A geographical and seasonal comparison of nitrogen uptake by phytoplankton in the Southern Ocean

Simple item page
dc.contributor.authorPhilibert, R
dc.contributor.authorWaldron, H
dc.contributor.authorClark, D
dc.date.accessioned2021-10-08T07:08:31Z
dc.date.available2021-10-08T07:08:31Z
dc.date.issued2015
dc.description.abstractThe impact of light and nutrients (such as silicate and iron) availability on nitrogen uptake and primary production vary seasonally and regionally in the Southern Ocean. The seasonal cycle of nitrogen uptake by phytoplankton in the Southern Ocean is not fully resolved over an annual scale due to the lack of winter in situ measurements. In this study, nitrate and ammonium uptake rates were measured using <sup>15</sup>N tracers during a winter cruise in July 2012 and a summer cruise in February–March 2013. The winter cruise consisted of two legs: leg 1 extended from Cape Town to the ice margin along the GoodHope line and leg 2 stretched from the ice margin to Marion Island. The summer cruise was mostly focused on the subantarctic zone of the Atlantic sector. In winter, nitrogen uptake rates were measured at 55 and 1% of the surface photosynthetically active radiation (sPAR). The summer uptake rates were measured at four light depths corresponding to 55, 30, 10 and 3% sPAR. The integrated nitrate uptake rates during the winter cruise ranged from 0.17 to 5.20 mmol N m<sup>−2</sup> d<sup>−1</sup> (average 1.14 mmol N m<sup>−2</sup> d<sup>−1</sup>) while the ammonium uptake rates ranged from 0.60 to 32.86 mmol N m<sup>−2</sup> d<sup>−1</sup> (average 6.73 mmol N m<sup>−2</sup> d<sup>−1</sup>). During the summer cruise, the mean-integrated nitrate uptake rate was 0.20 mmol N m<sup>−2</sup> d<sup>−1</sup> with a range between 0.10 and 0.38 mmol N m<sup>−2</sup> d<sup>−1</sup>. The integrated ammonium uptake rate averaged 4.39 mmol N m<sup>−2</sup> d<sup>−1</sup> and ranged from 1.12 to 9.05 mmol N m<sup>−2</sup> d<sup>−1</sup>. <br><br> The factors controlling nitrogen uptake in winter and summer were investigated. During the winter cruise, it was found that the different nitrogen uptake regimes were not separated by the fronts of the Antarctic Circumpolar Current (ACC). Light (in terms of day length) and ammonium concentration had the most influence on the nitrogen uptake. In the summer, increases in the mixed layer depth (MLD) resulted in increased nitrogen uptake rates. This suggests that the increases in the MLD could be alleviating nutrient limitations experienced by the phytoplankton at the end of summer.
dc.identifier.apacitationPhilibert, R., Waldron, H., & Clark, D. (2015). A geographical and seasonal comparison of nitrogen uptake by phytoplankton in the Southern Ocean. <i>Ocean Science</i>, 11(2), 251 - 267. http://hdl.handle.net/11427/34597en_ZA
dc.identifier.chicagocitationPhilibert, R, H Waldron, and D Clark "A geographical and seasonal comparison of nitrogen uptake by phytoplankton in the Southern Ocean." <i>Ocean Science</i> 11, 2. (2015): 251 - 267. http://hdl.handle.net/11427/34597en_ZA
dc.identifier.citationPhilibert, R., Waldron, H. & Clark, D. 2015. A geographical and seasonal comparison of nitrogen uptake by phytoplankton in the Southern Ocean. <i>Ocean Science.</i> 11(2):251 - 267. http://hdl.handle.net/11427/34597en_ZA
dc.identifier.issn1812-0784
dc.identifier.issn1812-0792
dc.identifier.ris TY - Journal Article AU - Philibert, R AU - Waldron, H AU - Clark, D AB - The impact of light and nutrients (such as silicate and iron) availability on nitrogen uptake and primary production vary seasonally and regionally in the Southern Ocean. The seasonal cycle of nitrogen uptake by phytoplankton in the Southern Ocean is not fully resolved over an annual scale due to the lack of winter in situ measurements. In this study, nitrate and ammonium uptake rates were measured using <sup>15</sup>N tracers during a winter cruise in July 2012 and a summer cruise in February–March 2013. The winter cruise consisted of two legs: leg 1 extended from Cape Town to the ice margin along the GoodHope line and leg 2 stretched from the ice margin to Marion Island. The summer cruise was mostly focused on the subantarctic zone of the Atlantic sector. In winter, nitrogen uptake rates were measured at 55 and 1% of the surface photosynthetically active radiation (sPAR). The summer uptake rates were measured at four light depths corresponding to 55, 30, 10 and 3% sPAR. The integrated nitrate uptake rates during the winter cruise ranged from 0.17 to 5.20 mmol N m<sup>−2</sup> d<sup>−1</sup> (average 1.14 mmol N m<sup>−2</sup> d<sup>−1</sup>) while the ammonium uptake rates ranged from 0.60 to 32.86 mmol N m<sup>−2</sup> d<sup>−1</sup> (average 6.73 mmol N m<sup>−2</sup> d<sup>−1</sup>). During the summer cruise, the mean-integrated nitrate uptake rate was 0.20 mmol N m<sup>−2</sup> d<sup>−1</sup> with a range between 0.10 and 0.38 mmol N m<sup>−2</sup> d<sup>−1</sup>. The integrated ammonium uptake rate averaged 4.39 mmol N m<sup>−2</sup> d<sup>−1</sup> and ranged from 1.12 to 9.05 mmol N m<sup>−2</sup> d<sup>−1</sup>. <br><br> The factors controlling nitrogen uptake in winter and summer were investigated. During the winter cruise, it was found that the different nitrogen uptake regimes were not separated by the fronts of the Antarctic Circumpolar Current (ACC). Light (in terms of day length) and ammonium concentration had the most influence on the nitrogen uptake. In the summer, increases in the mixed layer depth (MLD) resulted in increased nitrogen uptake rates. This suggests that the increases in the MLD could be alleviating nutrient limitations experienced by the phytoplankton at the end of summer. DA - 2015 DB - OpenUCT DP - University of Cape Town IS - 2 J1 - Ocean Science LK - https://open.uct.ac.za PY - 2015 SM - 1812-0784 SM - 1812-0792 T1 - A geographical and seasonal comparison of nitrogen uptake by phytoplankton in the Southern Ocean TI - A geographical and seasonal comparison of nitrogen uptake by phytoplankton in the Southern Ocean UR - http://hdl.handle.net/11427/34597 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/34597
dc.identifier.vancouvercitationPhilibert R, Waldron H, Clark D. A geographical and seasonal comparison of nitrogen uptake by phytoplankton in the Southern Ocean. Ocean Science. 2015;11(2):251 - 267. http://hdl.handle.net/11427/34597.en_ZA
dc.language.isoeng
dc.publisher.departmentDepartment of Oceanography
dc.publisher.facultyFaculty of Science
dc.sourceOcean Science
dc.source.journalissue2
dc.source.journalvolume11
dc.source.pagination251 - 267
dc.source.urihttps://dx.doi.org/10.5194/os-11-251-2015
dc.subject.otherG
dc.subject.otherEnvironmental sciences
dc.subject.otherGE1-350
dc.subject.otherGeography. Anthropology. Recreation
dc.titleA geographical and seasonal comparison of nitrogen uptake by phytoplankton in the Southern Ocean
dc.typeJournal Article
uct.type.publicationResearch
uct.type.resourceJournal Article
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
PhilibertR_A_geographicals_2015.pdf
Size:
466.47 KB
Format:
Adobe Portable Document Format
Description:
Download
Collections
Journal Articles