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Ecological Characteristics of Diatom Communities in Reference Streams from South Korea, with Morphological and Molecular Study on Achnanthidium

Ecological Characteristics of Diatom Communities in Reference Streams from South Korea, with Morphological and Molecular Study on Achnanthidium
Other Titles
한강수계 참조하천의 부착돌말군집의 생태학적 특성 및 Achnanthidium의 분류학적 연구
Minzi Miao
Alternative Author(s)
Issue Date
2019. 8
Reference stream surveys aim to establish the concept of a reference state. Selecting reference stream locations within a country is helpful to evaluate the health of stream ecosystem and compare with other streams. Moreover, it can guide the restoration and preservation of aquatic ecosystems. 36 reference streams were studied in the Hangang River Systems, to 1) understand the characteristics of diatom communities and evaluate the health of the aquatic ecosystem using a diatom index, and 2) to examine the morphological, molecular and ecological characteristics of genus Achnanthidium as an indicator of reference streams and clean water. Surveys were conducted in May 2018, and diatom communities and water quality were analyzed, simultaneously. The reference stream comprised 151 taxa with two dominant species, Achnanthidium minutissimum and A. alteragracillimum. A total of 36 sites were divided into three groups (A, B, C) by cluster analysis using the TDI index. Over the sites, grade A had the highest canopy, forest land-use and DO, while the lowest water temperatures. Group B had the highest urban land-use and turbidity. Group C had the lowest canopy whilst highest water temperatures, agricultural land use and conductivity. The dominant species in Group A and B were Achnanthidium while Group C was Encyonema, respectively. Biological assessment on the health of the aquatic system using various diatom indices (Diatom Assemblage Index to organic water pollution (DAIpo), the Trophic Diatom Index (TDI), Achnanthes/ (Achnanthes + Navicula) ratio (AAN), and the motile diatom ratio showed that Group A was significantly higher in TDI and AAN, and Group C had significantly higher motility. Additionally, Group A was the cleanest while Group C was most polluted. Therefore, I found 1) among 36 sites, there are 7 sites (TDI value: 90 ~ 100) can be defined as reference conditions of streams 2) that the genus Achnanthidium was more dominant in less-polluted water than other genus, 3) Achnanthidium species recorded in South Korea reached 18 while 7 species of them were found in this research. To study the morphological, molecular, and ecological characteristics of species within genus Achnanthidium, single Achnanthidium cells were isolated and cultured. Among these strains, two new species in genus Achnanthidium were defined by SEM and phylogenetic investigation of nuclear small subunit (SSU) rRNA and ribulose-1, 5-bisphosphate carboxylase/ oxygenase (rbcL). In addition, A. minutissimum was re-described since it differed slightly from those in previous studies. Morphologically, Achnanthidium ovalis differed from other species in the “A. pyrenaicum complex” in outline, striation pattern, raphe central endings, and “free-standing” areolae at apices. Achnanthidium cavitata differed from other species in the “A. minutissimum complex” in outline, broad axial central area in rapheless valve, and slit liked areolae near the axial central area. Achnanthidium minutissimum has been reported worldwide, but in this study, I found slight differences from those in previous studies. A. minutissimum in this study had more areolae on central area than that in the other descriptions. Achnanthidium ovalis and A. cavitata were defined as new species based on molecular studies. Phylogenetic tree, similarity scores, and genetic distance on achnanthoid strains with outgroups were assessed. The results provided strong evidence to support the recognition of A. ovalis and A. cavitata as two new species.
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