The Combined Effect of Shungite and Heavy Metals on the Growth of Microalgae Роpulation

The combined effect of 3 mg/L potassium dichromate, 1.5 mg/L cadmium sulfate, and 100 g/L shungite on the growth of chlorococcales green microalgae culture Scenedesmus quadricauda (Turp.) Bréb. is studied. The toxic effect of potassium dichromate and cadmium sulfate on S. quadricauda is estimated by calculating the share of living and dead cells and physiological parameters. The toxic effect of heavy metals does not manifest itself under the combined action of potassium dichromate or cadmium sulfate and shungite on S. quadricauda. The best growth of the algae culture occurred only when only shungite was added to the culture medium. Shungite can be used to neutralize the toxic effect of heavy metals.     

Experimental studies of the effect of beaver (<Emphasis Type="Italic">Castor fiber</Emphasis> L.) vital activity products on the formation of zooplankton structure (by the example of growth of two cladoceran species of different sizes)

Experiments in microcosms have demonstrated that beaver vital activity products (BVAPs) promote an increase in concentrations of total nitrogen (N) and total phosphorus (P), a decrease in the N/P value in water, and an increase in the abundance and biomass of bacterioplankton. Under such conditions, the abundance and biomass of small Ceriodaphnia dubia Richard and large Daphnia (Ctenodaphnia) magna Straus, which live separately, increase. The coexistence of these cladocerans in microcosms under the BVAP influences results in a high increase in the abundance and biomass of D. magna; in similar experiments without the influence of BVAP, Ceriodaphnia dubia becomes more abundant. The results of bioassay demonstrate that the number of newborns of Ceriodaphnia dubia decreases in water where Daphnia magna is numerous owing to BVAPs. It is suggested that the vital activity products of large representatives of the genus Daphnia inhibit the fecundity of small species of Cladocera. This fact, along with the high competitiveness of large cladoceran species under conditions of a high level of nutritive base, determine the formation of zooplankton communities in beaver ponds which are characterized by a high abundance and biomass and low uniformity     

Effect of the vital activity products of beaver (<Emphasis Type="Italic">Castor fiber</Emphasis> L.) on the formation of zooplankton structure: Changes in the quantitative parameters of two cladocera species of different sizes in a beaver pound (in situ experiment)

The experiments were performed in microcosms situated on a control site and on a site regulated by beavers. Two cladoceran species of different sizes were placed in microcosms in different proportions. It was found that the vital activity products of Castor fiber L. promote an increase in the concentration of total phosphorus (P), a decrease in the N/P ratio in water, and an increase in the chlorophyll a concentration and the abundance and biomass of bacterioplankton. In such conditions, the abundance and biomass of the large species Daphnia (Ctenodaphnia) magna Straus was increased to the greatest extent when compared with background values when it was placed in combination with Ceriodaphnia dubia Richard or without it. Moreover, in the case of the combination of two crustacean species in microcosms, the abundance of C. dubia was lower when compared with the control site, while the abundance of D. magna was higher. The results of a bioassay showed that the productivity of C. dubia decreases in waters where D. magna is most abundant. We concluded that the formation of zooplankton in beaver ponds with specific features determined by the presence of large cladoceran species is provided by changes in the quantitative and qualitative parameters of food resources. This contributes to the massive distribution of large D. magna and its competitive relations with small C. dubia. According to the results of a bioassay, the vital activity products of D. magna can inhibit the fecundity of C. dubia.     

Experimental study of indirect effects of fish on the demographic parameters of cladoceran species under eutrophic conditions

Indirect effects of fish on the demographic parameters of cladoceran species were studied under eutrophic conditions. Laboratory experiments were performed with water from control and fish mesocosms to avoid the direct impact of fish predation. In the experiments with the water from the fish mesocosms, fish indirectly negatively affected the demographic parameters of large cladocerans (Daphnia magna and D. pulicaria) due to the enhanced abundance of blue-green algae in the phytoplankton. However, small Ceriodaphnia quadrangula and littoral species Simocephalus vetulus did not respond to the presence of blue-greens. Due to this mechanism, the total abundance of cladoceran species can be sustained during the development of blue-green algae because large and small bodied species differ in their resistence to high concentratons of blue-green algae. Fish chemical signals (kairomones) did not influence the demographic parameters of any cladoceran species.     

Freshwater anostracan, <Emphasis Type="Italic">Branchinella kugenumaensis</Emphasis>, as a potential controlling consumer species on toxic cyanobacteria <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis>

To evaluate the potential of Branchinella kugenumaensis for cyanobacterial bloom control relative to Daphnia, we conducted several feeding experiments on microcystin-free and microcystin-containing unicellular strains of Microcystis aeruginosa and colonial forms of Microcystis using B. kugenumaensis and Daphnia magna in a laboratory. Branchinella kugenumaensis showed higher filtration rates than those of D. magna in all treatments. In particular, the microcystin-containing unicellular strain supported the highest filtration rates of B. kugenumaensis among treatments. Daphnia magna reduced colonies less than 75 μm in length, whereas B. kugenumaensis could graze colonies less than 100 μm. The middle-sized group of B. kugenumaensis had a higher filtration rate than the small and large sized groups in a continuous feeding experiment for 4 days. In survival experiments, survivorships were not different between the two species, whereas ages at the beginning of the experiments affected their survival time. Our results showed that B. kugenumaensis grazed on toxic and colonial cyanobacteria at relatively high rates, indicating that locally abundant grazers like Branchinella may offer a better potential for bloom control than Daphnia.     

Association Between Chronic Exposure to Tobacco Smoke and Accumulation of Toxic Metals in Hair Among Pregnant Women

Tobacco smoke contains various toxic heavy metals that individuals are exposed to when they smoke. Despite the presence of heavy metals in tobacco smoke, the relationship between smoking and the accumulation of toxic metals in pregnant women after long-term exposure remains under discussion. We examined the association between long-term exposure to tobacco smoke and the accumulation of toxic metals in the hair of female participants. Our study recruited 252 women from the Shanxi and Hebei provinces of Northern China; these participants were self-reported non-active smokers, and had previously delivered healthy babies without birth defects. Scalp hair was collected and analyzed for nicotine and cotinine and five potentially toxic metals (specifically, silver, chromium, cadmium, mercury, and lead). Our results showed significant positive correlations between cotinine and four metals, including silver (r?=?0.369, p?<?0.001), cadmium (r?=?0.185, p?<?0.01), mercury (r?=?0.161, p?<?0.05), and lead (r?=?0.243, p?<?0.001). Significant positive correlations were also found between nicotine and three metals—specifically silver (r?=?0.331, p?<?0.001), cadmium (r?=?0.176, p?<?0.01), and lead (r?=?0.316, p?<?0.001). A logistic regression model showed significant associations between cotinine and potentially toxic metals including mercury, silver, and lead (with or without adjusting for potential confounders). We thus conclude that long-term passive smoking could potentially increase the exposure level of toxic metals including lead, silver, and mercury in our study, which are especially harmful for pregnant women and their unborn fetus.     

Comparative assessment of toxic effects of surfactants using biotesting methods

This study assesses the comparative sensitivity and possibility of obtaining fast results of various methods of biotesting for several surfactants: Tween 85, sodium dodecyl sulfate (SDS), Fairy dishwashing gel, and Mif washing powder. The following test organisms are used for the study: luminescent bacteria Photobacterium phosphoreum (Beijerinck), preparation of Ecolum luminescent bacteria, unicellular algae Scenedesmus quadricauda (G.M. Smith), infusorian Paramecium caudatum (Ehrenberg), and crustacean Daphnia magna (Straus). It has been revealed that Fairy dishwashing gel possesses the strongest toxicity against the studied test objects. Daphnia and algae are most sensitive to the effects of Fairy and SDS, protozoan and luminescent bacteria are most sensitive to SDS, and Ecolum is most sensitive to Mif washing powder. The tested aquatic organisms and Ecolum are most tolerant to the effect of Tween 85.     

To eat or not to eat infected food: a bug’s dilemma

Parasites can adversely affect host population densities, but predators can regulate disease by reducing the density of susceptible hosts and consuming parasites contained in infected hosts. Some parasites induce phenotypic modifications in their hosts that potentially lead to increased predation. We investigated the role of parasite-induced modified appearance in the interactions between the crustacean Daphnia magna, its bacterial parasite Pasteuria ramosa, and its predator, the backswimmer Anisops sp. Our aim was to test the backswimmer’s prey preference between infected and uninfected D. magna to find out whether infection by P. ramosa can affect predation risk by Anisops. We found that Anisops sp. had a strong preference for uninfected D. magna under light, but under dark conditions the preference was reversed, which suggests that the modified appearance is the cause of this preference. Such anti-parasite preference by Anisops sp. could strongly influence host population dynamics as loss of fecundity, disease mortality, and predation are additive, resulting in host population decline.     

Cadmium and Nickel Toxicity for <Emphasis Type="Italic">Sinapis alba</Emphasis> Plants Inoculated with Endophytic Strains of <Emphasis Type="Italic">Bacillus subtilis</Emphasis>

We studied the effect of cadmium and nickel on Sinapis alba L. plants inoculated with endophytic strains of Bacillus subtilis. It was shown that treatment of S. alba seeds with endophytic strains of bacteria B. subtilis improves plant resistance to the toxic effect of cadmium and nickel and reduces manifestation of oxidative stress in the presence of higher levels of metal ions in the above-ground part of plants. Anti-stress effect and the ability of endophytic strains of B. subtilis to intensify uptake of cadmium and nickel ions by S. alba plants may be used for phytoextraction of heavy metals and stimulation of plant growth in contaminated areas.     

Effects of cadmium and lead stress on somatic embryogenesis of coniferous species. Part II: Changes of thiol substances

Conifers are often used as biomarkers of industrial pollution; however, little is known about the effects of heavy metals on them because only a few species have been tested. The aim of this work was to investigate the effects of cadmium (Cd²⁺) and lead (Pb²⁺) at three different concentrations (50, 250, and 500 µM) on the detoxification potential of Abies alba and Picea abies embryogenic cell masses throughout the 21-day proliferation period. Embryogenic cell masses of A. alba and P. abies responded to treatment with cadmium and lead by inducing phytochelatins and their biosynthetic intermediates. With increasing heavy metal concentrations, glutathione was used for the synthesis of phytochelatins enabling the tissues to bind to heavy metal ions and thereby avoiding the production of reactive oxygen species. Lead in A. alba and cadmium in both species caused similar increases of all antioxidative thiol compounds; thus, similar mechanisms involving a heavy metal-induced stress response can be assumed. In P. abies, the lowest lead concentration tested provoked the highest antioxidative response. Since a very low uptake of lead into the tissue was observed, the higher resistance of P. abies can be attributed to its ability to reduce lead uptake after longer exposure times. The results of cadmium treatment of both species and lead treatment of A. alba indicated the possibility of testing these coniferous species as potential phytoremediators. This is the first study to analyze the effects of heavy metals on the low-molecular-weight plant thiol content in A. alba embryogenic cell masses.     

Consortium of Higher Aquatic Plants and Microalgae Designed to Purify Sewage of Heavy Metal Ions

We selected higher aquatic plants (HAP) and microalgae possessing a high sorption capacity in respect to heavy metals to form a consortium designed to purify contaminated aquatic ecosystems. Accumulation of heavy metals Cd²⁺, Cu²⁺, Pb²⁺, and Zn²⁺ was investigated in plants Pistia stratiotes, Elodea canadensis, and Lemna minor and green microalgae Chlorella vulgaris ВВ-2, Ankistrodesmus sp. ВI-1, Chlamydomonas reinhardtii В-4, and Scеnеdеsmus quadricauda В-1. It was found that intense accumulation of metals occurs in cultures of HAP Pistia stratiotes and Elodea canadensis. These plants are macroconcentrators of zinc, lead, and copper and microconcentrators of cadmium. Out of the examined cultures of microalgae, effective bioaccumulators of heavy metals were C. vulgaris ВВ-2 and Ankistrodesmus sp. ВI-1. It was shown that heavy metals are selectively taken up from the medium in the series Zn²⁺ > Cu²⁺ > Cd²⁺ > Pb²⁺. In order to produce a consortium of higher aquatic plants and microalgae for purification of polluted aquatic ecosystems, we investigated interaction of HAP P. stratiotes and E. canadensis with microalgae C. vulgaris ВВ-2 and Ankistrodesmus sp. ВI-1 in the course of their cocultivation. Neutral relations were detected between the cells of microalgae C. vulgaris ВВ-2 and Ankistrodesmus sp. ВI-1 and HAP E. canadensis. At the same time, the cells of Ankistrodesmus sp. ВI-1 and HAP P. stratiotes formed a symbiosis. Microscopic examination showed numerous points where the cells of microalgae Ankistrodesmus sp. ВI-1 were attached to the roots of P. stratiotes plants. We tested an opportunity to employ the association between P. stratiotes and Ankistrodesmus sp. ВI-1 for purification of simulated wastewater polluted with heavy metal ions. This consortium proved to be capable of eliminating contaminants from the sewage, reducing their level in the sewage to standard values, and active accumulation of heavy metal ions.     

Acute toxicity of copper to <Emphasis Type="Italic">Daphnia galeata</Emphasis> under different magnesium and calcium conditions

A number of risk assessments of the adverse effects of Cu and its compounds have been conducted since it is one of the leading substances responsible for water contamination. However, with the exception of standard organisms, ecotoxicological knowledge is still scarce. Here, we examined the influence of Ca²⁺ and Mg²⁺ concentrations on acute toxicity of Cu toward a cladoceran, Daphnia galeata Sars. We found that the protective effects of Ca²⁺ against copper toxicity were larger than those of Mg²⁺. BLM parameters (log Ks) for Ca and Mg estimated based on our 48-h LC₅₀ (50 % lethal concentration), respectively, were 3.14 and 2.29. The log K of Ca was similar to that reported in previous studies using Daphnia magna; however, the log K of Mg was lower by one order of magnitude. Our results suggest that there is some mechanistic difference related to the Mg uptake between D. magna and D. galeata. The results obtained from the present study will contribute to the water quality criteria of copper in soft water because D. galeata is a widespread (distributed in Eurasia and North America) and common species, even in soft water lakes.     

Biotic factors in induced defence revisited: cell aggregate formation in the toxic cyanobacterium <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> PCC 7806 is triggered by spent <Emphasis Type="Italic">Daphnia</Emphasis> medium and disrupted cells

Bioassays with the toxic cyanobacterium Microcystis aeruginosa PCC 7806, its non-toxic mutant ΔmcyB, and Daphnia magna as grazer were used to evaluate biotic factors in induced defence, in particular cyanobacterial and grazer-released info-chemicals. Three main questions were addressed in this study: Does Daphnia grazing lead to a loss of cyanobaterial biomass? Is the survival time of Daphnia shorter in a culture of the toxic cyanobacterium? Does direct grazing or the presence of spent Daphnia medium or a high number of disrupted toxic Microcystis cells in the assays lead to an increase in the cellular microcystin content in the remaining intact cells? The biovolume (growth) as well as size and abundance of Microcystis aggregates were determined by particle analysis, while the survival time of Daphnia individuals was recorded by daily observation and counting, with the relative concentration of cell-bound microcystin-LR, was measured by HPLC analysis. Compared to some recent studies in the field of induced defence, in this study, evidence was found for a direct grazing effect, i.e. the loss of biovolume in the toxic culture. In addition, Daphnia magna ingested more non-toxic than toxic cells, and survived longer with non-toxic cells. In terms of increased cell-bound toxin concentration as a means of defence reported in some studies, a higher cell-bound microcystin-LR content was not measured in this study in any of the treatments (P > 0.05). Under low light conditions with impaired growth of Microcystis, and the presence of a high number of particles with less than 1-μm diameter (possibly heterotrophic bacteria), Daphnia medium was associated with a strong reduction in cell-bound toxin concentration (P < 0.05). This study showed no increased cell aggregation under direct grazing (P > 0.05), but increased aggregation with spent Daphnia medium under high light conditions (P < 0.05). Further, the addition of cell-free extract from disrupted toxic Microcystis cells strongly increased the aggregation of the intact cells under low light (P < 0.05). These findings are discussed with the possible role of microcystin and other infochemicals in the expression of proteins and morphology changes in Microcystis.     

Contents of Heavy Metals in Chinese Edible Herbs: Evidence from a Case Study of Epimedii Folium

Toxic heavy metal contamination in Chinese edible herbs has raised a worldwide concern. In this study, heavy metals in Epimedii Folium, an edible medicinal plant in China, were quantitatively analyzed. Variations of heavy metals in different species, in various organs (i.e., leaves, stems, and roots), in wild-growing and cultivated plants, and in 35 market samples of Epimedii Folium, were systematically investigated. In all of Epimedium samples, Hg (mercury) was not detectable (0.00 μg/g). Four species, Epimedium pubescens, Epimedium sagittatum, Epimedium brevicornu, and Epimedium wushanense, were found to contain Cu (copper) and Pb (lead). And contents of Cu and Pb in E. brevicornu were significantly higher than those in other species (P < 0.01). In wild-growing and cultivated Epimedium plants, Cd (cadmium) and As (arsenic) were not detectable, and concentrations of Cu and Pb in wild-growing plants were significantly higher than those in cultivated plants (P < 0.01). Cd was not detectable in leaves, roots, and stems, while organ specificity was apparent in the distribution of Cu, As, and Pb. And the highest levels of Cu and Pb were observed in roots and leaves, respectively. In Chinese markets, several samples of Epimedii Folium contained excessive Cu, Cd, As, and Pb beyond the national permissible limits. In summary, there was a large variation of heavy metals among Epimedii Folium samples, and Cu and Pb were the most important heavy metals contaminating the edible medicinal plant. Application of Epimedii Folium to drug and food industries will need to focus more on toxic heavy metal contamination.     

Acidification and the structure of crustacean zooplankton in mountain lakes: The Tatra Mountains (Slovakia,Poland)

Species composition of planktonic Crustacea in 102 lakes in the West and High Tatra Mountains, studied during the peak of anthropogenic acidification (1978–1996), is presented in this work. Zooplankton of the Tatra lakes have been studied since the middle of the 19^th century, which later enabled the recognition of lake acidification and the assessment of its effect on the plankton community of lake ecosystems. In the pre-acidification period, the distribution of zooplankton was determined namely by the lake altitude and orientation (north vs. south) and by the catchment character. Crustacean zooplankton in larger lakes consisted of a limited number of species, with Acanthodiaptomus denticornis and Daphnia longispina dominating lakes in the forest zone, and Arctodiaptomus alpinus, Cyclops abyssorum, Daphnia longispina, Daphnia pulicaria, and Holopedium gibberum dominating lakes in the alpine zone. Ceriodaphnia quadrangula, Daphnia obtusa, Daphnia pulex, and Mixodiaptomus tatricus occurred in lakes with high concentrations of dissolved organic matter and in strongly acidified waters. Anthropogenic acidification has caused drastic changes in both the chemistry and biology of the Tatra lakes. Based on their status during the acidification peak, lakes were divided into three categories: non-acidified (with no change in the species composition of crustacean zooplankton due to the acidification), acidified (planktonic Crustacea disappeared in lakes with meadow-rocky catchments), and strongly acidified lakes where original Crustacea in meadow-rocky catchment lakes disappeared and were replaced by populations of the acid-tolerant littoral species Acanthocyclops vernalis, Chydorus sphaericus, and Eucyclops serrulatus. The acidification-induced processes of oligotrophication and toxicity of aluminium played a key role in the extinction of species. Despite the first signs of biological recovery observed in the early 2000s, acidification remains the most important factor governing the structure of plankton in the Tatra lakes.     

Effects of cadmium and lead stress on somatic embryogenesis of coniferous species. Part I: Evaluation of the genotype-dependent response

Somatic embryogenesis is an important biotechnological tool that has significant potential to be used in studies related to environmental stress. In this study, embryogenic cell masses of Abies alba and Picea abies were grown on media enriched with 50–500 µM cadmium (Cd²⁺) or lead (Pb²⁺). The effects of cadmium and lead were evaluated during the subsequent stages of somatic embryogenesis: proliferation, maturation, and germination. The following characteristics were evaluated: proliferation potential, cell viability, average number of somatic embryos obtained per 1 g of fresh weight, and morphology of the developed somatic embryos. The tested heavy metals significantly reduced the proliferation rate of A. alba and P. abies embryogenic cell masses. The highest tested cadmium concentration markedly slowed or stopped the growth of embryogenic cell masses in both species. Unexpectedly, the proliferation ratio remained fairly high for the P. abies cell lines treated with lead at all concentrations tested. During the maturation stage, the total number of somatic embryos declined under cadmium exposure. The formation of early precotyledonary and cotyledonary somatic embryos in both species was similarly reduced, although cadmium caused a higher death rate and was more toxic than lead. To the best of our knowledge, this is the first report to study the effects of heavy metals on A. alba embryogenic cell masses during the proliferation stage as well as on the maturation and germination processes of both species. This in vitro system can be used for testing the response of large sets of genotypes, and the best performing lines can be used in the future for in vivo performance tests of heavy metal-polluted soils.     

Isolation and Characterization of Toxic Cyanobacteria from Different Natural Sources

We isolated seven algologically and five bacteriologically pure cultures of toxin-producing cyanobacteria from Turgen gorge (Kazakhstan), Karlovy Vary (Czech Republic), and Shar-Nuur Lake, Bayan Ulgiiregion (Mongolia) springs. According to the Daphnia magna test, Desertifilum sp. and Nostoc sp. strains were the most toxic in the test of isolated strains (complete death of all test organisms was detected after 48 h). These strains possessed the highest inhibitory effect on proliferation of the HeLa cancer cell line. The Anabaena sp. 35 and Nostoc sp. 4 strains were also high toxic. Model strains Synechocystis PCC 6803 and Synechococcus elongates PCC 7942, as well as the strain isolated in the present work, Synechococcus sp. 55, were less toxic. Mass spectrometry made it possible to assign cyanobacterial toxins to cyclic depsipeptides. Two cyclic depsipeptides, micropeptin T and oscillapeptin, were detected in Desertifilum sp. extracts. Cryptophycin and small amounts of cyclic depsipeptide micropeptin SD were detected in Nostoc sp. extract.     

Validation of Appropriate Reference Genes for Real-Time Quantitative PCR Gene Expression Analysis in Rice Plants Exposed to Metal Stresses

Environmental pollution by toxic heavy metals may lead to the possible contamination of the rice plant (Oryza sativa L.). Although gene expression analysis through real-time quantitative PCR (RT-qPCR) has increased our knowledge about biological responses to heavy metals, gene network that mediates rice plant responses to heavy metal stress remains elusive. In such scenario, validation of reference gene is a major requirement for successful analyzes involving RT-qPCR. In this study, we analyzed the expression stability of eight commonly used housekeeping genes (GAPDH, Actin, eIF-4α, UBQ 5, UBQ 10, UBC, EF-1α and β-TUB) in rice leaves exposed to four kinds of heavy metals (Zn, Cu, Cd and Pb). The expression stability of these genes was determined using geNorm, NormFinder, BestKeeper and RefFinder algorithms. The results showed that UBQ 10 and UBC were the most stable reference genes across all the tested samples. We measured the expression profiles of the heavy metal-inducible gene O. sativa METALLOTHIONEIN2b (OsMT2b) using the two most stable and one least stable reference genes in all samples. The relative expression of OsMT2b varied greatly according to the different reference genes. Our results may be beneficial for future studies involving the quantification of relative gene expression levels in rice plants.     

Light avoidance in Baikalian amphipods as a test response to toxicants

The dependence between the time of escape of Eulimnogammarus vittatus from light and toxicants in the medium has been studied. It has been shown that these amphipods display the most rapid response to light in pure Baikal water. Toxicants slow down the movement of E. vittatus in the dark. A similar effect has been observed during the experiments with heavy metals, detergents, and petroleum products. The results indicate a good prospect for using this reaction as a test response during the biological assay of toxic contamination with the help of E. vittatus.     

Synthesis and algicidal activity of new dichlorobenzylamine derivatives against harmful red tides

In the present study, we synthesized 65 dichlorobenzylamine derivatives and investigated their algicidal activity against harmful red tides. The 3,4-dichlorobenzylamine derivatives showed relatively high activity against Cochlodinium polykrikoides, Heterosigma akashiwo, Chattonella marina, and Heterocapsa circularisquama, and the synthesized compounds 27, 28, 33, 34, 35, and 36 showed the highest algicidal activity after 24 h at 0.1 ~ 1.0 μM LC₅₀ against the four harmful algae species. To verify the safety of the compounds, acute ecotoxicology tests using the water flea (Daphnia magna) and zebrafish (Danio rerio) were conducted, and the tests confirmed that compounds 33 and 34 were not harmful because the target organisms showed high survival rates at 15 μM. The results indicate that compounds 33 and 34 are suitable substances for use in controlling harmful algae species.