Jihae Park

The use of diatoms in ecotoxicology and bioassessment: Insights, advances and challenges

Diatoms are regularly used for bioassessment and ecotoxicological studies in relation to environmental and anthropogenic disturbances. Traditional taxonomical diatom parameters (cell counts, biovolume estimates, species richness, diversity indices and metrics using sensitive and tolerant diatom species) are regularly used for these studies. In the same context, very less focus was given on new endpoints of diatoms (life-forms, nuclear anomalies, alteration in photosynthetic apparatus shape, motility, lipid bodies, size reduction and deformities), in spite of their numerous merits, such as, their easiness, quickness, cheapness, global acceptation and no especial training in diatom taxonomy. In this review we analyzed 202 articles (from lab and field studies), with the aim to investigate the bioassessment and ecotoxicological advancement taken place in diatom research especially in terms of exploring new endpoints along with the traditional taxonomical parameters in a perspective which can greatly enhance the evaluation of fluvial ecosystem quality for biomonitoring practices.

The sensitivity of an hydroponic lettuce root elongation bioassay to metals, phenol and wastewaters.

The root elongation bioassay is one of the most straightforward test methods used for environmental monitoring in terms of simplicity, rapidity and economy since it merely requires filter paper, distilled water and Petri dishes. However, filter paper as a support material is known to be problematic as it can reduce the sensitivity of the test. The newly developed hydroponic method reported here differs from the conventional root elongation method (US EPA filter paper method) in that no support material is used and the exposure time is shorter (48 h in this test versus 120 h in the US EPA test). For metals, the hydroponic test method was 3.3 (for Hg) to 57 (for Cu) times more sensitive than the US EPA method with the rank orders of sensitivity, estimated from EC50 values, being Cu≥Cd>Ni≥Zn≥Hg for the former and Hg≥Cu≥Ni≥Cd≥Zn for the latter methods. For phenol, the results did not differ significantly; EC50 values were 124 mg L(-1) and 108-180 mg L(-1) for the hydroponic and filter paper methods, respectively. Lettuce was less sensitive than daphnids to wastewaters, but the root elongation response appears to be wastewater-specific and is especially sensitive for detecting the presence of fluorine. The new hydroponic test thus provides many practical advantages, especially in terms of cost and time-effectiveness requiring only a well plate, a small volume of distilled water and short exposure period; furthermore, no specialist expertise is required. The method is simpler than the conventional EPA technique in not using filter paper which can influence the sensitivity of the test. Additionally, plant seeds have a long shelf-life and require little or no maintenance.

Testing the toxicity of metals, phenol, effluents, and receiving waters by root elongation in Lactuca sativa L.

Phytotoxicity tests using higher plants are among the most simple, sensitive, and cost-effective of the methods available for ecotoxicity testing. In the present study, a hydroponic-based phytotoxicity test using seeds of Lactuca sativa was used to evaluate the water quality of receiving waters and effluents near two industrial sites (Soyo and Daejon) in Korea with respect to the toxicity of 10 metals (As, Cd, Cr, Cu, Fe, Pb, Mn, Hg, Ni, Zn) and phenol, and of the receiving waters and effluents themselves. First, the L. sativa hydroponic bioassay was used to determine whether the receiving water or effluents were toxic; then, the responsible toxicant was identified. The results obtained with the L. sativa bioassay ranked the EC50 toxicities of the investigated metal ions and phenol as: Cd > Ni > Cu > Zn > Hg > phenol > As > Mn > Cr > Pb > Fe. We found that Zn was the toxicant principally responsible for toxicity in Daejeon effluents. The Daejeon field effluent had a higher Zn concentration than permitted by the effluent discharge criteria of the Ministry of Environment of Korea. Our conclusion on the importance of Zn toxicity was supported by the results of the L. sativa hydroponic assay, which showed that the concentration of Zn required to inhibit root elongation in L. sativa by 50% (EC50) was higher in the Daejeon field effluent than that of pure Zn. More importantly, we proved that the L. sativa hydroponic test method can be applied not only as an alternative tool for determining whether a given waste is acceptable for discharge into public water bodies, but also as an alternative method for measuring the safety of aquatic environments using EC20 values, with respect to the water pollutants investigated (i.e., Cd, Cr, Cu, Pb, Mn, Hg, Ni, Zn, and phenol).

Toxicity tests using the kelp Undaria pinnatifida for heavy metal risk assessment

The toxicity of six metals (Cd, Cu, Hg, Ni, Pb and Zn) to the early life stages of the brown seaweed Undaria pinnatifida were tested using two endpoints: spore germination and germ tube elongation. The optimal test conditions determined for photon irradiance, pH, salinity and temperature were darkness, pH 8, 35‰ and 15°C, respectively. The EC50 values could be determined only for Hg and Cu and were 27 μg · L-1 and 186 μg · L-1, respectively, for germination and 16 μg · L-1 and 45 μg · L-1, respectively, for germ tube elongation. The variability of our U. pinnatifida test in response to the metal toxicants, as estimated from the coefficient of variation of the mean EC50 values, was less than 28%. When tested against two different wastewater samples (PCB manufacturer and TV & communication equipment manufacturer), U. pinnatifida exhibited an EC50 of 66.09-80.73% for germination and 24.98-62.62% for germ tube elongation with the CV (Coefficient of variation) range for both germination and germ tube elongation between 1.24 and 13.18%. The novel aspect of the present method is that the testing procedure requires no lighting or photoperiodic control. Additionally, the response of Undaria to the toxicity of Hg and Cu is very similar to that reported for other very sensitive macroalgal species. Because of its ecological and economic importance, the evaluation of toxicity using early stages of U. pinnatifida will provide useful scientific information, and we propose that this represents a valid bioassay within the battery of aquatic bioassays for the assessment of anthropogenic impacts on coastal ecosystems and commercial cultivation areas in nearshore environments.

Evaluating features of periphytic diatom communities as biomonitoring tools in fresh, brackish and marine waters

The aims of this study were to assess the biodiversity of periphytic diatom assemblages in fresh, brackish and marine waterbodies of Korea, and to assess the effect of environmental and anthropogenic factors on parameters such as the quantity and biovolume of lipid bodies and deformations of diatoms as early warning measures of anthropogenic impact. Diatom samples were collected from 31 sites (14 freshwater, 10 brackish and 7 marine), which included less impacted (upstream) and impacted (downstream) sites in each water type. Our results showed higher abundance and biodiversity of periphytic diatoms at the less impacted sites in terms of species richness, Shannon index, cell count and biovolume of the communities than at the impacted sites for freshwater and estuarine sites, but not for marine sites. 84 diatom species were noted in freshwater, 80 in brackish water and 40 in marine waters. In comparison to diatoms of the impacted sites, those of less impacted freshwater, brackish and marine sites had less lipid bodies (also less biovolume) and a lower percentage of teratological frustules, and showed more mobile forms in the community. Principal component analysis (PCA) also showed clear segregation of impacted from less impacted sites by the extent of the presence of lipid bodies (higher both in number and biovolume) and deformities in diatom frustules. Pearson correlation analysis revealed that lipid body induction and deformities were positively correlated with metals (Cd, Co, Cr, Cu, Fe, Pb and Zn) and nutrients (total phosphorus and total nitrogen), whereas they showed negative correlation with salinity, dissolved oxygen, suspended solutes and pH. Life-forms, lipid bodies and deformities in diatoms may be an effective biomonitoring tool for assessing biological effects of pollutants in non-marine aquatic ecosystems in Korea.

Phaeoviral infections are present in macrocystis, ecklonia and undaria (laminariales) and are influenced by wave exposure in ectocarpales

Two sister orders of the brown macroalgae (class Phaeophyceae), the morphologically complex Laminariales (commonly referred to as kelp) and the morphologically simple Ectocarpales are natural hosts for the dsDNA phaeoviruses (family Phycodnaviridae) that persist as proviruses in the genomes of their hosts. We have previously shown that the major capsid protein (MCP) and DNA polymerase concatenated gene phylogeny splits phaeoviruses into two subgroups, A and B (both infecting Ectocarpales), while MCP-based phylogeny suggests that the kelp phaeoviruses form a distinct third subgroup C. Here we used MCP to better understand the host range of phaeoviruses by screening a further 96 and 909 samples representing 11 and 3 species of kelp and Ectocarpales, respectively. Sporophyte kelp samples were collected from their various natural coastal habitats spanning five continents: Africa, Asia, Australia, Europe, and South America. Our phylogenetic analyses showed that while most of the kelp phaeoviruses, including one from Macrocystis pyrifera, belonged to the previously designated subgroup C, new lineages of Phaeovirus in 3 kelp species, Ecklonia maxima, Ecklonia radiata, Undaria pinnatifida, grouped instead with subgroup A. In addition, we observed a prevalence of 26% and 63% in kelp and Ectocarpales, respectively. Although not common, multiple phaeoviral infections per individual were observed, with the Ectocarpales having both intra- and inter-subgroup phaeoviral infections. Only intra-subgroup phaeoviral infections were observed in kelp. Furthermore, prevalence of phaeoviral infections within the Ectocarpales is also linked to their exposure to waves. We conclude that phaeoviral infection is a widely occurring phenomenon in both lineages, and that phaeoviruses have diversified with their hosts at least since the divergence of the Laminariales and Ectocarpales.

Implications of rising temperatures for gametophyte performance of two kelp species from Arctic waters

Abstract The aim of this study was to determine the temperature effects on photosynthesis, growth and reproduction in gametophytes of Alaria esculenta (Linnaeus) Greville and Saccharina latissima (Linnaeus) C.E. Lane, C. Mayes, Druehl et G.W. Saunders from the Artic waters. After 24 days of culture, no gametophytes of either species survived at 20°C. Most growth parameters were greater at 10–15°C than at 5°C. Length and width were similar for both species, but area was greater for A. esculenta and cell number was greater for S. latissima. Female gametophytes were larger than male gametophytes in width and area, but the opposite was observed in cell number. In A. esculenta, but not for S. latissima, the percentage of female gametophytes decreased with increasing temperature. Alaria esculenta female gametophytes produced more sporophytes at 5°C than at 10°C, with no sporophytes at 15°C. In S. latissima, all female gametophytes produced sporophytes at both 5°C and 10°C, with a small percentage of sporophytes at 15°C. Saccharina latissima still had a measurable Fv/Fm at 20°C, while the Fv/Fm of A. esculenta was zero at this temperature. Maximum relative electron transport rate (rETRmax) and non-photochemical quenching (NPQ) were constant in the male and female gametophytes of A. esculenta and the male gametophytes of S. latissima at temperatures between 5°C and 15°C. Photosynthesis was saturated at a higher irradiance in A. esculenta than in S. latissima.

Assessment of metal contamination in water and sediments from major rivers in South Korea from 2008 to 2015

This study is the first report to evaluate (8 years data) the contamination degree and distribution characteristics of metals in the surface water and sediments of four Korean rivers (Nakdong, Yeongsan, Geum, and Han). Eight years of data were evaluated, and metal concentrations in the river water were found to be below permissible limits but high enough to cause detrimental effects (under chronic exposure) to aquatic organisms. The analysis of metals in the river sediments showed the following trend: Zn > Cu > Cd > Pb > Ni > As > Cr > Hg. The concentrations of metals in sediments (especially in the Geum and Han rivers) were above the permissible limits reported by international agencies. Concentrations of Cu, Ni, and Zn were high enough to pose risks to aquatic communities. In sediments, metals pollution was also evaluated using different indices, such as enrichment factor (EF), geoaccumulation index (Igeo), contamination factor (CF), degree of contamination (Cd), modified degree of contamination (mCd), and pollution load index (PLI). The CF, EF, and Igeo indices demonstrated that most of the river sediment samples were moderately to heavily contaminated by Cd, Cu, Pb, and Zn. The PLI values were above one in the Geum and Han river sediments, which indicated polluted conditions. Similarly, Cd indicated a considerable to very high degree of contamination, while mCd indicated a low to moderate degree of contamination in all four river sediments. Finally, it was found that the extent of metals pollution in the Korean rivers reached a critical condition, which could be detrimental to the biota of the rivers, as well as to humans in the long term.

Microalgae and Alcohol

Abstract Microalgae have been considered as an excellent source of third-generation biofuels. Most microalgae studies have focused on biodiesel, nutritional supplements, or animal feeds. Very limited studies have been conducted for bioethanol although the carbohydrates of microalgae come mainly in the form of starch and cellulose with the absence of lignin. Both starch and cellulose can be converted into fermentable sugars for bioethanol production via microbial fermentation. Under stress conditions (e.g., nutrient depletion), some microalgal species accumulate carbohydrates at a significantly high level. In this paper, several perspectives of microalgae for alcohol production are discussed, including: (1) microalgal species suitable for bioethanol production; (2) cultivation and harvest technologies of microalgal biomass; and (3) process technologies of bioethanol production from microalgae (e.g., hydrolysis and fermentation, and photanol). In addition, alcohol products using microalgae and the health benefits of microalgae-sourced alcohol (beer and wine) are also presented. It is unclear if microalgae can provide additional health benefits in alcoholic beverages.