Application of carbon and nitrogen stable isotopes of biofilm as an index to indicate water environment in rivers and streams

다국어 초록 (Multilingual Abstract)

Along with the development of life quality, people pay more attention to monitoring of rivers and streams. Except for measuring water quality, using bioindicators becomes a common method, especially, the benthic diatom. It is easy to collect, and its community can be maintained relatively for a long time in the water. Recently, stable isotope analysis is also widely used for monitoring water changes, which not only can provide a chemical outline of food web structure, but also trace the nutrients sources. However, for monitoring water quality, most of the studies focus on stable isotope ratios of macroinvertebrates, fish, or macrophyte rather than benthic biofilm which includes dominant diatom species. In this study, we test the applicability of stable isotope ratios of benthic biofilm to monitor water quality changes in small and large rivers.
At first, we aim to detect stable isotope ratios of biofilm whether can indicate the changes of water quality compared with traditional approaches (water quality parameters and diatom indices) in small rivers and streams. Dual δ13C and δ15N values showed a stepwise distribution based on land type. δ15N enriched in urban rivers and depleted in non-pollution rivers, and the agricultural rivers mediated. The results suggested δ13C values could be affected by seasonal changes and δ15N can increase following by the nutrients accumulation. CCA analysis result showed δ13C related to diatom indices and δ15N related to water quality characteristics. Dual δ13C and δ15N could be a good indicator to monitor river changes both water quality and species aspects. Then, we test the applicability in large regulated rivers based on the study of small rivers. Comparing small rivers and large rivers, we suggested the main nutrient sources of the large river could be speculated by the land type of small rivers. Additionally, we found the weirs led to δ13C of biofilm changes between upstream and downstream. The result showed stable isotope ratios of biofilm were sensitive to monitor river changes.
As a conclusion, carbon and nitrogen stable isotopes could be a good indicator to monitor river environmental changes. For the small rivers, δ13C and δ15N could be divided by land type, for the large rivers, we could speculate the main nutrients sources of the river based on tributary changes.

목차 (Table of Contents)

• Chapter 1: Introduction and Literature Review 1
• 1.1 River and stream monitoring 1
• 1.1.1 River and stream monitoring 1
• 1.1.2 Importance of river monitoring 2
• 1.1.3 River monitoring using basic factors 3
• 1.1.4 River monitoring using stable isotope analysis 6
• 1.2 Aquatic biofilm and diatom 9
• 1.2.1 Biofilms 9
• 1.3.2 Application of biofilms 11
• 1.3 Summary of statistical analysis 14
• 1.3.1 Variation and correlation analysis 14
• 1.3.2 Similarity Cluster analysis 14
• 1.3.3 Canonical Correlation Analysis (CCA) 14
• 1.4 Purpose of the study 15
• Chapter 2: Methodology 17
• 2.1 Sampling in small rivers and streams 17
• 2.1.1 Study area 17
• 2.1.2 Experimental methods 18
• 2.1.3 Data analysis 19
• 2.2 Sampling in large regulated rivers 20
• 2.2.1 Study area 20
• 2.2.2 Sample treatment 21
• 2.2.3 Data analysis 22
• Chapter 3: Results and Discussion 24
• 3.1 Carbon and nitrogen stable isotope ratios 24
• 3.1.1 Stable isotopes of biofilm in spatial variation 24
• 3.1.2 Stable isotopes of biofilm in temporal variation 30
• 3.2 Comparing with diatom indices 35
• 3.2.1 Selection of diatom indices 35
• 3.2.2 Difference and Correlation with water quality 35
• 3.2.3 Relationship among diatom indices, water quality, and stable isotopes 37
• 3.3 Test the applicability in large regulated rivers 40
• 3.3.1 Stable isotopic distribution of biofilm in large rivers 40
• 3.3.2 Longitudinal changes and weir impact 42
• Chapter 4: Conclusion 44
• REFERENCE 46
• ACKNOWLEDGE 51