Multiple-source heterotrophy fueled by aged organic carbon in an urbanized estuary

TitleMultiple-source heterotrophy fueled by aged organic carbon in an urbanized estuary
Publication TypeJournal Article
Year of Publication2011
AuthorsGriffith, DR, Raymond, PA
Date PublishedMAR 20
Type of ArticleArticle
Keywords(13)C, (14)C, Carbon cycle, Carbon dioxide, Chlorophyll, dissolved organic carbon, Heterotrophy, Hudson River Estuary, Isotope mixing curves, Sewage, USA, Wastewater

The lower Hudson River is a highly urbanized estuary that receives large inputs of treated wastewater. To determine how organic matter from wastewater influences carbon cycling in this type of system, we measured chlorophyll a, pCO(2). dissolved organic carbon (DOC), delta(13)C-DOC, and Delta(14)C-DOC along the salinity gradient and at wastewater treatment plants. Isotopic mixing curves indicate a net removal of DOC that is (13)C enriched and (14)C depleted. The amount of DOC removed was consistent with CO(2) evasion from the estuary. During two transects at average to low flow, the lower Hudson River Estuary was a heterotrophic system with CO(2) evasion balanced by the utilization of aged DOC derived from wastewater and marine phytoplankton that enter the estuary at the seaward end-member. DOC removals were largest during a period of high river flow, when isotopic mixing curves also suggest large contributions from labile terrestrial OC sources. Overall, our results suggest that net heterotrophy in the lower Hudson River Estuary is fueled by aged labile DOC derived from a combination of sources, which are influenced by seasonal phytoplankton blooms, hydrological conditions, and the nature of wastewater inputs. (C) 2010 Elsevier B.V. All rights reserved.