Physical condition evaluation method for cascade development river ecosystem based on zooplankton biological integrity index

Abstract

The invention provides a cascade development river ecosystem health condition evaluation method based on a zooplankton biological integrity index, and belongs to the field of river ecosystem protection. The invention provides a method for evaluating the health condition of an existing cascade development river ecosystem and the limitation and deficiency of long-term tracking monitoring evaluation of the existing cascade development river ecosystem health condition evaluation method. Sampling survey method based on zooplankton biological integrity, zooplankton biological integrity index evaluation basic index system, zooplankton biological integrity index evaluation selection index system construction and zooplankton biological integrity index (Z-IBI)-based zooplankton biological integrity index (Z-IBI) Through the four parts of the cascade development river ecosystem health condition evaluation criterion system, a clear, complete, detailed and quantifiable evaluation criterion system is provided for cascade development of river water ecosystem health condition change and river ecosystem long-term tracking, monitoring and evaluation. Therefore, a scientific, simple, easy and economical evaluation method is provided for optimizing a river cascade development scheme and carrying out river ecosystem health condition evaluation and fixed-point long-term tracking monitoring.

Description

Technical Field

[0001] The present invention provides a method for evaluating the health status of a cascade - developed river ecosystem based on the zooplankton index of biological integrity, belonging to the technical field of river ecosystem protection and evaluation. Background Art

[0002] (1) Definition and Connotation of Zooplankton Index of Biological Integrity

[0003] Zooplankton, as an important part of the aquatic ecosystem and an important intermediate link in the food chain, takes phytoplankton, bacteria, and detritus as food sources, and is also the direct or indirect bait for many fish and aquatic organisms. The freshwater zooplankton community includes four major groups: Protozoa, Rotifera, Cladocera, and Copepoda. Its community composition, structure, and quantity characteristics are sensitive to changes in the aquatic ecosystem. The increase in reservoir water temperature, the extension of hydraulic retention time, and the enrichment of nutrients brought about by the cascade development of rivers can cause a large - scale reproduction of zooplankton and lead to water eutrophication. Therefore, the zooplankton community can be used as an indicator biological group for the changes in the cascade - developed river ecosystem and water eutrophication.

[0004] The index of biological integrity is widely used in the evaluation of the health status of aquatic ecosystems in the United States, the European Union, etc. Commonly used indicator biological groups include fish, plankton, benthic animals, and attached organisms, etc. Since zooplankton has a short life cycle and is sensitive to changes in the aquatic ecosystem, it is of great significance to construct a zooplankton index of biological integrity (Z - IBI) applicable to different research areas. In addition, due to the influence of the climate, river hydrology, and aquatic biota in the research area, the construction and selection of the specific index system of this index need to be continuously improved and perfected to be applicable to different rivers and research areas.

[0005] (2) Research Status of the Evaluation System of Zooplankton Index of Biological Integrity

[0006] In 2023, the Ministry of Ecology and Environment issued the Technical Guidelines for Aquatic Ecology Monitoring - Biological Monitoring and Assessment of Lakes and Reservoirs (Trial) (HJ 1296-2023), recommending the use of zooplankton to establish a biological integrity index and conduct aquatic ecological status monitoring. In recent years, many domestic related studies have evaluated the health status of aquatic ecosystems by establishing a biological integrity index of zooplankton. However, tracking of the current research status shows that there are relatively few domestic studies on evaluating the health of cascade - developed river ecosystems using the biological integrity index system of zooplankton, and an evaluation index system of zooplankton integrity based on long - term fixed - point tracking monitoring of cascade - developed rivers has not been established yet. For example:

[0007] 1) Chen Qing, Chai Yihan, Wang Tian'e, etc. carried out an evaluation of the aquatic ecological status of Zhalong Wetland based on zooplankton integrity. A total of 24 candidate biological indicators were selected in the study, and finally 5 indicators were determined to construct the zooplankton integrity index of Zhalong Wetland, and an evaluation standard was established using the ratio method. The monitoring time of the zooplankton integrity evaluation index system constructed in the article is relatively short. The 24 candidate zooplankton biological indicators and their distribution status, as well as the finally determined 5 indicators and evaluation standard, are only applicable to plain - type rivers and lakes in Northeast China, and are not applicable to the evaluation of the health status and long - term fixed - point tracking monitoring needs of cascade - developed river ecosystems in Southwest China (China Environmental Monitoring, 2022, 38(5), pp87 - 95);

[0008] 2) Wang Xiaodong, Yuan Hong, Li Shan, etc. carried out a study on the ecological system health evaluation of Wuyang River using the planktonic biological integrity index. 33 parameter indicators of phytoplankton and zooplankton were selected in the study, and factor scoring was used to conduct ecological integrity evaluation. A total of 6 common factors were extracted for planktonic biological integrity evaluation. The parameter indicators and common factors selected in the article lack control points and reference systems, and the monitoring time of the constructed planktonic biological integrity index is relatively short, which is not applicable to the evaluation of the health status and long - term fixed - point tracking monitoring needs of cascade - developed river ecosystems in Southwest China (Journal of Mountain Agriculture and Biology, 2025, 44(1): pp37 - 44);

[0009] 3) Ye Qiqing, Gan Yan, Zhao Xinying, etc. carried out a study on the aquatic ecological health assessment of the Qinhuai River using the biological integrity index. The study was based on the composition characteristics, biodiversity and key factors of periphytic algae, zooplankton, benthic animals and fish, and the aquatic ecological health status of the Qinhuai River was evaluated using the Aquatic Biological Integrity Index of the Yangtze River Basin. The "Evaluation Method for Aquatic Biological Integrity Index of the Yangtze River Basin (Trial)" adopted in the article has 14 mandatory indicators and 16 reference indicators for the biological integrity index evaluation, and among them, the one related to zooplankton is 1 reference indicator of zooplankton diversity. This biological integrity index is a comprehensive index and is not suitable for constructing a biological integrity index based on zooplankton, and this evaluation indicator is a general indicator and is not suitable for the evaluation of the ecological system health status of cascade-developed rivers in Southwest China and the needs of fixed-point long-term tracking monitoring (Acta Scientiae Circumstantiae, 2023, 43(10): pp407-418);

[0010] 4) Bian Rui, Qi Weixiao, Guo Jiaxun, etc. published a method for evaluating the health of a river ecosystem based on the aquatic biological integrity index. This method first judges the water quality situation in the area where the sampling point is located through the measured data of water quality evaluation indicators and the measured data of aquatic evaluation indicators, then determines the reference point and the damaged point, and then calculates the aquatic biological integrity index score of each sampling point based on the indicators of phytoplankton, zooplankton and benthic animals, and divides the aquatic biological integrity level of the sampling point accordingly. This method depends on multiple biological and water quality indicators such as water quality evaluation indicators, phytoplankton and benthic animals, and is more suitable for the evaluation of the health status of urban river ecosystems and is not suitable for the assessment of the ecological system status of cascade-developed rivers in Southwest China (China, CN115630764A).

[0011] 5) Li Yiping, Wang Chuer, Wang Yaning, etc. published an analysis method for the health status of a stratified lake and reservoir aquatic ecosystem. This method includes arranging several stratified sampling lines in the target lake and reservoir during the thermocline period and collecting water samples from each layer, obtaining water quality and ecological evaluation indicators based on the water samples from each layer, dividing each sampling line into a reference point and a damaged point, and calculating the final zooplankton integrity index of each sampling line based on the final evaluation indicators and dividing the zooplankton integrity level. This method is suitable for the health evaluation of stratified lake and reservoir aquatic ecosystems and is not suitable for the evaluation of the ecological system health status of cascade-developed rivers in Southwest China and the needs of fixed-point long-term tracking monitoring (China, CN119338101A);

[0012] In summary, the water volume of rivers in the southwestern region of China is abundant. In recent years, with large-scale cascade development, great changes have taken place in river ecosystems and their habitat conditions. Based on the above background technology, it is urgent to study and establish a guiding and highly operable evaluation method for the health status of cascade-developed river ecosystems based on the biological integrity index of zooplankton to provide support. Thus, a scientific, simple, easy-to-implement, and economical evaluation method can be provided for optimizing river cascade development plans, evaluating the health status of river ecosystems, conducting fixed-point long-term tracking monitoring, and protecting and restoring river ecosystems. Summary of the Invention

[0013] (1) Object of the Invention

[0014] The present invention is created in view of the limitations and deficiencies of the existing evaluation methods for the health status of cascade-developed river ecosystems and their long-term tracking monitoring evaluations. The present invention provides an evaluation method for the health status of cascade-developed river water ecosystems based on the biological integrity index of zooplankton. It includes four parts: a sampling and investigation method based on the biological integrity of zooplankton, a basic index system for evaluating the biological integrity index of zooplankton, the construction of a candidate index system for evaluating the biological integrity index of zooplankton, and an evaluation criterion system for the health status of cascade-developed river ecosystems based on the biological integrity index of zooplankton (Z-IBI). The present invention provides a clear, complete, detailed, and quantifiable evaluation criterion system for the changes in the health status of cascade-developed river water ecosystems in the southwestern region of China and long-term tracking monitoring, and provides a scientific, simple, easy-to-implement, and economical evaluation method for guiding the optimization of river cascade development plans, evaluating the health status of regional river water ecosystems, and conducting fixed-point long-term tracking monitoring.

[0015] (2) Technical Solution

[0016] The technical solution adopted by the present invention to solve its technical problems is: to provide an evaluation method for the health status of cascade-developed river ecosystems based on the biological integrity index of zooplankton, which consists of four parts: a sampling and investigation method based on the biological integrity of zooplankton, a basic index system for evaluating the biological integrity index of zooplankton, the construction of a candidate index system for evaluating the biological integrity index of zooplankton, and an evaluation criterion system for the health status of cascade-developed river ecosystems based on the biological integrity index of zooplankton (Z-IBI).

[0017] The sampling and investigation method based on the biological integrity of zooplankton is characterized as follows: Zooplankton community survey and monitoring sections are respectively arranged in the river sections below the dam site, above the dam site, at the tail of the reservoir, and in the main tributary sections of the cascade-developed river. Zooplankton community monitoring and investigations are carried out in three periods: the natural river state period, the impoundment period of each cascade, and the normal impoundment operation period of the cascade. Species identification and counting are carried out on the zooplankton obtained from each monitoring section.

[0018] The basic index system for evaluating the zooplankton biotic integrity index is characterized as follows: It consists of 4 types of indicators at two levels and 19 sub - basic indicators included therein. Among them, the first level includes 4 types of indicators: A1 biomass, A2 abundance, A3 biodiversity, and A4 trophic status; the second level includes 19 sub - basic indicators, which respectively correspond to the 4 types of indicators A1, A2, A3, and A4. The specific correspondence is as follows:

[0019] 1) A1 biomass: The 1 sub - basic indicator of A11 zooplankton biomass;

[0020] 2) A2 abundance: The 7 sub - basic indicators of A21 protozoan abundance, A22 rotifer abundance, A23 zooplanktonic crustacean abundance, A24 zooplankton abundance, A25 protozoan abundance ratio, A26 rotifer abundance ratio, and A27 zooplanktonic crustacean abundance ratio;

[0021] 3) A3 biodiversity: The 8 sub - basic indicators of A31 zooplankton species / genus number, A32 protozoan species / genus number, A33 rotifer species / genus number, A34 zooplanktonic crustacean species / genus number, A35 Margalef index, A36 Shannon index, A37 Simpson index, and A38 Pielou index;

[0022] 4) A4 trophic status: The 3 sub - basic indicators of A41 E / O index, A42 cladoceran and copepod abundance ratio, and A43 cladoceran and copepod biomass ratio.

[0023] The construction of the candidate index system for evaluating the zooplankton biotic integrity index includes the removal of candidate redundant indicators and the candidate index system for evaluating the zooplankton biotic integrity index. The specific content includes:

[0024] 1) Removal of candidate redundant indicators: The values of the 19 sub - basic indicators for evaluating the zooplankton biotic integrity index at each survey section in different periods are respectively counted. First, the basic indicators with the number of occurrences of sub - basic indicator values less than 5% are removed. Subsequently, the Spearman rank correlation coefficient of the remaining sub - basic indicator values is calculated. For the sub - basic indicators with the rank correlation coefficient value |R| greater than or equal to 0.70 and a highly significant correlation P < 0.01, only 1 item is retained as a candidate indicator;

[0025] 2) Candidate index system for evaluating the zooplankton biotic integrity index: The sub - basic indicators after the removal of candidate redundant indicators participate in the construction of the candidate index system for evaluating the zooplankton biotic integrity index, which consists of 4 types of indicators at two levels and 7 candidate indicators included therein. The specific details are as follows:

[0026]

[0027] The evaluation criterion system for the health status of cascade - developed river ecosystems based on the zooplankton biotic integrity index (Z - IBI) includes the determination of the distribution ranges of each candidate index for the zooplankton biotic integrity index evaluation, the calculation of the scores of each candidate index for the zooplankton biotic integrity index evaluation, the calculation method of the zooplankton biotic integrity index (Z - IBI) value, the grading standard of the zooplankton biotic integrity index and the corresponding health status of the river ecosystem. The specific content is as follows:

[0028] 1) Determination of the distribution ranges of each candidate index for the zooplankton biotic integrity index evaluation: Based on the values of 7 candidate indices surveyed at each investigation section in different periods, calculate the minimum value C min , the maximum value C max , the 5% quantile value C 5％ , and the 95% quantile value C 95％ respectively;

[0029] 2) Calculation of the scores of each candidate index for the zooplankton biotic integrity index evaluation: For the calculation method of the scores of candidate indices at each investigation section that is positively correlated with the health of the natural river ecosystem, SM i = C i / C 95％ * 100. For the calculation method of the scores of candidate indices at each investigation section that is negatively correlated with the health of the river ecosystem, SM i = (C max - C i ) / (C max - C 5％ ) * 100. If the calculated result of the candidate index score is greater than 100, it is counted as 100. If the calculated result is less than 0, it is counted as 0;

[0030] 3) Calculation method of the zooplankton biotic integrity index (Z - IBI) value: That is, the scores of each candidate index for the zooplankton biotic integrity index evaluation are summed up and then the simple arithmetic mean is taken to obtain the zooplankton biotic integrity index Z - IBI value of the monitoring section to be evaluated;

[0031] 4) Criteria for classifying the zooplankton biotic integrity index levels and their corresponding river ecosystem health status. Based on the calculated zooplankton biotic integrity index Z-IBI value, the health status of the river ecosystem is judged according to the following evaluation criteria: When 81 < Z-IBI value ≤ 100, the evaluation level is excellent, indicating a relatively natural and primitive river ecosystem; when 61 ≤ Z-IBI value ≤ 80, the evaluation level is good, indicating that the river ecosystem is disturbed by relatively low-intensity human activities; when 41 ≤ Z-IBI value ≤ 60, the evaluation level is medium, indicating that the river ecosystem is disturbed by medium-intensity human activities; when 21 ≤ Z-IBI value ≤ 40, the evaluation level is poor, indicating that the river ecosystem is disturbed by relatively high-intensity human activities; when 1 ≤ Z-IBI value ≤ 20, the evaluation level is bad, indicating that the river ecosystem is severely disturbed by human activities.

[0032] (3) Advantages and effects

[0033] The advantage of the present invention is to create an evaluation method for the health status of a cascade-developed river ecosystem based on the zooplankton biotic integrity index, including four parts: a sampling survey method based on zooplankton biotic integrity, a basic index system for evaluating the zooplankton biotic integrity index, a candidate index system for evaluating the zooplankton biotic integrity index, and an evaluation criterion system for the health status of a cascade-developed river ecosystem based on the zooplankton biotic integrity index (Z-IBI). Its advantages and effects are reflected in the following aspects:

[0034] 1) The proposed sampling survey method based on zooplankton biotic integrity, whose zooplankton community monitoring sections cover the reaches below the dam site, the reaches above the dam site, the tail reaches of the reservoir, and the main tributaries. The monitoring time includes the natural river state period, the cascade impoundment inundation period, and the cascade normal impoundment operation period. This survey method is applicable to the construction of the zooplankton biotic integrity index of cascade-developed rivers and the fixed-point long-term tracking monitoring of the health status of river ecosystems;

[0035] 2) The proposed basic index system for evaluating the zooplankton biotic integrity index includes two levels and 4 types of indicators, including biomass, abundance, biodiversity, and trophic status, and the 19 sub-item basic indicators it contains, providing a clear and complete evaluation index system for evaluating the health status of cascade-developed river ecosystems;

[0036] 3) The construction of the proposed candidate index system for evaluating the zooplankton biotic integrity index includes two levels, 4 types of indicators, and the 7 candidate indicators it contains, providing a detailed and quantifiable evaluation criterion system for evaluating the health status of cascade-developed river ecosystems;

[0037] 4) The established evaluation criterion system for the health status of cascade - developed river ecosystems based on the zooplankton biotic integrity index (Z - IBI) includes the determination of the distribution ranges of each candidate index for the zooplankton biotic integrity index evaluation, the calculation of the scores of each candidate index for the zooplankton biotic integrity index evaluation, the calculation method of the zooplankton biotic integrity index (Z - IBI) value, the grading standard of the zooplankton biotic integrity index and the corresponding health status of the river ecosystem. It provides a simple, feasible and economical evaluation method for quantitatively evaluating the health status of cascade - developed river ecosystems and long - term follow - up monitoring and evaluation.

[0038] The present invention makes up for the deficiencies in the evaluation of the health status of cascade - developed river ecosystems and their long - term follow - up monitoring and evaluation technologies, fills the gap in the comprehensive evaluation method of the health status of cascade - developed river ecosystems, and provides a scientific, simple, feasible and economical evaluation method for optimizing river cascade development plans, evaluating the health status of river ecosystems and conducting fixed - point long - term follow - up monitoring. Brief Description of the Drawings

[0039] Figure 1 : Basic Index System for Zooplankton Biotic Integrity Index Evaluation Detailed Implementation Modes

[0040] The following further illustrates the implementation modes of the present invention with cases.

[0041] The length of the Lancang River within China is about 2,160 km, the basin area is 174,000 km 4 ² 2 , and the annual runoff is 517.6 billion m 8 ³ 3 . The main - stream water energy resources are rich, and a total of 14 - level cascade developments are planned within China. This part takes the Xiaowan and Manwan cascade - developed reaches in the middle reaches of the Lancang River as specific implementation cases. Combining the construction and operation plans of each cascade in the middle reaches of the Lancang River, the investigations on the zooplankton community in the case study area were carried out in 1988 (natural river state period), 1997 (Manwan cascade impoundment inundation period), 2011 (Xiaowan cascade impoundment inundation period), and 2015 - 2016 (cascade normal impoundment operation period). The investigation sections for the zooplankton community in the middle reaches of the Lancang River include 10 sections from Xiaowan to Manwan in the main stream and 1 section of the main tributary, the Heiheijiang River. The 11 investigation sections cover the reaches below the dam site, the reaches above the dam site, the reservoir tail reaches, and the main tributary reaches. Therefore, the investigation in 1988 is considered to represent the natural original condition of the zooplankton community in the middle reaches of the Lancang River. The investigations in 1997 and 2011 are considered to represent the distribution status of the zooplankton community affected by the impoundment processes of the Manwan and Xiaowan cascades. The investigation in 2015 - 2016 is considered to represent the distribution status of the zooplankton community affected by the impoundment and normal operation of the Xiaowan and Manwan cascades.

[0042] The specific methods for zooplankton community surveys in this case are as follows: Due to the differences in the river hydrological processes of the Lancang River between the rainy season and the dry season, the surveys of zooplankton in the study area were conducted in April of each dry season. For the surveys of protozoa and rotifers, three water samples were collected at the water surface (0.5 m) using a 10 L plexiglass water sampler and mixed evenly. Then, 1 L of the mixed water sample was taken and stored in a plastic sampling bottle, and 1.5% Lugol's reagent was added and left to stand for 48 h before being concentrated to 30 ml. For cladocerans and copepods, 20 L of water samples were taken, filtered and concentrated through a No. 25 plankton net, and then stored in a plastic sampling bottle and fixed with 4% formaldehyde solution. The enriched and concentrated samples were taken back to the laboratory for identification and analysis under a microscope, generally identified to the species or genus level, and at the same time, the total species and quantities of the four types of zooplankton at each sampling point were counted. The identification of protozoa referred to "New Technologies for Microbial Monitoring", rotifers referred to "Freshwater Rotifers in China", cladocerans referred to "Fauna Sinica: Freshwater Cladocera", and copepods referred to "Fauna Sinica: Freshwater Copepods".

[0043] Combined with current domestic and international research, based on the species composition characteristics, biodiversity, trophic status, etc. of zooplankton in the Lancang River, two levels of four types of indicators and 19 sub-item basic indicators included in them were selected to construct the basic indicator system for the biological integrity assessment of zooplankton in the Lancang River. The specific calculation processes of the 19 sub-item basic indicators are as follows:

[0044] 1) A11 Zooplankton biomass: The zooplankton biomass at the survey section is the fresh biomass. The fresh biomass of each zooplankton species was approximated by its geometric volume (1.00 g·cm -3 ), and the fresh biomass of zooplankton per unit volume at each survey section was calculated, with the unit being mg / L;

[0045] 2) A21 Protozoan abundance: The individual number of zooplankton in the phylum Protozoa per unit volume at the survey section, with the unit being ind / L;

[0046] 3) A22 Rotifer abundance: The individual number of zooplankton in the class Rotifera per unit volume at the survey section, with the unit being ind / L;

[0047] 4) A23 Zooplankton crustacean abundance: The sum of the individual numbers of zooplankton in the classes Cladocera, Copepoda, and Nauplius belonging to the phylum Arthropoda, class Crustacea, per unit volume at the survey section, with the unit being ind / L;

[0048] 5) A24 Zooplankton abundance: The sum of the individual numbers of protozoa, rotifers, cladocerans, copepods, nauplii, and other zooplankton per unit volume of the survey section, measured in ind / L;

[0049] 6) A25 Protozoan abundance ratio: The ratio of the protozoan abundance to the total zooplankton abundance in the survey section, measured in %;

[0050] 7) A26 Rotifer abundance ratio: The ratio of the rotifer abundance to the total zooplankton abundance in the survey section, measured in %;

[0051] 8) A27 Planktonic crustacean abundance ratio: The ratio of the planktonic crustacean abundance to the total zooplankton abundance in the survey section, measured in %;

[0052] 9) A31 Number of zooplankton species / genera: The number of zooplankton species in the survey section, counted at the species level of the zooplankton classification system;

[0053] 10) A32 Number of protozoan species / genera: The number of zooplankton species belonging to the phylum Protozoa in the survey section, counted at the species level;

[0054] 11) A33 Number of rotifer species / genera: The number of rotifer zooplankton species in the survey section, counted at the species level;

[0055] 12) A34 Number of planktonic crustacean species / genera: The number of zooplankton species of cladocerans, copepods, and nauplii belonging to the class Malacostraca of the phylum Arthropoda in the survey section, counted at the species level;

[0056] 13) A35 Margalef index: The calculation formula for the Margalef richness index (d) of the zooplankton community in the survey section is as follows,

[0057] d = (S - 1) / lnN (1)

[0058] Where N is the zooplankton abundance in the survey section and S is the number of zooplankton species in the survey section;

[0059] 14) A36 Shannon index: The calculation formula for the Shannon diversity index (H′) of the zooplankton community in the survey section is as follows,

[0060]

[0061] Where n i is the abundance of the i-th taxonomic unit (species) of zooplankton in the survey section and N is the zooplankton abundance in the survey section;

[0062] 15) A37 Simpson Index: The calculation formula for the Simpson diversity index (1 - λ) of the zooplankton community in the surveyed section is as follows.

[0063]

[0064] In the formula, n i is the abundance of the i-th taxonomic unit (species) of zooplankton in the surveyed section, and N is the abundance of zooplankton in the surveyed section;

[0065] 16) A38 Pielou Index: The calculation formula for the Pielou evenness index (J ′ ) of the zooplankton community in the surveyed section is as follows.

[0066] J′ = H′ / lg(S) (Equation 4) where H′ is the Shannon index of the surveyed section and S is the number of zooplankton species in the surveyed section;

[0067] 17) A41 E / O Index: The ratio of the number of eutrophic species (E) to oligotrophic species (O) of zooplankton in the surveyed section;

[0068] 18) A42 Abundance Ratio of Cladocera and Copepoda: The ratio of the sum of the abundances of Cladocera and Copepoda in the surveyed section to the abundance of zooplankton;

[0069] 19) A43 Biomass Ratio of Cladocera and Copepoda: The ratio of the sum of the biomasses of Cladocera and Copepoda in the surveyed section to the biomass of zooplankton.

[0070] During the construction of the candidate index system for the evaluation of the zooplankton biological integrity index, the values of 19 sub - item basic indicators for the evaluation of the zooplankton biological integrity index of each surveyed section in different periods were respectively counted. To reduce the influence of redundant indicators, first, the basic indicators with the number of occurrences of sub - item basic indicator values less than 5% were removed. Subsequently, the Spearman rank - correlation analysis was used to analyze the correlation coefficients and significance of the remaining sub - item basic indicator values. In this study, for the sub - item basic indicators with the Spearman rank - correlation coefficient value |R| greater than or equal to 0.7 and showing a highly significant correlation (P < 0.01), only 1 item was retained as a candidate index. Therefore, these 12 sub - item basic indicators, namely A22 Rotifer Abundance, A24 Zooplankton Abundance, A25 Protozoan Abundance Ratio, A26 Rotifer Abundance Ratio, A27 Planktonic Crustacean Abundance Ratio, A31 Zooplankton Species / Genus Number, A32 Protozoan Species / Genus Number, A33 Rotifer Species / Genus Number, A34 Planktonic Crustacean Species / Genus Number, A37 Simpson Index, A42 Abundance Ratio of Cladocera and Copepoda, and A43 Biomass Ratio of Cladocera and Copepoda, were removed as redundant indicators. Finally, a total of 7 candidate indicators participated in the candidate index system for the evaluation of the zooplankton biological integrity index (Table 1).

[0071] Table 1 Candidate calculation indicators for the assessment of the health status of the river ecosystem in the middle reaches of the Lancang River based on the zooplankton biological integrity index (Z-IBI)

[0072]

[0073] Note: A positive correlation indicates a positive correlation with the health status of the river ecosystem; a negative correlation indicates a negative correlation with the health status of the river ecosystem.

[0074] Based on the criterion system for the assessment of the health status of the cascade-developed river ecosystem using the zooplankton biological integrity index (Z-IBI), an assessment of the health status of the river ecosystem before and after cascade development in the middle reaches of the Lancang River was carried out (Table 2). The results show that before the cascade development of the main stream in the middle reaches of the Lancang River in 1988, the health status of most river sections was excellent, and some river sections and the Heiheijiang tributary were in good condition; during the impoundment period of the Manwan cascade development in 1997, the health status of the water ecosystem in the still water area in front of the dam decreased to good, and the Xiaowan river section remained excellent and good; during the impoundment period of the Xiaowan cascade development in 2011, the health status of the water ecosystems in the Manwan and Xiaowan cascade reservoirs and the tributary reservoirs decreased to good; during the normal impoundment operation period of cascade development from 2015 to 2016, the health status of the water ecosystem in the still water area near the dam in the Manwan river section decreased to good and medium, and the river section at the tail of its reservoir, i.e., the river section below the Xiaowan dam, still maintained a good level. The health status of the water ecosystems in the still water area in front of the Xiaowan dam and the tributary reservoirs was excellent.

[0075] Table 2 Assessment results of the health status of the river ecosystem in the middle reaches of the Lancang River based on the zooplankton biological integrity index (Z-IBI)

[0076]

[0077] Note: "-" indicates not investigated.

[0078] Therefore, the above implementation cases show that the method for assessing the health status of the cascade-developed river ecosystem based on the zooplankton biological integrity index (Z-IBI) can provide a scientific, simple, feasible and economical technical support for the quantitative assessment and fixed-point long-term tracking and monitoring assessment of the health status of the water ecosystem in cascade-developed rivers.

Claims

1. A method for evaluating the health status of cascade-developed river ecosystems based on the zooplankton biological integrity index, which consists of four parts: a sampling survey method based on zooplankton biological integrity, a basic indicator system for zooplankton biological integrity index evaluation, a construction of a candidate indicator system for zooplankton biological integrity index evaluation, and a criterion system for evaluating the health status of cascade-developed river ecosystems based on the zooplankton biological integrity index Z-IBI; The sampling survey method based on zooplankton biological integrity, Its characteristics are as follows: zooplankton community monitoring sections are set up in the river sections below the dam site, above the dam site, at the end of the reservoir, and in the main tributaries of the cascade development rivers. Zooplankton community monitoring surveys are carried out in three periods: the natural river state period, the flooding period of each cascade impoundment, and the normal impoundment operation period of the cascade. The zooplankton species obtained from each monitoring section are identified and counted. The basic indicator system for evaluating the zooplankton biological integrity index is: Its characteristics are as follows: It consists of two levels of four indicators and their 19 sub-item basic indicators. The first level contains four indicators: A1 biomass, A2 abundance, A3 biodiversity, and A4 nutritional status; the second level contains 19 sub-item basic indicators, which correspond to the four indicators A1, A2, A3, and A4 respectively; The specific corresponding relationships are as follows: (1) A1 biomass: A11 zooplankton biomass 1 sub-item basic indicator; (2) A2 abundance: seven basic sub-items, namely, A21 protozoa abundance, A22 rotifer abundance, A23 planktonic crustacean abundance, A24 zooplankton abundance, A25 protozoa abundance ratio, A26 rotifer abundance ratio, and A27 planktonic crustacean abundance ratio; (3) A3 Biodiversity: 8 basic sub-indicators, including A31 number of zooplankton species / genera, A32 number of protozoan species and genera, A33 number of rotifer species / genera, A34 number of planktonic crustacean species and genera, A35 Margalef index, A36 Shannon index, A37 Simpson index, and A38 Pielou index; (4) A4 nutritional status: three basic sub-indicators: A41 E / O index, A42 abundance ratio of cladocerans and copepods, and A43 biomass ratio of cladocerans and copepods; The construction of the zooplankton biological integrity index evaluation candidate index system includes the removal of redundant candidate indexes and the zooplankton biological integrity index evaluation candidate index system, and the specific contents include: 1) Removal of redundant indicators: The 19 basic indicators of zooplankton biological integrity index evaluation in each survey section at different periods were counted respectively. First, the basic indicators with a frequency of less than 5% of the basic indicators were removed, and then the Spearman rank correlation coefficients of the remaining basic indicators were calculated. For the basic indicators with a rank correlation coefficient value |R| greater than or equal to 0.70 and a highly significant correlation P<0.01, one was retained as a candidate indicator; 2) Zooplankton Biointegrity Index Evaluation Indicator System: The sub-item basic indicators after the redundant indicators are removed are used to construct the zooplankton biointegrity index evaluation indicator system, including the following two levels of four types of indicators and the seven indicators they contain, as shown below: The health status evaluation criteria system of cascade development river ecosystem based on the zooplankton biological integrity index Z-IBI includes the determination of the distribution range of each candidate index for zooplankton biological integrity index evaluation, the score calculation of each candidate index for zooplankton biological integrity index evaluation, the calculation method of the zooplankton biological integrity index Z-IBI value, the zooplankton biological integrity index grade classification standard and its corresponding river ecosystem health status, and the specific contents include: a) Determination of the distribution range of each candidate index for evaluation of zooplankton biological integrity index: Based on the values ​​of the seven candidate indexes surveyed at each survey section at different periods, the minimum value C of each candidate index was calculated respectively. min , maximum value C max , 5% quantile value C 5％ , 95% quantile value C 95％ ; b. Calculation of the scores of each candidate index for evaluation of zooplankton biological integrity index: For each survey section that is positively correlated with the health of the river ecosystem, the calculation method for the score of the candidate index is SM i =C i / C 95％ *100, the calculation method for the candidate index scores of each survey section that is negatively correlated with the health of the river ecosystem is SM i =(C max -C i ) / (C max -C 5％ )*100. If the calculated score of the candidate index is greater than 100, it will be counted as 100. If the calculated score is less than 0, it will be counted as 0. c Calculation method of zooplankton biological integrity index Z-IBI value: That is, the score of each candidate index of the zooplankton biological integrity index is added up and a simple arithmetic average is taken to obtain the zooplankton biological integrity index Z-IBI value of the monitoring section to be evaluated; d. Classification standard of zooplankton biological integrity index and its corresponding health status of river ecosystems. The health status of river ecosystems is judged according to the calculated zooplankton biological integrity index Z-IBI value according to the following evaluation criteria: when 81≤Z-IBI value≤100, the evaluation grade is excellent, indicating a relatively natural and original river ecosystem; when 61≤Z-IBI value≤80, the evaluation grade is good, indicating that the river ecosystem is disturbed by relatively low intensity human activities; when 41≤Z-IBI value≤60, the evaluation grade is medium, indicating that the river ecosystem is disturbed by moderate intensity human activities; when 21≤Z-IBI value≤40, the evaluation grade is poor, indicating that the river ecosystem is disturbed by high intensity human activities; when 1≤Z-IBI value≤20, the evaluation grade is poor, indicating that the river ecosystem is seriously disturbed by human activities.

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