Moonho Son

Algicidal activity of the thiazolidinedione derivative TD49 against the harmful dinoflagellate Heterocapsa circularisquama in a mesocosm enclosure

To assess the algicidal effects of the thiazolidinedione derivative TD49 on the unarmored dinoflagellate Heterocapsa circularisquama and to evaluate the response of the planktonic community and the environment to this chemical, we undertook mesocosm (1,300xa0L) and small-scale experiments. The reduction ratio for H. circularisquama in each experiment was dependent on the concentration of TD49. At a TD49 concentration >0.4xa0μM, the abundance of H. circularisquama decreased by 99xa0% in the small-scale experiment and by 84xa0% in the mesocosm during the initial 2xa0days. At 0.2xa0μM TD49, the abundance of H. circularisquama decreased by up to 85xa0% in the small-scale experiment, whereas the abundance in the mesocosm increased, implying the absence of an algicidal effect. The decrease in planktonic organisms, including H. circularisquama, following TD49 treatment was correlated with abrupt declines in culture pH and dissolved oxygen concentration. Following addition of TD49, there was a significant increase in the abundance of diatoms and cryptophyta species, and after 8xa0days, the dominant species in the TD49 treatments shifted to small pennate diatoms including Cylindrotheca and Entomoneis species. The growth of some species among the zooplankton community was promoted at low TD49 concentrations (≤0.4xa0μM), whereas high concentrations (≥1.0xa0μM) had a negative effect. This study demonstrates that TD49 is an effective agent for the control for H. circularisquama blooms and that large-scale mesocosms play a crucial role in assessing the application of algicides such as TD49 in natural environments.

Algicidal effects on Heterosigma akashiwo and Chattonella marina (Raphidophyceae), and toxic effects on natural plankton assemblages by a thiazolidinedione derivative TD49 in a microcosm

The algicidal effects of the thiazolidinedione derivative TD49 on Heterosigma akashiwo and Chattonella marina (Raphidophyceae) were assessed, and the response of the planktonic community and environment to the algicide was evaluated in a microcosm, quantifying 12xa0L. The abundance of over 80xa0% of H. akashiwo and C. marina declined in a day significantly in microcosms to which TD49 was added (final concentration 2xa0μM), and this was correlated with an abrupt decline in the culture pH. The number of protists (i.e., ciliates) other than H. akashiwo and C. marina gradually increased with time in the TD49 treatments, implying that the decline in numbers of H. akashiwo and C. marina cells resulting from TD49 treatment was a major factor in the growth of the other organisms. However, TD49 may be toxic to aquatic zooplankton communities, even though it is a highly selective algicide for harmful algae bloom species. The study indicates that TD49 is an effective agent for the control for H. akashiwo and C. marina blooms in enclosed and eutrophic water bodies.

Enhanced species-specific chemical control of harmful and non-harmful algal bloom species by the thiazolidinedione derivative TD49

Culture experiments involving 23 algae strains were conducted to evaluate the algicidal effects of a newly developed algicidal thiazolidinedione (TD) derivative (TD49) on non-harmful and harmful algal bloom (HAB) species. We also assessed the effect of various concentrations of TD49 on various growth phases (lag, logarithmic, and stationary) of the harmful algae Heterocapsa circularisquama (Dinophyceae) and Heterosigma akashiwo (Raphidophyceae; hereafter, Heterosigma) and the non-harmful diatoms Skeletonema costatum and Chaetoceros didymus. The inhibitory ratios (%) for H. circularisquama and Heterosigma at 2.0xa0μM TD49 were significantly higher than those at other concentrations, and the inhibitory ratio varied depending on growth phase and species as follows: logarithmicu2009≥u2009stationaryu2009>u2009lag phase for H. circularisquama and logarithmicu2009≥u2009lagu2009>u2009stationary phase for Heterosigma. Although the inhibitory ratios for C. didymus were similar to those for the two harmful algae (H. circularisquama and Heterosigma), inhibitory effects on S. costatum were not apparent at >2.0xa0μM in any growth phase. The algicidal activity of TD49 on the harmful and non-harmful algae was as follows: unarmored HAB speciesu2009>u2009armored HAB speciesu2009>u2009diatom speciesu2009>u2009cryptophyte species. TD49 was algicidal to most HABs but had a little inhibitory effect on some non-harmful algae, implying that TD49 has selective algicidal activity. Our results indicate that TD49 is potentially of use in the control of HAB species within semi-enclosed bays.

Algicidal effects of yellow clay and the thiazolidinedione derivative TD49 on the fish-killing dinoflagellate Cochlodinium polykrikoides in microcosm experiments

In order to evaluate the potential to control the fish-killing dinoflagellate Cochlodinium polykrikoides, we compared the algicidal effects of the thiazolidinedione derivative TD49 with those of yellow clay in 10-L microcosms. The responses of higher trophic level marine organisms and microbial loop communities to the algicide were also evaluated. In the yellow clay treatments, the concentration of C. polykrikoides was slightly reduced at day 1 of the experiment but remained higher than that of the control, suggesting that the reduction ratio of C. polykrikoides was <20xa0%. In the 0.8-μM TD49 treatment, the abundance of C. polykrikoides declined by 98xa0% 1xa0day following the addition of the algicide. The algicide did not affect nontarget algae including Chaetoceros spp., Skeletonema spp., Cylindrotheca spp., and other species. In all microcosms, bacterial abundance increased abruptly after day 1, then declined over the next 2xa0days as a result of predation by heterotrophic nanoflagellates and the small protozoan Uronema sp. Predation by the large protozoan species Euplotes sp. on Uronema sp. gradually increased with increasing incubation time in the TD49 treatment. Zooplankton were particularly affected by the environmental changes that occurred in the microcosms following collapse of the C. polykrikoides populations. Striped beak perch were not affected by the yellow clay treatments and concentrations of TD49u2009<u20092.0xa0μM. The results suggested that the yellow clay has little effect on C. polykrikoides, whereas the algicide TD49 is effective in controlling the harmful alga. The results imply that the algicide has positive effects on natural microbial communities and is not toxic to nonharmful algae and higher trophic level marine organisms.

Assessing the ecosystem health status of Korea Gwangyang and Jinhae bays based on a planktonic index of biotic integrity (P-IBI)

To assess the responses of planktonic organisms to pollutants in the coastal ecosystems of Gwangyang and Jinhae bays in Korea, we investigated seasonal changes in various biological factors during the period from 2010 to 2012. Based on the characteristics of nutrient uptake by planktonic organisms under the coastal pollution conditions, we focused on four major parameters: total phytoplankton, harmful algal bloom (HAB) species, heterotrophic bacteria (HB) and Escherichia coli to develop a planktonic index of biotic integrity (P-IBI). The threshold values for abundances of total phytoplankton, HAB species and HB were based on the zero Z-score following normal distribution of the data for each parameter during the three years. Based on this approach, the threshold values were: 1.2 × 106 cells L−1 for total phytoplankton; 3.3 × 104 cells L−1 for HAB species; and 1.7 × 106 cells mL−1for HB. Five grade levels for the P-IBI were established, based on the zero Z-scores. The threshold value for E. coli not to be normalized was based on the USEPA and the Korean Ministry of Oceans and Fisheries guidelines. Validity of the grades and threshold values for each parameter established using the field data were tested by algal bioassays in a mesocosm enclosure, which supported the threshold values obtained in the field. In Gwangyang Bay, the annual integrated score for the P-IBI in 2010 was better than in the other years of the study. In Jinhae Bay, the P-IBI for the inner area of Masan Bay was Grade IV–V, indicating unhealthy conditions relative to the central and western outer areas, where the P-IBI varied from Grade II to III. The P-IBI values for Gwangyang and Jinhae bays were mostly rated as “Good (Grade II) or Fair (Grade III)”, except for a few stations in the semi-enclosed areas of the inner part of Jinhae Bay. From an overall view based on the P-IBI developed in this study, the coastal ecosystem health status in Gwangyang Bay was in a better condition than Jinhae Bay. The P-IBI indicated also a change to an unhealthy status during the rainy periods of spring and summer, whereas during winter and autumn the index indicated healthy conditions.

Algicidal Effects of a Newly Developed Thiazolidinedione Derivative, TD49, on Dinoflagellate Akashiwo sanguinea

Abstract : To evaluate the algicidal impact of a newly developed algicide thiazolidinedione derivative,TD49, on dinophyceae Akashiwo sanguinea in aquatic ecosystems, tentative culture experiments for thetarget species were conducted in small (SS), middle (MS), and large scale (LS) culture vessels. When TD49was introduced at the final concentration of 2 µM in SS and MS, as well as 1 µM in LS, the abundance of A.sanguinea decreased significantly in all the treatments. On the other hand, total phytoplankton abundance,except A. sanguinea in the TD49 treatments, gradually increased with culture time, which implies that a celldestruction of A. sanguinea by TD49 is a major cause of the population growth by other phytoplanktonspecies. Also, A. sanguinea was easily destroyed, which was likely to be a source of extracellularsubstances. In particular, a pH decrease was significant in the treatments than in the control, which indicatesthat the water in the treatments has been acidified, due to an increase in the heterotrophic metabolisms ofbacteria and degradation of A. sanguinea cells. Our results indicate that the TD49 substance is the potentialagents for the control of A. sanguinea in the enclosed and eutrophic water bodies.Key words :Akashiwo sanguinea, algicidal effect, thiazolidinedione, ecosystem*Corresponding author. E-mail : yokim@kordi.re.kr

Effects of the algicide, thiazolidinedione derivative TD49, on microbial communities in a mesocosm experiment

We investigated the effects of the algicide thiazolidinedione derivative TD49 on microbial community in mesocosm experiments. The TD49 concentration exponentially decreased over time, with half-life of 3.5xa0h, following addition in the seawater (R2u2009=u20090.98, Pu2009<u20090.001). Among microbial communities, heterotrophic bacteria and heterotrophic nanoflagellates (HNFs) grew well in all treatments following the addition of TD49. The abundance of HNFs lagged behind the increase in heterotrophic bacteria by 24xa0h in the 0.2 and 0.4xa0μM TD49 concentrations (R2u2009=u20090.28, Pu2009<u20090.05), and by 48xa0h in the 0.6 and 1.0xa0μM TD49 concentrations (R2u2009=u20090.30, Pu2009<u20090.05). This implies a strong concentration-dependent top-down effect of TD49 on microbial communities, with indications that the degradation of planktonic organisms, including the target alga, led to high heterotrophic bacteria concentrations, which in turn stimulated the population growth of predatory HNF. However, total ciliate numbers remained relatively low in the TD49 treatments relative to the control and blank groups, suggesting limited carbon flow from bacteria to these grazers even though the abundance of aloricate ciliates gradually increased toward the end of the experimental period, particularly at the high TD49 concentrations. TD49 appears to provide an environmentally safe approach to the control of harmful algal blooms (HABs) in aquatic ecosystems.

Effects of Chemically Enhanced Water-Accommodated Fraction of Iranian Heavy Crude Oil on Periphytic Microbial Communities in Microcosm Experiment

Exposure experiments were conducted to determine the effects of an oil spill on a periphytic microbial community with the chemically enhanced water-accommodated fraction (CEWAF) of Iranian Heavy Crude oil in a microcosm containing artificial benthic substrates. Bacteria and heterotrophic nano-flagellates (HNF) grew well in all the treatments, except for the 100xa0% CEWAF exposure. However, periphyton did not adapt to concentrations of CEWAFxa0≥xa020xa0%. Among the periphyton, Cylindrotheca spp. dominated under treatment conditions, and the response of Cylindrotheca spp. to CEWAF (i.e., particularly 10xa0%) closely followed the changes in chlorophyll a concentration. The concentrations of petroleum hydrocarbons from 10xa0% and 20xa0% CEWAF seemed to have a negative effect on periphyton and a growth-promoting effect on bacteria and HNF, respectively.

Distributional characteristics of phytoplankton and nutrient limitation during spring season in Jinhae Bay

We investigated to assess the relationships between the major nutrients and phytoplankton dynamics during the spring season in 2010 and 2011 at 23 stations in Jinhae Bay, Korea. The bay is divided into four different zones based on pollutant sources and geographical characteristics. Nutrient limitation (>80%) was significant in Zone II, which is located in central bay and is influenced by the water well mixed from outer bay. The limited nutrient was followed in Zone III and IV that was occupying between 17% and 83%. However, the low levels are being kept below 35% in Zone I, which is characterized by the semi-enclosed eutrophic area of Masan and Haegam bays. Based on the PCA (principle component analysis) analysis, the nitrogen (N) sources in 2010 were particularly dominant and it may be due to the water mixing and wastewater formed from bottom layers and sewage. In 2011, major nutrients including nitrogen, silicon and phosphorus were dominant in the bay and are supplied by the river discharge after rainfalls with low salinity conditions. In particular, the N nutrients being supplied in 2010 are correlated with pennate diatoms Pseudo-nitzchia spp. and is not related to the phytoplankton population densities in 2011. The present study suggests that N sources play an important role in the proliferation of diatom, and the rapid nutrient uptakes by them are potential nutrient limitation factors in the bay.

The study on the Fluorescence Characteristics of Several Freshwater Bloom Forming Algal Species and Its Application

【The freshwater blooms mainly blue-green algal blooms occur frequently in the lower Naktong River in summer, which provoke many socio-economical problems; therefore, the early detection of bloom events are demanding through the quantitative and qualitative analyses of blue green algal species. The in vivo fluorescence properties of cultured strains of Microcystis aeruginosa, M. viridis, M. wesenbergii, M. ichthyoblabe, Anabaena cylindrica, A. flos-aquae, and Synedra sp. were investigated. Wild phytoplankton communities of the lower Naktong River were also monitored at four stations in terms of their standing stocks, biomass and fluorescence properties compared with its absorption spectram. The 77K fluorescence emission spectra of each cultured strains normalized at 620 nm was very specific and enabled to detect of blue green algal biomass qualitatively and quantitatively. The relative chlorophyll a concentration determined by chlorophyll fluorescence analysis method showed significant relationship with chlorophyll a concentration determined by solvent extraction method (