Dynamics of Dissolved Forms of Carbon and Inorganic Nitrogen in Small Watersheds of the Coastal Atlantic Forest in Southeast Brazil

Abstract

Based on the fact that streamwater quality reflects landscape conditions, the objectives of this study were: to investigate nitrogen (N), carbon (C), and major ion concentrations in six streams crossing minimally disturbed Atlantic Forest areas, with similar geomorphological characteristics; to determine N and C fluxes in one of these pristine streams (Indaiá); and assess the impact of human activity on the biogeochemistry of two other streams in the same region, crossing urbanized areas. The distribution pattern of carbon and inorganic nitrogen dissolved forms, as well as the major ion and biogenic gas concentrations in the streamwater, was similar in pristine streams, indicating that the C and N dynamics were determined by influence of some factors, such as climate, atmospheric deposition, geology, soil type, and land covering, which were analogous in the forested watersheds. The urban streams were significantly different from the pristine streams, showing low dissolved oxygen concentrations, high respiration rates, and high concentrations of carbon dioxide, dissolved inorganic nitrogen, dissolved inorganic carbon, and major ion. These differences were attributed to anthropogenic impact on water quality, especially domestic sewage discharge. Additionally, in the Indaiá stream, it was possible to observe the importance of rainfall over temporal dynamics of dissolved carbon forms, and also, the obtained specific flux of dissolved inorganic nitrogen was relatively elevated (approximately 11 kg ha −1 year −1 ). These results reveal the influence of human activity over the biogeochemistry of coastal streams and also indicate the importance N export of Atlantic Forest to the ocean.

Influence of land use changes on water chemistry in streams in the State of São Paulo, southeast Brazil

“…Several studies reported the impact of land use effect on streams, both in temperate and tropical watersheds (Kamisako et al 2008, Rai et al 2010, Andrade et al 2011. Streams located in undisturbed sites were reported to be more affected by soil characteristics and precipitation, although the streams located in disturbed areas were affected by different sources according to the land use. )…”

“…The effects of change in land use on the biogeochemistry have also been described in the literature for both major rivers and streams. It has been shown that these changes affect nitrate, ammonium, calcium, potassium and aluminum concentrations in streams located in temperate (Wang et al 2006, Kamisako et al 2008, Rai et al 2010) and tropical regions (Neill et al 2006, Andrade et al 2011.…”

“…Several studies in tropical watersheds evaluated the impact of urbanization and agricultural practices on water quality (Ballester et al 1999, Neill et al 2001, Biggs et al 2004, Salomão et al 2008, Germer et al 2009, Andrade et al 2011. Studies in subcatchments in southeastern and southern Brazil have shown that small streams are severely affected by urbanization and agricultural practices such as pastures, considerably increasing dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) (Daniel et al 2002 in addition to several ions such as nitrate, chloride and ammonium , Germer et al 2009, Andrade et al 2011.…”

“…Studies in subcatchments in southeastern and southern Brazil have shown that small streams are severely affected by urbanization and agricultural practices such as pastures, considerably increasing dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) (Daniel et al 2002 in addition to several ions such as nitrate, chloride and ammonium , Germer et al 2009, Andrade et al 2011. As a result, the structure of biota communities is affected by these activities, decreasing some species while urbanization increases (Ometto et al 2000, Ramirez et al 2009).…”

Carbon and nitrogen stock and fluxes in coastal Atlantic Forest of southeast Brazil: potential impacts of climate change on biogeochemical functioning

“…At 100 m the litterfall was equal to 4.0 Mg C ha -1 year -1 , decreasing to 3.4 Mg C ha -1 year -1 at 400 m and further to 2.6 Mg C ha -1 year -1 at 1000 m . The export of carbon (dissolved organic + dissolved inorganic carbon) from rivers and streams was estimated also in the Atlantic Forest of Ubatuba, and it was estimated to be approximately 0.1 Mg C ha -1 year -1 (Andrade et al, 2010).…”