Identification method and application of stable components in dissolved organic carbon from large seaweed

Abstract

The present invention belongs to the technical field of seaweed, and discloses a method for identifying stable components in large seaweed algae-derived dissolved organic carbon and its application. The method for identifying stable components in large seaweed algae-derived dissolved organic carbon includes: evaluating the activity and inertness of large seaweed algae-derived DOC; identifying the fluorescent components of algae-derived DOC; and identifying the molecular composition of algae-derived DOC. The present invention combines the three contents of evaluating the activity and inertness of large seaweed algae-derived DOC, identifying the fluorescent components of algae-derived DOC, and identifying the molecular composition of algae-derived DOC, so as to realize the evaluation of the stable components of large seaweed algae-derived DOC, and finally realize the qualitative and quantitative evaluation of the inert DOC in the algae-derived DOC, which helps to break through the technical "bottleneck" of the difficulty in evaluating the water carbon sink contributed by seaweed at present, and has important application value and scientific significance for realizing a quantitative marine carbon trading system and promoting the development of large seaweed carbon sink industry in the future.

Description

Technical Field

[0001] The invention belongs to the technical field of seaweed, and in particular relates to a method for identifying stable components in dissolved organic carbon from large seaweed sources and an application thereof. Background Art

[0002] At present, large seaweed is a very productive plant in the ocean, with a global maximum net primary productivity of 2.9 Pg C yr -1 . During its growth, it fixes carbon through photosynthesis and releases 20% to 40% of its primary productivity into the water in the form of dissolved organic carbon (DOC). This part of algae-derived DOC in the water has a very complex composition, and its stability also varies greatly. Highly active DOC components can be quickly utilized by microorganisms, while highly stable DOC components (i.e., inert DOC) are difficult to be utilized and converted by microorganisms due to their high degree of inertness. They can remain in seawater for a long time, becoming an important contribution of large seaweed to the stable DOC reservoir of the ocean.

[0003] In the ocean, the DOC released by large seaweed contains many highly active components, which can be quickly absorbed and utilized by microorganisms and enter the micro-food loop. According to the ocean "microbial carbon pump" (MCP) theory, after entering the micro-food loop, most of this highly active dissolved organic carbon can be remineralized into CO2 through microbial respiration and released into the atmosphere, while a portion (about 5%) can be converted by microorganisms into very stable inert DOC components, which can be stored in the ocean for thousands of years.

[0004] Developing marine carbon sinks is one of the important ways to achieve the goal of "carbon neutrality". Although people recognize the importance of large seaweed in contributing inert DOC to water bodies, this part of carbon sink in the form of inert DOC has not yet been included in the quantitative assessment of seaweed carbon sinks. The main reason is that there is still a lack of in-depth understanding of this part of inert DOC, especially the difficulty in identifying the stable components it contains.

[0005] Through the above analysis, the problems and defects of the existing technology are as follows: for large seaweed, although people realize the importance of its contribution of inert DOC to water bodies, this part of carbon sink in the form of inert DOC has not yet been included in the quantitative assessment of seaweed carbon sink. The main reason is that there is still a lack of in-depth understanding of this part of inert DOC, especially the identification of the stable components it contains is still difficult.

[0006] The difficulty in solving the above problems and defects is: At present, it is still very difficult to identify the stable components of DOC from large seaweed sources. The main reason is that there is no accurate determination method for inert DOC in the world, and there is still a lack of in-depth understanding of inert DOC in water bodies.

[0007] The significance of solving the above problems and defects is: In view of the above defects, the present invention adopts long-term microbial degradation experiments, combines FDOM fluorescence components with DOC molecular composition identification, and analyzes the active, inert and stable components of algae-derived DOC from both qualitative and quantitative levels, which is of great significance for the scientific evaluation of the carbon sink function of large seaweed. Summary of the invention

[0008] In response to the problems existing in the prior art, the present invention provides a method for identifying stable components in dissolved organic carbon from large seaweed sources and its application, aiming to evaluate and analyze the inert DOC that can form a long-term carbon sink in the ocean.

[0009] The present invention is achieved by providing a method for identifying stable components in dissolved organic carbon derived from large seaweeds, the method comprising the following steps:

[0010] Step 1: Conduct activity and inertness evaluation of large seaweed-derived DOC, use long-term microbial degradation experiments to analyze the microbial availability of algae-derived DOC, and quantify the inert DOC that is ultimately not utilized by microorganisms;

[0011] Step 2: Identify the fluorescent components of algae-derived DOC, and analyze the fluorescent components with different stability in algae-derived DOC according to the changes in the components of fluorescent dissolved organic matter FDOM;

[0012] Step three: identify the molecular composition of algae-derived DOC and analyze the stability components of algae-derived DOC at the molecular level based on the molecular composition characteristics of DOC.

[0013] Furthermore, in step one, the activity and inertness evaluation of the large seaweed-derived DOC includes: conducting long-term microbial degradation experiments on the algae-derived DOC, evaluating the algae-derived DOC with different stabilities based on the dynamic change characteristics of DOC and combining a second-order exponential decay model.

[0014] Furthermore, the inert DOC obtained from the microbial degradation experiment is only microbial inertness, so a chemical and biological combination method is used to photodegrade the DOC that is not utilized by microorganisms and repeatedly degrade it with fresh microorganisms. Finally, the DOC that is not utilized by light and new microorganisms can be regarded as stable DOC.

[0015] Furthermore, in step one, the activity and inertness evaluation of the large seaweed-derived DOC also includes: fitting a model of DOC concentration and degradation time by analyzing the dynamic changes of DOC during long-term microbial degradation, and judging the DOC with different stabilities, i.e., active, semi-active and inert sizes, according to the fitting equation.

[0016] Furthermore, in step 1, the activity and inertness evaluation of the macroalgae-derived DOC further includes:

[0017] The DOCs with different stabilities: active DOC (C1), semi-active DOC (C2), and inert DOC (C3) were evaluated by using the Marquardt nonlinear least squares fitting procedure as shown in the following formula:

[0018] C T =C1e -k1t +C2e -k2t +C3;

[0019] Among them, C T is the total DOC concentration at time t, C1 represents the size of active DOC, C2 represents the size of semi-active DOC, C3 represents the size of inert DOC, and k1 and k2 are the decay constants of active DOC and semi-active DOC.

[0020] Furthermore, in step 2, the fluorescent component identification of the algae-derived DOC includes: analyzing the main components of the fluorescent dissolved organic matter FDOM in the long-term microbial degradation of the algae-derived DOC, wherein the protein-like substances contained therein can be quickly utilized by microorganisms due to their high activity, and the fluorescence intensity gradually decreases, which can be used to characterize the active components of DOC; and the humus-like substances are not easily utilized by microorganisms, and the fluorescence intensity gradually increases during degradation, which can characterize the stable components of DOC.

[0021] Furthermore, in step three, the molecular composition identification of the algae-derived DOC includes: performing ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry FT-ICR MS analysis on DOC in the long-term microbial degradation of algae-derived DOC, and dividing DOC into four types of molecules containing CHO-, CHNO-, CHOS- and CHNOS- by analyzing the molecular composition of DOC obtained at different degradation times. Molecules that exhibit low H / C, high O / C, high equivalent saturated double bonds DBE, and high aromaticity index AI* have higher inert characteristics and are identified as DOC stability molecules.

[0022] Furthermore, the method for identifying stable components in large seaweed-derived dissolved organic carbon also includes: by combining the three parts of activity and inertness evaluation of the large seaweed-derived DOC, fluorescent component identification of the algae-derived DOC and molecular composition identification of the algae-derived DOC, it is possible to evaluate the stability components of the large seaweed-derived DOC, and ultimately achieve qualitative and quantitative evaluation of the inert DOC in the algae-derived DOC.

[0023] Another object of the present invention is to provide an application of the method for identifying stable components in large seaweed-derived dissolved organic carbon in the evaluation of stable components of large seaweed-derived DOC.

[0024] Another object of the present invention is to provide an application of the method for identifying stable components in large seaweed-derived dissolved organic carbon in the qualitative and quantitative evaluation of inert DOC in algae-derived DOC.

[0025] In combination with all the above-mentioned technical solutions, the advantages and positive effects of the present invention are as follows: the method for identifying stable components in large seaweed-derived dissolved organic carbon provided by the present invention can realize the evaluation of stable components of large seaweed-derived DOC by combining the activity and inertness evaluation of large seaweed-derived DOC, the fluorescent component identification of algae-derived DOC and the molecular composition identification of algae-derived DOC, and ultimately realize the qualitative and quantitative evaluation of the inert DOC in the algae-derived DOC.

[0026] The present invention can qualitatively and quantitatively identify the inert DOC produced by large seaweed by conducting stability and component identification on large seaweed-derived DOC, which helps to break through the current technical "bottleneck" of difficult assessment of water carbon sinks contributed by seaweed, and has important scientific significance for quantifying the future marine carbon trading system and promoting the development of the large seaweed carbon sink industry.

[0027] The present invention evaluates the activity and inertness of algae-derived DOC from large seaweeds and identifies the stable fluorescent components and molecular composition contained therein, thereby achieving quantitative and qualitative evaluation of the stable DOC contributed by large seaweeds. This has important application value for quantifying the carbon sink contributed by seaweeds and promoting the development of the large seaweed carbon sink industry in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 It is a flow chart of a method for identifying stable components in dissolved organic carbon derived from large seaweeds provided in an embodiment of the present invention.

[0030] Figure 2 It is the time variation characteristics of the green algae-derived DOC in the long-term microbial degradation provided by Example 3 of the present invention, and a second-order exponential decay model is fitted for the DOC concentration and degradation time; wherein the DOC concentration decreases rapidly (0-10 days) that is active DOC, decreases slowly (10-100 days) that is semi-active DOC, and decreases extremely slowly in the later period (100-400 days) to a stable state that is inert DOC.

[0031] Figure 3This is the concentration change characteristic of DOC in the fresh microbial degradation (a) and photodegradation (b) of the remaining DOC after long-term microbial degradation provided in Example 3 of the present invention. Finally, the DOC that is not degraded by new microorganisms and light is the stable DOC.

[0032] Figure 4 This is the characteristic of the change in the intensity of the fluorescent components of FDOM during long-term microbial degradation provided in Example 3 of the present invention; wherein C1 and C2 are protein-like components, and C3 and C4 are humus-like components.

[0033] Figure 5 It is the time variation characteristics of brown algae-derived DOC in the long-term microbial degradation provided by Example 4 of the present invention, and a second-order exponential decay model is fitted for the DOC concentration and degradation time; wherein the DOC concentration decreases rapidly (0-10 days) that is active DOC, decreases slowly (10-80 days) that is semi-active DOC, and in the later period (80-360 days) it decreases extremely slowly to a stable state that is inert DOC.

[0034] Figure 6 This is the characteristic of the change in the intensity of the fluorescent components of FDOM during long-term microbial degradation provided in Example 4 of the present invention; wherein C1 and C2 are protein-like components, and C3 and C4 are humus-like components. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] In view of the problems existing in the prior art, the present invention provides a method for identifying stable components in dissolved organic carbon derived from large seaweed. The present invention is described in detail below in conjunction with the accompanying drawings.

[0037] like Figure 1 As shown, the method for identifying stable components in dissolved organic carbon from large seaweeds provided in an embodiment of the present invention comprises the following steps:

[0038] S101, evaluate the activity and inertness of DOC from large seaweed sources;

[0039] S102, identification of fluorescent components of algae-derived DOC;

[0040] S103, identify the molecular composition of algae-derived DOC.

[0041] The technical solution of the present invention is further described below in conjunction with embodiments.

[0042] Example 1

[0043] The present invention is achieved through the following technical solutions:

[0044] The first aspect is to provide a method for evaluating the activity and inertness of large seaweed-derived DOC. By implementing long-term microbial degradation experiments on algae-derived DOC, algae-derived DOC with different stabilities are evaluated based on the dynamic change characteristics of DOC and combined with a second-order exponential decay model. Specifically, it mainly analyzes the dynamic changes of DOC during long-term microbial degradation, fits the model for DOC concentration and degradation time, and judges the size of DOC with different stabilities (i.e., active, semi-active, and inert) based on the fitting equation. That is, mainly by using the Marquardt nonlinear least squares fitting program to evaluate DOC with different stabilities: active DOC (C1), semi-active DOC (C2), and inert DOC (C3), as shown in Formula 1:

[0045] C T =C1e -k1t +C2e -k2t +C3 (Formula 1)

[0046] Among them C T is the total DOC concentration at time t, C1 represents the size of active DOC, C2 represents the size of semi-active DOC, C3 represents the size of inert DOC, and k1 and k2 are the decay constants of active DOC and semi-active DOC. For example, in Example 3, according to the fitting results, the sizes of active, semi-active and inert DOC are 230, 230 and 396, respectively, and their corresponding degradation times are 0-10, 10-100, 100-400 days (see Figure 2 ).

[0047] In addition, the inert DOC obtained from the above microbial degradation experiment is only microbial inert. Therefore, the DOC that is not used by microorganisms is degraded again by light and fresh microorganisms by a combination of chemical and biological methods. The DOC that is not used by light and new microorganisms can be regarded as stable DOC. For example, in Example 3, the microbial inert DOC that is not used by microorganisms is 406μM, of which 4% and 6% are degraded by new microorganisms and light, respectively (see Figure 3 ), and the final remaining stable DOC was 366 μM.

[0048] The second aspect of the present invention provides a fluorescent component identification technology for algae-derived DOC. The fluorescent dissolved organic matter (FDOM) in the long-term microbial degradation of algae-derived DOC is analyzed for its main components. The protein-like substances contained therein can be quickly utilized by microorganisms due to their high activity, and their fluorescence intensity gradually decreases, which can be used to characterize the active components of DOC. The humus-like substances are not easily utilized by microorganisms, and their fluorescence intensity gradually increases during degradation, which can characterize the stable components of DOC. For example, in Example 3, C1 and C2 were identified as protein-like components. As the degradation time increases, the fluorescence intensity of the protein-like components gradually decreases (see Figure 4 a, Figure 4 b), which was identified as the DOC active component, while the fluorescence intensity of humus-like substances gradually increased (see Figure 4 c, Figure 4 d), can be identified as a DOC stabilizing component.

[0049] The third aspect of the present invention provides a molecular composition identification technology for algae-derived DOC. Ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis is performed on DOC in the long-term microbial degradation of algae-derived DOC. By analyzing the molecular composition of DOC obtained at different degradation times, DOC is divided into four types of molecules containing CHO-, CHNO-, CHOS- and CHNOS-. Molecules that exhibit low H / C, high O / C, high equivalent saturated double bonds (DBE), and high aromaticity index (AI*) have higher inert characteristics and are identified as DOC stability molecules. For example, in Example 3, by comparing the molecular composition of DOC on the 0th and 400th days, the 400-day DOC exhibits obvious low H / C, high O / C, high DBE and high AI* index, so the 400-day DOC molecules can be identified as DOC stability molecules (see Table 1).

[0050] The present invention combines the above three parts to achieve the evaluation of the stability components of large seaweed-derived DOC, and ultimately achieve the qualitative and quantitative evaluation of the inert DOC in the algae-derived DOC.

[0051] The present invention can qualitatively and quantitatively identify the inert DOC produced by large seaweed by conducting stability and component identification on large seaweed-derived DOC, which helps to break through the current technical "bottleneck" of difficult assessment of water carbon sinks contributed by seaweed, and has important scientific significance for quantifying the future marine carbon trading system and promoting the development of the large seaweed carbon sink industry.

[0052] Example 2

[0053] A specific embodiment of the present invention is to provide a method for evaluating the activity and inertness of DOC derived from large seaweed. DOC derived from large seaweed is mixed with microorganisms, and a long-term microbial degradation experiment is carried out under dark conditions. The time can be as long as more than 1 year, and samples are taken at the 0th, 5th, 10th, 20th, 30th, 60th, 90th, 120th, 150th, 180th, 210th, 240th, 270th, 300th and 360th day of the experiment. According to the time dynamic change characteristics of DOC, and combined with the second-order exponential decay model, the active DOC is used quickly by microorganisms in a short time, the semi-active DOC is used slowly and eventually, and the inert DOC can exist stably for a long time. In addition, after the long-term microbial degradation experiment is completed, a portion of fresh seawater microorganisms is added to the remaining DOC sample again, and degradation continues for 60 days, and the changes in DOC concentration are monitored to verify whether the DOC components remaining after long-term microbial degradation are consistent with the newly added microorganisms. In addition, the remaining DOC was placed in a quartz cup and continued to degrade under natural light for 10 days to verify the stability of the remaining DOC to light. Ultimately, the DOC that was not degraded by new microorganisms and light was called stable DOC.

[0054] In addition, in order to identify the stability components of DOC, FDOM and FT-ICR MS samples were collected in the long-term microbial degradation experiment of algae-derived DOC. First, the principal component analysis of FDOM was performed using three-dimensional fluorescence spectroscopy technology to resolve different fluorescent components, and the stability of the components was identified based on the changes in the fluorescence intensity of different components. The protein-like components have high activity and their intensity gradually decreases under the action of microorganisms, so they can be identified as DOC active components; while the humus-like components have high inertness and their intensity gradually increases, so they can be identified as DOC stability components. On the other hand, the FT-ICR MS technology was used to analyze the molecular composition information of DOC. First, the DOC samples were solid-phase extracted, and the samples after solid-phase extraction were diluted with methanol and injected into the mass spectrometer through the ApolloII electrospray ion source for measurement. Finally, the molecular composition information of algae-derived DOC was obtained through FT-ICR MS calibration, data acquisition and processing. According to the analyzed molecular formula, it is generally believed that molecules with low H / C, high O / C, high DBE, and high aromaticity index (AI*) have higher inert characteristics and can be identified as DOC stable molecules; while molecules with high H / C, low O / C, low DBE and low aromaticity index (AI*) have higher activity and can be identified as DOC active molecules.

[0055] Example 3: Identification of Stable Components of Green Algae-derived DOC

[0056] The large green algae Enteromorpha was used as the research object. The Enteromorpha algae were cultured under laboratory conditions for 30 days, and the cultured seawater was filtered through a 0.7μm GF / F filter membrane to obtain the algae-derived DOC. Nearshore microorganisms were added to the algae-derived DOC, and a long-term (400 days) microbial degradation experiment of Enteromorpha-derived DOC was carried out under dark conditions. The results showed that Enteromorpha-derived DOC underwent significant changes in dynamic and component characteristics under the action of microorganisms. Among them, the DOC concentration showed a characteristic of first increasing and then decreasing, and gradually stabilizing in the later period. According to the exponential decay equation, DOC in different time periods is divided into active DOC, semi-active DOC and inert DOC. According to the fitting results, the sizes of active, semi-active and inert DOC are 230, 230 and 396, respectively, and their corresponding degradation times are 0-10, 10-100, 100-400 days, respectively (see Figure 2 ). In addition, the decay constants of active DOC and semi-active DOC were 0.10 and 0.01, respectively. In addition, the generated microbial inert DOC (406 μM) was further subjected to fresh microbial degradation and photodegradation, of which 4% and 6% were degraded by fresh microorganisms and light, respectively (see Figure 3 ), the DOC that remains unchanged in the final system is the stable DOC, and its final content is 366μM.

[0057] During long-term degradation, microorganisms drive DOC to gradually transform from easily utilized active components (protein-like) to extremely stable inert components (humus-like), which can be seen from the changes in FDOM fluorescence intensity (see Figure 4 ), the gradually decreasing protein-like components, namely DOC active components (C1 and C2), and the gradually increasing humus-like components, namely DOC stable components (C3 and C4). In addition, according to the molecular composition analyzed by FT-ICR MS, the molecules that showed low H / C, high O / C, high DBE, and high aromaticity index (AI*) at the end of degradation (400 days) can be identified as DOC stable molecules (see Table 1).

[0058] Table 1 Changes in the molecular composition of DOC during long-term microbial degradation of DOC from green algae

[0059]

[0060] In Table 1, molecules with high H / C, low O / C, low DBE, and low AI* values ​​are DOC active molecules, and molecules with low H / C, high O / C, high DBE, and high AI* values ​​are DOC stable molecules.

[0061] Example 4: Identification of Stable Components of Brown Algae-derived DOC

[0062] The large brown algae - Laminaria japonica was taken as the research object. The kelp algae were cultured in the laboratory for 30 days, and the cultured seawater was filtered through a 0.7μm GF / F filter membrane to obtain the algae-derived DOC. Nearshore microorganisms were added to the algae-derived DOC, and a long-term (360 days) microbial degradation experiment of Enteromorpha-derived DOC was carried out under dark conditions. The results showed that Laminaria japonica DOC was significantly degraded under the action of microorganisms, among which the DOC concentration showed a characteristic of first increasing and then decreasing, and gradually stabilizing in the later period. According to the exponential decay equation, DOC in different time periods was divided into active DOC, semi-active DOC and inert DOC. According to the fitting results, the sizes of active, semi-active and inert DOC were 21, 20 and 58, respectively, and their corresponding degradation times were 0-10, 10-80, 80-360 days, respectively (see Figure 5 ), the decay constants of active DOC and semi-active DOC are 0.12 and 0.01 respectively. Figure 6 ), the gradually decreasing protein-like components, namely DOC active components (C1 and C2), and the gradually increasing humus-like components, namely DOC stable components (C3 and C4). In addition, according to the molecular composition analyzed by FT-ICR MS, compared with the initial DOC, the molecules that showed low H / C, high O / C, high DBE, and high aromaticity index (AI*) at the end of degradation can be identified as DOC stable molecules (see Table 2).

[0063] Table 2 Changes in the molecular composition of DOC during long-term microbial degradation of brown algae-derived DOC

[0064]

[0065] In Table 2, molecules with high H / C, low O / C, low DBE, and low AI* values ​​are DOC active molecules, and molecules with low H / C, high O / C, high DBE, and high AI* values ​​are DOC stable molecules.

[0066] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for identifying stable components in dissolved organic carbon from large seaweed, characterized in that: The method for identifying stable components in dissolved organic carbon from large seaweed sources comprises: Evaluation of the activity and inertness of DOC from macroalgae; Identification of fluorescent components of algae-derived DOC; Identification of the molecular composition of algae-derived DOC; The activity and inertness evaluation of the large seaweed-derived DOC includes: conducting a long-term microbial degradation experiment on the algae-derived DOC, evaluating the algae-derived DOC with different stability according to the dynamic change characteristics of DOC and combining a second-order exponential decay model; The activity and inertness evaluation of the macroalgae-derived DOC also includes: evaluating DOCs with different stabilities by using the Marquardt nonlinear least squares fitting program: active DOC, i.e. C1, semi-active DOC, i.e. C2, and inert DOC, i.e. C3: C T =C1e -k1t +C2e -k2t +C3; Among them, C T is the total DOC concentration at time t, C1 represents the size of active DOC, C2 represents the size of semi-active DOC, C3 represents the size of inert DOC, and k1 and k2 are the decay constants of active DOC and semi-active DOC; The fluorescent component identification of the algae-derived DOC includes: analyzing the main components of the fluorescent dissolved organic matter FDOM in the long-term microbial degradation of the algae-derived DOC, wherein the protein-like substances contained therein are rapidly utilized by microorganisms due to their high activity, and the fluorescence intensity gradually decreases, which can be used to characterize the active components of DOC; and the humus-like substances are not easily utilized by microorganisms, and the fluorescence intensity gradually increases during degradation, which can characterize the stable components of DOC; The molecular composition identification of the algae-derived DOC includes: performing ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry FT-ICR MS analysis on DOC in long-term microbial degradation of algae-derived DOC, and dividing DOC into four types of molecules containing CHO-, CHNO-, CHOS- and CHNOS- by analyzing the molecular composition of DOC obtained at different degradation times. Molecules that show low H / C, high O / C, high equivalent saturated double bonds DBE, and high aromaticity index AI* have higher inert characteristics and are identified as DOC stability molecules.

2. The method for identifying stable components in dissolved organic carbon derived from large seaweed as claimed in claim 1, characterized in that: The inert DOC obtained from the microbial degradation experiment is only microbial inertness, so a chemical and biological combination method is used to photodegrade the DOC that is not utilized by microorganisms and repeatedly degrade it with fresh microorganisms. Finally, the DOC that is not utilized by light and new microorganisms can be regarded as stable DOC.

3. The method for identifying stable components in dissolved organic carbon derived from large seaweed as claimed in claim 1, characterized in that: The method for identifying stable components in large seaweed-derived dissolved organic carbon also includes: by combining the activity and inertness evaluation of the large seaweed-derived DOC, the fluorescent component identification of the algae-derived DOC, and the molecular composition identification of the algae-derived DOC, the stability component evaluation of the large seaweed-derived DOC can be achieved, and ultimately the qualitative and quantitative evaluation of the inert DOC in the algae-derived DOC can be achieved.

4. An application of the method for identifying stable components in large seaweed-derived dissolved organic carbon as described in any one of claims 1 to 3 in evaluating the stability components of large seaweed-derived DOC.

5. An application of the method for identifying stable components in large seaweed-derived dissolved organic carbon as described in any one of claims 1 to 3 in qualitative and quantitative evaluation of inert DOC in algae-derived DOC.

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