The aim of this study was to collect crucial data for the improvement of water quality and ecosystem conservation by analyzing water samples, sediments, benthic macroinvertebrates, and fish in the Seosan reservoir. The average values of water quality parameters from 2001 to 2016 were a chemical oxygen demand of 10 mg/L, total nitrogen of 1.22 mg/L, and total phosphorus of 0.074 mg/L. Cadmium was detected in the range of 0.531–0.748 mg/kg in the reservoir sediment. Fish belonging to 6 families and 9 species were identified in the reservoir. The dominant species were Carassius auratus and Micropterus salmoides. Benthic macroinvertebrates belonging to 22 families and 28 species were identified. The ecological score of the benthic macroinvertebrate community was 15 inside the reservoir (St. 2). Micropterus salmoides, an invasive alien species, was determined to be the subdominant fish species based on the number of captures, and the presence of the invasive species, Sicyos angulatus L. and Paspalum distichum L. was confirmed among the land flora.

Abstract
 1. Introduction
 2. Materials and Methods
  2.1. Target area of investigation
  2.2. Analytical methods
 3. Results and Discussion
  3.1. Water quality
  3.2. Sediment
  3.3. Benthic macroinvertebrates
  3.4. Fish distribution
  3.5. Other major ecological groups of animals andplants
 4. Conclusion
 REFERENCES

• Dohun Lim(Konkuk University, Department of Civil and Environmental Engineering)
• Yoonjin Lee(Konyang University, College of General Education) Corresponding author