INVESTIGADORES
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congresos y reuniones científicas
Título:
Organic Matter characterization in a mosaic of phytoplankton blooms in the Southern Ocean.
Autor/es:
ORTEGA_RETUERTA, E.; MARRASÉ, C.; ZAMANILLO, M.; RODRIGUEZ-ROS, P.; PÉREZ, G. L.; ESTRADA, M.; SIMÓ, R.
Lugar:
Bremen
Reunión:
Simposio; The Biological Carbon Pump in a changing world; 2016
Institución organizadora:
Universidad de Bremen
Resumen:
Phytoplankton are the ultimate source of organic matter in the open ocean. How this organic matter (OM) is cycled through the ecosystem largely depends on its quality (i.e. size, reactivity) and the environment where this OM is produced. We explored OM quality associated with phytoplankton blooms in Antarctic and Subantarctic waters. For that purpose, we visited four areas with relative increments in chla respect to surrounding waters (hereafter referred as blooms). We then determined dissolved (DOC) and particulate organic carbon (POC) concentrations, fluorescence properties (suggestive of origin, composition and/or lability), particle abundance (estimated from particle backscattering at 532 nm, bbp) and transparent exopolymer particle (TEP) abundance. A unique OM signature in each phytoplankton bloom was observed: Bloom 1, located North of the South Orkney Islands (Weddell-Scotia Confluence), was dominated by cryptophytes and a mixed assemblage, with an average chla concentrations of 2 mg m-3. Here OM was characterized by high TEP content respect to DOC and POC, and also high TEP/bbp ratios, suggesting this OM to be prone to aggregation. Bloom 2, located South of the South Orkney Islands (Weddell Sea) in an ice-influenced area dominated by dinoflagellates, had the lowest average chla (0.3 mg m-3). OM was depleted in fluorescent compounds (low FDOM/DOC ratios). Also low TEP/bbp and low POC/bbp ratios suggest particles to be enriched in mineral compounds. Bloom 3, located Northwest of the South Georgia Island (Subantarctic) and dominated by large diatoms and dinoflagellates, showed an average chla of 6 mg m-3. OM here was rich in fluorescent compounds respect to the whole DOC pool, with a relative enrichment in humic-like compounds derived from bacterial OM reprocessing. Finally, bloom 4, located in coastal waters of the Western Antarctic Peninsula, large dominated by cryptophytes with average chla values of 4 mg m-3, showed the highest carbon content in particles and was enriched in protein-like fluorescent OM, suggestive of freshly-produced labile OM. Overall, our results show distinct OM signatures reflecting bloom composition and stage. This different OM composition would ultimately determine its fate in the water column (remineralization or reprocessing through the microbial carbon pump vs. export to the deep ocean).