Benthic Diatom Diversity Research Articles

Next-generation sequencing reveals the diversity of benthic diatoms in tidal flats

Next-generation sequencing reveals the diversity of benthic diatoms in tidal flats

Effects of a natural flood disturbance on species richness and beta diversity of stream benthic diatom communities

Natural hydrological disturbances in streams may reduce biomass and species richness and change community composition within streams. Disturbances can also affect beta diversity among streams if their effects are species specific or vary across sites. We investigated the effect of a natural flood on species richness, community composition and among-streams beta diversity of benthic diatoms (total community and three functional groups: low profile, high profile and motile) of seven streams in New Zealand. Sampling occurred shortly before, 10 days after and 40 days after the flood. Species richness of the total diatom community did not change after the flood. The high-profile group was the only one whose species richness declined after the flood, whereas species richness of the low-profile group increased. Community composition changed after the flood, mostly as a result of species replacement rather than richness differences over time. Finally, among-streams beta diversity did not change after the flood, suggesting that variation in species composition of benthic diatoms among streams may be maintained in the face of flood disturbances.

Diversity of benthic diatoms in the Guerrero Negro Lagoon (El Vizcaíno Biosfere Reserve), Baja California Peninsula, Mexico

High species diversity renders benthic diatoms that are useful in assessing environmental impact, as well as an adequate reference for measuring biodiversity in protected areas. Preliminary observations suggested that the Guerrero Negro Lagoon (LGN), located in the Baja California Peninsula, Mexico, is an area with a high diversity of benthic diatoms comprising numerous species of certain genera, orders, class, etcetera, which were not equally diverse or common in other areas, and could thus yield new records for the region. Thus, samples of subtidal sediments from LGN were collected in order to analyze the species composition of epipelic diatoms by means of optical microscopy. The taxonomic study yielded a list with 232 taxa, which comprised 42 centric diatoms (>18%) and 190 pennates from 74 genera; 14 new records for the Mexican Pacific are included. This supported the hypothesis that epipelic diatoms from the LGN subtidal constitute assemblages with a high species richness and numerous taxa characteristic of subtropical regions.

Spatio-temporal variation of benthic diatom diversity and community structure in a sandy intertidal zone of the Nanji Islands, China

Spatio-temporal variation of benthic diatom diversity and community structure in a sandy intertidal zone of the Nanji Islands, China

Testing the efficacy of an estuarine eutrophic condition index: Does it account for shifts in flow conditions?

Eutrophication of estuaries via anthropogenic nutrient enrichment is an issue being addressed extensively on a global scale, however it remains a topic that garners further attention due to its complexity. The aim of this study was to test the efficacy of a recently proposed eutrophic condition index in five permanently open estuaries, subsequent to flow variations. Further, in order to elucidate their potential role in augmenting eutrophic conditions, the influence of vegetated habitats on associated microalgal communities was investigated. The study took place in the summer of 2014 and 2015. On each sampling occasion, all of the proposed ‘state’ indicators (nutrients, oxygen and microalgal communities) were assessed and supplemented with a heuristic ‘pressure’ component (flow conditions). Overall, the proposed index was shown to be sensitive to environmental perturbations providing shifts in classification ratings illustrating the dilution (Swartkops Estuary) or augmenting (Kromme, Gamtoos, and Kariega estuaries) effect of freshwater pulse events. Additionally, the sensitivity of selected epiphyte and microphytobenthos (MPB) parameters to water quality variations was verified, thus supporting their inclusion as indicators in the proposed index. Regarding the role of microhabitats in promoting microalgal growth, it was found that MPB biomass was higher (5–290%) and benthic diatom diversity generally lower (5–50%) in vegetated compared to unvegetated habitats – an important consideration when applying the index. The habitat complexity and stabilisation provided by estuarine macrophytes (Phragmites australis and Zostera capensis) supported notable autotroph colonisation. This highlights their importance in structuring trophic pathways, whilst also potentially providing a corridor for the intensification of eutrophic symptoms in estuaries. Overall, this study provides an important step towards the verification of a proposed assessment methodology which may serve to provide a baseline from which the eutrophic status of estuaries can be monitored – particularly in countries where such assessment frameworks are lacking.

Caddisflies (Trichoptera) and diatoms of some springs in the vicinity of Łódź (Central Poland).

The distribution, species richness and ecology of Trichoptera, the diversity of benthic diatoms, and hydrochemical data in 7 springs in the vicinity of Łódź were investigated in 2011. In total, 17 Trichoptera taxa and more than 300 diatom taxa were collected from the studied springs. Trichoptera and especially diatom taxa are very sensitive indicators of ecological conditions; both showed a strong response to degradation in lowland springs. On the basis of faunal, diatom microfloral, and hydrochemical data, the typology of springs of the vicinity of Łódź is proposed. Two groups of factors (differentiating and non-differentiating) which contribute to distinguishing the studied springs are described. Additional experiments and observations were done on Trichoptera, including their life cycles, biology, and larval diet. In particular, the abundance of common diatom taxa in the guts of Silo sp. larvae was investigated.

Effects of agricultural land use on stream assemblages: Taxon-specific responses of alpha and beta diversity

Although biodiversity loss and homogenization of communities with increasing stress is an established axiom of pollution ecology, few studies have compared the concurrent response of multiple taxonomic groups to determine if environmental perturbation results in coherent patterns in assemblage composition. Here, data from 35 lowland European streams was used to explore the responses of multiple taxonomic groups to disturbance from agricultural land use, mainly gradients in total phosphorus (TP). We studied responses of fish, invertebrate, macrophyte and benthic diatom assemblages to TP, based on univariate metrics that characterize α-diversity (taxon richness, Simpson diversity, evenness, taxonomic distinctness) and abundance, and multivariate community structure. Multivariate dispersion was used to infer β-diversity characteristics in two groups of streams with low and high levels of TP. Three of the five metrics of α-diversity and abundance of primary producers were significantly related to resources, however, the direction of change was not always consistent with our predictions; macrophyte diversity decreased, whereas benthic diatom diversity increased with elevated nutrients. For consumers, taxon richness increased (fish) or decreased (invertebrates), while fish assemblages had lower phylogenetic diversity (taxonomic distinctness) associated with disturbance, implying a loss of functional diversity. In line with our predictions, fish and invertebrate assemblages showed homogenization of β-diversity with disturbance. Our finding that β-diversity of the two primary producers remained relatively high, while α-diversity either decreased (macrophytes) or increased (benthic diatoms), suggests that local disturbance is to some extent compensated for by among-site diversity. Our finding that secondary producers showed homogenization of β-diversity with disturbance has strong management perspectives, suggesting that these groups will need to be more carefully managed to maintain diversity at the landscape level, potentially sustaining resilient communities.

Woodland key habitats and stream biodiversity: Does small-scale terrestrial conservation enhance the protection of stream biota?

Riparian forests are biodiversity hotspots and key habitats for forest conservation, yet it is not known if the protection of these habitats also provides protection for stream organisms. We used data from 50 headwater stream-forest systems in northern Finland to address this question. Our study sites formed a gradient from highly modified (by forestry) to old-growth riparian forests. We assessed whether the community structure and diversity of benthic diatoms, aquatic bryophytes, stream macroinvertebrates and red-listed species (bryophytes+invertebrates) responded to riparian habitat alteration and whether habitat classification based on site naturalness is indicative of stream conservation value. Except for diatoms and chironomid larvae, all taxonomic groups studied, as well as red-listed species, responded negatively to site modification, showing peak diversity in unmodified habitats. Also in terms of community composition, most aquatic groups responded to the gradient of site naturalness. These results suggest that woodland key habitats, although initially targeted at the conservation of terrestrial biodiversity, may prove to be valuable for the protection of stream biodiversity as well, extending their potential importance to regional biodiversity conservation.

Diversity of Benthic Diatoms and Water Quality of the Mekong River Passing Through Ubon Ratchathani Province, Thailand

The study on the diversity of benthic diatoms and water quality in the Mekong River as it passes through Ubon Ratchathani, Thailand was carried out from February 2007 to January 2008. Samples were collected from 10 stations, which were situated in areas involving different geographical features and human activities. Three hundred and seven species of benthic diatoms were found. The majority of them were <em>Gomphonema lagenula</em> Kützing, <em>Navicula rostellata</em> Kützing, <em>Nitzschia palea</em> (Kützing) W. Smith, <em>Luticola goeppertiana</em> (Bleisch) D. G. Mann, <em>Nitzschia liebetruthii</em> Rabenhorst, <em>Sellaphora pupula</em> (Kützing) Mereschkowsky, <em>Navicula erifuga</em> Lange-Bertalot and <em>Cymbella tumida</em> (Brébisson) Van Heurck, respectively. The water quality was slightly different at each sampling site which was classified as moderate water quality (mesotrophic status). Ban Na Muang, Pak Seang Temple, Ban Ta Mui, Ban Na Sanarm, the location behind the Municipal Market and Wigittra Beach were all found to possess moderate water quality (mesotrophic status). Chang Mop Cataract, Ban Koom, Ban Dan and Ban Huay Phai were found to have moderate to polluted water quality (mesotrophic to eutrophic status). The Multivariate Statistical Package (MVSP) particularly Principal Correspondence Analysis (PCA), and the cluster analysis were used to determine the relationship between the water quality and the present of benthic diatoms, in terms of biomonitoring. It was found that <em>Cymbella tumida</em> (Brébisson) Van Heurck and <em>Navicula erifuga</em> Lange-Bertalot could be indicators of mesotrophic status, whereas <em>Cymbella turgidula</em> Grunow, <em>Gomphonema clevei var. javanica</em> Hustedt, <em>Luticola goeppertiana</em> (Bleisch) D. C. Mann, <em>Nitzschia liebetruthii</em> Rabenhorst and <em>Nitzschia palea</em> (Kützing) W. Smith could be indicator of the meso-eutrophic status.

Diatom distributions and species optima for phosphorus and current velocity in rivers from ZhuJiang Watershed within a Karst region of south-central China

The relationships between limestone bedrock geology (with extensive Karst topography), water chemistry and the community structure of benthic diatoms were examined for 35 riffle sites using multivariate analysis. The results showed that physical and chemical environmental variables had a notable effect on the biological diversity of benthic diatoms. Eighteen environmental variables were studied, including velocity (current flow), total phosphorus (TP), conductivity (COND), total nitrogen (TN), oxidation-reduction potential (ORP), chemical oxygen demand (COD), water temperature (WT), pH, silicon dioxide (SiO 2 ), turbidity, major ions (Na + , K + , Ca 2+ , Mg 2+ , HCO 3 ― +CO 3 2― , Cl ― , NO ― 3 , SO 4 2― ). Two variables, TP and velocity were found to be the most important factors explaining diatom distributions. With further analysis using weighted average inference models, the results showed good predictive statistics for diatom composition and TP (R 2 = 0.654, RMSE = 0.036; R 2 boot = 0.483; RMSE boot = 0.048) and velocity (R 2 = 0.641, RMSE = 0.378; R 2 boot = 0.416, RMSE boot = 0.500). Indicator diatom species for TP and velocity were identified and assessed using weighted average optima and tolerances. Fifty-seven taxa were identified as biological indicators, which included Fragilaria vaucheriae, Achnanthidium convergens, A. lineare, Kolbesia suchlandtii and Nitzschia frustulum for high TP (> 200 μg l ―1 ) and Reimeria sinuata, Achnanthidium minutissimum var. scoticum, A. exile, Cymbella leptoceris, and Navicula cf. pseudokotschyi for low TP (50―97 μg l ―1 ). These taxa are useful as monitoring tools for eutrophication in ZhuJiang watershed within a Karst region of south-central China. Diatom richness followed a Gaussian distribution with the most taxa observed in waters with moderate levels of TP This distribution supports the intermediate disturbance hypothesis which predicts that species richness and diversity will be highest under moderate environmental conditions. A Gaussian distribution was also observed for species richness under changing current flow. Measures of diatom diversity, richness, and species optima from the south-central highlands of China will be useful as indicator values for future water-quality assessments.

Diatom and dinoflagellate assemblages of the Hawkesbury River, N.S.W., over the last two centuries: evidence for changes in hydrology

Diatom and dinoflagellate cyst analysis of a 77 cm long sediment core from Cowan Creek, Hawkesbury River estuary, N.S.W., revealed changes in the catchment hydrology over the last 266 years. High abundances of the freshwater/brackish diatom genus Cyclotella at the base of the core imply sustained periods of reduced salinity that now no longer occur. Reduction of freshwater flow after approximately circa 1800 (60 cm) has allowed the development of marine planktonic diatoms Thalassiosira spp.,Ditylum brightwellii, Rhizosolenia setigera, Pseudo-nitzschia pungens and Chaetoceros spp. Benthic diatom diversity has remained relatively unchanged. The toxic dinoflagellate Gymnodinium catenatum, although identified in a cyst survey in April 1995, was not found in the sediment cores. Changes in dinoflagellate assemblage are consistent with the effects of increasing urbanisation and eutrophication.

Benthic marine diatom deformities associated with contaminated sediments in Hong Kong

Three thousand benthic diatoms were examined at each of twelve sites to determine the frequency of diatom deformities. Two basic types of diatom deformities were observed: 1) diatoms with deformed cell wall morphology; and 2) diatoms with deformed valve wall ornamentation. Only six deformed diatoms were observed. Deformed individuals of Fragilaria capucina and Achnanthes hauckiana displayed external cell wall deformities, while deformed individuals of Diatoma vulgare displayed valve walls with a wavy pattern of longitudinal lines in which the valve ornamentation, rather than the valve cell wall, was abnormal. The deformity frequency of Navicula rhyncocephala, Achnanthes hauckiana, Fragilaria capucina, and Diatoma vulgare was significantly lower at unpolluted sites than at polluted sites based on Fisher exact probability estimates. Cadmium reached 1.1 mg/kg dry wt. of sediment, while other levels were chromium (42 mg/kg of sediment), copper (440 mg/kg), nickel (31 mg/kg), lead (130 mg/kg), and zinc (450 mg/kg of sediment) at the most polluted site. There was a significant correlation (P < 0.05, r s = 0.652) between sediment toxicity, as reflected by the Microtox test, and benthic diatom diversity. The most polluted site exhibited the highest Microtox acute toxicity levels, the lowest diversity, and moderate diatom deformity levels. It was concluded that abnormal cell morphology of diatoms may be a valid indicator of ecosystem health. However, because the amount of time and effort required to identify a statistically meaningful number of deformed diatoms is so great, diatom deformity frequency is unlikely to become a useful tool unless an automated system of assessing diatom deformity frequency is developed.

The biological effects of nitrate fertilization and water replacement in an oligotrophic cold water pond

Plastic enclosures (limnocorrals) were used to assess the impact of adding NO3 - to an oligotrophic pond. The pond, Mare's Egg Spring, is spring fed at a constant temperature of 4.5 °C (the main portion of the pool never exceeded 6 °C) and a molar ratio of N:P of 0.5. The pool is dominated by the cyanobacterium (blue green alga), Nostoc pruniforme, which is capable of nitrogen fixation. This, in combination with the low N:P ratio, suggested that non-nitrogen fixing primary producers were limited by nitrogen. Over a period of one month, growth and nitrogen fixation of Nostoc, suspended chlorophyll, sediment denitrification, and benthic diatom diversity were not dependent upon nitrate concentration. However, sedimentary chlorophyll levels increased slightly when NO inf3 sup- levels were increased from 0.71 µM (ambient) to 214 µM. Limnocorrals with slit sides gave water replacement rates between those for complete enclosure and those in open water. In the open channel, Nostoc growth was highest, and suspended chlorophyll the lowest. In the closed corrals, Nostoc growth was the lowest and suspended chlorophyll the highest, with intermediate values in the slit corrals. Therefore, short term increases of NO inf3 sup- levels in nitrogen poor aquatic systems do not necessarily affect the biological community, but slowing water replacement in small ponds may have significant effects.