Inhibition Of Algal Photosynthesis Research Articles

Unraveling the toxicity response and metabolic compensation mechanism of tannic acid-Cr(III) complex on alga Raphidocelis subcapitata

Due to their assembly properties and variable molecular weights, the potential biological toxicity effects of macromolecular organic ligand heavy metal complexes are more difficult to predict and their mechanisms are more complex. This study unraveled the toxicity response and metabolic compensation mechanism of tannic acid-Cr(III) (TA-Cr(III)) complex on alga Raphidocelis subcapitata using multi-omics approaches. Results showed TA-Cr(III) complex caused oxidative damage and photosystem disruption, destroying the cell morphology and inhibiting algal growth by >80 % at high exposure levels. TA-Cr(III) complex stress down-regulated proteins linked to proliferation, photosynthesis and antioxidation while upregulating carbon fixation, TCA cycle and amino acid metabolism. The increase of fumarate, citrate, isocitrate and semialdehyde succinate was validated by metabolomics analysis, which improved the TCA cycle, amino acid metabolism and carbon fixation. Activation of the above cellular processes somewhat compensated for the inhibition of algal photosynthesis by TA-Cr(III) complex exposure. In conclusion, physiological toxicity coupled with downstream metabolic compensation in response to Cr(III) complex of macromolecular was characterized in Raphidocelis subcapitata, unveiling the adaptive mechanism of algae under the stress of heavy metal complexes with macromolecular organic ligands.

Evaluation of a full-scale wastewater treatment plant with ozonation and different post-treatments using a broad range of in vitro and in vivo bioassays

Micropollutants present in the effluent of wastewater treatment plants (WWTPs) after biological treatment are largely eliminated by effective advanced technologies such as ozonation. Discharge of contaminants into freshwater ecosystems can thus be minimized, while simultaneously protecting drinking water resources. However, ozonation can lead to reactive and potentially toxic transformation products. To remove these, the Swiss Federal Office for the Environment recommends additional "post-treatment" of ozonated WWTP effluent using sand filtration, but other treatments may be similarly effective. In this study, 48 h composite wastewater samples were collected before and after full-scale ozonation, and after post-treatments (full-scale sand filtration, pilot-scale fresh and pre-loaded granular activated carbon, and fixed and moving beds). Ecotoxicological tests were performed to quantify the changes in water quality following different treatment steps. These included standard in vitro bioassays for the detection of endocrine, genotoxic and mutagenic effects, as well as toxicity to green algae and bacteria, and flow-through in vivo bioassays using oligochaetes and early life stages of rainbow trout.Results show that ozonation reduced a number of ecotoxicological effects of biologically treated wastewater by 66 - 93%: It improved growth and photosynthesis of green algae, decreased toxicity to luminescent bacteria, reduced concentrations of hormonally active contaminants and significantly changed expression of biomarker genes in rainbow trout liver. Bioassay results showed that ozonation did not produce problematic levels of reaction products overall. Small increases in toxicity observed in a few samples were reduced or eliminated by post-treatments. However, only relatively fresh granular activated carbon (analyzed at 13,000 - 20,000 bed volumes) significantly reduced effects additionally (by up to 66%) compared to ozonation alone. Inhibition of algal photosynthesis, rainbow trout liver histopathology and biomarker gene expression proved to be sufficiently sensitive endpoints to detect the change in water quality achieved by post-treatment.

Conditions for Stably Detecting Comprehensive Toxicity of Water by Algal Photosynthesis Inhibition Method

Conditions for Stably Detecting Comprehensive Toxicity of Water by Algal Photosynthesis Inhibition Method

Evaluation of algal photosynthesis inhibition activity for dissolved organic matter with the consideration of inorganic and coloring constituents

The effect of waterborne ingredient on ecosystem has been of great interest. In the present study, the evaluation method using algal photosynthesis inhibition assay with dual-channel pulse amplitude modulation (PAM) system was established for a series of water samples to elucidate the potential effect of the total body of organic compounds including natural organic matter (NOM) on aquatic ecosystems. The more sensitive and less time-consuming monitoring method compared with algal growth inhibition assay was suggested, especially considering inorganic and coloring constituents. Algal photosynthesis inhibition activity was detected with high sensitivity for photosystem II (PSII) inhibitors, whereas the IC10 of the other chemicals was over the environmental standard concentration for Chlamydomonas moewusii (Chlorophyceae) and Pheodactylum tricornutum (Diatomea). The photosynthesis inhibition activity of Lake Biwa dissolved organic matter (LBDOM) and fulvic acid (LBFA) was significantly detected at ≥10 times the concentration and >10 mgC L-1, respectively, whereas prominent activity was confirmed for Suwannee River NOM (SRNOM) on the river original concentration (>30 mgC L-1) for both algae. Significant inhibition activity was detected in both algae at least in twice-concentration for water samples from a wastewater treatment pilot plant. There was no great difference in the activity between sewage secondary effluent and its filtrate with ultrafiltration (UF), and physically washing water for the UF membrane.

Assessment of Cyfluthrin commercial formulation on growth, photosynthesis and catalase activity of green algae

Aquatic environments of the pampasic region of Argentina are severely affected by agricultural contamination due to an increase in a glyphosate tolerant transgenic variety of soybean crops. The present study is aimed to determine the effects of a commonly used Cyfluthrin commercial formulation (CCF) on growth, some physiological and biochemical parameter of four species of green algae. Significant inhibition of algal growth was observed from 0.1mg Cyf/l. 96h IC50 were between 0.92 and 4.85mg Cyf/l. CCF caused algicidal effects. Photosynthesis was stimulated by 50% in Scenedesmus quadricauda cultures exposed to the lowest concentration (hormesis). Algal photosynthesis inhibition was observed at higher concentrations with IC50 values between 1.7 and 8.9mg Cyf/l. Similar toxicity endpoints were found as a consequence of applying the traditional methodology of short-term chronic toxicity test of 96h of exposition and the methodology developed using the Clark type photosynthetic oxygen evolution method. CAT activity was significantly increased between 23% and 33% considering the four species, at a lower concentration than those affecting algal growth and photosynthesis, indicating a potential biomarker. Taking into account that the extent of the soybean crops in the region is about fourteen million hectares, the improvement and extension of environmental tools for early detection of the action of pesticides on this essential group of organisms are discussed.

Evaluation of the efficacy of the photosystem II inhibitor DCMU in periphyton and its effects on nontarget microorganisms and extracellular enzymatic reactions

AbstractWe examined the efficacy of the photosystem II inhibitor 3-(3,4-diclorophenyl)-1,1-dimethyl urea (DCMU) for inhibition of algal photosynthesis in periphyton associated with submerged decomposing litter of Typha angustifolia. We also investigated the possible nontarget effects of DCMU exposure on heterotrophic microorganisms (i.e., bacteria and fungi) and extracellular enzyme activity associated with decaying litter. Standing-dead Typha leaf litter was submerged for 34 and 73 d, returned to the laboratory, and used for controlled laboratory experiments that examined the effect of DCMU on algal ([14C]bicarbonate, pulse-amplitude modulated fluorometry), bacterial ([3H]leucine), and fungal ([14C]acetate) production. Simultaneous assays also were conducted to examine the effect of DCMU on the activities of 4 extracellular enzymes (β-glucosidase, β-xylosidase, leucine-aminopeptidase, and phosphatase). DCMU significantly inhibited algal photosynthesis in light-exposed periphyton (p always < 0.0003), with...

Effect of Pseudokirchneriella subcapitata (Chlorophyceae) exudates on metal toxicity and colloid aggregation

The effects of Pseudokirchneriella subcapitata exudates on the acute toxicity of metals (Cd, Cu, Pb and Zn) were studied using (1 h) algal photosynthesis inhibition tests. The metal concentrations tested were 30, 60, 120, 250 and 500 μg L −1 for Cd and Zn; and 500, 1000, 2000, 3000, 4000 μg L −1 for Cu and Pb. It was established that P. subcapitata exudates markedly decreased metal toxicity. This effect was ascribed to: (i) the presence of organic ligands that bind metals and reduce the concentration of free ionic metal, and/or (ii) interaction of exudates with the cell surface with a subsequent decrease in metal uptake. The effects of the exudates on colloid aggregation were also examined using two different types of single particle counters (SPC). Exudates facilitated the colloid removal, likely via acceleration of aggregation (bridging). The results clearly demonstrate that algal exudates play an important role in the biogeochemical cycling of metals in natural surface water: (1) by reducing free metal concentrations and toxicity to living organisms and (2) by favoring colloid aggregation leading to the removal of colloid-bound metals (colloidal pumping). Such results highlight one potential application of the algae in the remediation of metal-contaminated waters. The results also suggest that current algal toxicity testing protocols, in particular long-term and static tests, may underestimate metal toxicity because of the presence of algal exudates.

Influence of humic substances on the toxic effects of cadmium and zinc to the green alga Pseudokirchneriella subcapitata

A method combining (1 h) algal photosynthesis inhibition tests and tangential-flow ultrafiltration (TFF) technique (cut-off 1 kDa) was used to determine the effect of humic substances (HS) on acute metal toxicity to Pseudokirchneriella subcapitata. Three “standard” HS (soil and peat humic acids and Suwannee River fulvic acids) at two concentrations (1 and 5 mg/l) and two metals (Zn at 390 μg/l and Cd at 200 μg/l) were studied. Toxicity of Cd and Zn to P. subcapitata was significantly ( p<0.05) reduced in the presence of humic acids (HA) but not in the presence of Suwannee River fulvic acids (SRFA). Metal partitioning between colloidal (1 μm–1 kDa) and truly dissolved (<1 kDa) fractions was found to match a decrease of metal toxicity in the presence of HA, but not in the presence of SRFA. The results suggested that HA reduced Cd and Zn toxicity in two different ways: (1) HA decrease the amount of free metal ions. Metal–HA complexes are high molecular weight, relatively stable with regard to metal-exchange reactions and consequently the metals were less bioavailable. (2) HA adsorbed onto algal surfaces, shielded the cells from free Cd and Zn ions. Several possible explanations can be postulated to account for the observed SRFA results: (1) Cd- and Zn-SRFA complexes are thought to be labile (i.e. undergo rapid dissociation); (2) SRFA coagulated, presumably during equilibration, and that coagulation altered metal complexing behavior of SRFA; (3) FA has a lower ability to adsorb on cell membranes at pH>7.

Inhibition of algal photosynthesis by a symbiotic coral

When symbiotic dinoflagellate algae (Symbiodinium sp.), isolated from the scleractinian coral Plesiastrea versipora were incubated in homogenized host tissue, carbon fixation was usually lower than in seawater only (43 cases of of 54), and this inhibition occurred throughout the year. Algae incubated in homogenized host tissue fixed a mean of 78.84% ± 22.6% of the amount fixed by algae in seawater (n = 54, range 33–142%). The difference between rates of fixation in seawater (mean ± SD of 61.300 ± 22.71 nmol C/105 cells) and in homogenates (mean ± SD of 47.377 ± 21.42 nmol C/105 cells) in individual experiments, was highly significant (p<0.0001, paired t-test). Homogenized host tissue from populations of P. versipora separated by 4000 km inhibited photosynthesis in algae from both their own and the distant coral population. Inhibition of photosynthesis was not observed when isolated algae from the anemone, Aiptasia pulchella were incubated in homogenate from P. versipora. An inhibitor of photosynthesis was isolated from a low molecular weight fraction of homogenized host tissue of P.versipora by cation-exchange chromatography and further purified by HPLC. This is the first natural inhibitor of photosynthesis that has been found in an invertebrate with symbiotic algae.

The Chlamydomonas test: A new phytotoxicity test based on the inhibition of algal photosynthesis enables the assessment of hazardous leachates from waste disposals in salt mines

Based on the inhibition of photosynthesis of the green-alga Chlamydomonas a new phytotoxicity test was elaborated. Feasibility was verified by comparative studies with standard phytotoxicity tests with Lemna (growth) and Lepidium (root elongation), using both solutions with distinct heavy metals and complex mixtures of heavy metals. A major advantage of the Chlamydomonas test is its salt tolerance. When toxic brines, e.g. leachates from heavy metal wastes deposited in salt mines, shall be analyzed the standard tests failed because of the salt sensitivity of Lemna and Lepidium. In contrast, the Chlamydomonas test revealed valid information on the phytotoxicity of such leachates.

Recirculation in a small sewage pond system

Recirculation in a small scale waste stabilization pond system operated over a period of 12 months. Effluent from the third pond in a series of four ponds was added to the primary pond at a ratio of 1:1 (recirculated effluent:settled sewage effluent). Recirculation was stopped during winter for 35 days and during summer for 21 days to ascertain the seasonal benefits of recirculation. Dissolved oxygen concentration in pond 1 increased by up to 234% during recirculation in summer, reducing the potential of algal photosynthesis inhibition by high concentrations of ammonia-nitrogen. Algal cell numbers did not increase significantly in pond 1 during recirculation. Recirculation was unable to reduce Total Suspended Solids (TSS) and Chemical Oxygen Demand (COD) concentrations of the final effluent to meet the Government effluent standards of 25 and 75 mg 1 −1, respectively. An increased recirculated effluent:settled sewage ratio is recommended.

Factors Determining Algal Populations in Waste Stabilization Ponds and the Influence of Algae on Pond Performance

In situ and laboratory experiments were performed on species of the waste stabilization pond algae Chlorella, Scenedesmus, Euglena and Chlamydomonas to investigate the utilization of various organic acids and sugars, light limitation on species dominance and the toxicity of ammonia and sulphide. Euglena showed the most flexible metabolism and was able to utilise butyrate. Scenedesmus did not grow on any of the substrates in the dark. Pond populations of Euglena and Chlamydomonas were able to incorporate acetate in situ in competition with the heterotrophic bacterial population but Chlamydomonas was the more successful. Light availability affected speciation in facultative ponds where rapid motility by flagellates was a clear advantage. All the algal species were sensitive to sulphide at µM concentrations in a tolerance sequence ChlamydomonasChlorellaScenedesmusEuglena. Ammonia was less toxic than sulphide and the tolerance sequence was ChlorellaScenedesmusChlamydomonasEuglena. It was the undissociated forms of both sulphide and ammonia which were toxic, Toxicity was influenced by pH and this would be a critical factor controlling ammonia inhibition of algal photosynthesis in ponds. The effects of these findings are related to species dominance and pond performance.

The Effect of pH on the Performance of High-Rate Oxidation Ponds

A common observation in high-rate oxidation ponds (HROP) is that pH riseswill usually be followed by decreases in algal production and in overall pond performance. It was found that pH has minor direct effects on algal production but has major indirect effects as it determines the ratios of the carbonate system species and the dissociation of ammonia in the pond. Thus, increased pH values may cause carbon limitation of algal production or free ammonia inhibition of algal photosynthesis in HROP.

Inhibition of algal photosynthesis to control pH and reduce ammonia volatilization from rice floodwater

When urea or ammoniacal-N fertilizers are applied to the floodwater of a rice crop, fertilizer use efficiency is often reduced because there are substantial losses of NH3 by volatilization. As pH rises the potential loss increases exponentially due to the increasing dominance of volatile NH3 gas in equilibrium with NH 4 + . We postulate that the daytime pH rise is caused mainly by photosynthesis of algae and Cyanobacteria, and that addition of a suitable photosynthetic inhibitor, concurrently with fertilizer, should suppress the pH rise, thus conserving N in the form of the non-volatile NH 4 + . We selected terbutryne (2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine) as the most promising inhibitor. In rice floodwater fertilized with urea the addition of terbutryne dampened the diurnal fluctuation in pH for 6 days and significantly increased the ammoniacal-N (AN) concentration measured in the floodwater. The concentration of ammonia gas in the air in equilibrium with the water,ϱ 0, which is proportional to the gaseous flux of NH3 at a given wind speed, was substantially reduced by terbutryne addition. Maximum values were reduced by over 50%. Terbutryne reduced the calculated cumulative NH3 emission by 43%, relative to the fertilizer (N + P) control. Terbutryne also suppressed photosynthetic oxygen production. Therefore, it may reduce N fertilizer losses by inhibiting nitrification, an aerobic process, so retarding subsequent denitrification losses of gaseous nitrogen and nitrogen oxides.

Establishment of the symbiosis inConvoluta roscoffensis

Of a wide range of algae tested, juvenileConvoluta roscoffensisingested onlyPlatymonas convolutae, the natural symbiont; related species of the generaPlatymonas, PrasinocladusandTetraselmis; andChlamydomonas coccoides. Platymonas convolutaewas not ingested to a greater extent thanPrasinocladus marinus, Tetraselmis tetratheleandTetraselmis verrucosa, or taken up in preference toT. verrucosawhen animals were exposed to a choice between the two species. Convoluta ingested fewer cells ofC. coccoidesthanP. convolutaeand related species. Uptake ofP. convolutaewas not affected by pretreatment of the cells with lectins or proteases, incubation in media of pH 5·0–9·0 or inhibition of algal photosynthesis, but was substantially reduced if the algae were killed.Cells ofP. convolutae, Pr. marinus, T. tetratheleandT. verrucosapersisted and divided in juvenile Convoluta. The algal population in the worms started to increase 2–3 d after ingestion and within 15–20 d the animals were uniformly green. These algae formed a viable symbiosis with Convoluta and promoted the growth of the animals. In contrast,C. coccoidescells did not persist in Convoluta for more than 12–24 h a nd were probably disrupted.P. convolutaecells lost their thecae within a few days of ingestion and before migration from the central to sub-epidermal region of the animal. Animal vacuoles surrounded recently ingested thecate algae. Structural studies of the adult symbiosis suggest that the algae were also intracellular and enclosed in vacuoles.It is proposed that Convoluta discriminates against algae unrelated toP. convolutaeon initial contact and in the central region of the host. The nature of the recognition mechanism(s) has not been established.

Free Ammonia Inhibition of Algal Photosynthesis in Intensive Cultures

The effect of free NH(3) inhibition on short-term photosynthesis was investigated in three microalgal species: the freshwater chlorophyte Scenedesmus obliquus, the marine diatom Phaeodactylum tricornutum and the marine chlorophyte Dunaliella tertiolecta. By performing a series of assays at various concentrations of added NH(4)Cl and culture pH, we demonstrated that the inhibitory compound was free NH(3) and that pH played no role in determining the magnitude of inhibition, other than in establishing the degree of dissociation of nontoxic NH(4) to toxic NH(3). When corrections were made for pH, all three species displayed the same sigmoidal response curve to free NH(3) concentration; 1.2 mM NH(3) led to 50% reduction in photoassimilation of C. Based on literature values, some marine phytoplankton appear to be significantly more sensitive to free NH(3) than were the test species, which are noted for their excellent growth characteristics. However, the combination of low algal biomass and strong pH buffering commonly found in most marine and many freshwater environments probably limits the possibilities for NH(3) toxicity to low alkalinity freshwaters and intensive algal cultures in which NH(4) is the main source of N. Such conditions occur commonly in algal wastewater treatment systems.

The Effects of Oil Spills on Phytoplankton in an Arctic Lake and Ponds

The effect of oil spilled on Alaskan freshwater phytoplankton populations was studied in waters affected by natural oil seeps, by controlled crude oil spills in tundra thaw ponds and in a morainal lake, by subpond manipulations and bioassay experiments. The studies were carried out over a period of seven years. Regardless of dose the effects of oil were predictable in the small ponds. The zooplankton populations were virtually eliminated, and after an initial depression of primary productivity the photosynthetic rates returned to approximately prespill levels with a small increase in algal biomass. A markedly altered algal composition was an invariable effect of the response, with the elimination of a dominant flagellated form, Rhodomonas spp., in the case of the ponds. From the results of subpond manipulation experiments, evidence supports the hypothesis that elimination of grazers is the principal cause of altered species composition and increased biomass in these ponds. In our lake system there was a severe reduction in primary production during the season of the experimental spill. During the second year only the spring boom was suppressed by the added oil. Bioassay experiments supported the hypothesis that in such lakes, direct inhibition of algal photosynthesis may be important, although zooplankton were greatly reduced.

EXTRACELLULAR LYSIS OF THE BLUEGREEN ALGA PHORMIDIUM LURIDUM BY BDELLOVIBRIO BACTERIOVORUS1

SUMMARYWhen either cells of the bacterium, Bdellovibrio bacteriovorus (Stolp &amp; Starr), strain 15143, or a heat‐resistant lytic factor derived from these cells is added to viable cultures of Phormidium luridum var. olivacea Boresch all the algal cells underwent gradual lysis. This effect was obtained with a mean initial bdellovibrio:algal cell ratio of 7.5:1. When P. luridum was mixed with the bdellovibrio cultures the algal chlorophyll content showed an 8‐fold decrease. Concomitantly, this interspecies interaction caused, a 75% inhibition of algal photosynthesis after‐4 h. Heat, treatment of the B. bacteriovorus culture supernatant fluid increased its ability to inhibit photosynthesis approximately 14%. Light, microscopy showed pale granules and intracellular spaces to form in the P. luridum within 16 h after adding the bdellovibrio lytic factor. Subsequent morphological changes included the development of large intracellular spaces, intercellular spaces, spheroplast formation and finally Complete lysis of the algal cells.

Complexing capacity of the nutrient medium and its relation to inhibition of algal photosynthesis by copper

The toxic effect of copper on phytoplankton production is investigated in waters having different complexing capacities. It is demonstrated that a water’s complexing capacity does not guarantee that an equivalent amount of copper could be tolerated without adversely affecting algal production. Possible explanations for these findings are offered and discussed. It is deduced that ionic copper probably is already toxic to planktonic algae at concentrations of about 10−10 mole/l.