낙동강 보 구간 자연형수로의 생태적 기능 평가 : 저서성 대형무척추동물 군집 분석 = Evaluating the Ecological Functions of Nature-like Channels in the Weir Reaches of the Nakdong River: Benthic Macroinvertebrate Community Analysis

다국어 초록 (Multilingual Abstract)

This study was conducted to elucidate the impacts of hydromorphological habitat modifications, caused by the continuous construction of large multi-purpose weirs in the mainstem of the Nakdong River, on benthic macroinvertebrate community structures, and to quantitatively evaluate the ecological refuge function of nature-like channels constructed to bypass the mainstem. To this end, spatiotemporal monitoring of physicochemical water quality, streambed substrates, riparian flora, and benthic macroinvertebrate communities was carried out from 2019 to 2022 at 15 sites across impounded reaches, tailwater reaches, and nature-like channels at five weirs in the Nakdong River （Sangju, Nakdan, Gangjeong-Goryeong, Dalseong, and Hapcheon-Changnyeong Weirs）. The Raunkiaer life-form analysis of riparian flora revealed that impounded reaches, which are directly affected by the weir structures, were dominated by hydrophytes and helophytes （HH） at 20.0%, demonstrating a typical impoundment mechanism that accelerates streambed siltation and benthic hypoxia. In contrast, nature-like channels were characterized by a predominance of hemicryptophytes （H） and therophytes （Th） exceeding 80%, forming a dynamic lotic ecotone. Benthic macroinvertebrate community analysis showed that impounded and tailwater reaches in the mainstem experienced extreme velocity reductions （〈 0.02 m/s） and silt deposition. This resulted in biotic homogenization, where pollution-tolerant taxa such as Chironomidae spp. （red type） and Limnodrilus gotoi monopolized over 90% of the total abundance. Furthermore, functional feeding groups （FFGs） and functional habitat groups （FHGs） were overwhelmingly skewed toward gathering-collectors （GC） and burrowers （BU）, while biological health indices （BMI, TESB） predominantly remained at the lowest grade （Grade E）. Conversely, nature-like channels, which maintained an average flow velocity of 0.31 m/s and coarse substrates （cobble and pebble）, exhibited more than twice the species richness of the mainstem and were composed of 27.6% E.P.T. （Ephemeroptera, Plecoptera, Trichoptera） taxa, which are clean-water indicators. Additionally, diverse functional groups such as scrapers （SC） and clingers （CL） coexisted, resulting in a high diversity index （H'）. The habitat of Cybister chinensis, a Class II endangered wildlife species, was also confirmed in these channels. Notably, the calculation of resistance （Rt） and resilience （Rs） indices against exogenous disturbances, such as summer floods and weir discharges, revealed that communities in nature-like channels converged to 1.0 for both indices. This proves their stable community maintenance during disturbances and complete recovery capability afterward. In contrast, impounded and tailwater reaches exhibited extreme vulnerability, characterized by community collapse or delayed recovery during and following disturbances. Multivariate ordination using Non-metric Multidimensional Scaling （NMDS） and Canonical Correspondence Analysis （CCA） statistically verified that the primary driving factor determining the community structures across the three aquatic habitats was not simple physicochemical water quality. Rather, it was an ecohydraulic gradient contrasting a 'velocity-dissolved oxygen-coarse substrate' axis against a 'silt deposition-nutrients-turbidity' axis. In conclusion, nature-like channels within large, multi-weir river sections fulfill a critical ecological refuge role by compensating for the disrupted continuity of lotic ecosystems and supporting sensitive taxa. For future river biodiversity conservation, the management paradigm must shift from traditional water-purification-centric approaches to physical habitat restoration. This should incorporate the restoration of hydraulic dynamism through flexible weir operations and the securement of continuous environmental flows in nature-like channels.

목차 (Table of Contents)

• Ⅰ. 서론 1
• Ⅱ. 연구배경 및 방법 6
• 2.1. 연구배경 6
• 2.1.1. 지리 및 수문학적 특성 6
• 2.1.2. 4대강 살리기 사업으로 인한 물리적 환경 변화 6
• 2.1.3. 물리적 변화에 따른 생태계 영향 7
• 2.2. 연구대상지 선정 7
• 2.2.1. 조사 기간 7
• 2.2.2. 조사 지점 8
• 2.3. 연구 방법 13
• 2.3.1. 수변 경관 조사 방법 13
• 2.3.2. 환경 요인 측정 및 분석 15
• 2.3.3. 저서성 대형무척추동물의 채집 및 동정 15
• 2.3.4. 데이터 전처리 및 군집 지수 환산 17
• 2.3.5. 저서성 대형무척추동물 군집 분석 17
• 2.3.6. 군집의 저항성 및 회복성 평가 23
• 2.3.7. 통계 분석 24
• Ⅲ. 결과 26
• 3.1. 수변환경 현황 및 이화학적 요인 특성 26
• 3.1.1. 정체수역 수변 경관 및 식물상 26
• 3.1.2. 정체수역 수질 측정 및 분석 31
• 3.1.3. 방류수역 수변 경관 및 식물상 34
• 3.1.4. 방류수역 수질 측정 및 분석 39
• 3.1.5. 자연형수로 수변경관 및 식물상 42
• 3.1.6. 자연형수로 수질 측정 및 분석 47
• 3.1.7. 서식처 유형별 수변 및 수생식물의 생활형 분석 50
• 3.2. 저서성 대형무척추동물 군집 구조 및 생물학적 건강성 평가 52
• 3.2.1. 정체수역의 군집 특성 52
• 3.2.2 방류수역의 군집 특성 64
• 3.2.3 자연형수로의 군집 특성 76
• 3.3. 서식처 유형별 섭식 및 서식 기능군(FFGs, FHGs) 특성 비교 88
• 3.3.1. 섭식기능군(Functional feeding groups, FFGs)의 공간적 분포 88
• 3.3.2. 서식기능군(Functional habit groups, FHGs)의 적응 양상 88
• 3.4. 서식처별 군집의 저항성 및 회복성 평가 91
• 3.5. 통계 분석 92
• 3.5.1. 서식처 및 계절에 따른 이화학적 환경과 생물 지수의 변동 특성 92
• 3.5.2. 저서성 대형무척추동물 군집 구조의 다변량 서열화 및 유사도 분석 96
• 3.5.3. 환경 변수와 군집 지수 간의 상관성 및 정준대응분석(CCA) 99
• Ⅳ. 고찰 103
• 4.1. 수변환경 현황 및 이화학적 요인 특성 103
• 4.2. 수리적 파편화가 식물 생활형 분포에 미치는 영향 105
• 4.3. 저서성 대형무척추동물 군집 구조 및 생물학적 건강성 평가 105
• 4.4. 저서성 대형무척추동물 군집의 저항성 및 회복성 110
• 4.5. 통계 분석 110
• 4.6. 연구의 한계점 및 향후 과제 112
• Ⅴ. 종합 결론 114
• Ⅵ. 참고문헌 116
• Abstracts 169