Relationship between Environmental Factors and Macrobenthos Assemblages in Geum Estuary Tidal-flat

금강하구 갯벌 내 환경요인과 저서성무척추동물 군집 분포의 상관관계

Abstract

The Seocheon and Yubu Island mudflats in Geum Estuary are important stopover sites for migratory birds as energy supplementation area in the East Asia-Australasian Flyway. Benthic invertebrates in the tidal flats are important food resources for the migratory birds. In other words, benthic invertebrates in the tidal flats play an important ecological role in energy flow. This study was conducted to investigate the relationship between benthic invertebrate assemblages and environmental factors in Seocheon and Yubudo tidal flats in the Geum Estuary. As a result of the benthic invertebrate assemblage during the fall migration season, the total species number was 147, density and biomass were $1,772{\pm}1,342individuals/m^2$ and $445.1{\pm}807.6g/m^2$, respectively. Based on the appearance species and the density data, the result of analysis of mutual similarity among sampling sites was divided into two groups. Group A was the Macrophthalmus-Heteromastus community and Group B was the Spio-Urothoe-Mandibulophoxus community. Group B showed higher mean species number, density and biomass than Group A. The BIO-ENV analysis showed that the benthic invertebrate assemblages were most affected by the combination of sand content % and sediment sorting (${\rho}=0.500$). The variables of significant relationship with species number and biomass were sediment sorting (p=0.015) and the pore water DO(Dissolved Oxygen, p=0.003) in sediment, respectively.

금강하구 서천 및 유부도 갯벌은 동아시아-대양주 철새의 이동경로상 에너지 보충을 위한 중요한 중간 기착지점으로, 갯벌의 저서성무척추동물은 이들의 중요한 먹이원이 된다. 즉, 갯벌의 저서성무척추동물은 에너지 흐름의 중요한 생태적 역할을 담당한다. 금강하구 서천 및 유부도 갯벌의 저서성무척추동물 군집 분포와 환경요인 관계를 파악하기 위해 본 연구가 수행되었다. 가을철 이주 기간에 실시한 저서성무척추동물의 군집 분포 조사 결과, 저서성무척추동물은 총 147종, 밀도와 생체량은 각각 $1,772{\pm}1,342$ 개체/$m^2$, $445.1{\pm}807.6g/m^2$으로 나타났다. 출현종과 서식밀도 자료를 기반으로 각 정점 간 상호 유사도 분석결과, 크게 2개의 군집으로 구분되었다. A 군집은 칠게-고리버들갯지렁이 군집(Macrophthalmus-Heteromastus community)이었고, B군집은 달걀얼굴갯지렁이류-단각류 군집(Spio-Urothoe-Mandibulophoxus community)이었다. B 군집이 A 군집에 비하여 평균 출현종수, 서식밀도, 생체량 등이 월등히 높았다. BIO-ENV 분석 결과, 저서성무척추동물 군집은 퇴적환경 변수인 모래함량과 분급도 조합에 의한 영향을 가장 크게 받는 것(${\rho}=0.500$)으로 나타났다. 종수와 가장 큰 상관성을 보이는 환경변수는 분급도(p=0.015)로 나타났고, 생체량과 가장 높은 상관관계를 보이는 환경변수는 공극수 DO(p=0.003)였다.

Fig. 1. The survey areas of tidal flat benthic invertebrate community in Geum Estuary, Korea (Seocheon: 1. Dodun-ri, 2. Seondo-ri, 3. Dasa-ri, 4. Songlim-ri / Yubu Island: 5. West side, 6. East side)

Fig. 2. The number of species, abundance and biomass of major benthic invertebrate taxa in Geum Estuary tidal flats.

Fig. 3. The spatial variations of benthic invertebrate community parameters in Geum Estuary tidal flats.

Fig. 4. Dendrogram of hierarchical clustering (upper) and 2-dimensional MDS configuration (lower) using group average linkage by Bray-Curtis similarities calculated on the log(X+1) tranformed abundance data in Geum Estuary tidal flats.

Fig. 5. Geographical distribution of benthic invertebrate communities in Geum Estuary tidal flats.

Table 1. Distribution of surface sediment textural parameters, organic matter contents and pore water characteristics along each surveyareas in Geum Estuary tidal flats (average and standard deviation).

Table 2. Selection of environmental factors related with spatial variation of benthic invertebrate community parameters in Geum Estuary tidal flats.

Table 2. Continued

Table 3. The estimation results and summary of regression models explaining spatial variation of benthic invertebrate community parameters in Geum Estuary tidal flats.

Table 4. Single and combinations of environment variables showing high correlation with distribution of invertebrate communities in Geum Estuary tidal flats.

Table 5. Biological/environmental properties (average and standard deviation) and characteristic species of the two major communities suggested from the cluster analysis