Open AccessEnvironmental controls on the stable isotopic composition of Mercenaria mercenaria : Potential application to paleoenvironmental studies
Author(s) -
Elliot Mary,
deMenocal Peter B.,
Linsley Braddock K.,
Howe Stephen S.
Publication year - 2003
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2002gc000425
Subject(s) - mercenaria , salinity , oceanography , δ13c , stable isotope ratio , latitude , isotopes of oxygen , radiocarbon dating , seasonality , surface water , geology , aragonite , environmental science , calcite , mineralogy , ecology , geochemistry , biology , paleontology , physics , geodesy , quantum mechanics , environmental engineering
We have investigated the environmental controls of seasonally resolved records of oxygen and carbon isotopes of modern Mercenaria mercenaria bivalves collected live from five coastal sites along the east coast of North America. Seasonal profiles of δ 18 O and δ 13 C obtained by subsampling the incremental growth layers of aragonite were compared with in situ historical records of temperature and salinity. We show that M. mercenaria δ 18 O profiles track accurately the seasonal variations of water temperature and that variations in growth rates do not affect the shell δ 18 O values. Growth rates are strongly reduced or interrupted below water temperatures ranging from 8 to 10°C, implying that only bivalves sampled in tropical areas track the full amplitude of seasonal variations. Although further measurements of water δ 18 O and a better understanding of seasonal variations of the water δ 18 O‐salinity relationships are necessary, Mercenaria mercenaria bivalves appear to precipitate their shell close to isotopic equilibrium. Whereas the amplitude of the seasonal profiles of δ 18 O reflects variations in water temperature, the annual average δ 18 O decreases with latitude, reflecting the trend of rainfall and riverwater δ 18 O with latitude over the Northern American continent.