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

Autor(es)

Braga, Elisabete de Santis ^[1] ; Benedetti Berbel, Glaucia Bueno ^[1] ; Chiozzini, Vitor Gonsalez ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Lab Biogeochem Nutrients Micronutrients & Traces, Inst Oceanog, Praca Oceanog 191, BR-05508120 Butanta, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Brazilian Journal of Oceanography; v. 66, n. 1, p. 30-46, JAN-MAR 2018.
• Citações Web of Science: 0

Resumo

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. The spatial distribution of DOC, DON, DOP and urea was analyzed in four regions: Itamaracá (ITA), Recife Inner Shelf (RIS), Fernando de Noronha Island (FN) and Recife Harbor (RH), all in Pernambuco State - Brazil. In the case of DOC, the values obtained varied from 51.60 µmol L-1 (0.62 mg L-1) to 358.47 µmol L-1 (4.30 mg L-1), DOP values varied from 0.01 to 2.16 µmol L-1, both presenting their highest values in RH, the most intensely urbanized area. In relation to DON, an extremely high value 92.89 µmol L-1, with urea reaching 12 µmol L-1, 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. (AU)

• Processo FAPESP: 11/50582-0 - Estudo do equilíbrio do ciclo do carbono na região costeira e de seu potencial transporte oceânico: com ênfase ao litoral de Pernambuco (Carecos)
• Beneficiário: Elisabete de Santis Braga da Graça Saraiva
• Modalidade de apoio: Auxílio à Pesquisa - Temático