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Distributional characteristics of Escherichia coli based on seasonal rainfall variations and extension of freshwater pollutant sources by salinity gradients at Ulsan Bay of Korea facing East Sea

동해 울산만에서 계절적 강우변화와 담수기원 오염원이 염분구배 및 유역별 대장균 분포에 미치는 영향

  • Lee, Minji (South Sea Research Institute, Korea Institute of Ocean Science & Technology) ;
  • Baek, Seung Ho (South Sea Research Institute, Korea Institute of Ocean Science & Technology)
  • 이민지 (한국해양과학기술원 남해특성연구센터) ;
  • 백승호 (한국해양과학기술원 남해특성연구센터)
  • Received : 2016.12.19
  • Accepted : 2017.04.07
  • Published : 2017.04.30

Abstract

In order to understand the seasonal and geographical characteristics of environmental factors and distribution of Escherichia coli by salinity gradient due to precipitation, we investigated abiotic and biotic factors during four seasons from February 2013 to November 2015. The study area was divided into three different zones based on salinity gradient and geo-oceanographic characteristics. During the study period, water temperature, salinity, Chlorophyll a, and secchi-depth varied in the range of $8.5-26.1^{\circ}C$, 13.5-34.4 psu, $0.4-74.0{\mu}g\;L^{-1}$, and 0.5-10.0 m, respectively. Salinity was low at Zone I, which was influenced by water flux from Tae-hwa River, especially in 2014. Salinity was gradually increased (one-way ANOVA; p < 0.05) toward Zone III located offshore of the bay. The highest colony form of E. coli was detected at Zone I. E. coli maintained a relatively low level at Zone III during all seasons. E. coli was correlated with transparency (r = -0.36; p < 0.05) and salinity (r = -0.53; p < 0.01), implying that those parameters might play important roles in the proliferation of E. coli. These results indicated that E. coli were strongly affected by frequent rain (< 50 mm) around inner stations in Ulsan Bay of Korea.

울산만에서 강우에 의한 염분구배 및 환경요인이 분변계 대장균의 계절적, 지역적 분포에 미치는 영향을 파악하기 위해, 2013년 2월부터 2015년 11월까지 계절 조사를 총 12회 수행하였다. 아울러 울산만 내측과 외측의 염분구배 및 지리학적 특성을 기반으로 13개 정점을 3개의 구역(I, II, III)으로 나누어 평가하였다. 조사기간 중 수온과 염분은 각각 $8.5-26.1^{\circ}C$와 13.5-34.4 psu의 범위, 엽록소-a는 $0.4-74.0{\mu}g\;L^{-1}$, 투명도는 0.5-10.0 m로 변화하였다. 특히 염분농도는 2014년 춘계, 하계, 추계 울산만 내측의 구역 I에서 낮은 농도로 관찰되었고, 만 외측의 구역 III으로 갈수록 증가하였다 (one-way ANOVA, p < 0.05). 아울러, 해역의 염분구배는 대장균의 분포에도 영향을 미쳤고, 특히 태화강의 영향을 강하게 받는 구역 I에서 가장 높게 관찰되었고, 다음으로 구역 II, 구역 III순으로 나타났다. 대장균 개체수는 투명도(r = -0.36; p < 0.05)와 더불어 염분과 음의 상관성(r = -0.53; p < 0.01)이 확인되었고, 이는 육상기원의 대장균이 해역으로 유입될 경우 염분이 낮은 환경에서 보다 유리하게 증식한다는 것을 의미한다. 결과적으로 울산만 내만에서는 잦은 집중강우(< 50 mm)로 인한 육상기원 오염원이 하천 및 태화강으로 유입되어 울산만 최내측인 구역 I에서 현저하게 영향을 미쳤고, 염분구배에 따라서 대장균 개체수도 희석되어 만 외측으로 향할수록 낮게 나타나는 것을 파악하였다.

Keywords

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