P. De Deckker et al., Uptake of Mg and Sr in the euryhaline ostracod Cyprideis determined from in vitro experiments, PALAEOGEO P, 148(1-3), 1999, pp. 105-116
This paper describes a series of in vitro experiments during which juvenile
s of the euryhaline ostracod Cyprideis australiensis were grown to adulthoo
d in waters of ranging salinities (from 10-70 parts per thousand) and Mg/Ca
and Sr/Ca ratios, and under two different constant temperature regimes, 20
degrees and 25 degrees C. Results indicate the following thermodependence
for Mg in the calcitic valves of adult Cyprideis australiensis: T(Mg) = 2.6
9 + 5230 x [Mg/Ca](ostracod)/[Mg/Ca](water). A minor thermodependence was a
lso found for this ostracod species with respect to the uptake of Sr. There
is a very strong relationship between the Mg/Ca of the ostracods and the M
g/Ca of the waters in which they moulted. The same can be said between the
Sr/Ca of the ostracods and the waters' Sr/Ca. There is no direct relationsh
ip between water salinity and either the Mg/Ca ratio nor the Sr/Ca ratio of
the ostracod valves. The 20 degrees and 25 degrees C experiments establish
ed the following partition coefficients which we believe can be applied to
any Cyprideis taxa grown in waters within the 5 to 20 Mg/Ca range: K-D[Mg]
= -0.000514 + 0.00019 x Temperature degrees C, and K-D[Sr] = 0.223 + 0.0086
x Temperature degrees C. This relationship for Sr, which has been mentione
d for the first time for Cyprideis is tentative. The Mg/Ca of ostracods is
strongly dependant on temperature, but this effect can easily be masked by
variations in the Mg/Ca of the host water commonly found in natural lakes.
Ostracod physiology is adapted to constructing valves from low-Mg calcite,
so when growing in waters with high (>30), or very low (<1) Mg/Ca, Cypridei
s species will not take up Mg in accordance with the calculated K-D. (C) 19
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