Short-term variation of zooplankton community in the southwestern East Sea coupling with physical processes

Abstract

Community structure and abundance of zooplankton were investigated in thesouthwestern East Sea in November and December 2015. Zooplankton samples werecollected by vertical tow (NORPAC net with 200 um mesh size) from 200 μm to thesurface. Temperature ranged from 13.2ºC to 14.3ºC (November) and 7.7ºC to 11.3ºC (December) in the study area with no vertical change in temperature from surfaceto 200m. Salinity ranged from 32.7 ± 0.3 psu (surface) to 34.1 ± 0.2 psu (200m) inNovember and 33.5 ± 0.8 psu (surface) to 34.0 ± 0.1 psu (200m) in December.Zooplankton abundance ranged from 396 ind./m3 to 565 ind./m3 (average biomass =19.69 ± 6.98 dry mg/m3) in November and 114 ind./m3 to 147 ind./m3 (averagebiomass = 9.14 ± 4.43 dry mg/m3) in December, respectively. Zooplanktoncommunity was dominated by copepods which comprised 80% (November) and 77%(December) of total zooplankton abundance. The next dominant groups wereappendicularians (9%), other crustaceans (4%) and chaetognaths (3%) in November,and copepodite (14%) and appendicularians (3%) in December. The averageabundance of zooplankton in November was 3.6 times higher than that of December.There were differences in zooplankton composition (except for copepods) inNovember and December. These differences could be associated with the physicalcharacteristic of water masses which affects zooplankton community and abundance.ace. Temperature ranged from 13.2ºC to 14.3ºC (November) and 7.7ºC to 11.3ºC (December) in the study area with no vertical change in temperature from surfaceto 200m. Salinity ranged from 32.7 ± 0.3 psu (surface) to 34.1 ± 0.2 psu (200m) inNovember and 33.5 ± 0.8 psu (surface) to 34.0 ± 0.1 psu (200m) in December.Zooplankton abundance ranged from 396 ind./m3 to 565 ind./m3 (average biomass =19.69 ± 6.98 dry mg/m3) in November and 114 ind./m3 to 147 ind./m3 (averagebiomass = 9.14 ± 4.43 dry mg/m3) in December, respectively. Zooplanktoncommunity was dominated by copepods which comprised 80% (November) and 77%(December) of total zooplankton abundance. The next dominant groups wereappendicularians (9%), other crustaceans (4%) and chaetognaths (3%) in November,and copepodite (14%) and appendicularians (3%) in December. The averageabundance of zooplankton in November was 3.6 times higher than that of December.There were differences in zooplankton composition (except for copepods) inNovember and December. These differences could be associated with the physicalcharacteristic of water masses which affects zooplankton community and abundance.