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La oligotropía y la fijación de nitrógeno durante los eventos de sapropel en el Mediterráneo oriental
1Department of Environmental Science, Barnard College, Columbia University, 3009 Broadway, New York, NY 10027, USA. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
Science (New York, N.Y.)
|January 5, 2000
Resumen
Los datos de isótopos de nitrógeno de la clorofila fósil indican aguas superficiales empobrecidas de nutrientes y alta fijación de nitrógeno durante la formación de sapropel del Pleistoceno tardío en el Mar Mediterráneo. Esto sugiere una floración especializada de fitoplancton, no una eutrofización, una deposición de sapropel alimentada por combustible.
Área de la Ciencia:
- La paleoceanografía es la paleoceanografía.
- La geoquímica marina es la geoquímica marina.
- Biogeoquímica La biogeoquímica es la bioquímica.
Sus antecedentes:
- Las sapropelas del Pleistoceno tardío en el Mar Mediterráneo oriental sugieren períodos de alta productividad.
- Estudios previos indicaron un potencial enriquecimiento de nutrientes o cambios en la circulación.
- Los mecanismos exactos que impulsan la formación de sapropel siguen siendo objeto de debate.
Objetivo del estudio:
- Para investigar la fuente de la materia orgánica y las condiciones de los nutrientes durante la formación de sapropel del Pleistoceno tardío.
- Para conciliar la evidencia geoquímica con los modelos existentes de deposición de sapropel en el Mediterráneo.
- Para probar las hipótesis con respecto a los patrones de eutrofización y circulación.
Principales métodos:
- Medidas isotópicas de nitrógeno de la clorofila fósil.
- Análisis de núcleos de sedimentos ricos en materia orgánica (sapropeles) del este del Mediterráneo.
- Interpretación geoquímica de datos isotópicos en el contexto de modelos paleoceanográficos.
Principales resultados:
- Los datos de isótopos de nitrógeno revelan aguas superficiales estratificadas y empobrecidas de nutrientes.
- La evidencia apunta a una fijación significativa de nitrógeno por los microorganismos.
- La formación de sapropel está vinculada a una floración especializada de fitoplancton y a eventos de hundimiento masivo.
- Los resultados no apoyan la eutrofización generalizada o la reversión de la circulación.
Conclusiones:
- La formación de sapropel fue impulsada por una comunidad única de fitoplancton adaptada a condiciones estratificadas y pobres en nutrientes.
- La fijación de nitrógeno jugó un papel crucial en el apoyo de este ecosistema.
- Los hallazgos desafían las interpretaciones anteriores de una mayor entrada fluvial o cambios importantes en la circulación como factores principales.
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