Oxygen isotopes of marine diatoms and relations to opal-A maturation

Isotope offsets in marine diatom δ18O over the last 200 ka

“…Despite this, the impact of changes in Fe availability on δ 18 Odiatom has yet to be investigated. Previous work, however, has suggested that δ 18 Odiatom may be influenced by changes in growth rates with less isotope fractionation occurring in fast-growing diatoms (Schmidt et al, 2001). While changes in diatom growth rates, in response to increased/decreased Fe deposition, would be expected to be constant across both the 38-75 μm and >100 μm fractions, we have previously questioned whether this diatom isotope growth effect may influence larger frustules to a greater extent than smaller frustules (Swann et al, 2007).…”

“…While vital effects have been widely documented in biogenic carbonates such as foraminifera and ostracods (Duplessy et al, 1970;Wefer and Berger, 1991;Lea, 1993, 1996;Spero et al, 1997;Xia et al, 1997;Bemis et al, 1998;von Grafenstein et al, 1999;Chivas et al, 2002;Holmes and Chivas, 2002), almost all culture (Binz, 1987;Brandriss et al, 1998;Schmidt et al, 2001), down-core (Juillet-Leclerc and Labeyrie, 1987;Shemesh et al, 1995) and water column studies have found no clear evidence of a vital effect in δ 18 Odiatom. Recent work, however, has shown the potential for δ 18 Odiatom vital effects to exist with offsets of up to 3.51‰ (mean offset = 1.23‰, n = 25) observed between two size fractions of diatoms at Ocean Drilling …”

“…A prominent issue affecting records of δ 18 Odiatom is the possibility of secondary isotope exchanges during sedimentation (Schmidt et al, 1997(Schmidt et al, , 2001Brandriss et al, 1998;Moschen et al, 2006). This process of silica maturation has yet to be fully understood but has previously been related to a 2.5‰ increase in δ 18 Odiatom between living and surface sediment diatoms in Lake Holzmaar, Germany (Moschen et al, 2006) and isotope deviations of up to 10‰ in laboratory experiments (Schmidt et al, 1997(Schmidt et al, , 2001Brandriss et al, 1998).…”

“…This process of silica maturation has yet to be fully understood but has previously been related to a 2.5‰ increase in δ 18 Odiatom between living and surface sediment diatoms in Lake Holzmaar, Germany (Moschen et al, 2006) and isotope deviations of up to 10‰ in laboratory experiments (Schmidt et al, 1997(Schmidt et al, , 2001Brandriss et al, 1998). …”

Stable isotopes from diatom silica

“…For δ 18 O diatom , a number of culture (Binz, 1987;Brandriss et al, 1998;Schmidt et al, 2001), sediment trap and down-core studies (Sancetta et al, 1985;Juillet-Leclerc and Labeyrie, 4/28 information for use in paleoenvironmental reconstructions (see Leng and Barker, 2006;Swann and Leng, 2009). …”