Monoraphidium Contortum Research Articles

Growth of Raphidiopsis raciborskii and Monoraphidium contortum from a subtropical Brazilian Reservoir: interaction, saxitoxin production and response to the trophic state

In order to investigate the influence of trophic state from a subtropical reservoir in the state of São Paulo, Brazil, in the competition between the species dominant, Raphidiopsis raciborskii and Monoraphidium contortum, an assay was carried out of interaction between these microorganisms simulating the reservoir in its current conditions, mesotrophic, and another in a supereutrophic condition, as well as detect the production of saxitoxin by cyanobacteria. The experiments were conducted in a climate-controlled room for 15days in triplicate for pure and mixed cultures of each species. Growth curves were developed according to the biovolume-to-biomass and were calculated the growth rates. The saxitoxin synthesis was determined by ELISA. When simulating the mesotrophic and supereutrophic environments, R. raciborskii did not show any differences in its growth and in the saxitoxin production in the interaction with M. contortum, when compared to its control. Concerning M. contortum, your growth was affected in the interactions with cyanobacteria in both trophic state, although the chlorophyceae presented an increasing specific growth rate. The reduction of the growth of M. contortum in interaction with R. raciborskii shows the increase in trophic state can increase the competitiveness of R. raciborskii in the reservoir and to favor your dominance.

Planktonic-based assessment of the landside-dammed lake (Erzurum-Turkey)

The aim of this study was to identify the variation of plankton communities in the Tortum Lake. Changes in phytoplankton and zooplankton communities in relation to the abiotic environment were analyzed using multivariate analysis. Water samples were taken monthly from three sampling points of the Tortum Lake between June 2012 and May 2013. Water temperature (5.28-23.05°C), dissolved oxygen (1.54-13.68 mgL-1), and pH (7.22-9.01) were measured in situ. Chlorophyll-a and total orthophosphate concentrations ranged from 0.18 to 5.70 mgL-1 and from 0.01 to 0.00 mgL-1, respectively. In the Tortum Lake, Ceratium hirundinella (18%), Botryococcus braunii (51%), Chlamydomonas microsphaerella (25%), Microcystis aeruginosa (7%), Melosira varians (1%), Monoraphidium contortum (1%), Copepoda (66%), Daphnia (33%) and Keratella (1%) were found. Some species such as M. aeruginosa were increased by organic and inorganic pollution in Tortum Lake.

Productivity and fuel quality parameters of lipids obtained from 12 species of microalgae from the northeastern region of Brazil

The present work evaluated the growth potential, lipid productivities and the fatty acids methyl esters profiles of 6 chlorophytes and 6 cyanobacteria isolated from the northeast of Brazil, aiming to predict the quality of the biodiesel that could be produced from these microalgae. Among the chlorophytes, Chlorella sp. (D101Z) stood out as having the greatest daily cell division rate (2.42 d−1). Among the cyanobacteria examined, the species Synechocystis sp. (M3C) and Synechococcus nidulans (D109WC) showed elevated lipid (54.2 and 93.8 mg L−1 d−1 respectively) and biomass productivities (0.39 and 0.69 g L−1 d−1 respectively). The lipids produced by the chlorophytes were mainly saturated, monounsaturated, and tri-unsaturated esters, while the cyanobacteria produced high levels of saturated esters and fatty acids with different degrees of unsaturation. Statistical analyses indicated D101Z and D109WC as promising species, as they showed high lipid productivity and the biodiesel produced from their lipids demonstrated low cold filter clogging point values, with a low iodine index for D101Z; the rather high iodine index of D109WC, however, disqualified it for biodiesel production purposes. Among the species studied, only the chlorophyte Monoraphidium contortum (D173WC) and the cyanobacteria D109WC did not meet all of the quality specifications.

Cultivation of freshwater microalgae in biodiesel wash water.

Biodiesel wash water is a contaminating industrial effluent that must be treated prior to disposal. The use of this effluent as a low-cost alternative cultivation medium for microalgae could represent a viable supplementary treatment. We cultivated 11 microalgae species with potential use for biodiesel production to assess their growth capacities in biodiesel industrial washing waters. Only Monoraphidium contortum, Ankistrodesmus sp., Chlorococcum sp., and one unidentified Chlorophyceae species grew effectively in that effluent. M. contortum showed the highest growth capacity and had the second highest fatty acid content (267.9mgg-1 of DW), predominantly producing palmitic (20.9%), 7,10,13-hexadecatrienoic (14%), oleic (16.2%), linoleic (10.5%), and linolenic acids (23.2%). In the second phase of the experiment, the microalgae were cultivated in biodiesel wash water at 75% of its initial concentration as well as in WC (control) medium. After 21days of cultivation, 25.8 and 7.2% of the effluent nitrate and phosphate were removed, respectively, and the chemical oxygen demand was diminished by 31.2%. These results suggest the possibility of cultivating biodiesel producing microalgae in industrial wash water effluents.

Influence of temperature and nutrient content on lipid production in freshwater microalgae cultures.

The production of biomass by microalgae is considered a clean alternative compared to other plant crops that require large areas for cultivation and that generate environmental impacts. This study evaluated the influence of temperature and nutrients on lipid contents of cultured species of freshwater microalgae, with a view toward using these lipids for biodiesel production. Two strains of Monoraphidium contortum, a culture containing Chlorella vulgaris and Desmodesmus quadricauda and another strain of Microcystis aeruginosa were maintained in the laboratory for six days, in five culture media: modified ASM-1 (control, with high concentrations of phosphate and nitrate; phosphorus-deficient; non-limiting phosphate; nitrogen-deficient; and non-limiting nitrate). The cultures were then exposed to temperatures of 13°C, 25°C (control) and 37°C for eight days (n=3). Lipids were extracted by the cold-solvent (methanol and chloroform) method. On average, the highest total lipid yields were observed when the strains were maintained at 13°C and in the non-limiting nitrate medium. The lipid percentage varied depending on the concentration of algal biomass. This study showed that manipulation of controlling factors can increase the lipid concentration, optimizing the total production in order to use this raw material for biodiesel.

Effects of Cadmium, Copper and Zinc on Growth of Four Isolated Algae from a Highly Polluted Argentina River

Toxicity of cadmium, copper and zinc was tested on four green algal species (Ankistrodesmus fusiformis, Chlorella ellipsoidea, Monoraphidium contortum and Scenedesmus acuminatus) isolated from a highly polluted river (Matanza-Riachuelo River, Buenos Aires, Argentina). The relative abundance of these species in river waters showed that C. ellipsoidea was the most abundant species (mean 4,540 ind mL(-1)), whereas the less abundant species was S. acuminatus (mean 220 ind mL(-1)). The most sensitive species was A. fusiformis, which EC50 were Cd = 141 μg L(-1), Cu = 72 μg L(-1), and Zn = 199 μg L(-1), whereas C. ellipsoidea was the most resistant species to copper (EC50 = 489 μg L(-1)) and cadmium (EC50 = 429 μg L(-1)), and M. contortum and S. acuminatus were the most resistant species to zinc (EC50 = 381 and 394 μg L(-1), respectively).

Effect of nitrate on lipid production by T. suecica, M. contortum, and C. minutissima

Abstract Microalgae are an alternative and sustainable source of lipids that can be used as a feedstock for biodiesel production. Nitrate is a good nitrogen source for many microalgae and affects biomass and lipid yields of microalgae. In this study, the effect of nitrate on cell growth and lipid production and composition in Monoraphidium contortum, Tetraselmis suecica, and Chlorella minutissima was investigated. Nitrate affected the production of biomass and the production and composition of lipids of the three microalgae tested. Increasing the nitrate concentration in the culture medium resulted in increased biomass production and higher biomass productivity. Furthermore, increasing the nitrate concentration resulted in a reduction in lipid content and productivity in M. contortum; however, the opposite effect was observed in T. suecica and C. minutissima cultures. C. minutissima and M. contortum lipids contain high levels of oleic acid, with values ranging from 26 to 45.7% and 36.4 to 40.1%, respectively. The data suggest that because of its high lipid productivity (13.79 mg L−1 d−1) and high oleic acid productivity (3.78 mg L−1 d−1), Chlorella minutissima is a potential candidate for the production of high quality biodiesel.

Identification of Monoraphidium contortum as a promising species for liquid biofuel production

In this work, 30 microalgae strains from 17 genera were investigated in regard to biomass productivity in photoautotrophic growth conditions, lipid amount, lipid quality and biomass degradability. Six strains could be identified with robust phototrophic growth properties and high biomass productivities equal or above 300mgl−1day−1. Anaerobic fermentation of the algal biomass was most efficient for the marine members of the genera Dunaliella and Navicula, while biogas production with the freshwater strains generally resulted in lower methane yields. Monoraphidium contortum was identified as promising candidate for liquid biofuel production, characterized by high biomass productivity during maximum growth (maximum increase of 896mg dry biomass weight (DW) l−1day−1) and a promising lipid profile. Neutral lipid production was strongly induced in M. contortum by nitrogen deficient conditions and accumulated to up to 20.4±2.2% of DW.

Bioavailability of riverine dissolved organic matter to phytoplankton in the marine coastal waters

Nutrient inputs from catchments with intensive agriculture are mostly dominated by inorganic nutrients, whereas the contribution of organic nutrients from catchments with natural forests can be considerable but there is a pooere understanding of this nutrient source. Consequently this study investigated spring, summer and autumn phytoplankton community responses to enrichment by riverine dissolved organic matter (DOM). Dissolved organic substances were extracted from the Daugava River, fractionated into three molecular size classes: 1) 5–100kDa, 2) 100–1000kDa, and 3) >1000kDa, and added to a microcosm with natural assemblages from the Gulf of Riga. During the spring the phytoplankton community was dominated (97%) by diatoms and the species composition did not change over the course of the experiment. Specific species and functional groups of the summer and autumn phytoplankton communities responded positively to these treatments. Small-celled cyanobacteria and Monoraphidium contortum responded to almost all size fractions of DOM for the summer and autumn experiments. Oocystis spp. characteristic for the summer and Chaetoceros wighamii, Cyclotella spp., Thalassiosira baltica for the autumn responded to treatment by two and three size classes of organic substances, respectively, while Merismopedia spp. shifted from one food source to another during the summer experiment.

Biodiesel production by hydroesterification of microalgal biomass using heterogeneous catalyst

This paper assesses the hydroesterification process for the production of Biodiesel from Monoraphidium contortum (MORF-1) microalgae biomass, as it is a sustainable alternative not only economically, but also environmentally and ecologically to replace petroleum diesel fuel. The Biodiesel studied in this work was obtained from fatty acid esterification, a product of microalgae and methanol biomass hydrolysis reaction. CBMM’s (HY-340) niobium oxide powder was used as catalyst. The reactions were carried out in a properly closed autoclave reactor (batch), where the reagents were mixed under constant stirring at 500 rpm for hydrolysis and esterification. The products generated were submitted to gas chromatography and oxidative stability analysis. The hydroesterification process showed itself to be a promising alternative to the conventional biodiesel production process (transesterification) as it favors the use of feedstocks with any acidity and moisture content and may be performed with acid catalyst, which favors high conversions in a small range of time (30 minutes).

Culture of microalgal strains isolated from natural habitats in Thailand in various enriched media

Six freshwater microalgal strains in the class of Chlorophyceae, including Chlorococcum humicola, Didymocystis bicellularis, Monoraphidium contortum, Oocystis parva, Sphaerocystis sp., and Scenedesmus acutus were isolated from natural habitats in Thailand. The six strains were compared for their biomass yield, lipid content, and lipid productivity in four enriched culture media in batch mode. Significant differences were found across algal strains and culture media. The best strain was found to be C. humicola, which had the highest biomass yield of 0.113g/l/d (in Kuhl medium), the highest lipid content of 45.94% (in BG-11 medium), and the highest lipid yield of 0.033g/l/d (in 3NBBM medium). The 3NBBM medium, which has the lowest nitrogen concentration among the four culture media, was considered the optimal culture medium for C. humicola for lipid production. The fatty acid profile of C. humicola was also found to be affected by the culture medium. More oleic acid (C18:1) but less linolenic acid (C18:3) was accumulated in BG-11 and 3NBBM than in Kuhl and N-8 media. Lipid profiles of C. humicola were comparable to palm oil in the percentage of palmitic acid and the total amount of saturated fatty acids; however, C. humicola made more poly-unsaturated fatty acids such as linoleic (C18:2) and linolenic (C18:3) acids than oil palms. Lipids from C. humicola were believed to be acceptable for biodiesel production.

Detection of geosmin from Coelosphaerium kuetzingianum separated by a step density gradient medium from suspended materials in water in Lake Shinji, Japan

To identify the geosmin-producing organisms in Lake Shinji, Japan, we conducted preliminary chemical and biological investigations from April to July 2008, during which odor occurrence was observed. Geosmin was mainly detected in the suspended substance (SS) of lake water, and its concentration corresponded to the cell numbers of Coelosphaerium kuetzingianum (Cyanophyceae) and Monoraphidium contortum. C. kuetzingianum and Pseudodictyosphaeriumminusculum (Chlorophyceae; which occurred only in April) were separated from the lake water of 30 April to the lighter, interlayers in a step density gradient medium. The highest concentration of geosmin was detected in the portion of the lightest layer separated from the water sample by gas chromatography mass spectrometry (GC/MS). Observation under optical microscope confirmed that abundant C. kuetzingianum with some P. minusculum and a very rare unknown material was retained in this portion. Similarly C. kuetzingianum was separated by the step density gradient medium from the sediment of 7 May. Abundant C. kuetzingianum with rare bacteria was recognized in the portion of the lightest layer, which contained the highest concentration of geosmin. The cell numbers of C. kuetzingianum correlated with the concentration of geosmin in the separated portions of water samples. These results suggest that C. kuetzingianum probably produced geosmin, although there has been no report about this to now.

Hydrological complexity supports high phytoplankton richness in the Doñana marshland (SW Spain)

Two hundred and twenty-four phytoplanktonic taxa were recorded in a riverine floodplain on the NE side of the Doñana marshland from September 2002 to 2004. This collection of 11 samples included 80 Bacillariophyceae (Diatoms), 71 Chlorophyta, 39 Cyanophyta, 19 Euglenophyta, 6 Chrysophyceae, 5 Cryptophyta, and 4 Dinophyceae. Fifty-five percent of the total taxa had a very low frequency of appearance (<5%), while only three species appeared with a frequency >90% (Monoraphidium contortum Komárková-Legnevorá, Cyclotella atomus Hustedt, and Nitzschia palea W. Smith). According to multivariate analyses, both temporal and spatial factors produced a pattern in the phytoplankton assemblages dominated by freshwater inputs during winter flooding, tidal inputs in summer, and transitional stages during the rest of the year. Spatial segregation of phytoplankton was likely due to differences in retention time and distance to water input. The main taxa involved in this segregation were Chrysidalis sp. 1 (June 2003 and 2004), Chlamydomonas sp. 4 (September 2003), C. atomus (December 2003), and Tetradesmus aff. crocini (February 2004). The hydrologic complexity of the study area could account for this high taxa richness by promoting replacement and colonization episodes following seasonal changes in water source (freshwater versus tidal inputs).

Mechanisms of microalgae selection during the assembly of a planktonic community

We attempt to ascertain the selection mechanisms that affect algal species’ abilities to thrive in a given environment, and how the variability of the response is reflected in the community structure (total biomass, diversity) and also in community function (photosynthesis and respiration). For that, we formed algal communities, assembling eight species of freshwater cosmopolite algae with distinct morphologies (Cosmarium contractum, Cryptomonas ovata, Euglena gracilis, Limnothrix redekei, Monoraphidium contortum, Pediastrum tetras, Planktothrix agardhii and Scenedesmus acutus) and performed four treatments combining low and high nutrient concentrations (N and P) in the culture media and a presence or absence of herbivores (a mixture of Daphnia magna, Keratella cochlearis and Brachionus calicyflorus). Competition between pairs of algae was also studied, and the viability of the species as inocula after a senescence period. The presence of herbivores (predation) and nutrient concentration (competition) are the mechanisms affecting (individually or synergistically) microalgae assemblages, originating different alternative states from the same pool of species. However, the effect of these mechanisms may vary, depending on algal properties such as size, growth rate and viability as an inoculum. The presence of herbivores and oligotrophic conditions reduce the primary producer biomass but increase diversity due to relaxation of competition and increase the uncertainty of final states. The variations in the community structure directly reflect on community function, affecting primary production and respiration.

Cytotoxic effects of free fatty acids on phytoplankton algae and cyanobacteria

Some free fatty acids are toxic to phytoplankton, and the toxic effects are multiple. However, precisely how they kill phytoplankton is debatable. Here we show that fatty acids result in damage to plasma membranes, which might account for their lethal effects on phytoplankton. In this study, we used two chlorophytes ( Chlorella vulgaris Beij. and Monoraphidium contortum (Thur.) Kom.-Legn.) and a cyanobacterium ( Anabaena P-9) as test organisms. When these organisms were treated with deleterious concentrations of fatty acids, a remarkable elevation of extracellular potassium (K +) was detected in the culture medium; this indicates that leakage of intracellular K + occurred as a result of damage to the plasma membranes. Exposure to unsaturated fatty acids resulted in higher levels of leaked K + than did exposure to saturated ones, and levels of leakage displayed a positive correlation with the susceptibility of the growth of organisms to fatty acids. Stressed phytoplankton cells also exhibited cell lysis followed by free release of phycobilins. The sequence of cytotoxic effects elucidated here suggests that fatty acids primarily affect the plasma membranes, leading to a change in membrane permeability and dissociation of phycobilins from the thylakoids. Severe damage to the plasma membranes would give rise to a disruption of the stressed cells.

Allelopathy of filamentous green algae

Allelopathy of filamentous green algae (FGA) has been less studied than that of macrophytes. Little Budworth Pool, Cheshire, UK is a small, shallow, clear-water lake with high TP concentrations, very high NO3-N concentrations, only moderate phytoplankton density, high FGA growth (mainly Spirogyra sp.) and no submerged plants. Experiments were carried out to test the possible allelopathic effects of Spirogyra on the phytoplankton of this lake and on a submerged plant Elodea nuttallii. Changes in phytoplankton growth, phytoplankton species dynamics and species composition were apparently not influenced by allelopathy of live or decaying Spirogyra. A shift from diatom (Cyclotella sp) – cryptomonad (Chroomonas acuta and Cryptomonas erosa) dominance to Chlorococcales (Micractinium pusillum, Monoraphidium contortum and Scenedesmus opoliensis) – Volvocales (Chlorogonium elongatum and Pandorina morum) dominance was recorded in both control and FGA treatments, suggesting an effect of nutrient enrichment. Nutrient concentrations and differences in competitiveness among phytoplankton species can also explain differences in their growth rates in Spirogyra filtrate. Spirogyra also did not influence apex number per plant, shoot length or growth rate of E. nuttallii. This FGA species probably cannot control phytoplankton or E. nuttallii growth in nutrient rich conditions through allelopathy.

Phytoplankton community responses to nutrient and iron enrichment under different nitrogen to phosphorus ratios in the northern Baltic Sea

The impact of nutrient enrichment on the phytoplankton community structure, and particularly cyanobacteria, was studied in a 3-week mesocosm experiment conducted in August 2001 in the Archipelago Sea, a part of the northern Baltic Sea. The factorial design experiment included daily additions of nitrogen (N) and phosphorus (P) at two mass ratios, 1N:1P and 7N:1P, respectively, additions of iron (Fe) and a synthetic chelator, ethylenediaminetetraacetic acid (EDTA). The floating enclosures (400 l) were sampled for analyses of phytoplankton biomass and community structure, phytoplankton primary production, chlorophyll a, nutrients, and hepatotoxins. Chlorophyll a concentration, phytoplankton biomass and primary production increased most in the 7N:1P treatment. The increase was mainly due to an abundant growth of chlorophytes ( Dictyosphaerium subsolitarium, Kirchneriella spp., Monoraphidium contortum, and Oocystis spp.), pennate diatoms (especially Nitzschia spp.), dinophytes and the chroococcalean cyanobacterium Synechococcus sp. The nutrient enrichments had no effect on the total biomass of N 2-fixing cyanobacteria. Nevertheless, the biomass of Anabaena spp. was highest in the enrichments with a low N/P ratio. Chlorophyll a concentration and total phytoplankton biomass were not affected by Fe or EDTA, but Fe alone had a positive effect on the chlorophyte Kirchneriella sp. The N 2-fixing cyanobacteria Aphanizomenon sp. responded positively to Fe alone and to both Fe and EDTA added together. The hepatotoxin concentration increased during the experiment, but no clear responses to nutrient enrichments were found. Our study showed species-specific responses to nutrient enrichments among the N 2-fixing cyanobacteria. Although the total phytoplankton production was not Fe-limited; the availability of Fe clearly affected the phytoplankton community structure.

Effect of temperature and light on growth of planktic green algae isolated from Lake Hovsgol, Mongolia

Four species of planktic green algae, Oocystella mongolica, Monoraphidium contortum, Pseudodidymocystis planctonica and Closterium parvulum were isolated from the ancient ultraoligotrophic Lake Hovsgol, Mongolia. While O. mongolica is considered to be an endemic species of the lake, the others are cosmopolitan species. Lake Hovsgol freezes between November and May, and the maximum water temperature in the pelagic area is ca. 14°C in summer. In order to clarify the growth characteristics on temperature and light of the strains, culture experiments were conducted. Although these algae live in cold habitats, the optimum temperatures for growth of the strains were 20-25 °C under high light conditions. All strains could grow at 5 °C, which was the lowest temperature examined, and showed their best growth rate at 10°C under the lowest light conditions (10 μmol photons m -2 . s -1 The results of culture experiments were discussed with regard to their natural habitats.

영산강의 식물플랑크톤 군집 동태

Dynamics of phytoplankton communities were investigated at five stations in Youngsan River from December 1995 to November 1996. Phytoplankton were identified to the total of 466 taxa, which were composed of 136 genera, 438 species, 27 varieties and 1 forma. The standing crops ranged 1,163-50,765 cells during the investigation periods. The variation of classes was in order to Chrysophyceae - Bascillariophyceae - Chlorophyceae at St. 1 and was only Bacillariophyceae at the other stations. The dominant species were 12 taxa including Aulacoseira ambigua, A. garnulata, Cyclotella meneghiniana, C. pseudostelligera, Chlorella vulgaris, Dinobryon sertularia, Flagilaria elliptica, Monoraphidium contortum, Micractinium pusillum, Nitzschia palea, Scenedesmus grahneisii and Stephanodiscus hantzschii f. tenuis. The standing crops of dominant species ranged from 10.6% to 94.7%. The genus Dinobryon in Chrysophyceae was dominant species at St. 1 in December 1995, but not recorded in the other months. The dominant species were composed with the planktonic diatoms from winter to spring and were the tychoplanktonic and the benthic species at St. 2-5 from summer to fall. The relationships between total standing crops and water temperature, pH, , , and showed low positive or negative coefficients. Stephanodiscus hantzschii f. tenuis had low positive or negative coefficients with water temperature, , , and . The fluctuations of standing crops in the Youngsan river phytoplankton community were not caused by a single factor but controlled by the complex factors with interaction between phytoplankton community and envirowmental factors.

Structure and variation of the Paraguay River phytoplankton in two periods of its hydrological cycle

The structure and distribution of the Paraguay River phytoplankton (between 16° 03′ and 26° 53′ S and between 57° 13′ and 58° 23′ W was studied during June–July/95 and December/95–January/96. Phytoplankton density values were lower in winter (mean value between 731 and 878 ind. ml−1) in summer (between 1113 and 1876 ind. ml−1), and mean biomass (biovolume) ranged between 0.215 and 0.372 mm3 l−1 and between 0.586 and 1.223 mm3 respectively. In all, 332 algal taxa were identified: 298 in the upper section (Pantanal) and 143 in the middle and lower sections. They pertained to the Cyanophyta, Chlorophyta, Euglenophyta, Cryptophyta, Pyrrhophyta, Bacillariophyceae, Chrysophyceae and Xanthophyceae. Small Chlorophyta (Chloromonas gracilis, Choricystis minor, Crucigenia quadrata, Scenedesmus ecornis, Monoraphidium contortum and M. minutum) and Cryptophyta (Cryptomonas marssonii, C. ovata and Rhodomonas minuta) dominated. Bacillariophyceae (genera Aulacoseira and Cyclotella) increased in the lower section of the river. Biomass was dominated by centric forms of the genus Aulacoseira (A. granulata and its morphotypes, and A. herzogii). The diversity index varied between 1.99 and 5.0 bits ind.−1 in winter and between 1.49 and 4.87 bits ind.−1 in summer. Species richness (between 4 and 105 taxa per sample) showed a decrease in north–south direction. The presence of one of the largest wetlands of the world may explain the high algal diversity in the upper section. The Bermejo River, with highly mineralized waters and a high content of suspended solids, causes a strong discontinuity in the lower section of the main course, viz, a decrease in water transparency and in the density, biomass, diversity and species richness values of phytoplankton, before its waters meet the Parana River.