δ18O and δ13C of Cyprideis torosa from coastal lakes: modern systematics and down-core interpretation

Roberts, L.R.; Holmes, J.A.; Sloane, H.J.; Arrowsmith, C.; Leng, M.J. ORCID:; Horne, D.J.. 2020 δ18O and δ13C of Cyprideis torosa from coastal lakes: modern systematics and down-core interpretation. Marine Micropaleontology, 160, 101907.

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Stable isotope analyses of ostracod shells are a commonly-used proxy for palaeoenvironmental reconstruction. Although the fundamental controls on isotope composition of ostracod shells are well understood and, in some instances, quantifiable, the paleoclimatic and palaeoenvironmental interpretation of records from lake sediments depends strongly on the characteristics of individual lakes including the climatic setting, depth, volume, hydrology, aquatic vegetation and catchment properties. This is particularly important for coastal lakes where physio-chemical variations may occur on diurnal timescales. Here, we combine variations in δ18Owater, δ18Oostracod and δ13Costracod, hourly water temperature, and Mg/Caostracod inferred water temperatures (constraining calcification temperature) to improve palaeoenvironmental interpretation and provide insights into lake carbon cycle. The dataset improves understanding of complex coastal lake site systematics and downcore interpretation of stable isotopes from C. torosa, a geographically widespread brackish water ostracod. The δ18Oostracod values show a complex relationship with temperature and suggest, in most circumstances, that δ18Owater is the dominant control on δ18Oostracod. During times of fresher water, δ13Costracod increases, suggesting increasing aquatic productivity. Above a certain δ18Owater threshold however, aquatic productivity begins to decline. The interpretation of δ13Costracod in some coastal lakes, may therefore be dependent on understanding of the range of expected δ18Owater. Due to short-term (diurnal to seasonal) variations that cause large ranges in δ18Owater and δ18Oostracod, stable isotope analyses of C. torosa should be: (1) undertaken on multiple single shells (2) where carapaces are preserved, paired with trace-element/Ca analyses on the same individual; and (3) undertaken alongside a study of the modern lake system.

Item Type: Publication - Article
Digital Object Identifier (DOI):
ISSN: 03778398
Date made live: 28 Aug 2020 10:18 +0 (UTC)

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