Dissolved organic matter (C, N, P) on the Pernambuco coast and Fernando de Noronha archipelago (Tropical Zone of Western South Atlantic, Brazil) - A contribution to the evaluation of environmental impact

Abstract

The dissolved organic compounds found in seawater offer an indication of biogeochemical processes and anthropogenic influence in the light of their concentrations and behavior associated with different oceanic areas. River inputs contribute with organic loads to seawater according to the level of natural and urban influence. A dilution of this material is expected toward ocean. Around oceanic islands, the quantity of organic matter results from the life cycle of marine organisms and from human occupation. The ratios of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved organic phosphorus (DOP) and the association with dissolved oxygen can be used to evaluate the environmental conditions in terms of natural and anthropogenic impacts. Available information about the essential dissolved organic compounds (C, N and P) in seawater is rare. This study seeks to encourage the use of dissolved organic compounds in environmental impact assessment in coastal areas of Brazil. , both in RH, reflects organic and sanitary discharge. Sometimes the urea concentration was associated with precarious sewage treatment combined with tourist activity, as in the case of FN. No significant spatial variation was observed for DOP taking into account all the stations and regions, and the values presented a greater range of variation in FN. The DOC:DON ratios were higher than 7 (2-4 times the Redfield ratio) and revealed the quality of the organic matter and the importance of the local process of remineralization, confirming that the N-limitation enhanced the use of organic forms, mainly on FN. The preserved oligotrophic conditions of the RIS, Itamaracá and FN were observed in relation to dissolved organic compounds (C, N, P), but, as regards FN, effective monitoring actions are advisable as it is a pristine area. , ambos em RH, refletem a descarga orgânica e de esgoto. Às vezes, a concentração de ureia esteve associada ao tratamento precário de esgoto combinado com a atividade turística, como no caso de FN. Nenhuma variação espacial significativa foi observada para DOP tendo em conta todas as estações e regiões, e os valores apresentaram maior variação de FN. Os índices DOC:DON foram superiores a 7 (2-4 vezes a relação Redfield) e revelaram a qualidade da matéria orgânica e a importância do processo local de remineralização, confirmando que a N-limitação aumentou o uso de formas orgânicas, principalmente em FN. As condições oligotróficas preservadas em RIS, Itamaracá e FN foram observadas em relação aos compostos orgânicos dissolvidos (C, N, P), mas no que diz respeito ao FN, são recomendáveis ações de monitoramento efetivas, pois é uma área remota preservada. AbstrAct resumoDescritores: Nitrogênio orgânico dissolvido, Fósforo orgânico dissolvido, Carbono orgânico total, ureia, Áreas costeiras e oceânicas.