Oedogonium Research Articles

Freshwater Macroalgae, Oedogonium, Grown in Wastewater Reduce Diet-Induced Metabolic Syndrome in Rats.

Macroalgae produce compounds with industrial, pharmaceutical and nutritional applications. In this study, biomass from the freshwater macroalgal genus Oedogonium was grown in either treated municipal wastewater (M) or ash dam water from a coal-fired power station (D). The biomass was investigated for its metabolic responses in high-carbohydrate, high-fat diet-fed rats, a model of human metabolic syndrome. The Oedogonium biomass cultured in M contained higher amounts of K, Mg, omega-3 polyunsaturated fatty acids (PUFA), insoluble fibre and β-carotene, while biomass grown in D contained higher amounts of Al, Fe, V, Zn, Mn and As. Biomass from M further increased body weight and inflammation in the heart and colon in high-carbohydrate, high-fat diet-fed rats. In contrast, biomass from D prevented changes in metabolic, cardiovascular and liver parameters without changing tissue histology. We suggest that increased intake of metals and metalloids through macroalgal biomass from D may decrease abdominal fat deposition while polysaccharides, PUFA and carotenoids from M may improve blood glucose responses in an obesogenic diet. Thus, macroalgal biomass grown in different wastewater sources could be acceptable for feed or food applications. This biomass could even provide potential health benefits in diet-induced metabolic syndrome.

Periphyton (microbiome) of filamentous algae studied by polarization microscopy, aided also by some contrasting optical methods.

Polarization microscopy, possibly together with some contrast techniques (dark field and color phase contrast), was used to study the periphyton (microbiome) growing on filamentous green algae. The material containing filamentous algae with periphyton on the surface was collected in the villages of Sýkořice and Zbečno (Křivoklátsko Protected Landscape Area). The objects were studied in a LOMO MIN-8 St. Petersburg polarizing microscope and a Carl Zeiss Jena NfpK laboratory microscope equipped with an In Ph 160 basic body with variable dark field or color phase contrast and a Nikon D70 DSLR digital camera. Cells of filamentous algae of the genera Cladophora, Vaucheria, and Oedogonium were studied and the periphyton attached to them formed by cyanobacteria of the genera Chamaesiphon and Pleurocapsa and algae of the genera Characium, including diatoms of the genera Eunotia and Synedra. In all cases, the cell walls of the host algae showed a very strong birefringence. In contrast, the walls of cyanobacteria of the genera Chamaesiphon and Pleurocapsa were characterized by a much weaker birefringence (Pleurocapsa somewhat thicker), and the diatom frustules of the genera Eunotia and Synedra were almost without a birefringence. Strongly birefringent granules were found in the cytoplasm of the green alga of the genus Characium, which forms periphyton on the filamentous green algae of the genus Vaucheria. The periphyton on the filamentous alga of the genus Oedogonium, formed by cyanobacteria of the genus Pleurocapsa and diatoms of the genera Eunotia and Synedra, deposited in a massive layer of mucus containing birefringent crystals, showed a particularly strong birefringence. At the end of the vegetation of filamentous algae, their parts and remnants of periphyton (diatom frustules and crystals) became part of the detritus at the bottom of the culture vessel. The use of polarization microscopy in the study of filamentous algae with periphyton on the surface allows us not only to determine the birefringence of the observed structures, but also to partially deduce their chemical composition, or regular arrangement ofparticles, so-called shape birefringence.

Morphology and Molecular Phylogeny of Genus Oedogonium (Oedogoniales, Chlorophyta) from China.

Oedogoniales comprises the three genera Oedogonium, Oedocladium, and Bulbochaete, which include more than 600 described species. The classification of Oedogoniaceae is currently based on morphology, and the complicated morphological characteristics make species identification difficult, with the limited molecular data also restricting the phylogenetic analysis. In the present study, we collected 47 Oedogonium specimens from China and sequenced 18S rDNA, ITS2, ITS (ITS1 + 5.8S + ITS2), and rbcL sequences to conduct phylogenetic analyses. We selected nine morphological characteristics, most of which were considered important in traditional systematics, for comparison with the molecular phylogeny results. All the topologies based on different datasets showed similar results; Oedogonium was a paraphyletic group, and Oedocladium and Bulbochaete clustered with Oedogonium. The morphological characteristics matching the phylogenetic results showed that the types of sexual differentiation, characteristics of the oogonium (including shape, types of aperture, and ornamentation of oospore wall), division types of antheridial, and number of sperm of each antheridial, which are considered the most important morphological characteristics in traditional taxonomy of Oedogonium, did not form monophyletic lineages respectively, indicating that traditional systematics may not reflect the real phylogeny of the genus Oedogonium. In addition, a new taxonomical classification of the genus Oedogonium was presented according to the shapes of basal cells, which matched well with the phylogenetic topologies. In addition, we propose to divide the genus Oedogonium into two sections, section Globosum and section Elongatum, representing the species with spherical or sub-hemispherical basal cells and elongated basal cells, respectively.

Chloroplast genomes of five Oedogonium species: genome structure, phylogenetic analysis and adaptive evolution

BackgroundThe order Oedogoniales within the single family Oedogoniaceae comprised of three genera, Oedogonium, Oedocladium, and Bulbochaete based on traditional morphological criteria. While several molecular phylogenetic studies have suggested that both Oedogonium and Oedocladium may not be monophyletic, broader taxon sampling and large amounts of molecular data acquisition could help to resolve the phylogeny and evolutionary problems of this order. This study determined five chloroplast (cp) genomes of Oedogonium species and aimed to provide further information on cp genome for a better understanding of the phylogenetic and evolutionary relationships of the order Oedogoniales.ResultsThe five Oedogonium cp genomes showed typical quadripartite and circular structures, and were relatively conserved in their structure, gene synteny, and inverted repeats boundaries in general, except for small variation in genome sizes, AT contents, introns, and repeats. Phylogenetic analyses based on 54 cp protein-coding genes examined by maximum likelihood and Bayesian analyses using amino acid and nucleotide datasets indicated that both Oedocladium and Oedogonium are polyphyletic groups. A positively selected gene (psbA) was identified in the two Oedocladium species and the terrestrial Oedogonium species, indicating that terrestrial Oedogoniales taxa may have undergone adaptive evolution to adjust to the difference in light intensity between aquatic and terrestrial habitats.ConclusionsOur results enrich the data on cp genomes of the genus Oedogonium. The availability of these cp genomes can help in understanding the cp genome characteristics and resolve phylogenetic and evolutionary relationships of the order Oedogoniales.

Molecular markers obtained from draft genomic sequence data characterise an isolate of Oedogonium (Chlorophyceae) used for biomass applications

ABSTRACT Local isolates of the species-rich, fast-growing chlorophyte genus Oedogonium have been employed in outdoor biomass cultivation for industrial applications such as wastewater remediation, but such isolates may not express structural traits needed for definitive species identification by microscopy alone. We used maximum likelihood and Bayesian phylogenetic methods to evaluate molecular marker gene sequences derived from genomic sequences to characterise an industrial isolate, Oedogonium sp. Lake Mendota strain, which could not be reliably classified at species level using only morphology. Molecular markers evaluated were rbcL, 23S rDNA, 28S rDNA, 18S rDNA, and a sequence that included ITS1+5.8S rDNA+ITS2. All five markers distinguished the Lake Mendota strain from other Oedogonium accessions in GenBank. Using full genome sequences allowed the efficient acquisition of multiple types of marker sequences whose sequencing depth was known. In the absence of a classical species determination, these markers provided a taxonomic reference background for future genomic, biochemical, and other investigations of the local isolate. Local isolates are advantageous for outdoor industrial biomass cultivation applications because such isolates are already adapted to climatic conditions prevailing at cultivation sites. The results should encourage industrial use of local isolates of Oedogonium because these can be characterised by molecular markers even if structural features needed for accurate species determinations are not expressed.

Periphytic algal community in lentic environments of the Upper Paraná River floodplain: seasonal and spatial variation

Abstract Aim: This study aimed to evaluate the influence of seasonal variation in the hydrological regime and of limnological variables on species richness of periphytic algae in lakes of the Upper Paraná River floodplain. Methods The study area is located in the last undammed stretch of the Paraná River in this floodplain, in which three lakes were sampled quarterly (May, August and November 2014, and February and May 2015) for one year. The periphytic material was obtained from petioles of the aquatic macrophyte Eichhornia azurea (Sw.) Kunth. Results We registered 149 taxa of periphytic algae, distributed in 9 classes. Algal richness changed as a function of the seasonal dynamics of the Paraná River’s hydrological regime. Water level fluctuations directly influenced periphytic algae species. During periods of high water level, species richness increased. Limnological variables showed a close relationship with the hydrological regime, and the dissolved nutrients and turbidity were the abiotic factors that most influenced the algal community. The following species were present in all lakes: Fragilaria capucina Desmazières, Gomphonema gracile Ehrenberg and Navicula cryptotenella Lange-Bertalot (Bacillariophyceae) and two species of the genus Oedogonium (Oedogoniophyceae). Conclusions The hydrological regime of the Paraná River played an important role in structuring communities of periphytic algae. Seasonal variation in hydrological regime and in limnological variables together influenced the species richness of these organisms in these floodplain lakes.

Association of a Specific Algal Group with Methylmercury Accumulation in Periphyton of a Tropical High-Altitude Andean Lake.

Periphyton relevance for methylmercury (MeHg) production and accumulation are now well known in aquatic ecosystems. Sulfate-reducing bacteria and other microbial groups were identified as the main MeHg producers, but the effect of periphyton algae on the accumulation and transfer of MeHg to the food web remains little studied. Here we investigated the role of specific groups of algae on MeHg accumulation in the periphyton of Schoenoplectus californicus ssp. (Totora) and Myriophyllum sp. in Uru Uru, a tropical high-altitude Bolivian lake with substantial fishing and mining activities accruing around it. MeHg concentrations were most strongly related to the cell abundance of the Chlorophyte genus Oedogonium (r 2=0.783, p=0.0126) and to no other specific genus despite the presence of other 34 genera identified. MeHg was also related to total chlorophyll-a (total algae) (r 2=0.675, p=0.0459), but relations were more significant with chlorophyte cell numbers, chlorophyll-b (chlorophytes), and chlorophyll-c (diatoms and dinoflagellates) (r 2=0.72, p=0.028, r 2=0.744, p=0.0214, and r 2=0.766, p=0.0161 respectively). However, Oedogonium explains most variability of chlorophytes and chlorophyll-c (r 2=0.856, p=<0.001 and r 2=0.619, p=0.002, respectively), suggesting it is the most influential group for MeHg accumulation and periphyton algae composition at this particular location and given time.

Heritable variation in growth and biomass productivity in the clonal freshwater macroalga Oedogonium

In an analogous manner to which selective breeding and propagation of heritable traits have improved terrestrial crops, the directional selection of target strains of commercial algae produced through clonal propagation is essential to realising their full potential for biomass applications and develop cost effective production. As a first step towards establishing a trait selection programme in clonal freshwater macroalgae of the genus Oedogonium, we determined whether there is heritable variation in growth and biomass productivity in 6 genetically distinct strains. Intraclonal variability in growth was quantified within clonal lineages of single filaments in laboratory cultures, and intraclonal variability in biomass productivity was quantified within clonal lineages of intensive cultures containing multiple filaments maintained in outdoor cultures. We found significant estimates of genetic variance (Broad-sense heritability, H2: 0.16–0.51) in growth among clonal replicates of 4 strains in laboratory cultures, and significant estimates of genetic variance (H2>0.69) in biomass productivity in two strains in outdoor intensive cultures. These results demonstrate that there is an important heritable component to variation in growth and biomass productivities among theoretically identical clonal lineages for these strains. Such data is rare for freshwater macroalgae and suggest that growth and biomass productivity for these strains could be improved by maintaining selected clonal lines.

Bioremediation for coal-fired power stations using macroalgae

Macroalgae are a productive resource that can be cultured in metal-contaminated waste water for bioremediation but there have been no demonstrations of this biotechnology integrated with industry. Coal-fired power production is a water-limited industry that requires novel approaches to waste water treatment and recycling. In this study, a freshwater macroalga (genus Oedogonium) was cultivated in contaminated ash water amended with flue gas (containing 20% CO2) at an Australian coal-fired power station. The continuous process of macroalgal growth and intracellular metal sequestration reduced the concentrations of all metals in the treated ash water. Predictive modelling shows that the power station could feasibly achieve zero discharge of most regulated metals (Al, As, Cd, Cr, Cu, Ni, and Zn) in waste water by using the ash water dam for bioremediation with algal cultivation ponds rather than storage of ash water. Slow pyrolysis of the cultivated algae immobilised the accumulated metals in a recalcitrant C-rich biochar. While the algal biochar had higher total metal concentrations than the algae feedstock, the biochar had very low concentrations of leachable metals and therefore has potential for use as an ameliorant for low-fertility soils. This study demonstrates a bioremediation technology at a large scale for a water-limited industry that could be implemented at new or existing power stations, or during the decommissioning of older power stations.

Microalgae Biomass as an Alternative Substrate in Biogas Production

The running down of fossil energy sources makes the production of bioenergy an expected need worldwide. Therefore, energy crops have gained increasing attention in recent years as a source for the production of bioenergy because they do not compete with food crops. Microalgae have numerous advantages such as fast growth rates and not competing with food production. Because of the fast growth, many high valuable products are generated, e.g. food, biofuel, etc. Due to the energy crisis, renewable energy becomes a popular issue in this world today and there are several alternatives such as bioenergy, solar, wind, tide, geothermal, etc. For bioenergy, algae are the third generation biofuel crop. There is an increased demand for biogas in the society and one way to meet this is to use cultivated microalgae as fermentation substrate. In the present study, we maintained algae growth process and biomass production in autotrophic condition continuously for over 2 month’s period. Growth system (photobioreactor) was setup under room temperature and continuous illumination light through fluorescent lamps; light intensity was average as 48.31 [µmol-1m-2 per µA]. In reactor, dominant microalgae species were including Anabaena sp., Chlorella sp., Oscillatoria sp., Oedogonium sp. and Scenedesmus sp. The content of total solids (TS) and volatile solids (VS) in the algae biomass was measured; the results were average as 12500 g/m3 and 6320 g/m3, respectively. Furthermore, microalgal biomass is a potentially valuable fermentation substrate, and produce over 60% of methane gas.

Algal Diversity in the Streams and Waterfalls of Eastern and North-Eastern Region of India

Two hundred fourteen species of algae were recorded from 12 mountain streams of Odisha and 21 streams and waterfalls of the Eastern Himalayan region covering West Bengal, Sikkim, Arunachal Pradesh, Nagaland and Mizoram. Of these Chlorophyta (39), Cyanophyta (31), Heterokontophyta (24) and Euglenophyta (3) were specifically from the streams in Odisha whereas Cyanophyta (43), Chlorophyta (34) and Bacillariophyceae (26) were from the streams and waterfalls of the eastern Himalayan region. The diversity of algae in these two regions of eastern India differing in topography and climatic regime showed a wide variation of occurrence of taxa in these specialized and mostly unpolluted habitats. Only 14 species of algae of which Phormidium grnulatum, Calothrix fusca, Dichothrix orsiniana, Nostoc commune under Cyanophyta, Spirogyra maravillosa, Staurastrum bieneanum var. ellipticum, Stigeoclonium longipilum, Oedogonium wyliei under Chlorophyta and Fragillaria virescence, Synedra ulna, Synedra ulna var. aequalis, Synedra ulna var. amphirhynchus , Synedra ulna var. oxyrhynchus , Cymbella tumida under Bacillariophyceae of Heterokontophyta were recorded in certain streams of both the regions. Of these 214 algal taxa, 97 were recoded first from the Eastern and North-eastern region.

Freshwater Macroalgae as a Biofuels Feedstock: Mini-Review and Assessment of Their Bioenergy Potential

Extensive efforts have been made to evaluate the potential of microalgae as a biofuel feedstock during the past 4–5 decades. However, filamentous freshwater macroalgae have numerous characteristics that favor their potential use as an alternative algal feedstock for biofuels production. Freshwater macroalgae exhibit high rates of areal productivity, and their tendency to form dense floating mats on the water surface imply significant reductions in harvesting and dewatering costs compared to microalgae. A review of the published literature on the elemental composition and energy content of five genera of freshwater macroalgae suggests that they compare very favorably with traditional biobased energy sources, including terrestrial residues, wood, and coal. In addition, we performed a semi-continuous culture experiment using the common Chlorophyte genus Oedogonium to investigate whether nutrient availability can influence its higher heating value (HHV), productivity, and proximate analysis. Our findings show that the most nutrient-limited growth conditions resulted in a significant increase in the HHV of the Oedogonium biomass (14.4–16.1 MJ/kg). Although there was no significant difference in productivity between the treatments, the average dry weight productivity of Oedogonium (3.37 g/m2/day) was higher than for common terrestrial plant crops. These results suggest that filamentous freshwater macroalgae have great potential as a feedstock for both liquid and solid fuels, especially if nutrient-rich wastewater can be used as the supply of water and mineral nutrients. In addition, this study demonstrates the importance of evaluating the algal cultivation conditions that influence trade-offs between biomass productivity and energy content.

Growth and metal bioconcentration by conspecific freshwater macroalgae cultured in industrial waste water.

The bioremediation of industrial waste water by macroalgae is a sustainable and renewable approach to the treatment of waste water produced by multiple industries. However, few studies have tested the bioremediation of complex multi-element waste streams from coal-fired power stations by live algae. This study compares the ability of three species of green freshwater macroalgae from the genus Oedogonium, isolated from different geographic regions, to grow in waste water for the bioremediation of metals. The experiments used Ash Dam water from Tarong power station in Queensland, which is contaminated by multiple metals (Al, Cd, Ni and Zn) and metalloids (As and Se) in excess of Australian water quality guidelines. All species had consistent growth rates in Ash Dam water, despite significant differences in their growth rates in “clean” water. A species isolated from the Ash Dam water itself was not better suited to the bioremediation of that waste water. While there were differences in the temporal pattern of the bioconcentration of metals by the three species, over the course of the experiment, all three species bioconcentrated the same elements preferentially and to a similar extent. All species bioconcentrated metals (Cu, Mn, Ni, Cd and Zn) more rapidly than metalloids (As, Mo and Se). Therefore, bioremediation in situ will be most rapid and complete for metals. Overall, all three species of freshwater macroalgae had the ability to grow in waste water and bioconcentrate elements, with a consistent affinity for the key metals that are regulated by Australian and international water quality guidelines. Together, these characteristics make Oedogonium a clear target for scaled bioremediation programs across a range of geographic regions.

Isolation and Identification of Oedogonium Species and Strains for Biomass Applications

Freshwater macroalgae from the genus Oedogonium have recently been targeted for biomass applications; however, strains of Oedogonium for domestication have not yet been identified. Therefore, the objective of this study was to compare the performance of isolates of Oedogonium collected from multiple geographic locations under varying environmental conditions. We collected and identified wild-type isolates of Oedogonium from three geographic locations in Eastern Australia, then measured the growth of these isolates under a range of temperature treatments corresponding to ambient conditions in each geographic location. Our sampling identified 11 isolates of Oedogonium that could be successfully maintained under culture conditions. It was not possible to identify most isolates to species level using DNA barcoding techniques or taxonomic keys. However, there were considerable genetic and morphological differences between isolates, strongly supporting each being an identifiable species. Specific growth rates of species were high (>26% day−1) under 7 of the 9 temperature treatments (average tested temperature range: 20.9–27.7°C). However, the variable growth rates of species under lower temperature treatments demonstrated that some were better able to tolerate lower temperatures. There was evidence for local adaptation under lower temperature treatments (winter conditions), but not under higher temperature treatments (summer conditions). The high growth rates we recorded across multiple temperature treatments for the majority of species confirm the suitability of this diverse genus for biomass applications and the domestication of Oedogonium.

Diet of tadpoles of Physalaemus biligonigerus (Leiuperidae) from agricultural ponds in the central region of Argentina

th June. Abstract. The intensification of agriculture has led an important loss of natural habitats, with significant consequences for biodiversity. In this sense, the studies on anuran amphibian tadpoles inhabiting these environments are relevant, because the larval stage is a phase of population regulation. The aim of this study was to analyze the diet in Physalae - mus biligonigerus tadpoles, an anuran species widely distributed in South America and that inhabit agroecosystems. Three sites were sampled; two agroecosystems with different alteration degrees (AG1 and AG2) and an uncultured (SM) third place. The captured tadpoles were anesthetized, fixed and preserved in formaldehyde (10%). Subsequently, the complete intestine was removed and analyzed for food items under a binocular microscope. The diet in P. biligoni- gerus tadpoles has a dominance of algae Bacillariophyceae, mainly in agroecosystems, due to the presence of the gen- era Navicula, Nitzschia and Gomphonema. There was a considerable abundance of the Gomphonema genus in the AG2 site. In addition, in the AG1 site several non-diatom algae were particularly abundant in the diet, such as the genera Euglena, Oedogonium and Chaetophora. In the SM site, the non-diatom genus Oscillatoria was well represented in the diet. Tadpoles inhabiting the site with abundant crop and livestock (AG1) ingested a significantly smaller amount of food. The presence of certain algae associated with eutrophic environments could indicate some pollution in agroeco- systems (AG1 and AG2). Larval diet is suggested as a potential bioindicator of environmental health for these areas.

The Effect of CO2 on Algal Growth in Industrial Waste Water for Bioenergy and Bioremediation Applications

The energy, mining and mineral processing industries are point sources of metal-contaminated waste water and carbon dioxide (CO2). Freshwater macroalgae from the genus Oedogonium can be grown in metal-contaminated waste water to generate biomass for bioenergy applications and concomitantly bioremediate metals. However, interactions between CO2 addition and algal growth, which can affect bioremediation, remain untested. The addition of CO2 to algal cultures in the Ash Dam Water (ADW) from a coal-fired power station increased the biomass productivity of Oedogonium sp. from 6.8 g dry weight (DW) m-2 d-1 to a maximum of 22.5 g DW m-2 d-1. The greater productivity increased the rate of bioremediation of most elements. However, over time carbon-amended cultures experienced a decline in productivity. Possible explanations include metal toxicity at low pH or essential trace element limitation as a result of competition between toxic and essential trace elements for uptake into algae. Higher productivity increased bioremediation rate and yielded more biomass for bioenergy applications, making maintenance of maximum productivity the central aim of the integrated culture model. To do so it will be necessary to resolve the mechanisms responsible for declining yields over time in carbon-amended cultures. Regardless, our data demonstrate that freshwater macroalgae are ideal candidates for bioremediation of metal-contaminated waste streams. Algal culture delivered significant improvement in ADW quality, reducing 5 elements that were initially in excess of water quality criteria (Al, As, Cd, Ni and Zn) to meet guidelines within two to four weeks.

Using CO2 to enhance carbon capture and biomass applications of freshwater macroalgae

AbstractA major limiting factor in the development of algae as a feedstock for the bioenergy industry is the consistent production and supply of biomass. This study is the first to access the suitability of the freshwater macroalgal genus Oedogonium to supply biomass for bioenergy applications. Specifically, we quantified the effect of CO2 supplementation on the rate of biomass production, carbon capture, and feedstock quality of Oedogonium when cultured in large‐scale outdoor tanks. Oedogonium cultures maintained at a pH of 7.5 through the addition of CO2 resulted in biomass productivities of 8.33 (±0.51) g DW m−2 day−1, which was 2.5 times higher than controls which had an average productivity of 3.37 (±0.75) g DW m−2 day−1. Under these productivities, Oedogonium had a carbon content of 41–45% and a higher heating value of 18.5 MJ kg−1, making it an ideal biomass energy feedstock. The rate of carbon fixation was 1380 g C m−2 yr−1 and 1073.1 g C m−2 yr−1 for cultures maintained at a pH of 7.5 and 8.5, and 481 g C m−2 yr−1 for cultures not supplemented with CO2. This study highlights the potential of integrating the large‐scale culture of freshwater macroalgae with existing carbon waste streams, for example coal‐fired power stations, both as a tool for carbon sequestration and as an enhanced and sustainable source of bioenergy.

Five new species of Oedogonium Link (Chlorophyta), a freshwater filamentous algae from Nepal

The present paper deals with six species of genus Oedogonium Link, among which five species are being recorded for the first time from Nepal. They are Oedogonium leave Wittrock, O. peipingense Jao, O. pisanum Wittrock, O. plagiostomum Wittrock and O. undulatum (Bréb.) A. Braun in De Bary. DOI: http://dx.doi.org/10.3126/njbs.v2i0.7485 Nepalese Journal of Biosciences 2 : 17-23 (2012)

Ultrastructure of multicellular dwarf males with external gametangium in Oedogonium macrandrium (Oedogoniales, Chlorophyta)

This is the first comprehensive ultrastructural study on dwarf males with external gametangia in the genus Oedogonium, from androspore germination to the liberation of mature male gametes. The ultrastructure of the process in O. macrandrium Wittrok is similar to that of Bulbochaete hiloensis (Nordstedt) Tiffany, but with two remarka- ble differences. In O. macrandrium : 1) instead of a true transverse wall, only condensed mucilage appears between the gametes of each antheridial cell, and 2) the cell wall between the basal cell and the basal most antheridial cell has sim- the cell wall between the basal cell and the basal most antheridial cell has sim- ple plasmodesmata similar to those present in the transverse walls of vegetative cells, which are absent in B. hiloensis.

The periphyton index of trophic status PIT: a new eutrophication metric based on non-diatomaceous benthic algae in Nordic rivers

Eutrophication is one of the major problems for surface water quality in Norway, particularly in the lowlands near settlements and agricultural areas. Here, we present a new index based on non-diatomaceous benthic algae (Periphyton index of trophic status, PIT) which is developed on a dataset of >500 samples from >350 sites from the Norwegian mainland and can be used to describe trophic status at a river site. PIT indicator values for benthic algae taxa are derived from water total phosphorus concentrations and range from 1.87 for Stigonema hormoides to 68.91 for Tribonema sp. PIT site values range from 3.42 to 44.45 and cover a range from oligotrophic to eutrophic conditions. The relationship between the PIT and the total phosphorus concentration has one major threshold at 10 μg/l TP, with a slow increase below and a steep increase above 10 μg/l. We conclude that benthic algae species composition at nutrient poor sites reacts only slightly to small increases in phosphorus concentration, while it is most sensible to eutrophication in the range between 10 and 30 μg TP/l. For the genus Oedogonium, we found a significant positive correlation between filament width and TP concentration, making Oedogonium an easy to use eutrophication indicator.