Baik-Ho Kim

Isolation and characterization of a bio‐agent antagonistic to diatom, Stephanodiscus hantzschii

Aims:  Identification of bacterium HYK0203‐SK02 and its lysis of Stephanodiscus hantzschii.

Pseudomonas fluorescens HYK0210‐SK09 offers species‐specific biological control of winter algal blooms caused by freshwater diatom Stephanodiscus hantzschii

Aims:  The study of an algicidal activity and mechanism of the isolated Pseudomonas fluorescens HYK0210‐SK09 (SK09) against a winter bloomed harmful diatom, Stephanodiscus hantzschii.

Enhancement of algicidal activity by immobilization of algicidal bacteria antagonistic to Stephanodiscus hantzschii (Bacillariophyceae)

Aims:  Enhancement of algicidal activity by immobilization of algicidal bacteria antagonistic to Stephanodiscus hantzschii.

Effects of fish introduction on the length of the tail of cryptomonads in mesocosm experiments.

Two different morphs of the small cryptomonad, Plagioselmis prolonga var. nordica with a posterior tail, were observed during summer and fall in the hypertrophic lake, Lake Kasumigaura, Japan. The tail shortened in mesocosms stocked with planktivorous silver carp (Hypophthalmichthys molitrix Val.) and elongated by more than 50% in mesocosms from which silver carp were removed. The density of Plagioselmis cells increased significantly upon fish stocking and decreased upon fish removal. The tail length was negatively correlated with algal abundance and positively correlated with crustacean densities, but there was no correlation with nutrient levels or physical environmental parameters in the mesocosms. The variation in tail length was induced by the presence/absence of fish, but was not related to their density. However, silver carp manipulation strongly affected the density of the majority of zooplankters and, interestingly, there was a strong correlation between zooplankton density and tail-length change in Plagioselmis. We propose a possible herbivore-induced defense mechanism triggered by the top predator, silver carp.

Paralytic shellfish toxin production by the dinoflagellate Alexandrium pacificum (Chinhae Bay, Korea) in axenic, nutrient-limited chemostat cultures and nutrient-enriched batch cultures.

Blooms of Alexandrium pacificum (formerly Alexandrium tamarense) are common in Chinhae Bay (Korea), presumably linked to anthropogenic eutrophication. Here we examine PSP toxin content and composition in axenic chemostat and batch cultures of A. pacificum using growth conditions that differed according to dilution rate, nutrient limitations, and enrichments. Phosphate (P)-limited cells in chemostat cultures had higher toxin content and a toxin composition that differed from that of nitrogen (N)-limited cells at the highest growth rates. Therefore, toxin composition changes do occur in axenic cultures of A. pacificum following extended growth under steady state conditions. In nutrient-limited batch cultures that received N and P enrichment, the N-enriched cultures showed a more diverse toxin profile than the P-enriched cells; the toxin content of N-enriched cells was lower than in the P-enriched cultures. We infer the following order for the biosynthesis of individual toxins: C1, C2>GTX3>GTX1>neoSTX.

Seasonal Variations of Planktonic Ciliates with Reference to Their Prey in a Shallow and Eutrophic Korean Stream

ABSTRACT Seasonal variations of planktonic ciliates, with reference to environmental variables, and the relationship between ciliates and their prey were examined for one year in a shallow and eutrophic Korean stream. Large-sized ciliates (>50 μm), such as Hypotrichia sp., Phascolodon vorticella, and Codonella cratera co-dominated with solitary phytoplankton like Stephanodiscus sp. and Cryptomonas ovata in winter and spring. Particularly, the abundance of Phascolodon vorticella was correlated with the abundance of Stephanodiscus sp. (r=0.85, p<0.0001), its apparently preferred prey. Food prey preference of Phascolodon vorticella was significantly higher for Stephanodiscus sp. (r=0.85, p<0.001) than for Cyclotella sp. (r=-0.14, p>0.318), which are similar in structure but different in size. Small-sized ciliates (<30 μm) mostly comprised Vorticella spp., Rimostrombidium hyalinum, and Halteria spp. and co-occurred with bacteria in warm seasons. These results suggest that the seasonal distribution of freshwater planktonic ciliates is determined by variations in their prey populations.

Accumulation of Microcystin (LR, RR and YR) in Three Freshwater Bivalves in Microcystis aeruginosa Bloom Using Dual Isotope Tracer

Stable isotope tracers were first applied to evaluate the Microcystis cell assimilation efficiency of Sinanodonta bivalves, since the past identification method has been limited to tracking the changes of each chl-a, clearity, and nutrient. The toxicity profile and accumulation of MC-LR, -RR and -YR in different organs (foot and digestive organs) from the three filter-feeders (Sinanodonta woodiana, Sinanodonta arcaeformis, and Unio douglasiae) were assessed under the condition of toxigenic cyanobacteria (Microcystis aeruginosa) blooms through an in situ pond experiment using 13C and 15N dual isotope tracers. Chl-a concentration in the manipulated pond was dramatically decreased after the beginning of the second day, ranging from 217.5 to 15.6 μg·L−1. The highest amount of MCs was incorporated into muscle and gland tissues in U. douglasiae during the study period, at nearly 2 or 3 times higher than in S. woodiana and S. arcaeformis. In addition, the incorporated 13C and 15N atom % in the U. douglasiae bivalve showed lower values than in other bivalves. The results demonstrate that U. douglasiae has less capacity to assimilate toxic cyanobacteria derived from diet. However, the incorporated 13C and 15N atom % of S. arcaeformis showed a larger feeding capacity than U. douglasiae and S. woodiana. Our results therefore also indicate that S. arcaeformis can eliminate the toxin more rapidly than U. douglasiae, having a larger detoxification capacity.

Molecular Identification of the Bloom-forming Cyanobacterium Anabaena from North Han River System in Summer 2012.

Molecular Identification of the Bloom-forming Cyanobacterium Anabaena from North Han River System in Summer 2012. LI, Zhun, Myung-Soo Han, Su-Ok Hwang, Myeong-Seop Byeon, Soon-Jin Hwang and Baik-Ho Kim* (Department of Life Science, Hanyang University, Seoul 133-791, Korea; K-waters, Korea Water Resources Corporation, Gwacheon, Gyeonggi 427-100, Korea; Han River Environment Research Center, National Institute of Environmental Research, Gyeonggi 427-100, Korea; Department of Environmental Science, Konkuk University, Seoul 143-701, Korea)

Phytoplankton Preferences of Young Silver Carp, Hypophthalmichthys molitrix, in Hypereutrophic Mesocosms during a Warm Season

ABSTRACT The feeding behavior of age-1 silver carp, Hypophthalmichthys molitrix (Val.), on phytoplankton species in a shallow hypereutrophic lake was studied in enclosures from 22 May to 18 September, 1997. Over the experimental period, the filter-pore sizes of the fish and the total biomass of the phytoplankton in each enclosure changed little with time. The fish biomass in each enclosure increased with time, while the percentage of weight gain correlated negatively to the stocking density, due perhaps to competition for prey. Analysis of gut contents of silver carp showed a strong similarity between the algae in the foregut and the algal communities in the water and this was significant (p<0.05) for the enclosure with a low fish density. There were weak relationships between the size/shape of phytoplankters and the selectivity of fish on them (r=0.001, p>0.5). Silver carp fed unselectively when cyanobacteria populations were high, even though the selectivity index for diatoms was slightly higher than those for cyanobacteria, green algae, and cryptomonads.

Effects of biocontrol with an atyid shrimp (Caridina denticulata) and a bagrid catfish (Pseudobagrus fulvidraco) on toxic cyanobacteria bloom (Microcystis aeruginosa) in a eutrophic agricultural reservoir

The biocontrol effects of Caridina denticulata, an atyid shrimp, on toxic cyanobacterial bloom (Microcystis aeruginosa) were evaluated in a mesocosm study with stable isotope tracers (13C and 15N) in a eutrophic agricultural reservoir. The accumulated assimilation (at.%) of M. aeruginosa into C. denticulata was increased, causing a significant reduction in the concentration of Chlorophyll-a. The ingestion rate of M. aeruginosa by C. denticulata was influenced by predation pressure exerted by bagrid catfish Pseudobagrus fulvidraco and was dependent on biomass ratio. C. denticulata affected zooplankton density, species composition, and ingestion rate, demonstrating that the number of small-sized cladocerans (Bosmina coregoni and Bosmina longispina) increased because they grazed M. aeruginosa for a food source. This study suggests that C. denticulata and P. fulvidraco can be feasible material to control a nuisance M. aeruginosa bloom in eutrophic agricultural reservoir.