigger rivers show lower number of divisions. The “bloom” events, which are important ecological factors, were not detected in the Siversky Donets river basin. Algal species composition in plankton samples of the basin was identified and series of ecological parameters, such as habitat preferences, temperature, pH, salinity, oxygenation and organic water pollution according to Watanabe and Sládeček’s index of saprobity (S) trophic state and nitrogen uptake metabolism were analyzed. The ecological conclusions were also verified by a canonical correspondence analysis (CCA). The significance of the Canonical Correspondence Analysis (CCA) results was estimated of by a Monte-Carlo permutation test. The high concentrations of inorganic phosphorus compounds (permanganate index (CODMn)) and nitrite ions favored the diversity of Chlorophyta and Cyanobacteria diversity correlated with the levels of bicarbonate and CODMn. High diversity of diatoms was facilitated by the total amount of dissolved solids and chemical oxygen demand (COD). It was found that low water quality could be associated with conditions leading to predominant growth of the mentioned groups of algae. According to the analysis, the highest water quality was characterized by balanced phytoplankton composition and optimal values of the environmental variables. The sites with reference conditions are proposed for future monitoring.

Benthic diatoms in relation to environmental factors in an allochthonous river from Patagonia, Argentina

Natural and human pressures increasingly threatening the biodiversity and water resources of dryland rivers. Fluvial environments of Patagonia harbour high diatom diversity, but their management value is overlooked. The aim of this study is to explore the diatom distribution in surface sediments of the Chubut River and evaluate their relationship with environmental variables. In total, 243 diatom taxa were identified in 16 littoral zone sites. The physical and chemical variables independently explained the variance in diatom data, whereas sediment texture had a low influence. Conductivity, major ions (HCO3–, Cl–, SO42–, Na+, K+, Ca2+ and Mg2+) and pH were the main environmental drivers explaining the diatom composition. As the highlighted variables increased near the mouth, so did the relative abundances of marine–brackish taxa such as Amphora copulatoides, Sarcophagodes alfred-wegeneri, Nitzschia fonticola and Tryblionella apiculata. Meanwhile, the presence of high pollution-tolerant diatoms can be put forward to explain the river health deterioration towards downstream areas. The marine–brackish taxa found at freshwater sites reflect a weak tidal influence in the estuary compared with other coastal systems of Patagonia. This study provides valuable information to test the hypothesis on the ecological status of aquatic resources and the potential effects of climatic and hydrological changes in the area.

A diatom-based Holocene record of sedimentary and oceanographic environmental changes within the Beibu Gulf, NW South China Sea

A sediment core from a nearshore setting (10.8 m in water depth) of the inner Beibu Gulf, northwestern South China Sea, was analyzed in terms of diatom assemblage composition, grain size distribution and radiocarbon dating, with aim to describe sedimentary and oceanographic environmental changes during the Holocene. The fossil diatom record and changes in granulometry reveal that sea-level fluctuations had a strong influence on the evolution of hydrographic system, which changed significantly with rapid sea-level rise in the early Holocene ca. 10,000–7800 cal. yr. BP. These fluctuations continued in a series of stages dated to the middle Holocene ca. 7800–6200 cal. yr. BP, with sea-level increase, followed by a prolonged sea-level retreat during ca. 6200 to 3300 cal. yr. BP, and finally a relatively high sea level from ca. 3300 cal. yr. BP to the present. The resultant sedimentary facies could be divided into seven stages inferred by the diatom distribution and grain size characteristics: a river channel/beach environment at ca. 10000–9500 cal. yr. BP, a lagoonal environment at ca. 9500–7800 cal. yr. BP, a relatively broad embayment at ca. 7800–6200 cal. yr. BP, a bay at ca. 6200–3300 cal. yr. BP and a coastal environment setting up to present day. The coastal environmental setting has been subject to some shifts in climate and sea-level beginning with strong terrestrial influx at ca. 3300–1400 cal. yr. BP, which was then replaced by strong hydrological circulation at ca. 1400–800 cal. yr. BP, and a relative stable sedimentary environment approximate to the coast from ca. 800 cal. yr. BP to present.A very obvious increase in diatom abundance in the early and late Holocene reflected terrestrial influx transporting nutrients, driven by precipitation changes influenced by the Asian monsoon circulation pattern, particularly in the early Holocene. Increased anthropogenic impact, i.e. an enhanced nutrient condition, was inferred from higher abundances and reasonably high diatom diversity in this local record from 1400 cal. yr. BP, especially in the last 800 years. Rapid shifts in the diatom composition and grain size distribution at about 1400 and 1000 cal. yr. BP were observed that could be interpreted as overlapping influences of a global scale paleo-climate anomaly and local human activities. This study demonstrates the effectiveness of using diatom for understanding regional paleoenvironment change driven by both global climate changes and anthropogenic impact in coastal area of the Beibu Gulf, northwestern South China Sea.

Soil diatom communities and their relation to environmental factors in three types of soil from four cities in central-west China

Diatoms constitute a major part of microbial biomass and species richness in soil habitats. However, in spite of a growing interest on soil diatoms, variations in soil diatom communities across different types of soil are poorly known. We hypothesize that diatom communities are different in distinct soil types and can serve as a potential bioindicator for soil environmental assessment. Thirty-four soil samples were collected from Wuhan (yellow brown soil, n = 11), Xi'an (yellow cinnamon soil, n = 10), Korla and Karamay cities (brown calcic soil, n = 13) in central-west China. Diatom flora and thirteen environmental variables were analysed in these soil samples. In total, 66 taxa belonging to 30 genera were identified. Analysis of similarity (ANOSIM) revealed that diatom communities are significantly different among the three types of soil. The indicator species of yellow brown soil in Wuhan City included Pinnularia microstauron, Nitzschia amphibia, Sellaphora nigri, Pinnularia borealis and Humidophila contenta. Brown calcic soil in Korla and Karamay cities was characterized by Luticola suecorum, Luticola cohnii, Luticola nivalis and Luticola mutica. Yellow cinnamon soil in Xi'an City was featured by Stauroneis lundii and three unidentified Luticola species. Results of RDA showed that diatom communities were significantly correlated with magnesia, total phosphorus, organic phosphorus and conductivity, suggestive of the effects of nutrients and ionic strength on soil diatom distribution. Our results reveal high diatom diversity in soil habitats and highlight the potential of diatoms as a bioindicator for soil environmental assessment.

The diversity of benthic diatoms affects ecosystem productivity in heterogeneous coastal environments.

The current decrease in biodiversity affects all ecosystems, and the impacts of diversity on ecosystem functioning need to be resolved. So far, marine studies about diversity-ecosystem productivity-relationships have concentrated on small-scale, controlled experiments, with often limited relevance to natural ecosystems. Here, we provide a real-world study on the effects of microorganismal diversity (measured as the diversity of benthic diatom communities) on ecosystem productivity (using chlorophyll a concentration as a surrogate) in a heterogeneous marine coastal archipelago. We collected 78 sediment cores at 17 sites in the northern Baltic Sea and found exceptionally high diatom diversity (328 observed species). We used structural equationmodels and quantile regression to explore relationships between diatom diversity and productivity. Previous studies have found contradictory results in the relationship between microorganismal diversity and ecosystem productivity, but we showed a linear and positive basal relationship between diatom diversity and productivity, which indicates that diatom diversity most likely forms the lowest boundary for productivity. Thus, although productivity can be high even when diatom diversity is low, high diatom diversity supports high productivity. The trait composition was more effective than taxonomical composition in showing such a relationship, which could be due to niche complementarity. Our results also indicated that environmental heterogeneity leads to substantial patchiness in the diversity of benthic diatom communities, mainly induced by the variation in sediment organic matter content. Therefore, future changes in precipitation and river runoff and associated changes in the quality and quantity of organic matter in the sea, will also affect diatom communities and, hence, ecosystem productivity. Our study suggests that benthic microorganisms are vital for ecosystem productivity, and together with the substantial heterogeneity of coastal ecosystems, they should be considered when evaluating the potential productivity of coastal areas.

Insights into global diatom distribution and diversity in the world’s ocean

Diatoms (Bacillariophyta) constitute one of the most diverse and ecologically important groups of phytoplankton. They are considered to be particularly important in nutrient-rich coastal ecosystems and at high latitudes, but considerably less so in the oligotrophic open ocean. The Tara Oceans circumnavigation collected samples from a wide range of oceanic regions using a standardized sampling procedure. Here, a total of ∼12 million diatom V9-18S ribosomal DNA (rDNA) ribotypes, derived from 293 size-fractionated plankton communities collected at 46 sampling sites across the global ocean euphotic zone, have been analyzed to explore diatom global diversity and community composition. We provide a new estimate of diversity of marine planktonic diatoms at 4,748 operational taxonomic units (OTUs). Based on the total assigned ribotypes, Chaetoceros was the most abundant and diverse genus, followed by Fragilariopsis, Thalassiosira, and Corethron We found only a few cosmopolitan ribotypes displaying an even distribution across stations and high abundance, many of which could not be assigned with confidence to any known genus. Three distinct communities from South Pacific, Mediterranean, and Southern Ocean waters were identified that share a substantial percentage of ribotypes within them. Sudden drops in diversity were observed at Cape Agulhas, which separates the Indian and Atlantic Oceans, and across the Drake Passage between the Atlantic and Southern Oceans, indicating the importance of these ocean circulation choke points in constraining diatom distribution and diversity. We also observed high diatom diversity in the open ocean, suggesting that diatoms may be more relevant in these oceanic systems than generally considered.

Algal Community Membership of Estuarine Mudflats from the Savannah River, United States

Algae represent a large and diverse group of photosynthetic organisms inhabiting all aquatic habitats. Although the traditional assessment of algal diversity relies mainly on microscopy-based morphological identification, certain limitations exist. In this study, we present a combined molecular and morphological assessment of algal diversity in mudflats from the Savannah River Estuary, Georgia. High diversity of diatoms was documented, and less than 20% of the algal community was physiologically active at the time of collection. From the total genomic DNA extracted from the field samples and lab isolates, 18S rDNA sequences were PCR amplified, cloned, sequenced, identified, and then compared to the taxa identified via microscopy. Only a few of the DNA sequences matched documented taxa, and the abundance of particular algal species was limited to morphological analysis. Surprisingly, upon examination of the remaining lysis buffer from the mechanical lysis step of algal cells, diatom species were left intact even in the presence of a detergent indicating that the diatom species resistant to lysis could be easily underrepresented. Generation of additional algal sequences data, tied to accurate taxonomic identification, is essential to current environmental sequencing projects and potentially would allow faster acquisition of algal community structure within these unique environments.

Beta diversity of stream diatoms at two hierarchical spatial scales: implications for biomonitoring

Summary Human‐induced loss of environmental heterogeneity may lead to homogenisation of biological communities. However, environmental heterogeneity is important for sustaining current levels of biodiversity. Hence, more ecological research should be directed on understanding the relationships between beta diversity and environmental heterogeneity. Benthic diatoms are among the most extensively studied taxa of primary producers in streams, yet their beta diversity patterns are not well documented at intermediate spatial scales, that is within and among streams, in a catchment. We tested how well one sampling site represents the total diatom diversity of a stream using 10 boreal streams, each comprising 10 sampled riffles. We also examined variation in diatom community structure at two hierarchical scales, within and among streams. Relationships between diatom beta diversity and environmental heterogeneity were studied using a combination of species accumulation curves, canonical analysis of principal coordinates, tests of homogeneity of dispersions and distance‐based redundancy analysis. We found large variation in community structure within each stream, which indicates thatone sample is not adequate to represent the diatom diversity of an entire stream. The variation in among‐stream diatom community structure was larger than among‐stream habitat heterogeneity. Although no positive relationship between within‐stream diatom beta diversity and environmental heterogeneity was detected, we found that diatom community variation was significantly related to physical habitat structure and, surprisingly, also to grazer abundance. We recommend that more than one sampling site is included in analyses aiming to cover the diatom diversity of a whole stream. This is especially true for pristine sites with high diatom diversity. In addition, we suggest that researchers incorporate physical and biological factors as explanatory variables when monitoring diatoms both at the within‐ and among‐stream scales.

Biodiversity of soil algae in the farmlands of mid-Taiwan.

BackgroundVery little information is available about soil algae in Taiwan. In this study, we investigated for the first time the soil algae inhabiting five types of farmland in mid-Taiwan: rice paddies, vegetable farms, tea plantations, sugar cane farms, and orchards.ResultsSixty-four taxa belonging to 33 genera of cyanobacteria, diatoms, green algae, and euglenoids were identified on the basis of fine structures observed under optical and electron microscopes and rDNA sequencing. The majority of the isolates were of the genera Oscillatoria, Navicula, Nitzschia, and Pinnularia. Five species were reported for the first time in Taiwan, namely Microcoleus paludosus, M. subtorulosus, Navicula subminuscula, Nitzschia levidensis, and Ni. pusilla.ConclusionsThe distribution and diversity of these species was shown to be strongly dependent on habitat, with the highest diversity of green algae in the orchards, a fairly high diversity of diatoms and cyanobacteria in the rice paddies, and a relatively low diversity in the tea plantations and sugar cane farms. The humidity and acidity were the most important environmental factors influencing the diversity of soil algae in these farmlands.Electronic supplementary materialThe online version of this article (doi:10.1186/1999-3110-54-41) contains supplementary material, which is available to authorized users.

Minnesota diatomists: The first 150 years

Minnesota boasts over 12,000 lakes, most of glacial origin, three major continental drainage systems (Mississippi River to the Gulf of Mexico, Lake Superior via the other Great Lakes to the Atlantic Ocean, and the Red River of the North via the Nelson River, to Hudson Bay), and a diversity of landforms comprising seven major ecological regions. Such landscape and aquatic variability hosts a high diversity of diatoms, which have been studied for over 150 years. Diatom communities range from saline and eutrophic in the southwest agricultural lands, to oligotrophic and endemic forms in the cold waters of Lake Superior. Early diatom collections were distributed to reknowned diatomists such as C.G. Ehrenberg and H.L. Smith. Other botanists and phycologists, including Tilden, Eddy, and Drouet, were active in Minnesota but only rarely included diatoms in their studies. Interest in Minnesota diatoms increased in the latter half of the 20th century with taxonomic and floristic surveys (e.g., Czarnecki, Koppen, and Kingston) and the inclusion of diatoms in applied research efforts that set the groundwork for understanding post-glacial ecology, effects of Euroamerican settlement, impacts of climate, and the effects of acid precipitation. Important to these latter developments were the efforts of Dr. Herb Wright Jr., who invited several European diatomists (e.g., Florin, Battarbee, and Haworth) to work on paleoecological projects in and near Minnesota. Although not a diatomist per se, Wright's subsequent efforts to promote diatom research included the appointment of Platt Bradbury as a research associate and later John Kingston, Dick Brugam, and Brian Cumming. Students Sheri Fritz, Kate Laird, and Virginia Card completed diatom research for their doctoral degrees. These workers and others have left a legacy that continues to fuel several active labs in Minnesota that have used diatoms to develop water quality standards, assess and restore impaired waters, and understand the impacts of climate, management, and landuse change across the state.

Holocene freshwater diatoms: palaeoenvironmental implications from southKamchatka,Russia

Holocene palaeolimnological conditions were reconstructed by analysing fossil diatom assemblages within a lacustrine sediment core fromLakeSokoch, southernKamchatka (Russia). Sediments of this proglacial lake cover the past 9400 years and hence represent almost the wholeHolocene history. The biosiliceous muddy sample material was analysed for several geochemical and biological parameters, such as the total organic carbon and biogenic silica content, and the diatom community (quantitative and qualitative changes). Based on changes in the relative abundances of the most frequent speciesAulacoseira subarctica,Staurosira martyiandStephanodiscus alpinusand a depth‐constrained cluster analyses (CONISS), five diatom assemblage zones could be identified. The oldest stage recovered lies between 9400 and 9000 cal. aBPand reflects the initial lake stage after the retreat of local glaciers, with a high detrital sediment supply, shallow‐water conditions and a high diatom diversity. The next zone (9000–6200 cal. aBP) shows a more mature lake system with accumulating biogenic remains and higher water levels during climate amelioration. This is followed by the most obvious change in the diatom assemblage, delineated by an occurrence ofS. alpinus, between 6200 and 2700 cal. aBP. Wet conditions in spring probably led to an enhanced fluvial runoff and eutrophic to hypertrophic conditions. The end of this period might reflect climate deterioration related to theNeoglacial epoch of theHolocene. Between 2700 and 1600 cal. aBPthe sediments ofLakeSokoch reveal oligotrophic water conditions in a windy high‐energy environment. The youngest interval, between 1600 cal. aBPand thePresent, indicates shallow‐water conditions and a very short growing season, which might reflect theLittleIceAge. The results may offer a baseline for the interpretation ofHolocene palaeoenvironmental changes inKamchatka and their relation to regional climate change from a palaeoecological perspective.

Effect of environmental variables on eukaryotic microbial community structure of land‐fast Arctic sea ice

Sea ice microbial community structure affects carbon and nutrient cycling in polar seas, but its susceptibility to changing environmental conditions is not well understood. We studied the eukaryotic microbial community in sea ice cores recovered near Point Barrow, AK in May 2006 by documenting the composition of the community in relation to vertical depth within the cores, as well as light availability (mainly as variable snow cover) and nutrient concentrations. We applied a combination of epifluorescence microscopy, denaturing gradient gel electrophoresis and clone libraries of a section of the 18S rRNA gene in order to compare the community structure of the major eukaryotic microbial phylotypes in the ice. We find that the community composition of the sea ice is more affected by the depth horizon in the ice than by light availability, although there are significant differences in the abundance of some groups between light regimes. Epifluorescence microscopy shows a shift from predominantly heterotrophic life styles in the upper ice to autotrophy prevailing in the bottom ice. This is supported by the statistical analysis of the similarity between the samples based on the denaturing gradient gel electrophoresis banding patterns, which shows a clear difference between upper and lower ice sections with respect to phylotypes and their proportional abundance. Clone libraries constructed using diatom-specific primers confirm the high diversity of diatoms in the sea ice, and support the microscopic counts. Evidence of protistan grazing upon diatoms was also found in lower sections of the core, with implications for carbon and nutrient recycling in the ice.

Structure of Benthic Diatom Assemblages from a Mangrove Environment in a Mexican Subtropical Lagoon1

'I'he taxonomic list and the structure of benthic diatom assemblages occurring in fine sediments (silt and sand) from the mangrove forest of the Balandra lagoon in Baja California Sur, Mkxico was determined based on seasonal samplings for one ycar. Assemblage structure was analyzed using several ecological indices for estimating diversity (H'), dominance (REDI), equitability, and similarity. A total of 230 diatom taxa were identified and include 109 new records for the Raja California peninsula coast. Taxa representative of highly productive and hypersaline environments were common. Assemblages were characterized by a few abundant species and many uncommon or rare taxa. High diatom diversity estimates at all sampling sites during all seasons suggest that diatom assemblages in sediments of the Balandra lagoon represent a quasi-pristine environment.