Export production depth of Emiliania huxleyi in the Gulf of Calfornia : an evaluation of the alkenone Ukʹ₃₇ paleosst-proxy

• Main Author: Pontius, Amanda S.
• Format: Thesis
• Language: English
• Published: 2007
• Subjects: Coccolithus huxleyi; Bering Sea; Pacific
• Online Access: http://hdl.handle.net/10125/20787

Thesis (M.S.)--University of Hawaii at Manoa, 2007. Includes bibliographical references (leaves 46-50). v, 50 leaves, bound 29 cm In the present study. alkenone unsaturation patterns (UK'37). alkenone-specific carbon isotopic variation (δK37:2). and seasonal alkenone concentration and production rate are determined throughout the upper water column (0-40 m) in the Gulf of California in order to better constrain the depth of alkenone export production and to identify factors that might cause calculated UK•37 temperatures to underestimate SST when SST>26°C. Field data were collected during one wintertime (January - February 2005) and two summertime (July 2004 & July-August 2005) cruises. Alkenone production rates were determined using an in situ 13C incubation method utilized in a related study in the subtropical oligotrophic North Pacific [Prahl at al., 2005; Popp at al., 2006a]. which was originally modified after that employed previously in the Sea of Japan [Hamanaka at al., 2000] and the Bering Sea [Shin et al., 2002]. Alkenone export production was determined to originate from a depth of ~20-30 m, which is well below the SML during the summer. Exported UK '37 did underestimate SST by up to -3°C, but this underestimate was not as large as expected based on the temperature gradient between the SML and the depth of export, and probably resulted from a concurrent physiological response to growth under light limiting conditions. As a result, SST estimates made by measuring UK' 37 fall within the ±3°C variability observed in the core-top calibrations of Muller at al. [1998] and Conte at al. [2006], indicating that subsurface alkenone growth could still lead to relatively accurate SST predictions (i.e. within ±3°C). Additionally, the efficiency of alkenone export production to sediment traps deployed at 100 m is determined to be ~20%. This alkenone export efficiency is the first measurement of this type to be reported in the literature and implies considerable loss of alkenones probably due to the ...