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Sediment microhabitat effects on carbon stable isotopic signatures of microcosm‐cultured benthic foraminifera
Author(s) -
Chandler G. Thomas,
Williams Douglas F.,
Spero Howard J.,
Xiaodong Gao
Publication year - 1996
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 - 10.4319/lo.1996.41.4.0680
Subject(s) - foraminifera , microcosm , benthic zone , sediment , calcite , water column , geology , population , pore water pressure , oceanography , mineralogy , environmental chemistry , chemistry , paleontology , demography , geotechnical engineering , sociology
Environmentally controlled sedimentary microcosms were used to experimentally determine temperature, salinity, and depth‐horizon effects on δ 13 C DIC profiles of dissolved inorganic carbon (DIC) in sediment pore water (PW) and near‐bottom water (BW). Simultaneously, benthic foraminiferal populations of Ammonia beccarii were cultured and assayed for calcite δ 13 C to establish how accurately foraminiferal shells recorded BW‐PW δ 13 C DIC . One treatment population was restricted to the 0–1‐cm sediment depth; in another treatment, the population could freely “roam” up and down in the sediment microcosm. Pore‐water DIC between the uppermost 0–0.5‐cm sediment layer and the overlying BW (i.e. 3 cm above the sediment‐water interface) showed steep gradients of core‐top Δδ 13 C PW averaging −3.6±1.6‰ at 25°C and −2.6±0.5‰ at 20°C. Correspondingly, shell calcite δ 13 C for A. beccarii collected from sediment microhabitats recorded a strong PW influence; δ 13 C shell values averaged 1.1±0.8‰ lighter than BW δ 13 C DIC but 1.6±0.6% enriched relative to average 0–5‐mm PW δ 13 C DIC . Foraminifera restricted to the uppermost 1‐cm sediment depth throughout their lives exhibited shell calcite Δδ 13 C values not significantly different from foraminifera allowed to free‐roam through the sediment column.