A method for analyzing the influence of a gate dam on a river food web based on fatty acids and ecological network analysis

Abstract

The application discloses a method for analyzing the influence of a gate dam on a river food web based on fatty acids and ecological network analysis. The method comprises the following steps: obtaining the nutrient structure of the river food web upstream and downstream of the gate dam and the measured results of fatty acids of various species through field sampling; determining the food resources and consumers of the food web through a classification library and a relationship library of nutritional groups; determining the number of nodes and the number of links between nodes in the ecological network diagram upstream and downstream of the gate dam; calculating the node size, the nutrient transmission efficiency and the interspecific energy flux in the ecological network diagram, determining the link width between nodes in the ecological network diagram, and drawing the ecological network diagram; calculating the total area of various types of nodes, the number of producer nodes and the number of consumer nodes of each nutritional group in the ecological network diagram upstream and downstream of the gate dam, and analyzing the influence of the gate dam on the key species and nutritional groups in the river food web and the influence of the gate dam on the stability and vulnerability of the river ecosystem food web.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ecological network analysis, and particularly relates to a method for analyzing the influence of a dam on a river food web based on fatty acids and ecological network analysis. BACKGROUND

[0002] Dams are one of the main human constructions that threaten global aquatic ecosystems. More than 60% of the rivers in the world have been dammed for various purposes such as flood control and hydropower generation. Current research shows that the construction and operation of dams will affect the longitudinal and lateral connectivity of rivers, change the river flow, thermal conditions and sediment transport, and its influence will extend to the ecological aspect and produce great species-ecosystem level changes. Although the negative effects of these changes on species such as algae, benthic animals and fish have been well documented, the structure and function of the ecosystem is one of the key directions of ecological research. At the level of ecosystem research, the influence of dams on river ecosystems is still poorly understood and difficult to characterize.

[0003] As a visual expression of the ecosystem, the river food web can quantitatively analyze the material circulation and energy transfer process of the river ecosystem, effectively reflecting the changes in diversity, structure and functionality of the river ecosystem under the influence of dams. In terms of energy flow regulation and function maintenance of the ecosystem, the food web plays a key role, and the method of analyzing and evaluating the comprehensive influence of dams on the river food web from the perspective of food web has broad prospects. The food web includes species composition and nutritional structure. In the spatial aspect, the interaction between biological predators and prey is the core of the food web; in the time aspect, the food web structure has high sensitivity to biogeochemistry and hydrological stress.

[0004] The ecological network analysis is an analysis technology for an ecological system by using a species fatty acid information, a species trophic level and an ecological network diagram constructed by a package fluxweb of an Rstudio software of an R language software platform. The R language is a programming language for statistical analysis and graphic display, and the package fluxweb is a set of products taking energy flux calculation of a food web as a core, and input parameters include a predation relationship, a biomass, a metabolic loss rate and a nutrient transmission rate. When the product is used for constructing the biomass conservation, only two biomass loss items of predation death and metabolic loss consumption are calculated, and the biomass loss caused by non-predation death of a biological group is not considered. Through analysis on related indexes and related changes of a food chain length, a species biomass content, a number of nutritional relationships between species and energy transmission flux in a river food web under the influence of a dam, the changes of the structure and function of the river food web under the influence of the dam can be effectively analyzed, the influence of a single species and a single nutritional group on the stability, vulnerability and the like of the river food web and the overall change of the river ecosystem restoration capacity are comprehensively described, and the method serves river water quality monitoring, aquatic organism prevention and control, target species conservation, watershed health evaluation, watershed ecological comprehensive management and the like.

[0005] Since the biomass usually uses the total weight of a species population, the weight of prey food contained in a digestive tract of an organism is included, the weight of the prey food has great space-time difference, and only the predation of the species close to the sampling time can be one-sidedly reflected, and the structure of the food web cannot be comprehensively understood in the time and space angles. For some producers with small individual size in the aquatic food web, the biomass is usually low, and the producers are important food sources and nutritional support for some consumers. Therefore, in the river food web, some small species have important effects on the complexity of the food web structure and energy support, and the influence of the dam on the river food web needs to be analyzed by using the nutritional concentration of the fatty acid, and the nutritional quantity of the biomass with large error cannot be simply analyzed and evaluated. SUMMARY

[0006] The present application provides a method for analyzing the influence of a dam on a river food web based on an ecological network, aiming at the problem that the biomass calculation of the prior art is inaccurate, and the constructed ecological network diagram and the analysis of the influence of the dam on the river food web have deviation.

[0007] The method is based on long-chain unsaturated fatty acid species and content to calculate node size and inter-node link width, and uses species species, species quantity, species interspecific predation relationship and calculated node size and inter-node link width obtained by field sampling to construct an ecological network graph. Since long-chain unsaturated fatty acids can usually only be synthesized by producers, their species and content have a greater impact on the growth, development and reproduction of organisms, and the synthesis capacity of consumers is limited and long-chain unsaturated fatty acids in food resources must be ingested through predation relationship, so long-chain unsaturated fatty acids can be used to evaluate the nutritional concentration of food resources and consumers in the aquatic food web. Compared with biomass which has spatial and temporal limitations, long-chain unsaturated fatty acids have better long-term tracking and accuracy in reflecting the nutritional concentration and growth state of organisms, so using fatty acid data for ecological network analysis can improve the accuracy of the results of analyzing the influence of the dam on the river food web.

[0008] Specifically, the application adopts the following technical scheme: a method for analyzing the influence of a dam on a river food web based on fatty acids and ecological network analysis, the method comprising:

[0009] (1) calculating the node size in the ecological network graph according to the long-chain unsaturated fatty acid information of each species in the river food web upstream and downstream of the dam;

[0010] (2) constructing an ecological network graph of the river food web upstream and downstream of the dam according to the node size, interspecific predation relationship of the nutritional group, node color, inter-node link width, link arrow size and nutritional transmission efficiency;

[0011] (3) analyzing the influence of the dam on the river food web, including:

[0012] based on the difference between the total node area of each nutritional group species representative in the ecological network graph upstream and downstream of the dam and the total node area of the corresponding nodes upstream and downstream of the dam, analyzing the influence of the dam on the key species in the river food web;

[0013] and, based on the number of food resource nodes and the number of consumer nodes of each nutritional group in the ecological network graph upstream and downstream of the dam, respectively analyzing the influence of the dam on the stability and vulnerability of the river ecosystem food web in the basin.

[0014] Further, the greater the proportion of the total node area of a single species and a single nutritional group in all total node areas, the greater the influence of the corresponding species and nutritional group on the river food web; the greater the proportion of the difference between the total node areas in all total node areas, the greater the influence of the corresponding species on the dam.

[0015] Further, the more the number of food resource nodes and the number of consumer nodes, the more the types of food resources and the types of consumers, and the higher the stability of the river ecosystem food web; otherwise, the higher the vulnerability of the river ecosystem food web.

[0016] Further, the calculation method of the node size comprises:

[0017] Obtain long-chain unsaturated fatty acid information of each species in the river food web upstream and downstream of the gate dam; the long-chain unsaturated fatty acids are one or more of docosahexaenoic acid (DHA), eicosapntemacnioc acid (EPA), alpha-linolenic acid (ALA), linoleic acid (LIN), arachidonic acid (ARA), and bacterial fatty acid (BAFA);

[0018] Based on the long-chain unsaturated fatty acid information of each species, determine the node size in the ecological network diagram to visualize the size of the nutrient concentration content represented by the long-chain unsaturated fatty acid content of each species;

[0019]

[0020] wherein, size is the node size, C i is the average fatty acid content of species i, nod max is the maximum fatty acid content of species i, V scale is a constant that can be self-defined according to the drawing effect of the ecological network analysis diagram, V min is the minimum size of the node.

[0021] Further, the calculation method of the link width comprises:

[0022] Obtain long-chain unsaturated fatty acid information of each species in the river food web upstream and downstream of the gate dam;

[0023] Based on the long-chain unsaturated fatty acid information of each species, determine the link width in the ecological network diagram to visualize the size of the energy transfer flux represented by the long-chain unsaturated fatty acid content between each species;

[0024]

[0025] wherein, wide is the link width, E is the activation energy contained in species i, E max is the maximum activation energy of species i, E scaleE is a constant that can be customized according to the effect of drawing an ecological network analysis diagram min is the minimum width of the link.

[0026] Further, the nutrient transfer efficiency of the food resources in the fallen leaves and vegetation to the phytophagous consumers is 0.40, the nutrient transfer efficiency of the food resources in the epilithic algae and phytoplankton to the phytophagous consumers is 0.77, and the nutrient transfer efficiency of the consumers to the carnivorous consumers is 0.906.

[0027] Further, the main nutrient groups of the species include: epilithic algae, fallen leaves, vegetation, phytoplankton, zooplankton, benthic animals, and fish; wherein the epilithic algae, fallen leaves, vegetation, and phytoplankton constitute the food resources in the nutrient groups.

[0028] Further, the construction of the ecological network diagram specifically includes:

[0029] Obtaining the nutrient structure of the food web of the river upstream and downstream of the gate dam;

[0030] Determining the food resources and consumers of the food web based on the classification library and the relationship library of the nutrient groups;

[0031] Determining the number of nodes and the number of links between nodes in the ecological network diagram of the gate dam upstream and downstream based on the number of species of the nutrient groups and the number of interspecific predation relationships.

[0032] And the interspecific predation relationship of the nutrient groups, the node color, the link width between nodes, the link arrow size, and the nutrient transfer efficiency, construct the ecological network diagram of the food web of the river upstream and downstream of the gate dam.

[0033] Further, based on the number of species of the nutrient groups and the number of interspecific predation relationships, the number of nodes and the number of links between nodes in the ecological network diagram of the gate dam upstream and downstream are determined, which specifically includes the following steps:

[0034] S3.1, based on the number of species of the nutrient groups, the total number of nodes is the total number of species in the river food web, and the number of nodes in the ecological network diagram of the gate dam upstream and downstream is one-to-one corresponding to the number of species; wherein the food resources include epilithic algae, fallen leaves, vegetation, and phytoplankton, and the consumers include zooplankton, benthic animals, and fish.

[0035] S3.2, based on the number of interspecific predation relationships of the species in the river food web, the total number of links is the total number of interspecific predation relationships of the species in the river food web, and the number of links between nodes in the ecological network diagram of the gate dam upstream and downstream is one-to-one corresponding to the number of interspecific predation relationships of the species; the link color and the link arrow of the species are assigned to the same color.

[0036] The beneficial effects of the present application are that: the present application uses long-chain unsaturated fatty acid species and content as a representative substance of species nutrition concentration, by processing and analyzing the fatty acid information of each species in the river food web under the influence of the dam, an accurate and reliable ecological network diagram can be drawn, the ecological network analysis is completed to analyze the influence of the dam on the river food web, the overall changes of the single species and the single nutrition group under the influence of the dam and the overall changes of the stability and vulnerability of the river food web are comprehensively described, and finally serve the river water quality monitoring, aquatic organism prevention and control, target species conservation, watershed health evaluation, watershed ecological comprehensive management and other work of the river ecosystem with dam structures. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the following specific embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0038] Figure 1 The flow chart of the ecological network analysis method of the upstream and downstream river food web of the dam according to the embodiment of the present application;

[0039] Figure 2 The architecture diagram of the ecological network analysis method of the upstream and downstream river food web of the dam according to the embodiment of the present application;

[0040] Figure 3 The example diagram of the ecological network diagram constructed by the eicosapentaenoic acid (EPA) information of each species in the upstream and downstream river food web of the dam according to the embodiment of the present application. DETAILED DESCRIPTION

[0041] In the present application, the concepts of the nutrition structure of the food web, the classification library and the relationship library of the nutrition group, the food resources and consumers of the food web, the number of nodes and the number of links between nodes in the ecological network diagram, the node size and the nutrition transmission efficiency in the ecological network diagram, the inter-species energy flux, the link width between nodes in the ecological network diagram, and the ecological network diagram are basic and important in ecology, which help us understand the complex dynamics and energy flow patterns inside the ecological system, as follows:

[0042] Nutrition structure

[0043] The nutrition structure refers to the nutrition relationship between organisms in an ecological system, which is mainly embodied through food chains and food webs. Food chain is a linear nutrition relationship, while food web is a complex network composed of many interwoven food chains.

[0044] Classification library of nutrition group

[0045] Trophic groups generally refer to groups of organisms that play similar roles in the food web. Common classifications include:

[0046] Producers: Usually plants and autotrophic microorganisms capable of photosynthesis or nitrification, which can convert solar energy into chemical energy and fix it in the organism.

[0047] Consumers: Divided into primary consumers (herbivores), secondary consumers (carnivores), etc., which directly or indirectly feed on producers or other consumers.

[0048] Decomposers: Including bacteria and fungi, etc., responsible for decomposing dead organisms and excreta, converting organic matter into inorganic matter for producers to use again.

[0049] Food resources and consumers

[0050] Food resources refer to the energy sources in the ecosystem that can be used by consumers, while consumers refer to organisms that directly or indirectly rely on these resources for survival.

[0051] Node size and trophic transfer efficiency

[0052] In ecological network diagrams, the size of a node is usually related to the importance of the species in the ecosystem, such as its biomass or nutrient concentration. Trophic transfer efficiency refers to the proportion of energy retained during the transfer from one species to the next or from one trophic level to the next. The trophic transfer efficiency from producers to herbivorous consumers is lower, while the trophic transfer efficiency from secondary consumers to the next level of consumers is higher. The transfer efficiency between trophic levels is usually between 10% and 20%.

[0053] In this invention, multiple fatty acid contents are used to calculate node size, which covers a wide range of fatty acids and has less systematic error in data acquisition methods within the field, thus obtaining more accurate node size information.

[0054] Interspecific energy flux

[0055] Interspecific energy flux refers to the amount of energy flowing between different species, which is very important in the food web as it determines the distribution and utilization efficiency of energy in the ecosystem.

[0056] Link width between nodes

[0057] In ecological network diagrams, link width can represent the size of energy flux between species or the strength or frequency of interaction. A wider link usually means stronger interaction or greater energy / material exchange.

[0058] Ecological network diagram

[0059] An ecological network diagram is a network diagram that represents the interactions between species in a food web in a graphical manner, in which:

[0060] The nodes represent species, and different trophic groups are often distinguished by different node colors or node shapes.

[0061] The links represent the trophic relationships between species, such as predation, symbiosis, competition, etc.

[0062] The link arrows represent the direction of energy flow between species.

[0063] The number of nodes and the number of links reflect the complexity of the network, and the more nodes and links, the more complex the network structure, and the more stable the food web and the ecosystem.

[0064] The position of the ecological network diagram is a common technical means in the art, and in the present application, only the calculation method of the node size in the ecological network diagram is optimized, and there is no improvement for drawing the ecological network diagram itself. Therefore, based on the node size obtained by the present application, the ecological network diagram can be drawn by combining the common technical means.

[0065] Effects on river food web

[0066] The effects on the river food web generally include the effects on key species in the river food web, the stability and vulnerability of the river ecosystem food web in the watershed. Based on the constructed ecological network diagram, the foregoing effects are known in the art. In the ecological network diagram, the greater the proportion of the total area of a single species and a single trophic group in the total area of all nodes, the greater the impact of the corresponding species and trophic group on the river food web; the greater the difference between the total area of the nodes in the proportion of all node area sums, the greater the impact of the corresponding species on the dam. The more the number of food resource nodes and consumer nodes, the more the number of food resource species and consumer species, the higher the stability of the river ecosystem food web; otherwise, the higher the vulnerability of the river ecosystem food web.

[0067] The present application will be further described in detail below in conjunction with the embodiments of the drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout the drawings. The embodiments described below by reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0068] In the description of the present application, it should be noted that for orientation words, if the terms "center", "transverse", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation and positional relationship based on the orientation or positional relationship shown in the drawings, only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and cannot be understood as limiting the specific protection scope of the present application. The terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise expressly and specifically limited.

[0069] Dams are one of the major human structures that threaten river food webs, which are widely distributed globally, and their impacts extend to river ecology and cause large changes in species-river ecosystem levels. River food webs play a key role in regulating energy flow and maintaining the function of river ecosystems, and can quantify material circulation and energy transfer processes in river ecosystems. Through ecological network analysis, changes in key species, stability and vulnerability in river food webs under the influence of dams can be effectively reflected.

[0070] The current data source type commonly used in ecological network analysis is biomass, however, biomass itself has spatial and temporal limitations, and aquatic organisms in river food webs are usually small in size, especially for the producers that play an important role in energy sources and nutrient concentrations of food webs, the biomass measurement of which is applicable to a small number of species and has a large error in measurement results. For example, in river food webs, some fish predators have strong mobility, and their diet will change accordingly with spatial movement and seasonal changes. Therefore, the food weight data in the digestive tract of fish in the biomass data collected at a certain point in a period of time has spatial and temporal limitations, and cannot well reflect the growth status and population nutrient concentration changes of fish species over a long period of time. In river food webs, small-sized food sources such as periphytic algae and detritus are unevenly distributed in rivers, and it is difficult to obtain accurate total biomass by field sampling of the biomass. Moreover, the biomass of periphytic algae is usually small, and periphytic algae have a high content of long-chain unsaturated fatty acids, which are essential nutrients to support the growth, development and reproduction of consumers, and the ability of consumers to synthesize long-chain unsaturated fatty acids is limited, and consumers have a high importance and necessity to ingest long-chain unsaturated fatty acids by predating periphytic algae. Therefore, the influence of periphytic algae on river food webs is usually smaller than the actual situation by judging the influence degree of periphytic algae on river food webs only by the size of biomass, and the results obtained by using biomass for ecological network analysis to analyze the influence of dams on river food webs are less accurate.

[0071] In view of the above problems, the present application provides a method for analyzing the influence of dams on river food webs based on fatty acids and ecological network analysis, which comprises the following steps: Figure 1 Figure 2 The present application provides a method for analyzing the influence of dams on river food webs based on fatty acids and ecological network analysis, which comprises the following steps:

[0072] Taking the headwater region of Dongjiang River in Guangdong Province of China as an example, the region affected by the dam in the lower reaches of Dongjiang River is taken as the river food web after the influence of the dam, and the headwater region of Dongjiang River is taken as the river food web before the influence of the dam.

[0073] ​Step S1, obtaining the measured results of the nutrient structure of the food web of the river upstream and downstream of the gate dam and the fatty acid of each species. The method for obtaining the measured results is to collect aquatic organism samples in the food web of the river upstream and downstream of the gate dam in the field. The species of the aquatic organism samples include: periphyton, fallen leaves, vegetation, phytoplankton, zooplankton, benthic animals and fish. Among them, 5 groups of fallen leaves of various types are collected, 5 pieces of each group, 5 plants of various types of vegetation are collected, 5 pieces of leaf parts submerged in the river are collected from each plant, 5 groups of various types of zooplankton are collected, 5 groups of various types of benthic organisms are collected, 5 of each group, 1 group of various types of fish is collected, 5 of each group, and the muscle tissue near the first dorsal fin is taken as the sample. The fallen leaves, vegetation, phytoplankton, zooplankton, benthic animals and fish muscle tissues are washed with distilled water as the samples to be measured.

[0074] In this embodiment, the field sampling method can be collected according to the conventional aquatic organism sampling method, which is not limited in this embodiment.

[0075] The pre-treatment of the aquatic organism samples to be measured to form samples includes freeze-drying treatment and grinding treatment. The lipids in the samples are extracted and methylated in a nitrogen and ice-cold environment, and the types and contents of long-chain unsaturated fatty acids in the treated sample lipids are determined by a gas chromatograph as fatty acid information; the measured results include the trophic level of each species determined according to the predator-prey relationship and the prey relationship, the nutrient structure of the river food web, and the fatty acid information.

[0076] In this embodiment, the fatty acid information refers to the types and contents of long-chain unsaturated fatty acids (Long chain-polyunsaturated fatty acid, LC-PUFA) of each species in the river food web affected by the gate dam.

[0077] In some embodiments, the long-chain unsaturated fatty acid information contained in the aquatic organisms includes but is not limited to information of one or more of docosahexaenoic acid (Docosahexaenoic acid, DHA), eicosapntemacnioc acid (Eicosapntemacnioc acid, EPA), alpha-linolenic acid (Alpha-linolenic acid, ALA), linoleic acid (Linoleic acid, LIN), arachidonic acid (Arachidonic acid, ARA) and bacterial fatty acid (Long-chain saturated fatty acids, BAFA).

[0078] In this embodiment, the trophic groups are divided into food resources, zooplankton, benthic animals and fish.

[0079] Step S2, according to the classification library and the relationship library of the trophic group, determine the food resources and consumers of the river food web. The classification library of the trophic group is the food resources and consumers, and the relationship library is the predation relationship between species. The food resources include periphyton, fallen leaves, vegetation and phytoplankton, and the consumers include zooplankton, benthic animals and fish.

[0080] In some embodiments, the trophic group includes but is not limited to: food resources, zooplankton, benthic animals and fish.

[0081] In some embodiments, the food resources include but are not limited to: periphyton, fallen leaves, vegetation and phytoplankton.

[0082] In some embodiments, the consumers include but are not limited to: zooplankton, benthic animals and fish.

[0083] In some embodiments, the species relationship in the relationship library of the trophic group includes but is not limited to: predation relationship.

[0084] In the Rstudio software of the R language software platform, the program package fluxweb is called to use the species fatty acid information, the species trophic level and the ecological network diagram drawn by the inter-species energy flux to respectively give four colors that can be represented in the R language to the four nodes respectively represented by the four trophic groups of food resources, zooplankton, benthic animals and fish, that is, each trophic group node is given a color different from each other, so as to achieve the purpose of distinguishing the four trophic groups from each other.

[0085] In some embodiments, the node color includes but is not limited to: red, blue, yellow and green.

[0086] Step S3, according to the number of species of the trophic group and the number of inter-species predation relationship, determine the number of nodes and the number of links between nodes in the ecological network diagram of the upstream and downstream of the dam.

[0087] Specifically, S3 includes the following steps:

[0088] Step S3.1, the number of nodes is the number of species of the trophic group, the total number of nodes is the total number of species in the river food web, and the number of nodes in the ecological network diagram of the upstream and downstream of the dam corresponds to the number of species one by one.

[0089] Step S3.2, the number of links between nodes is the number of inter-species predation relationship, the total number of links is the total number of inter-species predation relationship in the river food web, and the number of links between nodes in the ecological network diagram of the upstream and downstream of the dam corresponds to the number of inter-species predation relationship one by one.

[0090] The links between species and the link arrows are given the same color.

[0091] In some embodiments, the color of the link and the link arrow includes, but is not limited to, black, gray.

[0092] Step S4, based on the measured results of the fatty acid of the species, the size of the node in the ecological network diagram and the nutrient transmission efficiency are calculated.

[0093] Specifically, S4 includes the following steps:

[0094] Step S4.1, based on the measured results of the EPA in the long-chain unsaturated fatty acid content of each species, the size of the node in the ecological network diagram is calculated to visualize the nutrient concentration represented by the long-chain unsaturated fatty acid content of each species; compared with other types of fatty acids, consumers cannot only synthesize eicosapentaenoic acid (EPA) by themselves, and the eicosapentaenoic acid (EPA) contained therein only comes from food resources containing eicosapentaenoic acid (EPA). Compared with other types of fatty acids, the use of eicosapentaenoic acid (EPA) content contained in consumers to calculate the node size is the least interfered by the synthesis of fatty acids by the species itself, and the calculation result obtained is more accurate. The node size is calculated using the following formula:

[0095]

[0096] Wherein, size is the node size, C i is the average fatty acid content of species i, nod max is the maximum fatty acid content of species i, V scale is a constant that can be customized according to the drawing effect of the ecological network analysis diagram, V min is the minimum size of the node.

[0097] Generally, V scale is approximately constant 25, V min is approximately constant 5, the node size drawn is more appropriate and has a better drawing effect in the ecological network diagram.

[0098] In some embodiments, a plurality of fatty acid information can be used to comprehensively calculate the node size in a corresponding proportion.

[0099] Step S4.2, based on the measured results of the long-chain unsaturated fatty acid content of each species, the nutrient transmission efficiency between species is calculated. Compared with other types of fatty acids, consumers cannot only synthesize eicosapentaenoic acid (EPA) by themselves, and the eicosapentaenoic acid (EPA) contained therein only comes from food resources containing eicosapentaenoic acid (EPA). Compared with other types of fatty acids, the use of eicosapentaenoic acid (EPA) content contained in consumers to calculate the nutrient transmission efficiency is the least interfered by the synthesis of fatty acids by the species itself, and the calculation result obtained is more accurate.

[0100] The empirical value of the nutritional transmission efficiency of the fatty acid eicosapentaenoic acid (EPA) information calculated in this embodiment is: the nutritional transmission efficiency of the food resources of fallen leaves and vegetation to herbivorous consumers is 0.40, the nutritional transmission efficiency of the food resources of epiphytic algae and phytoplankton to herbivorous consumers is 0.77, and the nutritional transmission efficiency of the consumers to carnivorous consumers is 0.906.

[0101] In some embodiments, the nutritional transmission efficiency can be calculated by using multiple fatty acid information in corresponding proportions.

[0102] In this embodiment, the metabolic loss rate of inter-species energy transmission in the ideal state can be taken as 0.01 or below.

[0103] Step S5, based on the nutritional transmission efficiency of each species, calculate the inter-species energy flux to determine the link width between nodes of the ecological network diagram.

[0104] Specifically, S5 includes the following steps:

[0105] Step S5.1, input the fatty acid species, content, and nutritional transmission efficiency of each species in the food web of the upstream and downstream rivers of the dam into the adjacency matrix netmatrix, the nutritional transmission efficiency vector, and the metabolic loss rate vector.

[0106] The adjacency matrix netmatrix is a complete adjacency matrix based on the species and predatory relationship of the food web of the upstream and downstream rivers of the dam, with the predator species as the column and the prey as the row, stored in the variable netmatrix.

[0107] Step S5.2, use the fluxing function to calculate the inter-species energy flux in the food web and return the inter-species energy flux vector.

[0108] Step S5.3, determine the link width between nodes of the ecological network diagram to visualize the nutritional concentration transmission effect between species. The link width is the link width between nodes of the ecological network diagram, representing the inter-species energy flux of the species, determined by the inter-species energy flux of each species, the metabolic loss rate, and the inter-species energy flux vector. The link width is calculated using the following formula:

[0109]

[0110] where wide is the link width, E is the activation energy contained by species i, E max is the maximum activation energy of species i, E scale is a constant that can be customized according to the drawing effect of the ecological network analysis diagram, E min is the minimum link width.

[0111] Generally, Escale Approximate constant 15, E min When the approximate constant is 0.1 and the link arrow size is 0.05, the proportion of the drawn link in the ecological network diagram is appropriate, and the drawing effect is better.

[0112] The following table provides information of each part in the ecological network diagram constructed based on the eicosapentaenoic acid (EPA) information of each species in the food web of the upstream and downstream rivers of the gate dam according to the embodiments of the present application.

[0113]

[0114] In the embodiments of the present application, after processing the fatty acid information and other data of each species in the food web of the upstream and downstream rivers of the gate dam, the information of each part in the constructed ecological network diagram is as shown in the above table. In the table, part of the species, trophic groups, eicosapentaenoic acid (EPA) content, diet, nutritional transmission efficiency, metabolic loss, and corresponding node color, node size, and link width in the food web of the upstream and downstream rivers of the gate dam are listed.

[0115] Part of the species includes periphyton, fallen leaves, vegetation, phytoplankton, zooplankton, benthic animals, and fish. The benthic animals include invertebrate filter feeders, invertebrate scrap feeders, invertebrate predators, and invertebrate tear feeders. The fish includes omnivorous fish and carnivorous fish.

[0116] In the above table, the nutritional transmission efficiency calculated from the eicosapentaenoic acid (EPA) information takes an empirical value: the nutritional transmission efficiency of fallen leaves and vegetation in food resources to herbivorous consumers is 0.40, the nutritional transmission efficiency of periphyton and phytoplankton in food resources to herbivorous consumers is 0.77, and the nutritional transmission efficiency of consumers to carnivorous consumers is 0.906.

[0117] In the above table, the metabolic loss rate of energy transmission between species in an ideal state can be taken as 0.01 or below.

[0118] Step S6, according to the information of the trophic group interspecific predation relationship, node color, node size, link width between nodes, and link arrow size determined in the above steps, the ecological network diagram is drawn using the fluxweb package of the Rstudio software of the R language platform, with the trophic level order as the vertical axis and the first letter of the species name order as the horizontal axis.

[0119] In one embodiment, the ecological network diagram constructed based on the eicosapentaenoic acid (EPA) information of each species in the food web of the upstream and downstream rivers of the gate dam is as shown in Figure 3 Figure 3 ​In the embodiment, the left graph is an ecological network diagram of the river food web upstream of the dam, and the right graph is an ecological network diagram of the river food web downstream of the dam. The trophic level is used to represent the vertical direction, and the vertical coordinate represents the size of the trophic level of each species. The actual unit does not exist.

[0120] Figure 3 In the embodiment, one node in the ecological network diagram represents one species, and nodes of the same color represent the same trophic group, including: green nodes represent food resources, yellow nodes represent zooplankton, red nodes represent benthic animals, and blue nodes represent fish.

[0121] In the embodiment, the trophic level of the food resource is the lowest, and the vertical coordinate value of the node representing the food resource in the ecological network diagram is relatively the smallest. The trophic level of the fish is the highest, and the vertical coordinate value of the node representing the fish in the ecological network diagram is relatively the largest.

[0122] In step S7, the difference between the total area of the nodes representing each species in the ecological network diagrams upstream and downstream of the dam and the total area of the nodes corresponding to the species upstream and downstream of the dam is calculated to analyze the influence of the dam on the key species in the river food web.

[0123] Generally, the greater the proportion of the total area of the nodes of a single species in the total area of all nodes, the higher the trophic concentration of the corresponding species, the greater the influence on the total trophic concentration in the river food web, the higher the importance of the corresponding species to the consumers in the river food web and the river food web, and the more likely the corresponding species is to become a key species in the river food web. The greater the proportion of the total area of the nodes of a single trophic group in the total area of all nodes, the greater the influence of the corresponding trophic group on the total trophic concentration in the river food web, the higher the importance of the corresponding trophic group to the consumers in the river food web and the river food web, and the more likely the corresponding trophic group is to become a key trophic group in the river food web.

[0124] Under the influence of the dam, the changes of the key species and the key trophic group have the relatively greatest influence on the changes of the river food web.

[0125] The greater the proportion of the difference between the total area of the nodes of a single species in the total area of all nodes, the greater the influence of the trophic concentration, growth, development, and reproduction state of the corresponding species on the trophic intake, growth, development, and reproduction state of the corresponding predator. The greater the proportion of the difference between the total area of the nodes of a single trophic group in the total area of all nodes, the greater the influence of the trophic concentration, growth, development, and reproduction state of the corresponding trophic group on the trophic intake, growth, development, and reproduction state of the trophic group preying on the corresponding trophic group.

[0126] The greater the proportion of the total node area of all nodes in the total node area of a single species and a single trophic group, the greater the impact of the corresponding species and trophic group on the river food web. The greater the proportion of the difference between the node areas in the total node area of all nodes, the greater the impact of the corresponding species on the dam.

[0127] Because different species and different trophic groups contain different types of main fatty acids, the impact of the dam on the corresponding species and trophic groups in the river food web can be analyzed based on the corresponding fatty acid species information using ecological network analysis.

[0128] The total node area of the upstream and downstream ecological network diagrams of the dam and the difference between the total node areas of the upstream and downstream ecological network diagrams are calculated to analyze the impact of the dam on the upstream and downstream nutrient concentration changes in the river food web.

[0129] Generally, the greater the total node area, the higher the nutrient concentration of the river food web. The greater the difference between the total node areas between the upstream and downstream, the greater the impact of the dam on the nutrient concentration of the river food web. Compared with the upstream, the decrease in the total node area of the downstream indicates that the nutrient concentration of the river food web under the influence of the dam decreases, and the productivity of the river food web is lower. The increase in the total node area of the downstream indicates that the nutrient concentration of the river food web under the influence of the dam increases, and the productivity of the river food web is higher.

[0130] Step S8, based on the calculation of the number of producer nodes, the number of consumer nodes, and the number of links of each trophic group in the upstream and downstream ecological network diagrams of the dam, the impact of the dam on the stability and vulnerability of the river food web is analyzed respectively.

[0131] Specifically, S8 includes the following steps:

[0132] Step S8.1, the number of food resource nodes and the number of consumer nodes of each trophic group in the upstream and downstream ecological network diagrams of the dam are calculated to analyze the impact of the dam on the stability and vulnerability of the river food web in the river basin.

[0133] Generally, the more the number of food resource nodes and the number of consumer nodes, the more the types of food resources and consumers, and the higher the stability of the river food web. Generally, the fewer the number of food resource nodes and the number of consumer nodes, the fewer the types of food resources and consumers, and the higher the vulnerability of the river food web.

[0134] Step S8.2, calculate the number of links between each node in the ecological network diagram of the upstream and downstream of the dam, compare the sum of the number of nodes and the sum of the number of links of the upstream of the dam with the sum of the number of nodes and the sum of the number of links of the downstream of the dam, the greater the difference between the number of nodes and the number of links between the upstream and the downstream, the greater the impact of the dam on the river food web. Compared with the upstream, the number of nodes and the number of links of the downstream decrease, which indicates that the trophic level under the influence of the dam decreases and the structure of the river food web is simplified; the number of nodes and the number of links of the downstream increase, which indicates that the trophic level under the influence of the dam increases and the structure of the river food web is complicated.

[0135] In the present embodiment, the ecological network diagram based on the eicosapentaenoic acid (EPA) information of each species in the upstream and downstream river food web of the dam is analyzed by Rstudio software, and the corresponding network indicators of the ecological network diagram of the upstream river food web of the dam and the ecological network diagram of the downstream river food web of the dam are obtained.

[0136] The following table provides a corresponding network indicator of the ecological network diagram based on the eicosapentaenoic acid (EPA) information of each species in the upstream and downstream river food web of the dam.

[0137]

[0138] In the above table, the Connectance index represents the proportion of actual connections (or fluxes) in the ecological network to the possible connections. The proportion of actual links (or fluxes) in the network to the possible links (or fluxes) is represented. The connectance index of the upstream of the dam is higher, which means that the ecological network of the upstream of the dam is more complex and the interaction between species is more.

[0139] In the above table, the Generality index represents the average number of prey that each predator in the ecological network can prey on. The generality index of the upstream of the dam is slightly higher, which indicates that the predator in the upstream of the dam can usually prey on more types of prey. The generality index of the downstream of the dam is lower, which may indicate that the number of prey species preyed on by the predator in the downstream of the dam decreases.

[0140] In the above table, the Vulnerability index refers to the average number of predators that each prey can be preyed on. The vulnerability index of the upstream is higher, which means that the prey in the upstream faces more predators and greater predation pressure. The vulnerability index of the downstream is lower, which may indicate that the number of predators of the prey decreases.

[0141] In this embodiment, a comprehensive analysis of the three corresponding network indicators of the constructed upstream and downstream ecological network diagram of the dam shows that the river food web network structure upstream of the dam is relatively complex, with more interactive relationships and interactions between species, more prey species for predators, and greater predation pressure on prey. The river food web network structure downstream of the dam, which is more affected by the dam, becomes simpler, with reduced interactive relationships and interactions between species, fewer prey species for predators, and reduced predation pressure on prey.

[0142] According to the analysis results of the ecological network diagram and its corresponding network indicators constructed based on the eicosapentaenoic acid (EPA) information of each species in the upstream and downstream river food web of the dam, the influence of the dam on the river food web may have the following ecological implications:

[0143] The influence of the dam may lead to the simplification of the river food web ecological network downstream of the river, reducing the interactions between species. This may be due to the dam blocking the upstream and downstream of the river, reducing the connectivity between the upstream and downstream of the river, changing the habitat of aquatic species in the river, limiting the migration of aquatic species in the upstream and downstream of the river, and causing the disruption of food chains in the upstream and downstream river food web of the dam.

[0144] The influence of the dam may reduce the relative number and species of predators and prey, and may reduce the species diversity and interspecific interactions of predators and prey, leading to a decrease in species diversity, a decrease in stability, and an increase in vulnerability of the downstream river food web of the dam. The reduction of predators and prey in the downstream river food web of the dam reduces the predation pressure and predation opportunities downstream.

[0145] The node size, link width, Connectance index, Generality index, and Vulnerability index in the ecological network indicate that the influence of the dam is significant, changing the network structure, predator-prey interaction patterns, and overall ecological function of the upstream and downstream. This change may affect the stability and function of the ecosystem, and further research on the specific effects of the dam on the ecosystem and its mechanisms is needed.

[0146] In some embodiments, the indicators in the ecological network include but are not limited to node size, link width, Connectance index, Generality index, and Vulnerability index.

[0147] Obviously, the above-mentioned embodiments are only examples for clearly illustrating the present application, and the content is only a simple embodiment of the present application, and cannot be considered as a limitation to the present application. Based on the above description, other different forms of changes or variations can also be made by those skilled in the art. Here, it is not necessary and also impossible to enumerate all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the appended claims of the present application.

Claims

1. A method for analyzing the impact of dams on river food webs based on fatty acid and ecological network analysis, characterized in that, The method includes: (1) Calculate the node size in the ecological network diagram based on the long-chain unsaturated fatty acid information of each species in the upstream and downstream river food webs of the dam; the methods for calculating the node size include: The content of long-chain unsaturated fatty acids of various species in the food web of the river upstream and downstream of the dam was obtained; the long-chain unsaturated fatty acids were one or more of the following: docosahexaenoic acid, eicosapentaenoic acid, α-linolenic acid, linoleic acid, arachidonic acid, and bacterial fatty acids. Based on the long-chain unsaturated fatty acid information of each species, the node size in the ecological network diagram is determined to visualize the nutrient concentration represented by the long-chain unsaturated fatty acid content of each species. ； Where size is the node size, C i The average fatty acid content of species i. The maximum fatty acid content of individual species i. A customizable constant that can be used to generate an ecological network analysis diagram. The minimum size of the node; (2) Based on the node size, as well as the predation relationship among trophic groups, node color, the width of the link between nodes, the size of the link arrow, and the nutrient transfer efficiency, construct an ecological network diagram of the food web of the upstream and downstream rivers of the dam. (3) Analysis of the impact of dams on river food webs, including: Based on the difference between the sum of the node areas represented by each trophic group species in the ecological network diagram upstream and downstream of the dam and the sum of the corresponding node areas upstream and downstream of the dam, the impact of the dam on key species in the river food web is analyzed. Furthermore, based on the calculation of the number of food resource nodes and consumer nodes for each trophic group in the upstream and downstream ecological network diagram of the dam, the impact of the dam on the stability and vulnerability of the river ecosystem food web within the basin is analyzed.

2. The method according to claim 1, characterized in that, The larger the proportion of the total node area of ​​a single species and a single trophic group in the total node area, the greater the influence of the corresponding species and trophic group on the river food web. The larger the proportion of the difference in the total area of ​​all nodes in the total area, the greater the impact of the dam on the corresponding species.

3. The method according to claim 1, characterized in that, The more food resource nodes and consumer nodes there are, the more diverse the food resources and consumers there are, and the higher the stability of the river ecosystem food web; conversely, the more vulnerable the river ecosystem food web is.

4. The method according to claim 1, characterized in that, The methods for calculating link width include: Obtain information on long-chain unsaturated fatty acids of various species in the food web of the river upstream and downstream of the dam; Based on the long-chain unsaturated fatty acid information of each species, the link width in the ecological network diagram is determined to visualize the energy transfer flux between species represented by the content of long-chain unsaturated fatty acids. ； Where wide represents the link width, and E represents the activation energy contained in species i. The maximum activation energy of individual species i. A customizable constant that can be used to generate an ecological network analysis diagram. Minimum width for the link.

5. The method according to claim 1, characterized in that, The average nutrient transfer efficiency from fallen leaves and vegetation to herbivorous consumers was 0.40, from attached algae and phytoplankton to herbivorous consumers was 0.77, and from consumers to carnivorous consumers was 0.

906.

6. The method according to claim 1, characterized in that, The main trophic groups of the species include: attached algae, deciduous leaves, vegetation, phytoplankton, zooplankton, benthic animals, and fish; among them, attached algae, deciduous leaves, vegetation, and phytoplankton constitute the food resources in the trophic groups.

7. The method according to claim 1, characterized in that, The construction of the ecological network diagram is as follows: To obtain the trophic structure of the food web of the river upstream and downstream of the dam; Based on the classification and relation databases of nutrient groups, the food resources and consumers of the food web are identified; Based on the number of species in trophic groups and the number of predation relationships between species, the number of nodes and the number of links between nodes in the ecological network diagram upstream and downstream of the dam are determined. An ecological network diagram of the food web of the upstream and downstream rivers of the dam is constructed by considering predation relationships among nutrient groups, node colors, link widths between nodes, link arrow sizes, and nutrient transfer efficiency.

8. The method according to claim 7, characterized in that, Based on the number of species in trophic groups and the number of predatory relationships between species, the number of nodes and the number of links between nodes in the ecological network diagram upstream and downstream of the dam are determined, specifically including the following steps: S3.1, based on the number of species in trophic groups, the total number of nodes is the total number of species in the river food web, and the number of nodes in the ecological network diagram upstream and downstream of the dam corresponds one-to-one with the number of species; among them, food resources include attached algae, deciduous leaves, vegetation, and phytoplankton, and consumers include zooplankton, benthic animals, and fish. S3.2 Based on the number of interspecific predation relationships in the river food web, the total number of links is the total number of interspecific predation relationships in the river food web. The number of links between nodes in the ecological network diagram upstream and downstream of the dam corresponds one-to-one with the number of interspecific predation relationships. The link colors between species and the link arrows are assigned the same color.

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