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Most lakes worldwide are supersaturated with carbon dioxide (CO2) and consequently act as atmospheric net sources. Since CO2 is a major greenhouse gas (GHG), the accurate estimation of CO2 exchanges at air/water interfaces of aquatic ecosystems is vital in quantifying the carbon budget of aquatic ecosystems overall. To date, lacustrine CO2 emissions are poorly understood, and lake carbon source proportions remain controversial, largely due to a lack of integration between aquatic and terrestrial ecosystems. In this paper a new process-based model (TRIPLEX-Aquatic) is introduced incorporating both terrestrial inputs and aquatic biogeochemical processes to estimate diffusive emissions of CO2 from lake systems. The model was built from a two-dimensional hydrological and water quality model coupled with a new lacustrine CO2 diffusive flux model. For calibration and validation purposes, two years of data collected in the field from two small boreal oligotrophic lakes located in Québec (Canada) were used to parameterize and test the model by comparing simulations with observations for both hydrodynamic and carbon process accuracy. Model simulations were accordant with field measurements in both calibration and verification. Consequently, the TRIPLEX-Aquatic model was used to estimate the annual mean CO2 diffusive flux and predict terrestrial dissolved organic carbon (DOC) impacts on the CO2 budget for both lakes. Results show a significant fraction of the CO2 diffusive flux (~30–45%) from lakes was primarily attributable to the input and mineralization of terrestrial DOC, which indicated terrestrial organic matter was the key player in the diffusive flux of CO2 from oligotropical lake systems in Québec, Canada.

Dans cet article nous nous sommes intéressés à la pêche vivrière et artisanale pratiquée par les riverains de l’Amazonie. Les résultats présentés, touchant le savoir traditionnel de ces populations, leurs perceptions des changements environnementaux et de l’évolution des ressources halieutiques, ainsi que les solutions à y apporter, proviennent de deux questionnaires administrés à douze communautés du bassin du Tapajós. Ces résultats apportent un nouvel éclairage sur les enjeux liés à la gestion des ressources halieutiques et soulèvent les lacunes empêchant une réelle appropriation des problèmes environnementaux et l’émergence locale de solutions. Nous avons en effet mis en évidence que le déboisement et l’érosion des berges étaient perçus comme les plus importants changements environnementaux observés au fil du temps. La diminution de l’abondance et/ou la réduction des tailles des poissons a également été signalée par les personnes rencontrées. Le manque de lien entre les changements observés sur les écosystèmes naturels et ceux observés sur la ressource halieutique a attiré notre attention. En conséquence, toute intervention visant l’élaboration et/ou l’implantation de méthodes durables d’exploitation des ressources halieutiques doit absolument passer par une activité préalable d’information. Ceci dans le but de générer une appropriation locale des problèmes environnementaux et de favoriser l’émergence de solutions au sein des communautés concernées. Nesse artigo nós nos interessamos a pesca artesanal praticada pelos ribeirinhos da Amazônia. Os resultados apresentados, tocando o saber tradicional dessas populações, suas percepções sobre as mudanças ambientais e a evolução dos recursos haliêuticos, assim como as soluções para essas mudanças, provêm da análise de dois questionários aplicados em doze comunidades da bacia do Tapajós. Esses resultados lançam uma nova luz sobre as questões relacionadas a gestão dos recursos hídricos e levantam lacunas impedindo uma real apropriação dos problemas ambientais e o surgimento de soluções locais. De fato, nós mostramos que o desmatamento e a erosão das margens do rio foram percebidos como as principais mudanças ambientais observadas ao longo do tempo. A diminuição na abundância e/ou a redução do tamanho dos peixes também foi relatada pelos entrevistados. A falta de conexão pelos pescadores entre as mudanças observadas nos ecossistemas naturais e as mudanças ocorridas nas populações de peixes chamou a nossa atenção. Por conseguinte, qualquer intervenção visando o desenvolvimento e/ou a implementação de métodos sustentáveis de exploração dos recursos haliêuticos deve passar por uma atividade preliminar de informação. A intenção sendo gerar a apropriação local das questões ambientais e de favorecer a emergência de soluções ao seio mesmo das comunidades em questão. In this paper we are interested on subsistence fishing practiced by riparian Amazonian populations. The results presented, concerning the traditional knowledge of inhabitants, their perceptions about the environmental changes and the evolution of fishery resources as well as the some solutions regarding these changes, derived from two surveys administated to twelve communities of the Tapajós Basin. These results shed new light on issues related to the management of fisheries resources and highlight the gaps preventing a real appropriation of environmental problems and the emergence of local solutions. Indeed, we show that deforestation and erosion of river banks were perceived as the major environmental changes observed over the time. The decrease in abundance and/or reduction in the sizes of fish was also been reported by respondents. The lack of connection between the observed changes in natural ecosystems and changes in fish stocks caught our attention. Consequently, any intervention aimed at developing and/or implementing of methods for sustainable exploitation of fisheries resources must integrate preliminary activity information. The intention is to generate local ownership of environmental issues and encourage the emergence of solutions within the communities concerned.