The absence of standardized, biology-based assessment criteria for lake ecosystems at the national level underscores the need for developing systematic and integrative phytoplankton-based evaluation tools. Phytoplankton are primary producers that regulate energy flow and nutrient cycling in lake ecosystems, and their rapid responses to environmental changes such as eutrophication, altered hydrodynamics, and seasonal fluctuations make them highly effective biological indicators. Multimetric indices (MMIs) offer a structured and integrative approach for capturing complex community level responses to environmental stressors, thereby enhancing the ecological relevance and management utility of biological assessment tools for lentic systems. This study presents the Lake Phytoplankton Assessment Index (LPAI), developed using long term ecological and water quality data from 90 lakes and reservoirs across South Korea. The LPAI comprises six ecologically meaningful metrics: total cell density (M2), cell density of flagellated algae (M10), cell density of harmful cyanobacteria (M17), cell density of eutrophic Chlorophyta (M18), relative abundance of saprophilous diatoms (M23), and relative abundance of eutraphentic diatoms (M25). Application of the LPAI demonstrated that lake health grades exhibited a broad and near-normal distribution across seasons, while summer assessments showed a marked increase in lower grade (C~E) lakes associated with elevated temperatures and cyanobacterial blooms. Conversely, winter assessments showed improved conditions due to reduced phytoplankton biomass and the dominance of low eutrophic diatom assemblages. Correlation analyses confirmed that the selected metrics captured distinct ecological gradients, particularly nutrient enrichment and organic matter driven turbidity, while PCA results indicated that the LPAI performed consistently across lake types without structural bias. Overall, the LPAI reliably reflects trophic conditions, harmful algal risks, and structural changes in phytoplankton communities, offering a scientifically grounded and management-relevant tool for evaluating the ecological health of Korean lakes and reservoirs.

Abstract
서 론
재료 및 방 법
    1. 조사 지점
    2. 데이터 수집
    3. 지수 산정 및 검증
결과 및 고 찰
    1. 메트릭 선정 및 구성
    2. 식물플랑크톤 지수 메트릭 검증
    3. 식물플랑크톤 평가지수 (LPAI)를 활용한호소 건강성 평가
적 요
REFERENCES

• 심연보(건국대학교 환경보건과학과) | Youn-Bo Sim (Department of Environmental Health Science, Konkuk University, Seoul 05029, Republic of Korea)
• 황순진(건국대학교 환경보건과학과, 건국대학교 휴먼앤에코케어센터) | Soon-Jin Hwang (Department of Environmental Health Science, Konkuk University, Seoul 05029, Republic of Korea, Human and Eco Care Center, Konkuk University, Seoul 05029, Republic of Korea) Corresponding author
• 김난영(건국대학교 휴먼앤에코케어센터) | Nan-Young Kim (Human and Eco Care Center, Konkuk University, Seoul 05029, Republic of Korea)
• 문정숙(국립환경과학원 물환경연구부 수자원연구과) | Jeongsuk Moon (Water Resources Research Division, Water Environmental Research Department, National Institute of Environmental Research, Incheon 22689, Republic of Korea)
• 장민호(공주대학교 생물교육과) | Min-Ho Jang (Department of Biology Education, Kongju National University, Gongju 32588, Repubic of Korea)