AU2020101936A4

AU2020101936A4 - Method of eutrophic water body restoration based on ecosystem model and biomanipulation technology

Info

Publication number: AU2020101936A4
Application number: AU2020101936A
Authority: AU
Inventors: Yunv Dai; Yiping TAI; Ran TAO; Sai Wang; Yang Yang; Jinhua Zhang; Xiaomeng Zhang
Original assignee: Jinan University; University of Jinan
Current assignee: Jinan University
Priority date: 2018-05-04
Filing date: 2020-08-21
Publication date: 2020-10-01
Anticipated expiration: 2026-06-05

Abstract

The present invention relates to a method of eutrophic water body restoration based on an ecosystem model and a biomanipulation technology. First, an ECOPATH model is used to fit an energy flow pattern of a current ecosystem; when it is determined that annual production of phytoplankton or macroohytes in a water body is too high, according to output results of the model, on the basis of minimum primary production required for maintaining operation of the system, a method of quantitatively adding fish consumers is adopted for excess primary production, and a predation effect of the fish consumers is used to increase consumption of the primary production in the system; at the same time, a top-down effect is produced to control biomass and community structure of a primary producer. After the restoration is completed, fish catch is evaluated using the ECOPATH model, and the economic fish species added in the current year are harvested according to evaluation results, to maintain energy balance of the ecosystem. 2/2 Performing sample collection of aquatic organisms in a current damaged water body Species Individual Parameters of Trophic predation composition biomass functional groups relationship Inputing data into an ECOPATH model, and performing data fitting, pilot run, checkout, and regrouping Evaluating output results of the model (before restoration) Determininga Evaluating whether Determiningthe main primary productivity exceeds the amount exceeding producer standard the standard Determining the biomass of the added consumer functional groups (herbivorous/filter feeding/omnivorous/carnivorous) Quantitatively adding fish consumers Evaluating output results of the model (after restoration) Determiningfish Comparing system energy Evaluating changes in c flow changes before and ecosystem performance after restoration parameters FIG. 3

Description

2/2

Performing sample collection of aquatic organisms in a current damaged water body

Species Individual Parameters of Trophic predation composition biomass functional groups relationship

Inputing data into an ECOPATH model, and performing data fitting, pilot run, checkout, and regrouping

Evaluating output results of the model (before restoration)

Determininga Evaluating whether Determiningthe main primary productivity exceeds the amount exceeding producer standard the standard

Determining the biomass of the added consumer functional groups (herbivorous/filter feeding/omnivorous/carnivorous)

Quantitatively adding fish consumers

Evaluating output results of the model (after restoration)

Determiningfish Comparing system energy Evaluating changes in c flow changes before and ecosystem performance after restoration parameters

FIG. 3

METHOD OF EUTROPHIC WATER BODY RESTORATION BASED ON ECOSYSTEM MODEL AND BIOMANIPULATION TECHNOLOGY

TECHNICAL FIELD The present invention relates to the technical field of ecological environment governance, and more specifically, relates to a method of eutrophic water body restoration based on an ecosystem model and a biomanipulation technology.

BACKGROUND With a rapid economic and social development, some freshwater lakes and municipal lakes in China are facing tremendous pressure from water body eutrophication, and water body pollution is very serious in some places, such as Chaohu Lake, Dianchi Lake, and Taihu Lake, etc. The main source of water body eutrophication pollution is the large amount of nutrients contained in water bodies, mainly nitrogen and phosphorus pollutants. Water body eutrophication is a natural process of evolution and aging of water bodies. Under the influence of human activities, this slow natural process accelerates very fast. In many areas of China, especially areas where degree of agricultural intensification is high and nitrogen fertilizers are used in large quantities, problem of water body eutrophication is more prominent. At present, 65% of China's water bodies are in eutrophic state, and 29% are turning to a eutrophic state. Water body eutrophication has become one of the major environmental problems that China's water bodies are facing. Due to excessive amount of nutrients in water bodies, biomass and production of aquatic organisms (such as macrophytes, periphyton, and phytoplankton) continue increasing, especially represented by "algal bloom" of phytoplankton. The large amount of dissolved oxygen consumed in the respiration of macrophytes and algae and the process of death and decomposition thereof cause water bodies to be in a serious hypoxic state, producing toxic substances (such as hydrogen sulfide), seriously reducing water body quality, and threatening survival of aquatic organisms. Currently, restoration on eutrophic water bodies by ecological means is mainly based on biomanipulation technology. Biomanipulation technology is based on energy flow patterns of ecosystems, by means of predation relationship among each trophic level in food chain, through changing biological community structure of a damaged water body, especially through adding high-level fish consumers, to exert a top-down effect thereof, and to achieve the purposes of improving water body quality and restoring ecological balances of water ecosystems. Biomanipulation is a cost-efficient and pure natural restoration technology. However, during the implementation process, there are mainly the following scientific issues difficult to determine: 1) the biomass of fish added, 2) the recapture amount of fish, 3) whether the ecosystem has become more perfect, and 4) how to evaluate the system restoration effect. How to use a scientific and effective method to carry out ecological restoration on a damaged water body is a pressing problem needed to be solved at present.

SUMMARY OF THE INVENTION The technical problem to be solved by the present invention is to overcome shortcomings and deficiencies of the above-mentioned prior art, and to provide a method of eutrophic water body restoration based on an ecosystem model and a biomanipulation technology. The method provides a new thinking reference and a technical support for current restoration methods by means of scientific experiments from the perspectives of ecology, quantity and energetics, and has a very important application value for ecological restoration of the damaged water body. The above-mentioned purposes of the present invention are achieved through the following technical solution. A method of eutrophic water body restoration based on an ecosystem model and a biomanipulation technology includes the following steps: Si, collecting detritus and aquatic organisms in a damaged water body, determining species composition thereof, and then classifying functional groups according to a predation mode of each of the species; S2, further determining ecological parameters of each of the functional groups in S1, including biomass, productivity, consumption and trophic predation relationship, combining basic parameters obtained in Si, inputing into an ECOPATH model, and performing data fitting, pilot run, checkout, and regrouping; S3, checking output results of the ECOPATH model, determining a main primary producer, and evaluating whether primary productivity of a current system exceeds the standard, that is, whether the ratio of total primary productivity to total respiration is greater than 1, and determining an amount exceeding the standard; and S4, quantitatively adding a consumer functional group according to the amount exceeding the standard determined by S3, to maintain a minimum primary production required for operation of ecosystem. The ecosystem model ECOPATH is a well-developed, easy-to-operate packaged software that combines a variety of ecological analyses, which is used to construct ecosystem food web patterns and can perform ecological simulations, to provide effective scientific references for ecosystem management. This model relies on principles of quantitative ecology and energy ecology to quantitatively analyze biomass, production, and consumption of each of the functional groups in the ecosystem, and uses predation relationship among each trophic level as a network, to construct energy flow patterns for various water bodies. Advantages of the ECOPATH model are that it can simulate energy flow change trend of the system by changing relevant parameters, and provide general ecosystem indicators so that managers can judge pros and cons of the system changes. In the present invention, the ECOPATH model is first used to fit an energy flow pattern of the current ecosystem; when it is determined that annual production of phytoplankton or macroohytes in a water body is too high, according to output results of the model, on the basis of minimum primary production required for maintaining operation of the system, a method of quantitatively adding filter-feeding, herbivorous, omnivorous and carnivorous fish is adopted for excess primary production, and a predation effect of the fish consumers is used to increase consumption of the primary production in the system; at the same time, a top-down effect is produced to control biomass and community structure of the primary producer. Preferably, after dosage of the consumer functional group is determined, new system parameters are input into the ECOPATH model, a second simulation is performed, and output results of the second simulation are compared with the results of the first simulation, that is, model fitting results before restoration. Changes in parameters of integrity of food web structure, trophic function diversity, and energy transfer effectiveness of the target water body before and after restoration are compared, to ensure that restoration effect can achieve improvement of the ecosystem, and to achieve the purposes of reducing energy redundancy of the system, increasing the number of cycles per unit of energy flow and increasing the length of food chain. Preferably, the consumer functional group is fish consumers. Specifically, the fish consumers are filter-feeding fish, herbivorous fish, omnivorous fish or carnivorous fish. The herbivorous and filter-feeding fish are added to control the primary production of the system and to reduce nutrients, while the omnivorous and carnivorous fish are added to improve the maturity, diversity, and energy flow transfer efficiency of the system. On the basis of ensuring that the consumption of the herbivorous and filter-feeding fish can effectively reduce the nutrient content in the system, the dosage of the omnivorous and carnivorous fish can be adjusted according to the development degree of the system. Preferably, after all the fish consumers are added in S4, the output results of the ECOPATH model are used to calculate recyclable fish catch in units of years, and determination of a maximum fish catch shall meet that: 1) the remaining herbivorous and filter-feeding fish after fishing are sufficient to continue consuming the excess primary production in the following year; 2) structural changes of parameters such as system energy flow, ecological attribute, and food web knot, etc. are quantitatively reduced; and 3) the system is maintained in a relatively mature and stable state. After the ecosystem restoration is completed, the present invention further uses the ECOPATH model to evaluate the fish catch. According to evaluation results, economic fish species added in the year are harvested, so that the ecosystem maintains energy balance, and the catches can directly take away a large amount of nutrients from the water body and produce a certain economic value. Preferably, the main primary producers in S3 are macrophytes and phytoplankton, primary productions of unutilized macrophytes and phytoplankton are calculated and calculation formulas are as follows:

UPmacrophyte (TP - TR) x macrophyte

UPphytoplankton (TP - TR) x phytoplankton

where, UPmacrophyte (unutilised production) and UPphytoplankton are the primary

productions of the unutilized macrophytes and the unutilized phytoplankton, respectively;

Pmacrophyte (production) and Pphytoplankton are primary productions of the macrophytes and

the phytoplankton, respectively; TP (total production) is a total primary production of the system, that is, the sum of Pmacrophyte and Pphytoplankton; and TR is a total respiration of the 2 2. 1 system, and the above data are all in a unit of g-m- yea Preferably, in S4, based on primary productions of unutilized macrophytes and unutilized phytoplankton, fish species to be added are started to select, a suitable dosage of each of the species is calculated, fries are purchased and added, where the added species can be selected according to the differences between areas; biomass of the added herbivorous or omnivorous fish is calculated and calculation formulas are as follows: UP -Dma-ht Bherbivorous fish macrophyte Cherbivorous fish X macrophyte - X herbivorousfish

UPphytoplankton Cfilter-feeding fish X Dphytoplankton

Bfilter-feeding fish A \B/filter-feeding fish

where, UPmacrophyte and UPphytoplankton are the primary productions of the unutilized

macrophytes and the unutilized phytoplankton, respectively, in a unit of g-m-2. yea

Cherbivorous fish (consumption) and Cfilter-feeding fish are consumptions of the herbivorous fish

and the filter-feeding fish, respectively, in a unit of g-m-2. year; Dmacrophyte (diet) and

Dphytoplankton are a proportion of the macrophytes in food of the herbivorous fish and a

proportion of the planktonic algae in food of the filter feeding fish, respectively, in a unit of %; Bherbivorous fish (biomass) and Bfilter-feeding fish are biomass of the added herbivorous fish and

the added filter-feeding fish, respectively, in a unit of g-m-2; A (area) is a water body area of a

restoration area, in a unit of m2; and - and - are Bherbivorous fish \filter-feeding fish

consumption rates of the herbivorous fish and the filter-feeding fish provided in the model, respectively, without a unit. Preferably, the dosage of the omnivorous and carnivorous fish in the system is aimed at improving the maturity, diversity, and energy flow transfer efficiency of the system. The method of the present invention only provides an upper limit of the dosage that the system can withstand, within this limit, the dosage of the omnivorous and carnivorous fish can be selected according to specific conditions such as restoration speed of the restored water body, available fish biomass, market economic value of catches, etc., and dosage calculation formulas are as follows: Pi 1 > EE = Pi Carnivorous fish X Di

1 > EE = Comnivorous fish X Dj where, EEj (ecotrophic efficiency) is an ecotrophic efficiency of a functional group i in the system; Pi and Pj are productions of functional groups i and j, in a unit of g-m-2.year-;

Ccarnivorous fish and Comnivorous fish are consumptions of the carnivorous fish and the omnivorous fish, respectively, in a unit of g-m-2.year-; D and Dj are proportions of the

functional groups i andj in the food of the carnivorous and omnivorous fish, respectively. These formulas mainly illustrate that the consumptions of the carnivorous fish and the omnivorous fish in the system cannot exceed the production of any functional group. Preferably, the aquatic organisms are phytoplankton, zooplankton, macrobenthos or fish. Preferably, the filter-feeding fish are Hypophthalmichthys molitrix and Hypophthalmichthys nobilis, the herbivorous fish is Ctenopharyngodonidellus, the omnivorous fish are Parabramis pekinensis and Megalobrama amblycephala, and the carnivorous fish are Channa maculata and Channa argus. Compared with the prior art, the present invention has the following beneficial effects. (1) The present invention adopts the method of combining the ECOPATH model and biomanipulation to design a restoration scheme for a damaged water body which is the first international application. The successful operation of this method will provide important scientific basis and technical support for protection and restoration of aquatic ecosystems.

(2) The present invention performs restoration based on the ecological model, can achieve the improvement of the ecosystem from the perspectives of integrity of food web structure, trophic function diversity, and energy transfer effectiveness, etc., to achieve the purposes of reducing energy redundancy of the system, increasing the number of cycles per unit of energy flow and increasing the length of food chain, making the system develop towards a more stable and mature direction. After the restoration is completed, the ECOPATH model is used to evaluate the fish catch. According to the evaluation results, economic fish species added in the year are harvested to maintain the energy balance of the ecosystem, and the catches can directly take away a large amount of nutrients from the water body and produce a certain economic value. The method of the present invention provides a new thinking reference and a technical support for current restoration methods by means of scientific experiments from the perspectives of ecology, quantity and energetics, and has a very important application value for ecological restoration of the damaged water body.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of Bainikeng Reservoir Bay in the tail area of Yantian Reservoir as an ecological restoration demonstration area in Embodiment 1. FIG. 2 is a comparison picture of water quality and eutrophication status of a test area before and after restoration. FIG. 3 is a flowchart of a method of eutrophic water body restoration based on an ecosystem model and a biomanipulation technology according to the present invention.

DETAILED DESCRIPTION The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field. Unless otherwise specified, the reagents and materials used in the following embodiments are all commercially available.

Embodiment 1 Bainikeng Reservoir Bay in the tail area of Yantian Reservoir as an ecological restoration demonstration area (FIG. 1) has a total area of about 10,200 m2 (170 meters long and 60 meters wide). The demonstration area is divided into three test areas, among which an area of Area I is

1200 m 2, an area of Area II is 6000 m2 , and an area of Area III is 3000 m2 Design of restoration scheme for the restoration area of this Reservoir in the present invention includes the following steps: 1. Investigation of existing organisms in the water body to be restored Dift nets and fixed shrimp cages, Peterson mud harvesters, and plankton nets were used to collect existing fish, macrobenthic invertebrates, zooplankton and phytoplankton in the water body, respectively, and their biomass were determined. Production/biomass, consumption/biomass and non-assimilation rate were provided by the model itself. The specific parameters are shown in Table 1. Table 1 Basic input parameters of the system before restoration Functional Biomass Production/biomass Consumption/biomass Non-assimilation groups g-m- 2 yea- 1 year- 1 rate Pelteobagrus 1.42 0.91 8.14 0.20 fulvidraco Clariasfuscus 1.06 1.63 4.61 0.20 Coilia grayi 1.67 1.61 10.76 0.20 Rhinogobius 2.55 1.90 35.37 0.20 giurinus Cyprinus carpio 2.07 1.82 12.68 0.40 Cirrhinus 2.19 1.91 8.78 0.60 molitorella Carassius 0.77 2.16 9.85 0.60 auratus Coptodon zilli 4.48 3.73 20.54 0.60 Pseudorasbora 0.87 1.93 28.83 0.60 parva Misgurnus 2.63 0.62 47.45 0.60 anguillicaudatus Insect predator 0.47 7.31 54.94 0.20 Insect collector 3.11 12.72 164.46 0.50 Gastropod 3.72 5.50 42.41 0.40 Bivalve 8.49 4.41 28.72 0.40 Annelid 1.39 19.76 135.72 0.40

Shrimp and crab 1.85 19.09 151.73 0.36 Zooplankton 4.62 67.26 356.02 0.56 Phytoplankton 13.24 172.21 Macrophyte 2.54 10.24 Detritus 30.05

2. Determination of the predation relationship among each biological group A gastric content analysis method was used to quantitatively analyze diet composition of main functional groups, and diet composition modules required for model construction process were determined, as shown in Table 2. Table 2 Predation relationship among each functional group in the system

Channa Pelteobagrus Clarias Coilia Rhinogobius Cyprinus maculata fulvidraco fuscus grayi giurinus carpio

Channa maculata Pelteobagrus fulvidraco Clariasfuscus Coilia grayi 0.05 Rhinogobius 0.05 0.10 giurinus Cyprinus carpio 0.05 0.10 Carassiusauratus 0.05 0.10 Hypophthalmichthys 0.10 0.10 nobilis Hypophthalmichthys 0.10 0.10 molitrix Oreochromis 0.40 0.50 0.20 niloticus Ctenopharyngodon 0.10 0.10 idellus Pseudorasbora 0.05 0.05 parva

Misgurus 0.05 0.10 0.10 anguillicaudatus Insectpredator 0.05 0.20 Insect collector 0.10 0.10 0.10 Gastropod 0.20 Bivalve 0.10 0.15 Annelid 0.20 0.20 0.10 Shrimp and crab 0.20 0.10 Zooplankton 0.60 0.10 Phytoplankton 0.35 0.20 Macrophyte 0.10 Detritus 0.30

(continued) Carassius Hypophthalmichthys Hypophthalmichthys Oreochromis auratus nobilis molitrix niloticus Channa maculata Pelteobagrus fulvidraco Clariasfuscus Coilia grayi Rhinogobius giurinus Cyprinus carpio Carassiusauratus Hypophthalmichthys nobilis Hypophthalmichthys molitrix Oreochromis niloticus Ctenopharyngodon idellus

Pseudorasbora parva Misgurnus anguillicaudatus Insect predator 0.10 Insect collector 0.10 Gastropod 0.10 Bivalve 0.10 0.10 Annelid Shrimp and crab 0.20 Zooplankton 0.05 0.70 0.10 0.15 Phytoplankton 0.30 0.20 0.80 Macrophyte 0.30 Detritus 0.15 0.10 0.10 0.35

(continued) Ctenopharyngodon Pseudorasbora Misgurnus Insect idellus parva anguillicaudatus predator Channa maculata Pelteobagrus fulvidraco Clariasfuscus Coilia grayi Rhinogobius giurinus Cyprinus carpio Carassiusauratus Hypophthalmichthys nobilis Hypophthalmichthys molitrix Oreochromis niloticus

Ctenopharyngodon idellus Pseudorasbora parva Misgurnus anguillicaudatus Insect predator Insect collector 0.10 Gastropod 0.10 Bivalve 0.10 Annelid Shrimp and crab 0.10 0.30 Zooplankton 0.40 0.10 0.10 Planktonicalgae 0.10 0.20 0.20 Macrophyte 1.00 0.10 0.10 Detritus 0.40 0.30 0.30

(continued)

Shrimp Insect Bivalve Annelids and Zooplankton collector Gastropod crab Channa maculata Pelteobagrus fulvidraco Clariasfuscus Coilia grayi Rhinogobius giurinus Cyprinus carpio Carassiusauratus Hypophthalmichthys nobilis Hypophthalmichthys molitrix Oreochromis niloticus Ctenopharyngodon idellus Pseudorasbora parva Misgurnus anguillicaudatus Insect predator Insect collector Gastropod Bivalve Annelid Shrimp and crab Zooplankton 0.10 0.10 0.10 0.10 0.05 Phytoplankton 0.20 0.20 0.15 0.20 0.20 Macrophyte 0.10 0.10 0.10 Detritus 0.60 0.90 0.70 0.75 0.60 0.75

3. Model operation and result output The analysis results of step 1 and step 2 were input into the ECOPATH model, the model was run to check output results, and whether primary productivity of the current system exceeds the standard was determined, that is, whether the ratio of total primary productivity to total respiration is greater than 1. The larger the ratio is, the higher the unutilized primary productivity is. This embodiment found out that the ratio of total primary productivity to total respiration (TP/TR) is 3.15, according to the calculation method of the following formula (1):

UPmacrophyte (TP - TR) x macrophyte

UPphytoplankton (TP - TR) xpPhytoplankton TPak

where, UPmacrophyte (unutilised production) and UPphytoplankton are primary

Pmacrophyte (production) and Pphytoplankton are primary productions of the macrophytes and the phytoplankton, respectively; TP (total production) is a total primary production of the system, that is, the sum of Pmacrophyte and Pphytoplankton; and TR is a total respiration of the 2. 1 system, and the above data are all in a unit of g-m-2 yea After calculations, the unutilized primary productivity in the system is 45.6 g-m-year, of which 2.7 g-m-2. yea comes from the unutilized macrophytes and the remaining 42.9 g-m-2. yea comes from the unutilized phytoplankton.

4. Calculation of fish dosage After obtaining data of the unutilized primary productivity, the biomass of herbivorous and filter-feeding fish to be added in the restoration scheme was calculated according to the calculation method of the following formula (2): UP -CDmar Bherbivorous fish -ht macrophyte -- herbivorous fish X macrophyte -A XBhbi A X @ herbivorous fish

UPherbivorous fish Cfilter-feeding fish X Dherbivorous fish

Bfilter-feeding fish

A \B/filter-feeding fish

macrophytes and the unutilized phytoplankton, respectively, in a unit of g-m-2. yea Cherbivorous fish (consumption) and Cfilter-feeding fish are consumptions of the herbivorous fish and the filter-feeding fish, respectively, in a unit of g-m-2. year-1; Dmacrophyte (diet) and Dphytoplankton are a proportion of the macrophytes in food of the herbivorous fish and a proportion of the phytoplankton in food of the filter feeding fish, respectively, in a unit of %; Bherbivorous fish (biomass) and Bfilter-feeding fish are biomass of the added herbivorous fish and the added filter-feeding fish, respectively, in a unit of g-m-2; A (area) is a water body area of a

consumption rates of the herbivorous fish and the filter-feeding fish provided in the model, respectively, without a unit. After calculations, the dosage of Ctenopharyngodonidellus is 5.12 g-m-2, and a total dosage offilter-feeding Hypophthalmichthys molitrix and Hypophthalmichthys nobilis is 10.62 g-m-2 , calculated based on the area of the demonstration area as 10000 m2 , the amount of Ctenopharyngodon idellus to be added is 51.2 kg and the total amount of Hypophthalmichthys molitrix and Hypophthalmichthys nobilis to be added is 106 kg. On the basis that the herbivorous and filter-feeding fish can be fully consumed, the biomass of the carnivorous fish in the system was calculated according to the calculation method of the following formula (3): Pi 1>EE = Pi Carnivorous fish X Di

1>EE= Comnivorous fish X Dj where, EEj (ecotrophic efficiency) is an ecotrophic efficiency of a functional group i in the system; Pi and Pj are productions of functional groups i andj, in a unit of g-m-2.year-1;

Carnivorous fish and Comnivorousfish are consumptions of the carnivorous fish and the omnivorous fish, respectively, in a unit of g-m-2.year-; D and Dj are proportions of the

functional groups i andj in the food of the carnivorous and omnivorous fish, respectively. These formulas mainly illustrate that the consumptions of the carnivorous fish and the omnivorous fish in the system cannot exceed the production of any functional group. In this embodiment, the upper limit of the biomass of carnivorous fish in the system depends on the production of Rhinogobius giurinus, that is, PRhinoobiusiurinus the upper

limit of the biomass of the omnivorous fish in the system depends on the production of bivalves, that is, Pbivalve. Take the adding of Channa maculata and Parabramispekinensis as an example, after calculations, the upper limits of dosage of the two in the demonstration area are 1.54 and 2.21 g-m-2 , respectively. To ensure the survival rate in this embodiment, the dosage was set as the upper limit. Newly added data of the restoration scheme are summarized in Table 3. Table 3 Input parameters added to the system after restoration (new functional groups added on the basis of Table 1) Biomass Production/biomass Consumption/biomass Non-assimilation Functional groups 2-m yer 1 1 g -m2 year: yer year- rt rate

Channa maculata 1.54 0.86 4.73 0.20 Parabramis 2.21 2.31 20.42 0.40 pekinensis Hypophthalmichthys 5.31 1.37 8.78 0.60 nobilis Hypophthalmichthys 5.31 1.51 9.85 0.60 molitrix Ctenopharyngodon 5.12 1.93 10.60 0.60 idellus

5. Comparison of ecosystem performance parameters before and after restoration

After the fish dosage of each functional group is determined, the newly added data in Table 3 were respectively input into the ECOPATH model, a second simulation was performed, and output results of the second simulation were compared with results of the first simulation, that is, model fitting results before restoration. Changes in parameters of integrity of food web structure, s trophic function diversity, and energy transfer effectiveness of the target water body before and after restoration were compared. Table 4 Comparison of ecosystem performance parameters before and after restoration Ecosystem parameters Unit Before restoration After restoration Total system consumption g-m 2 -year' 3525 3922 Total system output g-m z year 1504 530 Total system respiration g-m-2 -year' 1267 1418 Total system flow to detritus g-m z-year 3780 2575 Total system energy flow amount g-m-2 -year' 10077 8447 Total system production gm y ear 3290 2530 Total system net primary productivity g-m year 2772 1949 Total primary productivity/total ratio 2.19 1.01 respiration System net production g-m -year- 1504 530 Total primary production/total ratio rto42 18 respiration Total system biomass g-m z year 64 103 Total amount of fishing g-m-2 -year-' 4.15 16.30 System connectivity index No unit 0.20 0.18 Omnivority index No unit 0.15 0.15 Diversity index No unit 2.71 2.64

The results show that according to the restoration design scheme, the system can achieve the efficacies of reducing energy redundancy of the system, increasing the number of cycles per unit of energy flow, and increasing the length of food chain. At the same time, the system has higher stability and maturity.

6. Design of recapture amount The annual ecological transfer efficiency (EE) value is designed as 1, that is, the increased biomass of herbivorous and filter-feeding fish after one year are harvested. The EE value of 1 is only theoretically feasible. In order to ensure the survival amount of fish in the second year, the EE value can be reduced to 0.8-0.9 to ensure that the fish in the system can maintain their own steady growth. In this embodiment, the EE value was designed as 0.85, after calculations, the available recapture amount of Hypophthalmichthys nobilis was 32 kg, that of Hypophthalmichthys molitrix was 27 kg, and that of Ctenopharyngodon idellus was 85 kg.

7. Comparison of water quality parameters before and after restoration After the implementation of the present invention, on-site monitoring results show that the water quality and eutrophication status of the test area have been significantly improved (FIG. 2, Table 5), and indicators such as nitrogen, phosphorus, chlorophyll and suspended solids in the water body have decreased by 30%-60%, of which the total phosphorus content is below 0.05 mg L 1, and the chlorophyll content is less than 15 g 1-

. Table 5 Comparison of water quality indicators before and after restoration

Water body TN TP Chl-a Suspended Losson solids ignition indicators (mg L) (mg L) ( g L') ld igitio (mg L ) (mgUL1

) Before 0.88 0.061 15.97 15.60 5.33 restoration After 1.15 0.044 9.14 5.25 2.75 restoration

The method of the present invention provides a new thinking reference and a technical support for current restoration methods by means of scientific experiments from the perspectives of ecology, quantity and energetics, and has a very important application value for ecological restoration of the damaged water body.

Claims

What is claimed is:

1. A method of eutrophic water body restoration based on an ecosystem model and biomanipulation technology, characterized in that, the method comprises the following steps: Si, collecting detritus and aquatic organisms in a damaged water body, determining species composition thereof, and then classifying functional groups according to a predation mode of each of the species; S2, further determining ecological parameters of each of the functional groups in Si, including biomass, productivity, consumption and trophic predation relationship, combining basic parameters obtained in Si, inputing into an ECOPATH model, and performing data fitting, pilot run, checkout, and regrouping; S3, checking output results of the ECOPATH model, determining a main primary producer, and evaluating whether primary productivity of a current system exceeds the standard, and determining an amount exceeding the standard; and S4, quantitatively adding a consumer functional group according to the amount exceeding the standard determined by S3, to maintain a minimum primary production required for operation of ecosystem.

2. The method according to claim 1, characterized in that, after a dosage of the consumer functional group is determined, new system parameters are input into the ECOPATH model, a second simulation is performed, and output results of the second simulation is compared with model fitting results before restoration.

3. The method according to claim 1 or claim 2, characterized in that, the consumer functional group is fish consumers.

4. The method according to claim 3, characterized in that, the fish consumers are filter-feeding fish, herbivorous fish, omnivorous fish or carnivorous fish.

5. The method according to claim 4, characterized in that, after all the fish consumers are added in S4, the output results of the ECOPATH model are used to calculate recyclable fish catch in units of years, and determination of a maximum fish catch shall meet that: 1) the remaining herbivorous and filter-feeding fish after fishing are sufficient to continue consuming the excess primary production in the following year; 2) structural changes of parameters such as system energy flow, ecological attribute, and food web knot, etc. are quantitatively reduced; and

3) the system is maintained in a relatively mature and stable state.

6. The method according to claim 1, characterized in that, the main primary producers in S3 are macrophytes and phytoplankton, primary productions of unutilized macrophytes and unutilized phytoplankton are calculated and calculation formulas are as follows:

UPmacrophyte (TP - TR) X macrophyte

UPphytoplankton (TP - TR) X phytoplankton

macrophytes and the unutilized phytoplankton, respectively; Pmacrophyte and Pphytoplankton

are primary productions of the macrophytes and the phytoplankton, respectively; TP is a total primary production of the system, that is, the sum of Pmacrophyte and Pphytoplankton; and TR

is a total respiration of the system.

7. The method according to claim 4, characterized in that, according to primary productions of unutilized macrophytes and unutilized phytoplankton, biomass of the herbivorous fish or the omnivorous fish added is calculated and calculation formulas are as follows: UP -Dmr -ht Bherbivorous fish macrophyte Cherbivorous fish X macrophyte -A X herbivorousfish

UPphytoplankton -filter-feeding fish X Dphytoplankton

Bfilter-feeding fish A \B/filter-feeding fish

macrophytes and the unutilized phytoplankton, respectively; Cherbivorous fish and

Cfilter-feeding fish are consumptions of the herbivorous fish and the filter-feeding fish, respectively; Dmacrophyte and Dphytoplankton are a proportion of the macrophytes in food of

the herbivorous fish and a proportion of the phytoplankton in food of the filter-feeding fish, respectively; Bherbivorous fish and Bfilter-feeding fish are biomass of the added herbivorous fish

and the added filter-feeding fish, respectively; A is a water body area of a restoration area; and

(- B herbivorous fish and - 'CBfilter-feeding fish are consumption rates of the herbivorous fish and

the filter-feeding fish provided in the model, respectively.

8. The method according to claim 4, characterized in that, calculation formulas of dosage of the omnivorous fish or the carnivorous fish are as follows: Pi 1>EE = Pi Carnivorous fish X Di

1>EE= Comnivorous fish X Dj where, EEj is an ecotrophic efficiency of a functional group i in the system; Pi and Pj are productions of functional groups i and j; Ccarnivorous fish and Comnivorous fish are consumptions of the carnivorous fish and the omnivorous fish, respectively; and Di and Dj are proportions of the functional groups i andj in food of the carnivorous fish and the omnivorous fish, respectively.

9. The method according to claim 1, characterized in that, the aquatic organisms are phytoplankton, zooplankton, macrobenthos or fish.

10. The method according to claim 4, characterized in that, the filter-feeding fish are Hypophthalmichthys molitrix and Hypophthalmichthys nobilis, the herbivorous fish is Ctenopharyngodon idellus, the omnivorous fish are Parabramispekinensis and Megalobrama amblycephala, and the carnivorous fish are Channa maculata and Channa argus.