Species composition and spatial distribution of euphausiids of the yellow sea and relationships with environmental factors |
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| Authors: | Won Duk Yoon Joon Yong Yang Donghyun Lim Sung Hwan Cho Gyung Soo Park |
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| Institution: | (1) Ocean Research Team, Headquarters for Marine Environment, NFRDI, 408-1 Shirang-ri, Gjang-eup, Gijang-gun, 619-902 Busan, Korea;(2) Marine Harmful Organisms Team, Headquarters for Marire Environment, NFRDI, 408-1 Sirang-ri, Gijang-eup, Gijarg-gun, 619-902 Busan, Korea;(3) Jeju Fisheries Research Institute, NFRDI, 1928 Oe-dong, Jeju, 690-190 Jeju, Korea;(4) West Sea Fisheries Research Institute, NFRDI, 707 Eulwang-dong, 400-420 Jung-gu, Incheon, Korea |
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| Abstract: | We investigated species composition and spatial distribution of the euphausiid community in the Yellow Sea and identified
the relationship with environmental factors (temperature, salinity, chlorophyll a, nitrate, phosphate, and silicate) using
bimonthly data from June, 1997 to April, 1998. The environment varied during the sampling period. In warm seasons, thermocline
was well developed rendering lower temperature and higher salinity and nutrient concentrations in the bottom layer. During
cold seasons the water column was well mixed and no such vertical stratification was noted. Horizontal distribution of temperature,
however, differed slightly between near-coast and offshore areas because of the shallow depth of the Yellow Sea, and between
southern and northern areas because of the intrusion of water masses such as Yellow Sea Warm Current and Changjiang River
Diluted Water. Four euphausiid species were identified:Euphausia pacifica, E. sanzoi, Pseudeuphausia sp. andStylocheron affine. E. sanzoi andS. affine were collected, just one juvenile each, from the southern area in June and December, respectively.Pseudeuphausia sp. were collected in the eastern area all the year round except June.E. pacifica occurred at the whole study area and were the predominant species, representing at least 97.6% of the euphausiid abundance.
Further, the distribution pattern of the species was varied in regards to developmental stages (adult, furcilia, calyptopis,
egg). From spring to fall,E. pacifica adults were abundant in the central area where the Yellow Sea Bottom Cold Water prevailed. Furcilia and calyptopis extended
their distribution into nearly all the study area during the same period. From late fall to winter, adults were found at the
near-coastal area with similar pattern for furcilia and calyptopis. The distribution pattern ofE. pacifica was consistent regarding temperature, salinity, and three nutrients during the sampling period, whereas chlorophyll a showed
a different pattern according to the developmental stages. The nutrients should indirectly affect via chlorophyll a and phytoplankton
concentration. With respect to these results, we presented a scenario about how the environmental factors along with the water
current affect the distribution ofE. pacifica in the Yellow Sea. |
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| Keywords: | Eupahusia pacifica Yellow Sea Seasonal spatial distribution Yellow Sea Bottom Cold Water |
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