Distribution pattern of zooplankton in the han river estuary with respect to tidal cycle

The monthly distribution of zooplankton communities in Han River estuary was investigated at two stations from July 1998 to June 1999. Monthly mean abundance of total zooplankton varied remarkably, with the range from 20 indiv.·m^-3 to 19,600 indiv.·m^-3. During the study period, dominant species of zooplankton community were dinoflagellateNoctiluca scintillans, copepodsParacalanus indicus, Paracaanus crassirostris, Acartia hongi, Acartia ohtsukai, and meroplanton cirriped larvae. According to tidal states, relative high abundance occurred at high tide without regard to season. The temporal distribution of abundance implied that the reduced salinity probably limited the zooplankton populations and the fluctuations of salinity were an important factor in the variation of abundance. However, the results of salinity tolerance test shows that the variations in salinity do not directly influence the decrease of abundance. This study shows that the relatively high abundance of zooplankton near high tide seems to be related with the expansion of abundant zooplankton inhabiting Incheon coastal waters through tidal currents.     

Enhanced photobiological H2 production by the addition of carbon monoxide and hydrogen cyanide in two unicellular N2-fixing cyanobacterial strains isolated from Korean coasts

Photobiological H₂ from marine cyanobacterial strains is widely accepted to be an ideal clean and renewable energy source. Using the two Korean N₂-fixing unicellular cyanobacterial strains (Cyanothece sp. KNU CB MAL-031 and Cyanothece sp. KNU CB MAL-058) and the Synechococcus sp. Miami strain BG043511 we performed flask-scale experiments to measure the effect of CO and HCN addition on photobiological H₂ production. For the test, 1, 5, 10 and 30% v/v of CO in the N₂ atmosphere was applied. Enhancement of H₂ production was remarkable at 1–5% concentration range of CO addition. At CO concentrations over 5% no further cost-effective enhancement of H₂ production was detectable, which suggests to us that 1–5% CO addition should be adopted for practical photobiological H₂ production by the cyanobacterial strains. Maximum enhancement of the photobiological H₂ production by CO additions was 2–6 times over the control flasks without CO. When 3 ppm of HCN was injected into the cell suspension of BG043511, the enhancement of hydrogen production was 50–60% of that under 5% CO. Present result implies the possible recycling of waste CO and HCN for the enhancement of the photobiological H₂ production using marine cyanobacterial strains.     

Development and application of a novel miniature in situ microprofiler (NAFRI BelpI)

We have developed a novel miniature in situ microprofiler (NAFRI BelpI) for coastal and deep-sea studies. The BelpI can carry up to three oxygen microsensors, and it allows for simultaneous replicate measurements in a relatively small area. All functions can be controlled and programmed via a small magnetic bar and three reed switches; this feature facilitates the initial setup both onboard and underwater. The large LCD window shows basic information such as the movement intervals of the linear stage, number of replicate measurements, waiting time between measurements, and the pA from the microsensors. From high-resolution vertical profiles of oxygen in coastal sediment measured using the microsensors, the diffusivity boundary layer thicknesses was determined to be in the range 0.30–0.35 mm. In addition, the time-series measurement of oxygen profiles in permeable sandy sediment showed advective transport of oxygen into pore water by tidal agitation. Two examples of in situ measurement using a BelpI suggest that it can be widely applied to the study of the sediment-water interface.     

New polymorphic microsatellite markers derived from hemocyte cDNA library of Manila clam <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis> challenged by the protozoan parasite <Emphasis Type="Italic">Perkinsus olseni</Emphasis>

Manila clam Ruditapes philippinarum is one of the most important benthic animals in the coastal north Pacific region, where clam populations have been mixed genetically through trade and aquaculture activities. Accordingly, identification of the genetically different clam populations has become one of the most important issues to manage interbreeding of the local and introduced clam populations. To identify genetically different populations of clam populations, we developed 11 expressed sequence tag (EST)-microsatellite loci (i.e., simple sequence repeat, SSR) from 1,128 clam hemocyte cDNA clones challenged by the protozoan parasite Perkinsus olseni. Genotype analysis using the markers developed in this study demonstrated that clams from a tidal flat on the west coast contained 6 to 19 alleles per locus, and a population from Jeju Island had 4 to 20 alleles per locus. The expected heterozygosity of the 2 clam populations ranged from 0.472 to 0.919 for clams from the west coast, and 0.494 to 0.919 for clams from Jeju Island, respectively. Among the 11 loci discovered in this study, 7 loci significantly deviated from the Hardy-Weinberg equilibrium after Bonferroni correction. The 5 loci developed in this study also successfully amplified the SSRs of R. variegatus, a clam species taxonomically very close to R. philippinarum, from Hong Kong and Jeju Island. We believe that the 11 novel polymorphic SSR developed in this study can be utilized successfully in Manila clam genetic diversity analysis, as well as in genetic discrimination of different clam populations.     

First Investigation of Microbial Community Composition in the Bridge (Gadeok Channel) between the Jinhae-Masan Bay and the South Sea of Korea

Microbial community composition varies based on seasonal dynamics (summer: strongly stratified water column; autumn: weakly stratified water column; winter: vertically homogeneous water column) and vertical distributions (surface, middle, and bottom depths) in the Gadeok Channel, which is the primary passage to exchange waters and materials between the Jinhae-Masan Bay and the South Sea waters. The microbial community composition was analyzed from June to December 2016 using 16S rRNA gene sequencing. The community was dominated by the phyla Proteobacteria (45%), Bacteroidetes (18%), Cyanobacteria (15%), Verrucomicrobia (6%), and Actinobacteria (6%). Alphaproteobacteria (29%) was the most abundant microbial class, followed by Flavobacteria (15%) and Gammaproteobacteria (15%) in all samples. The composition of the microbial communities was found to vary vertically and seasonally. The orders Flavobacteriales and Stramenopiles showed opposing seasonal patterns; Flavobacteriales was more abundant in August and December while Stramenopiles showed high abundance in June and October at all depths. The genus Synechococcus reached extremely high abundance (14%) in the June surface water column, but was much less abundant in December water columns. Clustering analysis showed that there was a difference in the microbial community composition pattern between the strongly stratified season and well-mixed season. These results indicate that the seasonal dynamics of physicochemical and hydrologic conditions throughout the water column are important parameters in shaping the microbial community composition in the Gadeok Channel.     

Physiological Responses of Cultured Seaweed Pyropia yezoensis to Phosphorous Limitation in the Nakdong River Estuary,Korea

Ocean Science Journal - Pyropia yezoensis cultured in the estuary of the Nakdong River in Korea is an important fisheries resource for the local economy. Over the past few decades, the...