Nitzschia Frustulum Research Articles

Comparison of Metabarcoding and Microscopy Methodologies to Analyze Diatom Communities in Five Estuaries Along the Southern Coast of the Korean Peninsula

The study of microalgal communities is critical for understanding aquatic ecosystems. These communities primarily comprise diatoms (Heterokontophyta), with two methods commonly used to study them: Microscopy and metabarcoding. However, these two methods often deliver different results; thus, their suitability for analyzing diatom communities is frequently debated and evaluated. This study used these two methods to analyze the diatom communities in identical water samples and compare the results. The taxonomy of the species constituting the diatom communities was confirmed, and both methods showed that species belonging to the orders Bacillariales and Naviculales (class Bacillariophyceae) are the most diverse. In the lower taxonomic levels (family, genus, and species), microscopy tended to show a bias toward detecting diatom species (Nitzschia frustulum, Nitzschia inconspicua, Nitzschia intermedia, Navicula gregaria, Navicula perminuta, Navicula recens, Navicula sp.) belonging to the Bacillariaceae and Naviculaceae families. The results of the two methods differed in identifying diatom species in the communities and analyzing their structural characteristics. These results are consistent with the fact that diatoms belonging to the genera Nitzschia and Navicula are abundant in the communities; furthermore, only the Illumina MiSeq data showed the abundance of the Melosira and Entomoneis genera. The results obtained from microscopy were superior to those of Illumina MiSeq regarding species-level identification. Based on the results obtained via microscopy and Illumina MiSeq, it was revealed that neither method is perfect and that each has clear strengths and weaknesses. Therefore, to analyze diatom communities effectively and accurately, these two methods should be combined.

Exploring a unique water ecosystem under long-term exposure to hexavalent chromium – An in situ study of natural diatom (Bacillariophyceae) communities

This paper reports the third in a series of three studies of a unique aquatic phytobial consortium that developed in a polluted ditch situated near an old chromium waste landfill. The ditch is a specific ecological niche having increased loads of several chemical compounds, including extreme hexavalent chromium concentrations up to two thousand times the allowed limit (0.02 mg dm−3 in Poland) in the more polluted section B; the moderate concentrations in section A are twice the limit. We focus on the microscopic algae group of diatoms, one of the most important components of the phytobial consortium, and continue our novel attempt to analyze the bioremediation potential of the entire consortium under those environmental conditions. We used numerical methods to analyze differences in diatom biodiversity between sections A and B, and assessed the relations between diatoms and selected water chemistry properties, including hexavalent chromium, chlorides and sulphates, the latter two known to positively influence the resistance of algae to the impact of hexavalent chromium. We noted 37 diatom taxa in section A of the ditch and 30 in section B. The most frequently observed diatoms were cosmopolitan taxa and/or characteristic taxa of saline waters. Sulphates were the most important factor influencing the diatom composition in the ditch, explaining 52% of the total variability, followed by chlorides (30%) and hexavalent chromium (9%). Gomphonema acuminatum, Melosira varians and Nitzschia frustulum var. frustulum were found to be most resistant to hexavalent chromium and were selected for further experimental studies on their biotechnological usefulness.

Diversity and distribution of lacustrine diatoms along the Trans‐Mexican Volcanic Belt

Abstract The Trans‐Mexican Volcanic Belt is recognised as a highly biodiverse zone and we present a study of diatom diversity and species distributions in its lakes. We aimed to identify diatom taxa with the highest regional occupancy, explore diversity at a regional level, identify the main variables associated with species distributions, and present weighted average optima for variables that could provide a valuable reference for future palaeoenvironmental research. We used the relative abundances of diatoms in surficial lake sediments to estimate different diversity metrics and alpha, beta and gamma diversities. Groups of lakes with similar diatom assemblages were identified by means of cluster analysis whereas canonical correspondence analysis (CCA) was used to evaluate the association between diatom composition and climatic, morphometric, hydrochemical and trophic status related variables. Weighted average optima were estimated for salinity and temperature. From a total of 184 diatom taxa, three were endemic to one or two lakes and eight had the largest regional occupancy, two of which were associated with high salinity environments (Stephanocyclus meneghinianus, Nitzschia frustulum) and the rest with freshwater conditions (Aulacoseira ambigua, A. granulata, A. granulata var. angustissima, Discostella stelligera, Fragilaria crotonensis, Achnanthidium minutissimum). Surprisingly, endemic taxa as well as those with high regional occupancy were mostly planktic or epipelic motile forms, with high dispersal potential. Our results showed 13 clusters of lakes with similar diatom assemblages, in close agreement with beta diversity which predicted the presence of 12 communities. There was high species turnover (βSIM = 0.97) and CCA showed not only that the main environmental variable defining these groups was salinity, but also that temperature, precipitation, depth, and soluble reactive phosphorus were meaningful variables. There was no evidence of an altitude–diversity pattern. This study emphasises the strong influence that climatic variables have on species distribution when relatively broad geographical areas, with large climatic gradients are analysed.

The impact of drought in the Karoo - revisiting diatoms as water quality indicators in the upper reaches of the Great Fish River, Eastern Cape, South Africa

This paper examines the efficacy of diatoms as bioindicators of water quality in the upper reaches of the Great Fish River following a period of reduced flow from drought conditions. Of the five sites, three were sampled three times in an 18 month period while the remaining two were sampled once. As a comparison, one headwater site within Mountain Zebra National Park, situated in the same district, was sampled. A total of 166 diatom taxa belonging to 29 genera were identified. Dominant taxa for the Great Fish River were identified as Amphora pediculus; Epithemia sorex; Nitzschia frustulum; Navicula veneta and Craticula buderi. These species, indicative of high nutrient concentrations and moderately saline to brackish conditions can tolerate low flow conditions. The Generic Diatom Index (GDI), the Specific Pollution sensitivity Index (SPI) the Biological Diatom Index (BDI) and the% Pollution Tolerant Valves (%PTV) – part of the UK Trophic Diatom Index (TDI) were used for interpretation of the results. The indices showed that this river is in poor condition. By comparison the headwater site in the Mountain Zebra National Park had Cocconeis placentula var. euglypta, Achnanthidium minutissimum and Cocconeis placentula var. lineata as dominant species and, using the same indices, the river was classified as in moderate to good condition with respect to water quality. When compared to a previous study (2010 – 2012), these sites showed a shift in dominant species indicating a change in water flow conditions and quality.

Multiple Estuarine Gradients Influencing Tidal Flat Benthic Algal Biomass and Community Structure in the Yaquina Estuary, OR, USA

Tidal flat is often the dominant habitat type in US Pacific Northwest (PNW) estuaries. This research examined environmental factors that explain the spatial patterns of microphytobenthos (MPB) biomass and community structure in a PNW estuary with complex nutrient dynamics. MPB biomass, individual species abundances, diatom community metrics, and diatom community structure were strongly correlated with distance from the estuary mouth, salinity, substrate composition, and pore water-soluble reactive phosphorus (SRP). The microphytobenthos was dominated by diatoms and diatom diversity and species richness were negatively associated with salinity, substrate sand content, and pore water SRP. Diatom community structure varied with estuary position, with the epipsammic taxa Catenula adhaerens, Opephora spp. 1, and Planothidium delicatulum dominating the assemblage at sites near the estuary mouth and epipelic taxa, such as Nitzschia frustulum and Nitzschia palea, being more abundant at sites in the middle and upper estuary. Distance from the estuary mouth and salinity were the most important predictors of diatom assemblage structure, based on CCA analysis. MPB biomass was highest at sites in the lower estuary, characterized by higher salinities, SRP, and substrate sand composition. Pore water nitrogen and surrounding land use were not important predictors of MPB biomass or community structure. We attribute our findings to the nutrient dynamics of Yaquina estuary, which is high in nutrients due to both coastal upwelling and watershed-derived nitrate and exhibits an increasing gradient of phosphorus towards the estuary mouth.

Composition and Distribution of Benthic Diatoms in Different Habitats of Burdur River Basin

Diatoms constitute an essential component for biomonitoring studies to determine the ecological quality of waterbodies. In this study, benthic diatoms of Burdur River Basin were investigated as a consequence of a project on river basin management plan. This is the first detailed taxonomical study of diatoms taken from 13 streams, 4 lakes and 6 reservoirs of Burdur River Basin and a total of 223 taxa have been observed. Among genera, Navicula Bory (27) and Nitzschia Hassal (27) were represented with the highest numbers of taxa and followed by Gomphonema Agardh with a total of 22 species. Navicula antonii Lange-Bertalot and Nitzschia palea var. debilis (Kützing) Grunow had the highest relative abundance with 17.1% and 15.5% respectively. As a closed basin, salinity varied greatly from fresh to saline water between the sampling stations and diatom composition contained species with a different tolerance level. Navicula antonii and Nitzschia frustulum (Kützing) Grunow observed in all habitats indicating their euryhaline characters; however Navicula digitoconvergens was only detected in saline Acıgöl lake with a high relative abundance (38%) in autumn. Other two dominant species were Halamphora coffeiformis (Kützing) Levkov and Navicula cincta (Ehrenberg) Ralfs in Acıgöl lake showing their tolerance to high salt content as a brackish species. According to first results, 11 species were new records for Turkish diatom flora. The high biodiversity of diatoms revealed the presence of different habitat characteristics within the basin. These results are an important contribution of Turkish diatom flora and could be useful for monitoring specific areas like Burdur River Basin.

Temporal and seasonal variations in phytoplankton community structure in Uzuncayir Dam Lake (Tunceli, Turkey).

Seasonal variations in species composition and growth dynamics of phytoplankton in Uzuncayir Dam Lake (Tunceli, Turkey) were studied in relation to ecological factors by collecting horizontal water and phytoplankton samples for over a year. A total of 46 phytoplankton taxa were recorded, where Bacillariophyta was the most abundant in species number representing 24 taxa. Diatoms were the most conspicuous phytoplankton in terms of abundance as well as occurrence frequency. Charophyta, Chlorophyta, Cyanobacteria, Ochrophyta, Miozoa, and Euglenozoa were the least abundant. However, some Diatoms (Gyrosigma attenuatum, Hippodonta hungarica, Meridion circulare, Nitzschia clausii, Nitzschia frustulum, Pantocsekiella ocellata, Rhoicosphenia abbreviata), Charophytes (Cosmarium granatum, Mougeotiopsis calospora), Cyanobacteria (Leiblenia epiphytica, Planktothrix agardhii); Dinoflagellates (Ceratium hirundinella, Parvodinium africanum, Parvodinium inconspicuum, Peridinium cinctum), and Ochrophyta (Dinobryon pediforme) were also noticeable, with their occurrence in all seasons. Canonical correspondence analysis (CCA) and principal component analysis (PCA) were employed to analyze the relationship between occurrence and abundance of phytoplankton species as well as the ecological factors. The results showed that pH and the concentrations of NH4, NO3, and PO4 influenced seasonal occurrence and abundance of phytoplankton species in the lake. Uzuncayir Dam Lake may be classified as an oligotrophic lake with the mean value of nitrate 2.62mgL-1 and phosphate 0.23mgL-1 as supported by the occurrence of various phytoplankton groups. Findings related to pollution indices yielded that Uzuncayir Dam Lake is on the edge of the moderate state of organic pollution.

Epipelic Diatom Communities in Pengilon Lake Dieng, Central Java

Diatom communities in the lake have an advantage of environmental assessment and paleo reconstruction study, due to the ability of diatom preserved in the sediment. There are only limited studies about taxonomy, ecology, and diversity of diatom flora in tropical areas, especially Indonesia. The main objective of the research is to describe the structure of benthic diatom communities in Pengilon Lake, together with physical chemical variables. Sediment samples were collected at an altitude of more than 2,000 msal habitats with pH around 5.40-6.86. A total of 83 diatom species identified as belonging to 16 families. The diversity index ranges from about 2.25 to 3.01 indicated the ecosystem that naturally stable with none diatom dominant. The most abundant genera were Eunotia with high diversity around 14 taxa. The composition of Eunotia assemblages was different among habitat and season variation. Eunotia has a wide tolerance of pH because of its ability to survive in an area with an acidic environment and circumneutral water. The most dominance diatom species in Pengilon Lake were Eunotia paludosa (Grunow) 39.2%, Nitzschia frustulum (Kutzing) 28.1%, Pinnularia viridis (Krammer & Lange-Bertalot) and Pinnularia divergentissima (Grunow) 24.6%.

Unexpected consequences of bombing. Community level response of epiphytic diatoms to environmental stress in a saline bomb crater pond area.

The spatial response of epiphytic diatom communities to environmental stress was studied in a moderately saline wetland area located in the plain of Danube-Tisza Interfluve, Hungary. The area is characterised by World War II bomb crater ponds and can be regarded as an excellent ecological model system where the dispersion of species is slightly limited by distance. To study the effect of environmental variables on the communities, canonical correspondence analysis was applied. Salinity, pH, total suspended solids, total phosphorous and depth proved to be significant environmental drivers in this analysis. The ecological status of the ponds was assessed with Ziemann’s halobity index, as the trophity-depending metric cannot be applied to these habitats (due to the naturally high phosphorus content). Ponds in “good” ecological status significantly differed from those appertaining to water quality category of “not-good” ecological status considering characteristic of natural astatic soda pans (e.g. salinity, pH, ammonium, total phosphorous concentration, nitrogen:phosphorous ratio and turbidity). The differences between epiphytic diatom communities inhabiting the ponds were detected using non-parametric multidimensional scaling. The samples formed three groups according to the types of ponds (“transparent”, “transitional” and “turbid”) based on the width of the macrophyte belt around them. Indicator species related to the ecological status of the ponds and diatom communities contributing to the separation of groups of ponds were identified. One of the indicator species differed from species already described. Light and scanning electron microscopy features and phylogenetic analyses based on three genes (18S and 28S rRNA genes, rbcL) proved that it was a new species of Nitzschia genus, closely related to Nitzschia frustulum and Nitzschia inconspicua. Therefore, description of a new species, Nitzschia reskoi Ács, Duleba, C.E.Wetzel & Ector is proposed. We concluded that the increasing abundance of Nitzschia reskoi was a signal of the degradation of the intermittent saline wetlands.

Effect of TiO2 nanoparticles and multiwall carbon nanotubes on the freshwater diatom Nitzschia frustulum: evaluation of growth, cellular components and morphology

ABSTRACTGreat attention should be paid to the possible impacts of various nanoparticles on aquatic organism. Freshwater diatoms are essential components of phytoplankton and play a critical role in bioassessment of nanoparticle exposure in the environment. In this study, cell growth was inhibited by TiO2-NPs and MWCNTs, the 24 h EC50 values of TiO2-NPs and MWCNTs to Nitzschia frustulum were 20.75 and 24.64 mg L−1, respectively. Significant decreases of Chl a content after TiO2-NPs exposures were detected and the Chl a content of N. frustulum was obviously increased by MWCNTs treatment at lower concentration. The ROS was detected in N. frustulum after TiO2-NPs and MWCNTs exposures. The MDA content was significantly induced by TiO2-NPs at lower concentrations of 24 and 48 h exposure; meanwhile, it increased at all tested concentrations at 24 h MWCNTs exposure. The SOD enzyme was induced by 72 and 96 h TiO2-NPs exposure, and increased by MWCNTs treatment at 96 h in N. frustulum. Scanning electron microscopy results revealed that N. frustulum had obvious cell deformation after TiO2-NPs treatment. The result showed that the physiological and biochemical response mechanisms after NPs exposure of diatom were species-specific, and in relation to the exposure concentration and time.

The Alterations of Biofilm Formation and EPS Characteristics of a Diatom by a Sponge-Associated Bacterium Psychrobacter sp.

A sponge-associated bacterium, which was identified as Psychrobacter sp. in this study, was found with high activity against biofilm formation of benthic diatoms, including Amphora sp., Nitzschia closterium, Nitzschia frustulum, and Stauroneis sp. The activity against diatom biofilm formation by the tested strain was confirmed mostly in the culture supernatant and could be extracted using organic solvents. Treatment with its supernatant crude extract significantly reduced the cells of Stauroneis sp. forming biofilm and slightly increased the cells floating in the culture medium, which results in the ratio of biofilm cell/floating cell altering from 0.736 in control to 0.414 in treatment. Use of the supernatant crude extract led to increased production of extracellular polymeric substances (EPSs) by diatom Stauroneis sp. from 16.66 to 41.59 (g/g cell dry weight). The increase in EPS production was mainly contributed by soluble EPS (SL-EPS) and followed by the EPS that was tightly bound to biofilm cells (BF-TB-EPS). In addition, the supernatant crude extract caused significant changes in the monosaccharides composition of the EPS of Stauroneis sp. Specifically, glucuronic acid (Glc-A) and N-acetyl-D-glucosamine (Glc-NAc) in BF-TB-EPS were 55% fold decreased and 1219% fold increased, respectively. Based on our findings, we proposed that these changes in monosaccharides composition might lead to a decreased biofilm formation efficiency of diatom.

Microfossil evidence for recurrent coseismic subsidence around Lake Hamana, near the Nankai-Suruga trough, central Japan

We reconstructed recurrent coseismic subsidence during the middle Holocene from analyses of sedimentary facies and fossil diatom assemblages in a small drowned valley, the Shinjo lowland, bordering Lake Hamana, near the Nankai–Suruga trough, central Japan. The Lake Hamana region is known for coseismic subsidence during the 1707 Hoei (M8.6) and 1854 Ansei-Tokai (M8.4) earthquakes along the Nankai–Suruga trough subduction zone.A coring survey revealed three widely distributed peat layers in the lowland, with a mud layer overlying each of the two lower peats with a sharp contact. We traced the alternating peat–mud beds for over 300 m along the long axis of a valley. The fossil diatom assemblage analysis revealed that the peat layers were deposited in a freshwater pond/marsh environment, which changed abruptly to an estuarine to inner bay environment, recorded by the mud layers. From the sudden environmental change at the two peat–mud contacts and our radiocarbon dating results, we inferred that coseismic subsidence followed by an invasion of seawater into the lowland occurred at least twice, during a great earthquake that occurred between 5645 and 6635 cal yr BP and during another great earthquake at ca. 5700 cal yr BP.Within the mud layers, the dominant diatom species changed gradually upward from Nitzschia frustulum and Cocconeis scutellum in the lower part to Cyclotella striata and Achnanthes submarina in the upper part. These changes suggest that water depth and salinity gradually increased after the coseismic subsidence. A possible cause of this gradual subsidence is postseismic subsidence following great Nankai-Suruga trough earthquakes.

Microcystins and cyanophyte extracts inhibit or promote the photosynthesis of fluvial algae. Ecological and management implications.

The ecological influence of cyanotoxins on aquatic biota remains unclear despite the numerous published references on toxicological and sanitary problems related with cyanophyte proliferation. The effects of microcystins and cyanophyte extracts on the photosynthesis of the algae that belong to two taxonomic groups, Rhodophyta and Bacillariophyta, were studied in an attempt to elucidate their role in the intraspecific competence and physiognomy of fluvial communities. The data showed that both cyanobacteria extracts and pure microcystin-LR affected the photosynthetic activity of all the tested organisms, diatoms (Fistulifera pelliculosa, Gomphonema parvulum, Nitzschia frustulum and Stephanodiscus minutulus) and red algae (Chroothece richteriana) at environmentally relevant concentrations. Effects varied with strains and time, and promoted or inhibited photosynthesis. The microcystins and the other compounds present in cyanobacteria extracts may explain the competence effects observed in nature, especially in calcareous environments where they predominate, and after disturbing events like heavy rains or floods, which may destroy cyanophyte mats and release toxic or inhibitory compounds in a seasonal scale pattern.

Upper Quaternary evolution of the dune field of the Bolsón de Fiambalá, Catamarca: Sand dispersal at the Andes piedmonts

The South American Arid Diagonal extends in Argentina from Puna to Patagonia regions. Several dune fields are scattered between the Andes and Pampas ranges, covering plains and plateaus. One of the northernmost dune fields is occupying the tectonic valley known as Bolsón de Fiambalá (27°S; 67°W) White transverse dunes extend from west to east, climbing to the Fiambalá Range. Some outcrops from the surrounding area allow to understand the evolution of this dune field. At the Chaschuil valley, a profile composed of 4 m of stratified sands and gravels were sampled at Las Lozas site. Epiphytes and benthic diatom assemblages suggest a shallow lake located at 3700 m altitude. Many of these brackish/freshwater aerophilous taxa tolerate desiccation periods and salt concentration. The assemblages were dominated by Nitzschia frustulum, Nitzschia linearis, Achnanthes thermalis var. rumrichorum, Epithemia adnata, Pinnularia viridis y Nitzschia capitellata. Limestones from this outcrop were dated on 32,000 ± 520 and 29,380 ± 410 14C years BP (Garleff et al., 1993), suggesting the Marine Isotopic Stage 3. The Holocene Interglacial is recorded either at the Chaschuil and Abaucán rivers valleys. Lake deposits at 3000 m altitude gave ages between 6175 ± 70 and 2990 ± 70 14C years BP (Garleff et al., 1993). The sand of this dune field at the northern part of the Bolsón de Fiambalá was supplied by the fanglomerates located to the west, at Medanitos. There is also a significant supply of pumicite, derived from the Cerro Blanco volcanic dome. An aridity increase have been previously recorded from archaeological data and confirmed by the discharge records of the Abaucán River during the 1919–1957 interval. Although these sand dunes with a high content in volcanic glass clearly derived from the Andes, other sand dunes of central Argentina derived from the deactivation of the Desaguadero-Curacó system.

Changes in the algal composition and water quality of the Sundays River, Karoo, South Africa, from source to estuary

A first survey was done on algae present in the Sundays River from its source to its confluence with the sea. Species found in the upstream sections of the river included indicators of good water quality, but the quality deteriorated downstream with peaks in algal abundance being ascribed to peaks in nutrient concentrations. Cyanobacteria and euglenoids were present in the upper and middle reaches of the river, but were absent downstream. Dinoflagellates became more important downstream, especially in the estuary. Dominant species, reaching high concentrations along the river, included Nitzschia frustulum, Nitzschia capitellata, Carteria klebsii, Chlorella vulgaris and Anabaena species. The presence of the diatom Eolimna comperei is a first record of its occurrence in South Africa. The Sundays River can be described as a brackish, hard water system with high nutrient concentrations in certain sections. The most important contributors to high nutrient concentrations were point sources in the vicinity of towns along the river banks, as well as diffuse sources contributing to high nitrogen concentrations in the fertile Sundays River valley. Increasing salinities were due to pollution, evaporation and agricultural activities in the valley.

Diatoms as water quality indicators in the upper reaches of the Great Fish River, Eastern Cape, South Africa

This study focused on the spring-fed upper reaches of the economically important Great Fish River with the aim of determining if diatoms could be used for biomonitoring in semi-arid conditions in southern Africa. Five sites were monitored monthly from 2010 to 2012. Of the 269 diatom taxa belonging to 51 genera identified, the dominant taxa were mostly those considered to be pollution-tolerant: Amphora pediculus, Craticula buderi, Fragilaria biceps, Nitzschia frustulum, Nitzschia paleacea, Planothidium lanceolatum and Rhopalodia gibba. A number of diatom-based numerical indices were used to infer water quality, including the generic diatom index, the specific pollution sensitivity index, the biological diatom index, and percentage pollution-tolerant valves, which forms part of the UK trophic diatom index. All index scores showed the Great Fish River to be impacted, and showed significant correlations of diatom species abundance with pH, NO3-N, electrical conductivity, NH4-N and CaCO3. Analysis revealed EC and NO3-N as the main environmental drivers affecting diatom community composition, followed by pH and PO4-P. The percentage of diatom deformities at all sites was high, at 3.5%. Diatom indices showed the river to be impacted by decades of agricultural activity, which was confirmed by chemical water analysis. Thus diatom indices can be used for biomonitoring in semi-arid areas.

Ecological guilds of epiphytic diatoms (Bacillariophyta) on Acrostichum danaeifolium Längst. & Fisch in a subtropical wetland in southern Brazil

Abstract Aim: Seasonal patterns diatom community on Acrostichum danaeifolium were examined in a wetland in southern Brazil. Methods The adhered diatoms were removed from the plant, species identification and growth forms were performed, and determined physical-chemical parameters of water. Results In total, 96 taxa belonging to 46 genera were identified. Nitzschia frustulum, Pseudostaurosira brevistriata and Plagiogramma tenuissimum were abundant species. Distinct growth forms that formed low-and high-profile ecological guilds and a mobile guild were observed. Navicula and Nitzschia were the genera with the greatest number of species, and these diatoms formed mucilage tubes. The water temperature varied from 10-26 °C, the depth from 0.35-0.80 m, the transparency from 0.20-0.23 m, the flow from 9.4-42.12 m3 s–1, the pH from 7.08-8.89, the electrical conductivity from 0.65-15.83 mS cm–1, the total organic phosphorus from 0.03-0.11 mg L–1, and the total organic nitrogen from 0.29-0.49 mg L–1. In summer, marine species such as Thalassiosira eccentrica and Rhaphoneis castracanii were also present. Conclusions The high-profile guild prevailed in all seasons of the year, with higher number of growth forms in the guild in winter. The richness found on A. danaeifolium shows that this plant provide a favorable habitat for epiphytic diatoms in wetlands such as Lagoa Pequena.

Photosynthetic characteristics of the benthic diatom species Nitzschia frustulum (Kützing) Grunow isolated from a soda pan along temperature-, sulfate- and chloride gradients

The Carpathian Basin hosts a number of small, shallow, saline, alkaline ponds. As being endorheic basins, they are highly threatened by the climate change and response of biota to changing climate has been largely unexplored. We investigated the effects of salinity changes on the photosynthetic activity of Nitzschia frustulum, which is one of the main dominant taxa of the saline lakes in the Fertő-Hansag Region of the Carpathian Basin. The photosynthetic activity of the species was measured along temperature (5, 10, 15, 20, 25, 30, 35, 40 °C), light (0–8–35–70–110–200–400–800–1200 µmol m−2 s−1), SO4 2− (0–50–600–1200–2400–3600–4800 mg L−1) and Cl− (0–36–437.5–875–1750–3500–5250 mg L−1) gradients under laboratory conditions in photosynthetron. The conductivity optimal of N. frustulum was around 5600 µS cm−1 with wide salinity tolerance. The species preferred the HCO3 −–SO4 2−-type waters since its photosynthetic activity (3.62 mg C mg Chl-a −1 h−1) was more than twice higher than in HCO3 −–Cl−-type media. Its photosynthesis saturated at very low-light intensity, and photoinhibition was not observed during the experiments. The maximal photosynthesis was measured at 28–29 °C. However, above 30 °C, the decline of photosynthesis of N. frustulum can be forecasted.

Zooplankton and diatoms of temporary and permanent freshwater pans in the Mpumalanga Highveld region, South Africa

This paper provides a description of the zooplankton and epiphytic diatom communities of permanent and temporary freshwater pans in the Mpumalanga Highveld region of South Africa. Few studies have investigated the biota of pans in this area, which is seriously threatened by mining and agricultural development. Nineteen pan sites within a 20 kmradius covering a wide range of water chemistries were sampled once for zooplankton, epiphytic diatoms and water physico-chemical data in 2009. Collected zooplankton and diatom samples were identified to species or genus level. Many of the zooplankton taxa reported in this study were not recorded in similar pan studies in South Africa and southern Africa. The study revealed a difference among the compositions of zooplankton and diatom communities between temporary pans and permanent pans. Zooplankton found exclusively in freshwater temporary pans included cladocerans (Megafenestra aurita and Scapholeberis kingi), calanoids (Mesocyclops major and Thermodiaptomus mixtus), a cyclopoid (Acanthocyclops vernalis) and a rotifer (Platyias quadricornis). Permanent pans were characterized by taxa such as cladocerans (Ceriodaphnia rigaudi and Dunhevedia crassa), a calanoid (Metadiaptomus transvaalensis), cyclopoids (Paracyclops fimbriatus and Eucyclops gibsoni) and rotifers (Brachionus dimidiatus and Brachionus plicatilis). The most commonly occurring diatom taxa in temporary pans included taxa indicative of slightly acidic to circumneutral, dystrophic and nutrient-poor waters such as Nitzschia acidoclinata, Gomphonema gracile and Eunotia bilunaris. Permanent pan assemblages were characterized by taxa typical of saline waters, including Nitzschia frustulum, Amphora veneta and Planothidium engelbrechtii. Species of the genera Pinnularia and Eunotia were almost totally absent from permanent pans.

Zooplankton and Diatoms of Temporary and Permanent Freshwater Pans in the Mpumalanga Highveld Region, South Africa

This paper provides a description of the zooplankton and epiphytic diatom communities of permanent and temporary freshwater pans in the Mpumalanga Highveld region of South Africa. Few studies have investigated the biota of pans in this area, which is seriously threatened by mining and agricultural development. Nineteen pan sites within a 20 kmradius covering a wide range of water chemistries were sampled once for zooplankton, epiphytic diatoms and water physico-chemical data in 2009. Collected zooplankton and diatom samples were identified to species or genus level. Many of the zooplankton taxa reported in this study were not recorded in similar pan studies in South Africa and southern Africa. The study revealed a difference among the compositions of zooplankton and diatom communities between temporary pans and permanent pans. Zooplankton found exclusively in freshwater temporary pans included cladocerans (Megafenestra aurita and Scapholeberis kingi), calanoids (Mesocyclops major and Thermodiaptomus mixtus), a cyclopoid (Acanthocyclops vernalis) and a rotifer (Platyias quadricornis). Permanent pans were characterized by taxa such as cladocerans (Ceriodaphnia rigaudi and Dunhevedia crassa), a calanoid (Metadiaptomus transvaalensis), cyclopoids (Paracyclops fimbriatus and Eucyclops gibsoni) and rotifers (Brachionus dimidiatus and Brachionus plicatilis). The most commonly occurring diatom taxa in temporary pans included taxa indicative of slightly acidic to circumneutral, dystrophic and nutrient-poor waters such as Nitzschia acidoclinata, Gomphonema gracile and Eunotia bilunaris. Permanent pan assemblages were characterized by taxa typical of saline waters, including Nitzschia frustulum, Amphora veneta and Planothidium engelbrechtii. Species of the genera Pinnularia and Eunotia were almost totally absent from permanent pans.