כיול פרוקסים גאוכימיים באמצעות סדרת זמן של פורמיניפרים פלנקטוניים בים סוף
Planktic foraminifera (PF) are widely used paleoceanographic archives because their shell chemistry record environmental conditions such as temperature and salinity. However, in highly saline, oligotrophic basins, PF ecology and proxy systematics remain insufficiently constrained which limits robust paleoenvironmental reconstructions. To address this, we investigate the trace element/Ca of individual chambers (TE/Ca; measured using LA-ICP-MS), the δ1⁸O and δ13C, and morphology (using SEM and NanoSIMS) of two flux-dominant species, Turborotalita clarkei and Globigerinoides ruber (albus), in the Gulf of Aqaba (northern Red Sea) using monthly sediment-traps (June 2014–June 2015) from five water column depth horizons (120–570 m), complemented by concurrent water measurements.
While some TE/Ca’s appear to robustly record the water column conditions (e.g., Mg/Ca for temperature in G. ruber) others reveal complex trends. For example, in T. clarkei the TE/Ca of whole-shells and chambers of numerous elements (e.g., Mg/Ca, Na/Ca) peak in variability during late winter-spring (March–April 2015) linking TE/Ca variations to shifting mixed-layer depth. In both species, chamber-specific TE/Ca analyses show systematic offsets in the youngest final (F0) chamber relative to older chambers, suggesting that F0 may be excluded from the pooled mean chamber values for more robust proxy reconstructions. Shell δ1⁸O values and trends compared to predicted surface and deep layer δ1⁸O, reveal that G. ruber predominantly records shallow calcification (above the thermocline), while T. clarkei, characterized by more negative δ1⁸O values, may have rapidly calcified. Additionally, T. clarkei appears as two distinct phenotypes (big and encrusted) with increasing abundance ratio (encrusted/big) in winter and decreasing in summer, supporting its potential as an indicator of changing seasonal hydrological and ecological conditions. Together, these results refine PF proxy interpretation in stratified, high-salinity settings and provide a framework transferable to other oligotrophic basins.
