Your browser doesn't support javascript.
loading
Genotypic and phenotypic variation in diatom silicification under paleo-oceanographic conditions.
Finkel, Z V; Matheson, K A; Regan, K S; Irwin, A J.
Afiliação
  • Finkel ZV; Environmental Science Program, Mount Allison University, Sackville, NB, Canada. zfinkel@mta.ca
Geobiology ; 8(5): 433-45, 2010 Dec.
Article em En | MEDLINE | ID: mdl-20597991
Diatoms have co-evolved with the silicon cycle and are largely responsible for reducing surface concentrations of silicate in the ocean to their present levels. We quantify silicification in marine diatoms at a range of high silicate concentrations representative of environments found over their geological history. The species examined include Stephanopyxis turris, an ancient centric species found throughout the Cenozoic, Thalassiosira pseudonana and Thalassiosira weissflogii, two younger centric species, and two pennate ecotypes of Staurosirella pinnata isolated from different nutrient regimes. Frustule thickness and micromorphological structure are strongly affected by silicate concentration. All species become increasingly silicified with silicate concentrations at concentrations vastly in excess of surface ocean concentrations today. In contrast, the half-saturation constant for silicate uptake for most modern diatoms is below 2 µM. Based on the results, we hypothesize that silicate uptake is multiphasic in diatoms and that multiple silicate transport systems may have evolved in response to decreases in surface silicate concentration over geological time. The oldest species examined is more heavily silicified than the more modern species, presumably reflecting the conditions under which it originated. Yet diversification in silicification can be rapid, as illustrated by greater silicification in onshore versus the offshore ecotype of the same modern species. This work suggests that silicification of fossil frustules may eventually provide a paleoproxy for surface silicate concentrations over the Cenozoic, although development of species-specific calibrations will be necessary and the effects of a range of environmental conditions must be investigated.
Assuntos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Silício / Diatomáceas / Fósseis Limite: Animals Idioma: En Revista: Geobiology Assunto da revista: BIOLOGIA Ano de publicação: 2010 Tipo de documento: Article País de afiliação: Canadá País de publicação: Reino Unido

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Silício / Diatomáceas / Fósseis Limite: Animals Idioma: En Revista: Geobiology Assunto da revista: BIOLOGIA Ano de publicação: 2010 Tipo de documento: Article País de afiliação: Canadá País de publicação: Reino Unido