Woong-Seo Kim

Spring dominant copepods and their distribution pattern in the yellow sea

We investigated the relationship between mesoscale spatial distribution of environmental parameters (temperature, salinity, and sigma-t), chlorophyll-a concentration and mesozooplankton in the Yellow Sea during May 1996, 1997, and 1998, with special reference to Yellow Sea Bottom Cold Water (YSBCW). Adult calanoid copepods,Calanus sinicus, Paracalanus parvus s.l.,Acartia omorii, andCentropages abdominalis were isolated by BVSTEP analysis based on the consistent explainable percentage (-32.3%) of the total mesozooplankton distributional pattern. The copepods, which accounted for 60 to 87% of the total abundances, occupied 73-78% of the copepod community. The YSBCW consistently remained in the northern part of the study area and influenced the spatial distribution of the calanoid copepods during the study periods. Abundances of C.sinicus andP. parvus s.l., which were high outside the YSBCW, were positively correlated with the whole water average temperature (p<0.01). In contrast, the abundances of C.abdominalis andA. omorii, which were relatively high in the YSBCW, were associated with the integrated chl-a concentration based on factor analysis. These results indicate that the YSBCW influenced the mesoscale spatial heterogeneity of average temperature and integrated chl-a concentration through the water column. This consequently affected the spatial distribution pattern of the dominant copepods in association with their respective preferences for environmental and biological parameters in the Yellow Sea during spring.

Responses of Benthic Animals in Spatial Distribution to the Sedimentary Environments on the Deep-sea Floor, the Clarion-Clipperton Fracture Zone, Northeastern Pacific Ocean

Relationships between sedimentary environments and abundance of benthic animals were examined on the deep-sea floor, the Clarion-Clipperton Fracture Zone, in the northeast equatorial Pacific Ocean. Specimens were collected using a box corer at 8 stations by sieving through 0.3 mm mesh screen. Sediments showed finer grain size ranged from 5.63 to , 83.1% of mean porosity, 1.81 kPa of mean shear strength and organic carbon content in sediment ranged from 0.97 to . Manganese nodules covered on the bottom layer from 4 to 57% of coverages. A total of 26 faunal groups in 6 phyla was sampled and comprised 1,467 individuals. Mean biomass were calibrated to 0.5 gWWt/. Small-sized animals including foraminiferans and nematods were dominated among the faunal group which comprised 49.1% (892 ind.) and 11.5% (320 ind.), respectively. In SPI-analysis, vertical bio-disturbance marks were not observed except to Beggiatoa-type bacterial mats. As the results of relationship between environments and benthos, abundance of benthic animals, especially nematode, showed only a negative correlation to the coverage of nodules, and any other sedimentary factors analyzed in this study were rarely affected to the spatial distribution of benthic animals.

Diel vertical migration of the copepod Calanus sinicus before and during formation of the Yellow Sea Cold Bottom Water in the Yellow Sea

To understand the effects of the Yellow Sea Cold Bottom Water (YSCBW) on the diel vertical migration (DVM) of the copepod Calanus sinicus, we surveyed vertical distribution of C. sinicus at a fixed station in the Yellow Sea before (spring) and during (summer) formation of the YSCBW. Cold water (<10°C) was observed in the bottom layer when the water column was thermally stratified in summer, but the water column was thermally well-mixed in spring 2010. Samples were collected from five different layers at 3-h intervals using an opening-closing net. Adult females (1–155 ind./m3) showed a clear normal DVM pattern throughout the entire water column in spring, whereas adult males did not migrate. DVM of copepodite V (CV) individuals was not clear, but the maximum abundance of CI-CIV occurred consistently in the upper 10–20 m layer, where there was a high concentration of chlorophyll-a (Chl-a) (0.49–1.19 µg/L). In summer, weak DVM was limited to cold waters beneath the thermocline for adult females (<30 ind./m3), but not for adult males. The maximum abundance of CI-CIV also occurred consistently in the subsurface layer (20–40 m) together with high concentrations of Chl-a (0.81–2.36 µg/L). CV individuals (1–272 ind./m3) moved slightly upward nocturnally to the near-surface layer (10–20 m), where the average temperature was 25.74°C, but they were not found in the surface layer (0–10m; 28.31°C). These results indicate that the existence of the YSBCW affected food availability at depth and the vertical temperature distribution, leading to variation in the amplitude and shape of stage-specific vertical distributions (CI to adults) in C. sinicus before and during the formation of cold waters in the Yellow Sea during the study period.

Regional Comparisons of Heterotrophic Protists Grazing Impacts and Community in Northwest Pacific Ocean

Community structure of heterotrophic protists and their grazing impact on phytoplankton were studied in Northwest Pacific Ocean during October, 2007. The study area was divided into four regions based on physical properties (temperature and salinity) and chlorophyll-α distribution. They were Region Ⅰ of North Equatorial Currents, Region Ⅱ of Kuroshio waters, Region Ⅲ of shelf mixed water, and Region Ⅳ of Tsushima warm current from East China Sea. The distribution of chlorophyll-α concentrations and community structure of heterotrophic protists were significantly affected by physical properties of the water column. The lowest concentration of chlorophyll-a was identified in Region Ⅰ and Ⅱ, where pico-sized chlorophyll-α was most dominant (>80% of total chlorophyll-a). Biomass of heterotrophic protists was also low in Region I and Ⅱ. However, Region Ⅲ was characterized by low salinity and temperature and high chlorophyll-α concentration, with relatively lower pico-sized chlorophyll-α dominance. The Highest biomass of heterotrophic protists appeared in Region Ⅲ, along with the relatively less important nanoprotists. In Region Ⅰ, Ⅱ and Ⅳ, heterotrophic dinoflagellates were dominant among the protists, while ciliates were dominant in Region Ⅲ. Community structure varied with physical (salinity and temperature) and biological (chlorophyll-α) properties. Biomass of heterotrophic protists correlated well with chlorophyll-α concentration in the study area (r²=0.66, p<0.0001). The potential effect of grazing activity on phytoplankton is relatively high in Region Ⅰ and Ⅱ. Our result suggest that biomass and size structure of heterotrophic protists might be significantly influenced by phytoplankton size and concentration.

Latitudinal Differences in the Distribution of Mesozooplankton in the Northeastern Equatorial Pacific

To investigate latitudinal variations in the zooplankton community along the meridian line (5 o N- 12 o N, 131.5 o W), we measured temperature, salinity, nitrate, chlorophyll- a and zooplankton at depths above 200 m from July 10 th to 25 th , 2003. For comparative analysis, data of the physico-chemical properties and chl-a were matched to the two sampling depths (surface mixed layer and thermocline depth-200 m) of zooplankton. Latitudinal differences in the mesozooplankton distribution were mainly influenced by diver- gence formed at a boundary line formed by currents of opposing directions, consisting of North Equatorial Current (NEC) and North Equatorial Counter Current (NECC). High concentrations of chl- a south of 9 o N, caused by equatorial upwelling related nutrients, is thought to be affected by the role of this divergence bar- rier, supported by relatively low concentrations in waters north of 9 o N. The latitudinal differences of the chl-a were significantly associated with the major groups of zooplankton, namely calanoid and cyclopoid copepods, appendicularians, ostracods, chaetognaths, invertebrate larvae, and others. And temperature sig- nificantly affected the latitudinal variation of radi olarians, siphonophores, salps and immature copepods. The latitudinal differences in the two factors, temperature and chl- a, which explained 71.0% of the total zooplankton variation, were characterized by the eq uatorial upwelling as well as the divergence at 9 o N. The physical characteristics also aff ected the community structure and abundance of zooplankton as well as average ratios of cyclopoid versus calanoid copepods. The abundance of dominant copepods, which were consistent with chl-a, were often associated with the carnivorous zooplankton chaetognaths, implying the relative importance of bottom-up regulation from phy sical properties to predatory zooplankton during the study period. These results suggested that latitudinal distribution of zooplankton is primarily controlled by current-related divergences, while biological processe s are of secondary importance in the northeastern Equatorial Pacific during the study period in question.

A new species of the dentipes-subgroup of Triconia and a redescription of T. giesbrechti and T. elongata (Copepoda: Cyclopoida: Oncaeidae) from the tropical Pacific and the Korea Strait

A new species of Triconia in the family Oncaeidae, Triconia pacifica sp. nov., and a new form variant each of Triconia giesbrechti Böttger-Schnack and Triconia elongata Böttger-Schnack are described from two sites in the Pacific. Triconia pacifica can be distinguished from its sibling Triconia dentipes (Giesbrecht) by (1) morphometric characters, including the proportional lengths of distal endopod spines of swimming leg 4, and the relative length of the outer basal seta on P5, and by (2) a number of micro-structures on the appendages. The Pacific specimens of T. elongata and T. giesbrechti resemble the typical forms in morphometric characters, with some minor differences in proportional spine lengths on the swimming legs, and differ in a few micro-structures. The hitherto unknown male of T. giesbrechti is newly described. For all species/forms described, the intraspecific variability of proportional spine lengths on the endopods of P2–P4 is examined and discussed. http://www.zoobank.org/urn:lsid:zoobank.org:pub:6B41B0E2-0A5C-458B-8F9C-25000F208E24

The diel vertical migration of the sound-scattering layer in the Yellow Sea Bottom Cold Water of the southeastern Yellow sea: focus on its relationship with a temperature structure

Using the hydroacoustic method with a 200 kHz scientific echo sounding system, the diel vertical migration (DVM) of the sound-scattering layer (SSL) in the Yellow Sea Bottom Cold Water (YSBCW) of the southeastern Yellow Sea was studied in April (spring) and August (summer) of 2010 and 2011. For each survey, 13–27 hours of acoustic data were continuously collected at a stationary station. The acoustic volume scattering strength (Sv) data were analyzed with temperature profile data. In the spring of both 2010 and 2011, the SSL clearly showed the vertical migration throughout the entire water column, moving from the surface layer at night to near the bottom during the day. Conductivity, temperature, and depth data indicated that the entire water column was well mixed with low temperature of about 8°C. However, the SSL showed different patterns in the summers of 2010 and 2011. In the summer of 2010 (≈28°C at the surface), the SSL migrated to near the bottom during the day, but there were two SSLs above and below the thermocline at depth of 10–30 m at night. In the summer of 2011 (≈20°C at the surface), the SSL extended throughout the entire water column at night, possibly owing to an abrupt change in sea weather conditions caused by the passage of a Typhoon Muifa over the study area. It was concluded that the DVM patterns in summer in the YSBCW area may be greatly influenced by a strengthened or weakened thermocline.

A new species of the genus Goniopsyllus Brady (Copepoda, Harpacticoida, Clytemnestridae) from Korean waters

Abstract A new species, Goniopsyllus dokdoensis, is described from the adjacent waters of Dokdo Island in the East Sea of Korea. The new species is closely related to G. clausi in the triangular shape of the rostrum, the length of the thoracopod 5 exopod, and the constricted genital double somite. However G. dokdoensis is distinguished from G. clausi by its smaller body size, genital field with additional pores adjacent to the copulatory pore, urosomites without dorsal ornamentation, and differences in the length of caudal setae. Also, the sixth pair of legs in the male has two setae at the outer distal corner of each lobe. This study is the first to report the presence of the genus Goniopsyllus in Korean waters.

Long-term variation of zooplankton around Dokdo in the East Sea

We investigated the abundance and composition of the zooplankton community around Dokdo in the East Sea from 2006 to 2015. Zooplankton samples were collected in the surface mixed layer by vertical hauls using a standard type net at the monitoring stations. There were no clear long-term trends in the average temperature and salinity, but relatively low salinity was recorded in the summer of 2013 and 2015. The average abundances of zooplankton in the summer increased by two orders of magnitude from 317 inds./m in 2008 to 10,242 inds./m in 2015. This long-term increase was accompanied by a slight increase in the chlorophyll-a concentration and a decrease in the catch of potential crucial predators (anchovy, mackerel pike, squid, herring and horse mackerel) in the study area. The dominant zooplankton, accounting for most of the long-term increase, consisted of appendicularian (Oikopleura spp.), which showed a steady increase since 2012, summer species such as Noctiluca scintillans and the cladoceran Penilia avirostris, which showed an abrupt increase, and the copepod Paracalanus parvus s.l., which showed a rapid increase after its first occurrence in summer 2010. These results suggest that the long-term increase of zooplankton could be related to the increase in the concentration of prey and the decrease in the predation pressure of potential predators around Dokdo in the study area.

Deep-sea floor exploration in the East Sea using ROV HEMIRE

HEMIRE is a 6,000-meter-class remotely operated vehicle (ROV) that has been developed for observation and sampling of objects of interest on the deep seabed. We first carried out deep-seabed exploration around the slopes of the Hupo Bank and the Ulleung Basin in the East Sea in June 2015. Over two weeks, a total of 10 dives were made from a support ship, the R/V Onnuri, at eight stations with water depth ranging between 194 and 2,080 m. The dive times ranged from 1 to 6 hours, depending on the operating conditions. We obtained the following results: 1) video images of the deep seafloor; 2) red snow crab density data (a major fishery resource) and inventories of deep-sea fauna, including an unrecorded organism; 3) specific topographies such as canyons slopes; 4) an undisturbed sediment core obtained using a push corer; and 5) observations of the seabed surface covered with discarded anthropogenic waste material.