Carbon export from natural iron fertilisation in the Southern Ocean
It has long been recognised that some oceanic regions have persistently low chlorophyll levels, even though inorganic nutrients are plentiful. Studies have shown that these high-nutrient, low-chlorophyll (HNLC) areas are depleted in iron, which is an essential micronutrient for phytoplankton growth....
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ftsouthampton:oai:eprints.soton.ac.uk:66262 2023-07-30T04:03:07+02:00 Carbon export from natural iron fertilisation in the Southern Ocean Morris, Paul James 2008-08 text https://eprints.soton.ac.uk/66262/ https://eprints.soton.ac.uk/66262/1/Morris_PJ_2008_PhD.pdf en eng https://eprints.soton.ac.uk/66262/1/Morris_PJ_2008_PhD.pdf Morris, Paul James (2008) Carbon export from natural iron fertilisation in the Southern Ocean. University of Southampton, School of Ocean and Earth Science, Doctoral Thesis, 205pp. Thesis NonPeerReviewed 2008 ftsouthampton 2023-07-09T21:05:17Z It has long been recognised that some oceanic regions have persistently low chlorophyll levels, even though inorganic nutrients are plentiful. Studies have shown that these high-nutrient, low-chlorophyll (HNLC) areas are depleted in iron, which is an essential micronutrient for phytoplankton growth. In HNLC regions biological production can be enhanced with artificial mesoscale iron fertilisation. However, the ability of artificially induced phytoplankton blooms to efficiently sequester carbon to mesopelagic depths is still an open question. SubAntarctic islands in the HNLC Southern Ocean are a natural source of iron and thus fuel the annual phytoplankton blooms observed in their proximity. One such bloom, tied to the Crozet Islands (52ºE, 46ºS), provided the opportunity to examine particulate organic carbon (POC) export during the austral summer of 2004/5. This work was imbedded into the multi-disciplinary CROZEX project thus providing a rich context for data interpretation. Based on satellite imagery, a high chlorophyll region (max = 4 µg l-1) north and downstream of the Crozet Islands was distinguished from a low chlorophyll region (typically 0.3 µg l-1) south and upstream of the islands. POC export estimates, obtained with the naturally occurring particle reactive radionuclide tracer, 234Th, were initially D15 mmol C m-2 d-1 in the high chlorophyll region, compared with D5 mmol C m-2 d-1 in the low chlorophyll region. After a moderately small increase in chlorophyll in the south (max = 0.7 µg l-1) the spatial variability in POC export was lost, resulting in equally high levels of POC export (ca. 20 mmol C m-2 d-1) throughout the study area. After comparing the daily rates of POC export with temporally integrated new production calculated from nitrate budgets, a different spatial pattern emerged. New production (NP) presented consistently higher values in the north, when compared to the south. Two hypotheses were formulated to explain this, 1) dissolved organic matter (DOM) and suspended particulate organic ... Thesis Crozet Islands Southern Ocean University of Southampton: e-Prints Soton Southern Ocean Austral |
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University of Southampton: e-Prints Soton |
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ftsouthampton |
language |
English |
description |
It has long been recognised that some oceanic regions have persistently low chlorophyll levels, even though inorganic nutrients are plentiful. Studies have shown that these high-nutrient, low-chlorophyll (HNLC) areas are depleted in iron, which is an essential micronutrient for phytoplankton growth. In HNLC regions biological production can be enhanced with artificial mesoscale iron fertilisation. However, the ability of artificially induced phytoplankton blooms to efficiently sequester carbon to mesopelagic depths is still an open question. SubAntarctic islands in the HNLC Southern Ocean are a natural source of iron and thus fuel the annual phytoplankton blooms observed in their proximity. One such bloom, tied to the Crozet Islands (52ºE, 46ºS), provided the opportunity to examine particulate organic carbon (POC) export during the austral summer of 2004/5. This work was imbedded into the multi-disciplinary CROZEX project thus providing a rich context for data interpretation. Based on satellite imagery, a high chlorophyll region (max = 4 µg l-1) north and downstream of the Crozet Islands was distinguished from a low chlorophyll region (typically 0.3 µg l-1) south and upstream of the islands. POC export estimates, obtained with the naturally occurring particle reactive radionuclide tracer, 234Th, were initially D15 mmol C m-2 d-1 in the high chlorophyll region, compared with D5 mmol C m-2 d-1 in the low chlorophyll region. After a moderately small increase in chlorophyll in the south (max = 0.7 µg l-1) the spatial variability in POC export was lost, resulting in equally high levels of POC export (ca. 20 mmol C m-2 d-1) throughout the study area. After comparing the daily rates of POC export with temporally integrated new production calculated from nitrate budgets, a different spatial pattern emerged. New production (NP) presented consistently higher values in the north, when compared to the south. Two hypotheses were formulated to explain this, 1) dissolved organic matter (DOM) and suspended particulate organic ... |
format |
Thesis |
author |
Morris, Paul James |
spellingShingle |
Morris, Paul James Carbon export from natural iron fertilisation in the Southern Ocean |
author_facet |
Morris, Paul James |
author_sort |
Morris, Paul James |
title |
Carbon export from natural iron fertilisation in the Southern Ocean |
title_short |
Carbon export from natural iron fertilisation in the Southern Ocean |
title_full |
Carbon export from natural iron fertilisation in the Southern Ocean |
title_fullStr |
Carbon export from natural iron fertilisation in the Southern Ocean |
title_full_unstemmed |
Carbon export from natural iron fertilisation in the Southern Ocean |
title_sort |
carbon export from natural iron fertilisation in the southern ocean |
publishDate |
2008 |
url |
https://eprints.soton.ac.uk/66262/ https://eprints.soton.ac.uk/66262/1/Morris_PJ_2008_PhD.pdf |
geographic |
Southern Ocean Austral |
geographic_facet |
Southern Ocean Austral |
genre |
Crozet Islands Southern Ocean |
genre_facet |
Crozet Islands Southern Ocean |
op_relation |
https://eprints.soton.ac.uk/66262/1/Morris_PJ_2008_PhD.pdf Morris, Paul James (2008) Carbon export from natural iron fertilisation in the Southern Ocean. University of Southampton, School of Ocean and Earth Science, Doctoral Thesis, 205pp. |
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