Distribution and origin of sedimentary organic matter in an eutrophic estuary: Pina Sound – NE Brazil

Eutrophic estuaries receive organic matter (OM) inputs from multiple sources. This study evaluated the distribution and origin of sedimentary OM in an eutrophic estuary (Pina Sound, NE Brazil). Thirteen samples were collected sublittoral addition to major local Biochemical (chlorophyll - Chl), elemental [(C/N)a C/S ratios] isotopic (δ 15N δ 13C) analyses carried out for characterizing redox conditions. The SIAR mixing model was used quantify contribution main At Pina is associated with mud, reflecting hydrodynamics control on deposition suspended particles. Microphytobenthic production limited ([Chl a] < 1000 µg/g carbon) where Chl degradation products prevail (mean [Pheopigments] = 2643 ± 958 carbon). Anoxic conditions (C/S ratio ≈ 2) are typically observed sediments deeper portions Sound. Such high loads subject poor water renewal. According model, Sound composed of, average: 50% phytoplankton, 24% sewage 26% C3 plants. reflects fertilization untreated sewage. has a great potential retain sewage-derived OM.