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Source‐age dynamics of estuarine particulate organic matter using fatty acid δ 13 C and Δ 14 C composition
Author(s) -
McIntosh Hadley A.,
McNichol Ann P.,
Xu Li,
Canuel Elizabeth A.
Publication year - 2015
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.10053
Subject(s) - estuary , environmental chemistry , salinity , terrigenous sediment , bay , δ13c , organic matter , particulates , environmental science , oceanography , dissolved organic carbon , total organic carbon , stable isotope ratio , sediment , chemistry , geology , ecology , biology , paleontology , physics , quantum mechanics
This study used a multiproxy approach to elucidate the source and age composition of estuarine particulate organic matter (POM) using bulk stable isotopes ( δ 13 C POC ), fatty acid (FA) biomarkers, and compound specific isotopic analyses in surface waters along the Delaware River and Bay (Delaware Estuary, hereafter). δ 13 C values of FA ( δ 13 C FA ) ranged more widely (−30.9‰ to −21.8‰) than δ 13 C POC (−27.5‰ to −23.5‰), providing greater insight about POM sources along the estuary. δ 13 C values of C 16:0 phospholipid FA (primarily, aquatic sources) increased along the salinity gradient (−29.8‰ to −23.4‰), while δ 13 C FA values of long‐chain neutral fatty acid (terrestrial sources) decreased (−28.6‰ to −30.9‰). δ 13 C FA values for C 18's FA indicated the importance of marsh‐derived organic matter within Delaware Estuary. Compound specific radiocarbon analysis showed the heterogeneous age structure of FA associated with POM (FA POM ). 14 C ages of FA ranged from modern (postbomb) to 1790 BP; aged FA (120 BP to 1700 BP) derived primarily from the watershed, whereas modern FA were produced within Delaware Estuary. 14 C ages of short‐chain FA (aquatic sources) reflected differences in the age of dissolved inorganic carbon along the estuary and had older 14 C ages at the river end‐member. 14 C ages of FA from terrigenous sources were older than water and sediment residence times indicating this source derived from the watershed. This study is the first to document the complex age distribution of FA POM along the estuarine salinity gradient and shows that inorganic carbon sources, watershed inputs and autochthonous production contribute to variation in the ages of POM.