{"id":{"repo_id":"cadiz","oai_identifier":"oai:rodin.uca.es:10498/36228"},"canonical_url":"https://search.dev.ndltd.org/etd/cadiz/oai:rodin.uca.es:10498/36228","repository":{"repo_id":"cadiz","name":"Universidad de Cadiz","base_url":"https://rodin.uca.es/oai/request"},"display":{"title":"Carbon dynamics in coastal vegetated communities: evaluation of anthropogenic impacts, chemical characterization of dissolved organic matter, and its influence on blue carbon sequestration","abstract":"Climate change (a variation in temperatures and weather patterns) is a natural phenomenon that has been accelerating since the 19th century. The rapid increase in global temperature is mainly due to the emission of large amounts of greenhouse gases, resulting from anthropogenic activities such as the burning of fossil fuels or from livestock activities. This concern was expressed globally with the Kyoto Protocol in 1997, the first international agreement aimed at committing industrialized countries to reduce greenhouse gas emissions. Since then, policies and adaptation and mitigation measures have been adopted by the different countries involved. In the Paris Agreement in 2015, a commitment was made not to exceed the pre-industrial temperature by 1.5°C, focusing strategies on reducing global greenhouse gas emissions by 85%. In addition, one of the most innovative mitigation measures of this agreement was the possibility of capturing and removing carbon through natural ecosystems. In this context, coastal vegetated communities have been noted for their fundamental role in sequestering and storing carbon in the sediment (blue carbon), incorporating carbon dioxide (CO2) and removing it from the atmosphere in the long term. In addition, these communities play a key role in ocean carbon cycling through dissolved organic matter (DOM) fluxes where part of this organic matter feeds heterotrophic organisms (labile DOM) and another fraction contributes to the carbon pool stored in the deep ocean for thousands of years (refractory DOM). Indeed, the role of coastal vegetated ecosystems as CO2 sinks has attracted the attention of a diverse group of stakeholders including the scientific community, private sector, governments and intergovernmental bodies committed to marine conservation and climate change mitigation and adaptation. However, these communities are currently among the most threatened ecosystems in the biosphere, largely due to various anthropogenic impacts resulting in deteriorating water quality, habitat destruction due to coastal development and also, more recently, the occurrence of extreme events such as storms (e.g., DANA) and heatwaves resulting from climate change. All this produces direct and indirect impacts that affect both biomass and DOM fluxes and carbon stocks in the sediment, leading to a decrease in the capacity to store carbon in the long term, as well as to a loss of sediment carbon being released back into the atmosphere in the form of CO2. In this scenario, and from an integrated perspective, this thesis has addressed the response of certain coastal vegetated ecosystems (seagrass meadows and macroalgae) to some of the main global threats that affect them. This perspective is based on the fact that the response of these ecosystems to different impacts is far from being simple and individual, and that the final behavior must integrate the responses of each of the components that make up the community (dominant primary producer, bacterial activity in water and sediment and macrofauna, mainly). This thesis is composed of four chapters in which the direct and indirect impact of anthropogenic activities on coastal vegetated communities (seagrass meadows and macroalgae) has been estimated. In addition, and as a pioneering milestone, the DOM of the different coastal vegetated communities in the Bay of Cádiz has been chemically characterized. In chapter 1, the direct impact of the construction of several coastal infrastructures on the organic carbon stocks of the meadows of Zostera noltei in Ria Formosa (Portugal) was studied. In this study was observed that impacted meadows contained 1.5 times less organic carbon stock than non-impacted meadows. Although the area affected was relatively small (0.05-0.07 ha), the coastal infrastructure caused a significant reduction of the carbon stock, between 1.1 and 2.2 Megagrams (Mg) organic carbon, and a total loss of the carbon sequestration capacity of the impacted meadows. These results contribute to understanding the spatial variability of blue carbon stocks in coastal systems heavily impacted by urban development. Chapters 2 and 3 estimate the integrated community response (through community metabolism and dissolved organic carbon (DOC) fluxes) of the coastal vegetated communities of the Bay of Cádiz at two times of the year (winter and summer) to the chronic impact of reduced shoot density (chapter 2) and to the indirect impact of climate change such as marine heatwaves (chapter 3). In Chapter 2, changes in Cymodocea nodosa communities was observed when the shoot density was reduced to 40 and 75% of the control. The net primary production of the community decreased up to 10-fold when the shoot density was reduced from an autotrophic to a heterotrophic community. In addition, DOC fluxes (up to 5.5 times) and sediment organic matter decreased significantly. This clearly indicates that the prolonged chronic stress to which these communities have been subjected is having a negative impact on their ability to capture and store blue carbon. In chapter 3, it was observed that the heat caused an increase in net primary production in C. nodosa communities (1.9 times more than the control) and a decrease in Caulerpa prolifera communities. DOC fluxes in C. prolifera communities shifted towards negative values, i.e. from being DOC producers to DOC consumers. Furthermore, an increase in the percentage of refractory DOC was observed when the communities were subjected to a simulated heatwave, which could indicate that the increase in temperature would also increase carbon stocks. In chapter 4, the dissolved organic matter of the seagrass communities C. nodosa and Z. noltei and the macroalgal community C. prolifera were chemically characterized using a methodology based on nuclear magnetic resonance and high-resolution mass spectrometry. The chemical profile of the DOM of the different coastal vegetated communities showed that the major compounds were the highly unsaturated and aromatic ones. In addition, the DOM was characterized after a bioavailability test, which revealed the highest percentage of lability in the C. prolifera community (86%), followed by C. nodosa (81%) and Z. noltei (76%). According to van Krevelen diagrams, a significant fraction of labile compounds belonged to lipid-, peptide-, amino sugar-, and carbohydrate-like classes, while the refractory compounds mainly belonged to lignin-, tannin-, and aromatic-like classes. In conclusion, this thesis highlights the negative effects of anthropogenic impacts on coastal vegetated communities, affecting the functions and services they provide, such as climate change mitigation. The results of this thesis show not only the significant loss of biomass and blue carbon stocks in the coastal communities studied as a consequence of direct impacts (coastal infrastructures), but also that the metabolism and DOC fluxes of the community are affected by indirect (heatwaves) and chronic impacts (reduction in shoot density), leading to a decrease in the functions and services provided by these ecosystems. In addition, this thesis has contributed, for the first time, to the study of the chemical characterization of DOM from coastal vegetated communities using high-resolution techniques, revealing the chemical profile of labile and refractory DOM. Our results provide further arguments for the growing need to protect and conserve these valuable ecosystems in order to maintain the ecosystem services they provide to our planet, such as the ability to mitigate climate change.","abstract_html":"Climate change (a variation in temperatures and weather patterns) is a natural phenomenon that has been accelerating since the 19th century. The rapid increase in global temperature is mainly due to the emission of large amounts of greenhouse gases, resulting from anthropogenic activities such as the burning of fossil fuels or from livestock activities. This concern was expressed globally with the Kyoto Protocol in 1997, the first international agreement aimed at committing industrialized countries to reduce greenhouse gas emissions. Since then, policies and adaptation and mitigation measures have been adopted by the different countries involved. In the Paris Agreement in 2015, a commitment was made not to exceed the pre-industrial temperature by 1.5°C, focusing strategies on reducing global greenhouse gas emissions by 85%. In addition, one of the most innovative mitigation measures of this agreement was the possibility of capturing and removing carbon through natural ecosystems. In this context, coastal vegetated communities have been noted for their fundamental role in sequestering and storing carbon in the sediment (blue carbon), incorporating carbon dioxide (CO2) and removing it from the atmosphere in the long term. In addition, these communities play a key role in ocean carbon cycling through dissolved organic matter (DOM) fluxes where part of this organic matter feeds heterotrophic organisms (labile DOM) and another fraction contributes to the carbon pool stored in the deep ocean for thousands of years (refractory DOM). Indeed, the role of coastal vegetated ecosystems as CO2 sinks has attracted the attention of a diverse group of stakeholders including the scientific community, private sector, governments and intergovernmental bodies committed to marine conservation and climate change mitigation and adaptation. However, these communities are currently among the most threatened ecosystems in the biosphere, largely due to various anthropogenic impacts resulting in deteriorating water quality, habitat destruction due to coastal development and also, more recently, the occurrence of extreme events such as storms (e.g., DANA) and heatwaves resulting from climate change. All this produces direct and indirect impacts that affect both biomass and DOM fluxes and carbon stocks in the sediment, leading to a decrease in the capacity to store carbon in the long term, as well as to a loss of sediment carbon being released back into the atmosphere in the form of CO2. In this scenario, and from an integrated perspective, this thesis has addressed the response of certain coastal vegetated ecosystems (seagrass meadows and macroalgae) to some of the main global threats that affect them. This perspective is based on the fact that the response of these ecosystems to different impacts is far from being simple and individual, and that the final behavior must integrate the responses of each of the components that make up the community (dominant primary producer, bacterial activity in water and sediment and macrofauna, mainly). This thesis is composed of four chapters in which the direct and indirect impact of anthropogenic activities on coastal vegetated communities (seagrass meadows and macroalgae) has been estimated. In addition, and as a pioneering milestone, the DOM of the different coastal vegetated communities in the Bay of Cádiz has been chemically characterized. In chapter 1, the direct impact of the construction of several coastal infrastructures on the organic carbon stocks of the meadows of Zostera noltei in Ria Formosa (Portugal) was studied. In this study was observed that impacted meadows contained 1.5 times less organic carbon stock than non-impacted meadows. Although the area affected was relatively small (0.05-0.07 ha), the coastal infrastructure caused a significant reduction of the carbon stock, between 1.1 and 2.2 Megagrams (Mg) organic carbon, and a total loss of the carbon sequestration capacity of the impacted meadows. These results contribute to understanding the spatial variability of blue carbon stocks in coastal systems heavily impacted by urban development. Chapters 2 and 3 estimate the integrated community response (through community metabolism and dissolved organic carbon (DOC) fluxes) of the coastal vegetated communities of the Bay of Cádiz at two times of the year (winter and summer) to the chronic impact of reduced shoot density (chapter 2) and to the indirect impact of climate change such as marine heatwaves (chapter 3). In Chapter 2, changes in Cymodocea nodosa communities was observed when the shoot density was reduced to 40 and 75% of the control. The net primary production of the community decreased up to 10-fold when the shoot density was reduced from an autotrophic to a heterotrophic community. In addition, DOC fluxes (up to 5.5 times) and sediment organic matter decreased significantly. This clearly indicates that the prolonged chronic stress to which these communities have been subjected is having a negative impact on their ability to capture and store blue carbon. In chapter 3, it was observed that the heat caused an increase in net primary production in C. nodosa communities (1.9 times more than the control) and a decrease in Caulerpa prolifera communities. DOC fluxes in C. prolifera communities shifted towards negative values, i.e. from being DOC producers to DOC consumers. Furthermore, an increase in the percentage of refractory DOC was observed when the communities were subjected to a simulated heatwave, which could indicate that the increase in temperature would also increase carbon stocks. In chapter 4, the dissolved organic matter of the seagrass communities C. nodosa and Z. noltei and the macroalgal community C. prolifera were chemically characterized using a methodology based on nuclear magnetic resonance and high-resolution mass spectrometry. The chemical profile of the DOM of the different coastal vegetated communities showed that the major compounds were the highly unsaturated and aromatic ones. In addition, the DOM was characterized after a bioavailability test, which revealed the highest percentage of lability in the C. prolifera community (86%), followed by C. nodosa (81%) and Z. noltei (76%). According to van Krevelen diagrams, a significant fraction of labile compounds belonged to lipid-, peptide-, amino sugar-, and carbohydrate-like classes, while the refractory compounds mainly belonged to lignin-, tannin-, and aromatic-like classes. In conclusion, this thesis highlights the negative effects of anthropogenic impacts on coastal vegetated communities, affecting the functions and services they provide, such as climate change mitigation. The results of this thesis show not only the significant loss of biomass and blue carbon stocks in the coastal communities studied as a consequence of direct impacts (coastal infrastructures), but also that the metabolism and DOC fluxes of the community are affected by indirect (heatwaves) and chronic impacts (reduction in shoot density), leading to a decrease in the functions and services provided by these ecosystems. In addition, this thesis has contributed, for the first time, to the study of the chemical characterization of DOM from coastal vegetated communities using high-resolution techniques, revealing the chemical profile of labile and refractory DOM. Our results provide further arguments for the growing need to protect and conserve these valuable ecosystems in order to maintain the ecosystem services they provide to our planet, such as the ability to mitigate climate change.","abstract_has_math":false,"creators":["Casal Porras, Isabel"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Brun Murillo, Fernando Guillermo","Pérez Lloréns, José Lucas"],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-03-14","date_published":"2025-03-14","updated_at":"2026-07-24T01:29:24Z","subjects":[],"languages":["eng"],"rights":["Attribution-NonCommercial-NoDerivatives 4.0 Internacional"],"rights_urls":["http://creativecommons.org/licenses/by-nc-nd/4.0/"],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/10498/36228","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Brun Murillo, Fernando Guillermo","Pérez Lloréns, José Lucas"]},{"key":"dc:contributor.other","label":"Dc Contributor Other","values":["Biología"]},{"key":"dc:creator","label":"Author","values":["Casal Porras, Isabel"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2025-04-30T11:14:00Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2025-04-30T11:14:00Z"]},{"key":"dc:date.issued","label":"Date","values":["2025-03-14"]},{"key":"dc:type","label":"Dc Type","values":["doctoral thesis"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Attribution-NonCommercial-NoDerivatives 4.0 Internacional"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://creativecommons.org/licenses/by-nc-nd/4.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10498/36228"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Climate change (a variation in temperatures and weather patterns) is a natural phenomenon that has been accelerating since the 19th century. The rapid increase in global temperature is mainly due to the emission of large amounts of greenhouse gases, resulting from anthropogenic activities such as the burning of fossil fuels or from livestock activities. This concern was expressed globally with the Kyoto Protocol in 1997, the first international agreement aimed at committing industrialized countries to reduce greenhouse gas emissions. Since then, policies and adaptation and mitigation measures have been adopted by the different countries involved. In the Paris Agreement in 2015, a commitment was made not to exceed the pre-industrial temperature by 1.5°C, focusing strategies on reducing global greenhouse gas emissions by 85%. In addition, one of the most innovative mitigation measures of this agreement was the possibility of capturing and removing carbon through natural ecosystems. In this context, coastal vegetated communities have been noted for their fundamental role in sequestering and storing carbon in the sediment (blue carbon), incorporating carbon dioxide (CO2) and removing it from the atmosphere in the long term. In addition, these communities play a key role in ocean carbon cycling through dissolved organic matter (DOM) fluxes where part of this organic matter feeds heterotrophic organisms (labile DOM) and another fraction contributes to the carbon pool stored in the deep ocean for thousands of years (refractory DOM). Indeed, the role of coastal vegetated ecosystems as CO2 sinks has attracted the attention of a diverse group of stakeholders including the scientific community, private sector, governments and intergovernmental bodies committed to marine conservation and climate change mitigation and adaptation. However, these communities are currently among the most threatened ecosystems in the biosphere, largely due to various anthropogenic impacts resulting in deteriorating water quality, habitat destruction due to coastal development and also, more recently, the occurrence of extreme events such as storms (e.g., DANA) and heatwaves resulting from climate change. All this produces direct and indirect impacts that affect both biomass and DOM fluxes and carbon stocks in the sediment, leading to a decrease in the capacity to store carbon in the long term, as well as to a loss of sediment carbon being released back into the atmosphere in the form of CO2. In this scenario, and from an integrated perspective, this thesis has addressed the response of certain coastal vegetated ecosystems (seagrass meadows and macroalgae) to some of the main global threats that affect them. This perspective is based on the fact that the response of these ecosystems to different impacts is far from being simple and individual, and that the final behavior must integrate the responses of each of the components that make up the community (dominant primary producer, bacterial activity in water and sediment and macrofauna, mainly). This thesis is composed of four chapters in which the direct and indirect impact of anthropogenic activities on coastal vegetated communities (seagrass meadows and macroalgae) has been estimated. In addition, and as a pioneering milestone, the DOM of the different coastal vegetated communities in the Bay of Cádiz has been chemically characterized. In chapter 1, the direct impact of the construction of several coastal infrastructures on the organic carbon stocks of the meadows of Zostera noltei in Ria Formosa (Portugal) was studied. In this study was observed that impacted meadows contained 1.5 times less organic carbon stock than non-impacted meadows. Although the area affected was relatively small (0.05-0.07 ha), the coastal infrastructure caused a significant reduction of the carbon stock, between 1.1 and 2.2 Megagrams (Mg) organic carbon, and a total loss of the carbon sequestration capacity of the impacted meadows. These results contribute to understanding the spatial variability of blue carbon stocks in coastal systems heavily impacted by urban development. Chapters 2 and 3 estimate the integrated community response (through community metabolism and dissolved organic carbon (DOC) fluxes) of the coastal vegetated communities of the Bay of Cádiz at two times of the year (winter and summer) to the chronic impact of reduced shoot density (chapter 2) and to the indirect impact of climate change such as marine heatwaves (chapter 3). In Chapter 2, changes in Cymodocea nodosa communities was observed when the shoot density was reduced to 40 and 75% of the control. The net primary production of the community decreased up to 10-fold when the shoot density was reduced from an autotrophic to a heterotrophic community. In addition, DOC fluxes (up to 5.5 times) and sediment organic matter decreased significantly. This clearly indicates that the prolonged chronic stress to which these communities have been subjected is having a negative impact on their ability to capture and store blue carbon. In chapter 3, it was observed that the heat caused an increase in net primary production in C. nodosa communities (1.9 times more than the control) and a decrease in Caulerpa prolifera communities. DOC fluxes in C. prolifera communities shifted towards negative values, i.e. from being DOC producers to DOC consumers. Furthermore, an increase in the percentage of refractory DOC was observed when the communities were subjected to a simulated heatwave, which could indicate that the increase in temperature would also increase carbon stocks. In chapter 4, the dissolved organic matter of the seagrass communities C. nodosa and Z. noltei and the macroalgal community C. prolifera were chemically characterized using a methodology based on nuclear magnetic resonance and high-resolution mass spectrometry. The chemical profile of the DOM of the different coastal vegetated communities showed that the major compounds were the highly unsaturated and aromatic ones. In addition, the DOM was characterized after a bioavailability test, which revealed the highest percentage of lability in the C. prolifera community (86%), followed by C. nodosa (81%) and Z. noltei (76%). According to van Krevelen diagrams, a significant fraction of labile compounds belonged to lipid-, peptide-, amino sugar-, and carbohydrate-like classes, while the refractory compounds mainly belonged to lignin-, tannin-, and aromatic-like classes. In conclusion, this thesis highlights the negative effects of anthropogenic impacts on coastal vegetated communities, affecting the functions and services they provide, such as climate change mitigation. The results of this thesis show not only the significant loss of biomass and blue carbon stocks in the coastal communities studied as a consequence of direct impacts (coastal infrastructures), but also that the metabolism and DOC fluxes of the community are affected by indirect (heatwaves) and chronic impacts (reduction in shoot density), leading to a decrease in the functions and services provided by these ecosystems. In addition, this thesis has contributed, for the first time, to the study of the chemical characterization of DOM from coastal vegetated communities using high-resolution techniques, revealing the chemical profile of labile and refractory DOM. Our results provide further arguments for the growing need to protect and conserve these valuable ecosystems in order to maintain the ecosystem services they provide to our planet, such as the ability to mitigate climate change."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Carbon dynamics in coastal vegetated communities: evaluation of anthropogenic impacts, chemical characterization of dissolved organic matter, and its influence on blue carbon sequestration"]}]}],"canonical_facts":{"dc:contributor.advisor":["Brun Murillo, Fernando Guillermo","Pérez Lloréns, José Lucas"],"dc:contributor.other":["Biología"],"dc:creator":["Casal Porras, Isabel"],"dc:date.accessioned":["2025-04-30T11:14:00Z"],"dc:date.available":["2025-04-30T11:14:00Z"],"dc:date.issued":["2025-03-14"],"dc:description.abstract":["Climate change (a variation in temperatures and weather patterns) is a natural phenomenon that has been accelerating since the 19th century. The rapid increase in global temperature is mainly due to the emission of large amounts of greenhouse gases, resulting from anthropogenic activities such as the burning of fossil fuels or from livestock activities. This concern was expressed globally with the Kyoto Protocol in 1997, the first international agreement aimed at committing industrialized countries to reduce greenhouse gas emissions. Since then, policies and adaptation and mitigation measures have been adopted by the different countries involved. In the Paris Agreement in 2015, a commitment was made not to exceed the pre-industrial temperature by 1.5°C, focusing strategies on reducing global greenhouse gas emissions by 85%. In addition, one of the most innovative mitigation measures of this agreement was the possibility of capturing and removing carbon through natural ecosystems. In this context, coastal vegetated communities have been noted for their fundamental role in sequestering and storing carbon in the sediment (blue carbon), incorporating carbon dioxide (CO2) and removing it from the atmosphere in the long term. In addition, these communities play a key role in ocean carbon cycling through dissolved organic matter (DOM) fluxes where part of this organic matter feeds heterotrophic organisms (labile DOM) and another fraction contributes to the carbon pool stored in the deep ocean for thousands of years (refractory DOM). Indeed, the role of coastal vegetated ecosystems as CO2 sinks has attracted the attention of a diverse group of stakeholders including the scientific community, private sector, governments and intergovernmental bodies committed to marine conservation and climate change mitigation and adaptation. However, these communities are currently among the most threatened ecosystems in the biosphere, largely due to various anthropogenic impacts resulting in deteriorating water quality, habitat destruction due to coastal development and also, more recently, the occurrence of extreme events such as storms (e.g., DANA) and heatwaves resulting from climate change. All this produces direct and indirect impacts that affect both biomass and DOM fluxes and carbon stocks in the sediment, leading to a decrease in the capacity to store carbon in the long term, as well as to a loss of sediment carbon being released back into the atmosphere in the form of CO2. In this scenario, and from an integrated perspective, this thesis has addressed the response of certain coastal vegetated ecosystems (seagrass meadows and macroalgae) to some of the main global threats that affect them. This perspective is based on the fact that the response of these ecosystems to different impacts is far from being simple and individual, and that the final behavior must integrate the responses of each of the components that make up the community (dominant primary producer, bacterial activity in water and sediment and macrofauna, mainly). This thesis is composed of four chapters in which the direct and indirect impact of anthropogenic activities on coastal vegetated communities (seagrass meadows and macroalgae) has been estimated. In addition, and as a pioneering milestone, the DOM of the different coastal vegetated communities in the Bay of Cádiz has been chemically characterized. In chapter 1, the direct impact of the construction of several coastal infrastructures on the organic carbon stocks of the meadows of Zostera noltei in Ria Formosa (Portugal) was studied. In this study was observed that impacted meadows contained 1.5 times less organic carbon stock than non-impacted meadows. Although the area affected was relatively small (0.05-0.07 ha), the coastal infrastructure caused a significant reduction of the carbon stock, between 1.1 and 2.2 Megagrams (Mg) organic carbon, and a total loss of the carbon sequestration capacity of the impacted meadows. These results contribute to understanding the spatial variability of blue carbon stocks in coastal systems heavily impacted by urban development. Chapters 2 and 3 estimate the integrated community response (through community metabolism and dissolved organic carbon (DOC) fluxes) of the coastal vegetated communities of the Bay of Cádiz at two times of the year (winter and summer) to the chronic impact of reduced shoot density (chapter 2) and to the indirect impact of climate change such as marine heatwaves (chapter 3). In Chapter 2, changes in Cymodocea nodosa communities was observed when the shoot density was reduced to 40 and 75% of the control. The net primary production of the community decreased up to 10-fold when the shoot density was reduced from an autotrophic to a heterotrophic community. In addition, DOC fluxes (up to 5.5 times) and sediment organic matter decreased significantly. This clearly indicates that the prolonged chronic stress to which these communities have been subjected is having a negative impact on their ability to capture and store blue carbon. In chapter 3, it was observed that the heat caused an increase in net primary production in C. nodosa communities (1.9 times more than the control) and a decrease in Caulerpa prolifera communities. DOC fluxes in C. prolifera communities shifted towards negative values, i.e. from being DOC producers to DOC consumers. Furthermore, an increase in the percentage of refractory DOC was observed when the communities were subjected to a simulated heatwave, which could indicate that the increase in temperature would also increase carbon stocks. In chapter 4, the dissolved organic matter of the seagrass communities C. nodosa and Z. noltei and the macroalgal community C. prolifera were chemically characterized using a methodology based on nuclear magnetic resonance and high-resolution mass spectrometry. The chemical profile of the DOM of the different coastal vegetated communities showed that the major compounds were the highly unsaturated and aromatic ones. In addition, the DOM was characterized after a bioavailability test, which revealed the highest percentage of lability in the C. prolifera community (86%), followed by C. nodosa (81%) and Z. noltei (76%). According to van Krevelen diagrams, a significant fraction of labile compounds belonged to lipid-, peptide-, amino sugar-, and carbohydrate-like classes, while the refractory compounds mainly belonged to lignin-, tannin-, and aromatic-like classes. In conclusion, this thesis highlights the negative effects of anthropogenic impacts on coastal vegetated communities, affecting the functions and services they provide, such as climate change mitigation. The results of this thesis show not only the significant loss of biomass and blue carbon stocks in the coastal communities studied as a consequence of direct impacts (coastal infrastructures), but also that the metabolism and DOC fluxes of the community are affected by indirect (heatwaves) and chronic impacts (reduction in shoot density), leading to a decrease in the functions and services provided by these ecosystems. In addition, this thesis has contributed, for the first time, to the study of the chemical characterization of DOM from coastal vegetated communities using high-resolution techniques, revealing the chemical profile of labile and refractory DOM. Our results provide further arguments for the growing need to protect and conserve these valuable ecosystems in order to maintain the ecosystem services they provide to our planet, such as the ability to mitigate climate change."],"dc:format":["application/pdf"],"dc:identifier.uri":["http://hdl.handle.net/10498/36228"],"dc:language.iso":["eng"],"dc:rights":["Attribution-NonCommercial-NoDerivatives 4.0 Internacional"],"dc:rights.uri":["http://creativecommons.org/licenses/by-nc-nd/4.0/"],"dc:title":["Carbon dynamics in coastal vegetated communities: evaluation of anthropogenic impacts, chemical characterization of dissolved organic matter, and its influence on blue carbon sequestration"],"dc:type":["doctoral thesis"]},"updated_at":"2026-07-24T01:29:24Z"}