The oxygen isotopic composition of planktonic foraminifera tests is one of the widest used geochemical tools to reconstruct past changes of physical parameters of the upper ocean. It is common practice to analyze multiple individuals from a mono-specific population and assume that the outcome reflects a mean value of the environmental conditions during calcification of the analyzed individuals. Here we present the oxygen isotope composition of individual specimens of the surface-dwelling species <i>Globigerinoides ruber</i> and <i>Globigerina bulloides</i> from sediment cores in the Western Arabian Sea off Somalia, inferred as indicators of past seasonal ranges in temperature. Combining the δ<sup>18</sup>O measurements of individual specimens to obtain temperature ranges with Mg/Ca based mean calcification temperatures allows us to reconstruct temperature extrema. Our results indicate that over the past 20 kyr the seasonal temperature range has fluctuated from its present value of 16 °C to mean values of 13 °C and 11 °C for the Holocene and LGM, respectively. The data for the LGM suggest that the maximum temperature was lower, whilst minimum temperature remained approximately constant. The rather minor variability in lowest summer temperatures during the LGM suggests roughly constant summer monsoon intensity, while upwelling-induced productivity was lowered
ABSTRACT-Sedimentation rates were determined daily over a 2 wk period (late April -early May 1992) under post spring bloom conditions at a permanent station in the Bjernafjorden, Norway. Samples collected using floating sediment traps deployed at 50 and 100 m depth showed that sedimented seston, particulate organic matter, carbonate and lithogenic + opal fractions were, on average, twice as high at 100 m (221, 99, 51 and 76 mg m-2 d ', respectively) as at 50 m (119, 62. 27 and 34 mg m-2 d ' l , respectively). Faecal pellets made up the bulk of sedimenting matter, accounting for 87 and 92% of the average total organic carbon recorded at 50 and 100 m, respectively. The remaining sedimented matter consisted mainly of tintinnids. Diatoms cells and resting spores, coccolithophorids and flagellates contributed a minor fraction. It is postulated that the vertical flux of faecal pellets was determined by a combination of 3 factors: (1) relatively high standing stock of actively grazing mesozooplankton dominated by calanoid copepods and appendicularians, which are known for t h e~r high faeces production rates; (2) a relatively high abundance of the cyclopoid copepod Oithona s~rnllls, which is reported to feed on faecal pellets produced by calanoid copepods, suggesting that coprophagy in the water column was high; (3) a phytoplankton community dominated by diatoms and coccollthophorids, whose mineral skeletons accelerate sinking rates of faecal pellets.
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