Dissolved organic carbon （DOC） is an important component for both carbon cycle and energy balance. The concentration, UV absorbance, and export flux of DOC in the natural environment dominate many important transpor...Dissolved organic carbon （DOC） is an important component for both carbon cycle and energy balance. The concentration, UV absorbance, and export flux of DOC in the natural environment dominate many important transport processes. To better understand the temporal and spatial variation of DOC, 7 sites along the Lower Dagu River were chosen to conduct a comprehensive measure- ment from March 2013 to February 2014. Specifically, water samples were collected from the Lower Dagu River between the 26th and 29th of every month during the experimental period. The DOC concentration （Cooc） and UV absorbance were analyzed using a total organic carbon analyzer and the ultraviolet-visible absorption spectrum, and the DOC export flux was estimated with a simple empirical model. The results showed that the CDoc of the Lower Dagu River varied from 1.32 to 12.56 mg/L, consistent with global rivers. The CDoc and UV absorbance showed significant spatial variation in the Dagu River during the experiential period because of the upstream natural processes and human activities in the watershed. The spatial variation is mainly due to dam or reservoir constructions, riverside ecological environment changes, and non-point source or wastewater discharge. The seasonal variation of CDoc was mainly related to the source of water DOC, river runoff, and temperature, and the UV absorbance and humification degree of DOC had no obvious differences among months （P〈 0.05）. UV absorbance was applied to test the CDOC in Lower Dagu River using wave lengths of 254 and 280 nm. The results revealed that the annual DOC export flux varied from 1.6 to 3.76x 105 g C^rn2/yr in a complete hydrological year, significantly lower than the global average. It is worth mentioning that the DOC export flux was mainly concentrated in summer （-90% of all-year flux in July and August）, since the runoff in the Dagu River took place frequently in summer. These observations implied environment change could bring the temporal-spatial variation of DOC and the exports, which would further affect the land-ocean interactions in the Lower Dagu River and the global carbon cycle.展开更多
Mauritania is characterized by fast-growing fisheries that have developed over the past several decades from low levels of fishing to intense fishing and have led to severe decreases in biomass and severe signs of ove...Mauritania is characterized by fast-growing fisheries that have developed over the past several decades from low levels of fishing to intense fishing and have led to severe decreases in biomass and severe signs of overexploitation.To ensure sustainable fisheries,a primary goal of science-based fisheries policy is to provide an adequate conservation status of marine habitats that are directly,or indirectly,fundamental for the lifecycle of fish populations of commercial interest.The National Park of Banc d’Arguin has been recognized for its nursery and fish biomass export functions.In this paper,we present the economic value of the fish provisioning service of marine coastal ecosystems of the protected area.We estimated the added value of artisanal fisheries,the spatial distribution of fishing activities,the contribution of the Park to the Mauritanian fisheries and the heritage value of artisanal fisheries.Overall,the average added value for artisanal fisheries is about 43 million MRU(1 million euros)over the period 2006–2017.It mainly benefits to the ship-owners,which generates inequalities and threatens the livelihoods of the Imraguen.The spatial distribution of fishing activities and associated revenues shows high variability throughout the years,the seasons and the geographic areas,and reveals the high adaptability of Imraguen fishers.Fishing grounds are mostly located close to the shore,associated with seagrass beds,confirming the service of fish provisioning rendered by this ecosystem.Furthermore,the high productivity of seagrass beds contributes to the spill-over of biomass.The contribution of the Park to fishing activities that occur within the Mauritanian Exclusive Economic Zone is estimated to 15%,representing an added value creation of 3.2 billion MRU(71 million euros).The heritage value of the fisheries is assessed,through fishers’willingness to accept to stop their fishing activities,at 17.5 million MRU(0.4 million euros).Thus,this paper highlights the necessity of incorporating an ecosystem-based approach along with fishers’knowledge and adaptability into future conservation plan of the National Park of Banc d’Arguin and fisheries management at the local,national and regional scale.展开更多
文摘Dissolved organic carbon （DOC） is an important component for both carbon cycle and energy balance. The concentration, UV absorbance, and export flux of DOC in the natural environment dominate many important transport processes. To better understand the temporal and spatial variation of DOC, 7 sites along the Lower Dagu River were chosen to conduct a comprehensive measure- ment from March 2013 to February 2014. Specifically, water samples were collected from the Lower Dagu River between the 26th and 29th of every month during the experimental period. The DOC concentration （Cooc） and UV absorbance were analyzed using a total organic carbon analyzer and the ultraviolet-visible absorption spectrum, and the DOC export flux was estimated with a simple empirical model. The results showed that the CDoc of the Lower Dagu River varied from 1.32 to 12.56 mg/L, consistent with global rivers. The CDoc and UV absorbance showed significant spatial variation in the Dagu River during the experiential period because of the upstream natural processes and human activities in the watershed. The spatial variation is mainly due to dam or reservoir constructions, riverside ecological environment changes, and non-point source or wastewater discharge. The seasonal variation of CDoc was mainly related to the source of water DOC, river runoff, and temperature, and the UV absorbance and humification degree of DOC had no obvious differences among months （P〈 0.05）. UV absorbance was applied to test the CDOC in Lower Dagu River using wave lengths of 254 and 280 nm. The results revealed that the annual DOC export flux varied from 1.6 to 3.76x 105 g C^rn2/yr in a complete hydrological year, significantly lower than the global average. It is worth mentioning that the DOC export flux was mainly concentrated in summer （-90% of all-year flux in July and August）, since the runoff in the Dagu River took place frequently in summer. These observations implied environment change could bring the temporal-spatial variation of DOC and the exports, which would further affect the land-ocean interactions in the Lower Dagu River and the global carbon cycle.
基金The study was financially supported under the contract number 3/CPMP/PNBA/2017 by the French Development Agency(AFD-Agence França),the French Facility for Global Environment(FFEM)and the Trust-Fund for the Banc d’Arguin and the Coastal&Marine Biodiversity Trust Fund(BACoMaB-Mauritania.
文摘Mauritania is characterized by fast-growing fisheries that have developed over the past several decades from low levels of fishing to intense fishing and have led to severe decreases in biomass and severe signs of overexploitation.To ensure sustainable fisheries,a primary goal of science-based fisheries policy is to provide an adequate conservation status of marine habitats that are directly,or indirectly,fundamental for the lifecycle of fish populations of commercial interest.The National Park of Banc d’Arguin has been recognized for its nursery and fish biomass export functions.In this paper,we present the economic value of the fish provisioning service of marine coastal ecosystems of the protected area.We estimated the added value of artisanal fisheries,the spatial distribution of fishing activities,the contribution of the Park to the Mauritanian fisheries and the heritage value of artisanal fisheries.Overall,the average added value for artisanal fisheries is about 43 million MRU(1 million euros)over the period 2006–2017.It mainly benefits to the ship-owners,which generates inequalities and threatens the livelihoods of the Imraguen.The spatial distribution of fishing activities and associated revenues shows high variability throughout the years,the seasons and the geographic areas,and reveals the high adaptability of Imraguen fishers.Fishing grounds are mostly located close to the shore,associated with seagrass beds,confirming the service of fish provisioning rendered by this ecosystem.Furthermore,the high productivity of seagrass beds contributes to the spill-over of biomass.The contribution of the Park to fishing activities that occur within the Mauritanian Exclusive Economic Zone is estimated to 15%,representing an added value creation of 3.2 billion MRU(71 million euros).The heritage value of the fisheries is assessed,through fishers’willingness to accept to stop their fishing activities,at 17.5 million MRU(0.4 million euros).Thus,this paper highlights the necessity of incorporating an ecosystem-based approach along with fishers’knowledge and adaptability into future conservation plan of the National Park of Banc d’Arguin and fisheries management at the local,national and regional scale.
