Control of phytoplankton growth by iron supply and irradiance in the subantarctic Southern Ocean: Experimental results from the SAZ Project
The influence of irradiance and iron (Fe) supply on phytoplankton processes was investigated, north (47 S, 142 E) and south (54 S, 142 E) of the Subantarctic Front in austral autumn (March 1998). At both sites, resident cells exhibited nutrient stress (Fv/ Fm < 0.3). Shipboard perturbation experi...
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Language: | English |
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American Geophysical Union
2001
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Online Access: | https://doi.org/10.1029/2000JC000348 http://ecite.utas.edu.au/22375 |
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ftunivtasecite:oai:ecite.utas.edu.au:22375 2023-05-15T18:26:01+02:00 Control of phytoplankton growth by iron supply and irradiance in the subantarctic Southern Ocean: Experimental results from the SAZ Project Boyd, PW Crossley, AC DiTullio, GR Griffiths, FB Hutchins, DA Queguiner, B Sedwick, PN Trull, T 2001 https://doi.org/10.1029/2000JC000348 http://ecite.utas.edu.au/22375 en eng American Geophysical Union http://dx.doi.org/10.1029/2000JC000348 Boyd, PW and Crossley, AC and DiTullio, GR and Griffiths, FB and Hutchins, DA and Queguiner, B and Sedwick, PN and Trull, T, Control of phytoplankton growth by iron supply and irradiance in the subantarctic Southern Ocean: Experimental results from the SAZ Project, Journal of Geophysical Research, 106, (C12) pp. 31573-31583. ISSN 0148-0227 (2001) [Refereed Article] http://ecite.utas.edu.au/22375 Biological Sciences Ecology Marine and Estuarine Ecology (incl. Marine Ichthyology) Refereed Article PeerReviewed 2001 ftunivtasecite https://doi.org/10.1029/2000JC000348 2019-12-13T21:04:19Z The influence of irradiance and iron (Fe) supply on phytoplankton processes was investigated, north (47 S, 142 E) and south (54 S, 142 E) of the Subantarctic Front in austral autumn (March 1998). At both sites, resident cells exhibited nutrient stress (Fv/ Fm < 0.3). Shipboard perturbation experiments examined two light (mean in situ and elevated) and two Fe (nominally 0.5 and 3 nM) treatments under silicic acid-replete conditions. Mean in situ light levels (derived from incident irradiances, mixed layer depths (MLDs), wind stress, and a published vertical mixing model) differed at the two sites, 25% of incident irradiance I0 at 47 S and 9% I0 at 54 S because of MLDs of 40 (47 S) and 90 m (54 S), when these stations were occupied. The greater MLD at 54 S is reflected by tenfold higher cellular chlorophyll a levels in the resident phytoplankton. In the 47 S experiment, chlorophyll a levels increased to >1 g L-1 only in the high-Fe treatments, regardless of irradiance levels, suggesting Fe limitation. This trend was also noted for cell abundances, silica production, and carbon fixation rates. In contrast, in the 54 S experiment there were increases in chlorophyll a (to >2 g L-1), cell abundances, silica production, and carbon fixation only in the high-light treatments to which Fe had been added, suggesting that Fe and irradiance limit algal growth rates. Irradiance by altering algal Fe quotas is a key determinant of algal growth rate at 54 S (when silicic acid levels are nonlimiting); however, because of the integral nature of Fe/light colimitation and the restricted nature of the current data set, it was not possible to ascertain the relative contributions of Fe and irradiance to the control of phytoplankton growth. On the basis of a climatology of summer mean MLD for subantarctic (SA) waters south of Australia the 47 and 54 S sites appear to represent minimum and maximum MLDs, where Fe and Fe/ irradiance, respectively, may limit/colimit algal growth. The implications for changes in the factors limiting algal growth with season in SA waters are discussed. Copyright 2001 by the American Geophysical Union. Article in Journal/Newspaper Southern Ocean eCite UTAS (University of Tasmania) Southern Ocean Austral Journal of Geophysical Research: Oceans 106 C12 31573 31583 |
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Open Polar |
collection |
eCite UTAS (University of Tasmania) |
op_collection_id |
ftunivtasecite |
language |
English |
topic |
Biological Sciences Ecology Marine and Estuarine Ecology (incl. Marine Ichthyology) |
spellingShingle |
Biological Sciences Ecology Marine and Estuarine Ecology (incl. Marine Ichthyology) Boyd, PW Crossley, AC DiTullio, GR Griffiths, FB Hutchins, DA Queguiner, B Sedwick, PN Trull, T Control of phytoplankton growth by iron supply and irradiance in the subantarctic Southern Ocean: Experimental results from the SAZ Project |
topic_facet |
Biological Sciences Ecology Marine and Estuarine Ecology (incl. Marine Ichthyology) |
description |
The influence of irradiance and iron (Fe) supply on phytoplankton processes was investigated, north (47 S, 142 E) and south (54 S, 142 E) of the Subantarctic Front in austral autumn (March 1998). At both sites, resident cells exhibited nutrient stress (Fv/ Fm < 0.3). Shipboard perturbation experiments examined two light (mean in situ and elevated) and two Fe (nominally 0.5 and 3 nM) treatments under silicic acid-replete conditions. Mean in situ light levels (derived from incident irradiances, mixed layer depths (MLDs), wind stress, and a published vertical mixing model) differed at the two sites, 25% of incident irradiance I0 at 47 S and 9% I0 at 54 S because of MLDs of 40 (47 S) and 90 m (54 S), when these stations were occupied. The greater MLD at 54 S is reflected by tenfold higher cellular chlorophyll a levels in the resident phytoplankton. In the 47 S experiment, chlorophyll a levels increased to >1 g L-1 only in the high-Fe treatments, regardless of irradiance levels, suggesting Fe limitation. This trend was also noted for cell abundances, silica production, and carbon fixation rates. In contrast, in the 54 S experiment there were increases in chlorophyll a (to >2 g L-1), cell abundances, silica production, and carbon fixation only in the high-light treatments to which Fe had been added, suggesting that Fe and irradiance limit algal growth rates. Irradiance by altering algal Fe quotas is a key determinant of algal growth rate at 54 S (when silicic acid levels are nonlimiting); however, because of the integral nature of Fe/light colimitation and the restricted nature of the current data set, it was not possible to ascertain the relative contributions of Fe and irradiance to the control of phytoplankton growth. On the basis of a climatology of summer mean MLD for subantarctic (SA) waters south of Australia the 47 and 54 S sites appear to represent minimum and maximum MLDs, where Fe and Fe/ irradiance, respectively, may limit/colimit algal growth. The implications for changes in the factors limiting algal growth with season in SA waters are discussed. Copyright 2001 by the American Geophysical Union. |
format |
Article in Journal/Newspaper |
author |
Boyd, PW Crossley, AC DiTullio, GR Griffiths, FB Hutchins, DA Queguiner, B Sedwick, PN Trull, T |
author_facet |
Boyd, PW Crossley, AC DiTullio, GR Griffiths, FB Hutchins, DA Queguiner, B Sedwick, PN Trull, T |
author_sort |
Boyd, PW |
title |
Control of phytoplankton growth by iron supply and irradiance in the subantarctic Southern Ocean: Experimental results from the SAZ Project |
title_short |
Control of phytoplankton growth by iron supply and irradiance in the subantarctic Southern Ocean: Experimental results from the SAZ Project |
title_full |
Control of phytoplankton growth by iron supply and irradiance in the subantarctic Southern Ocean: Experimental results from the SAZ Project |
title_fullStr |
Control of phytoplankton growth by iron supply and irradiance in the subantarctic Southern Ocean: Experimental results from the SAZ Project |
title_full_unstemmed |
Control of phytoplankton growth by iron supply and irradiance in the subantarctic Southern Ocean: Experimental results from the SAZ Project |
title_sort |
control of phytoplankton growth by iron supply and irradiance in the subantarctic southern ocean: experimental results from the saz project |
publisher |
American Geophysical Union |
publishDate |
2001 |
url |
https://doi.org/10.1029/2000JC000348 http://ecite.utas.edu.au/22375 |
geographic |
Southern Ocean Austral |
geographic_facet |
Southern Ocean Austral |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
http://dx.doi.org/10.1029/2000JC000348 Boyd, PW and Crossley, AC and DiTullio, GR and Griffiths, FB and Hutchins, DA and Queguiner, B and Sedwick, PN and Trull, T, Control of phytoplankton growth by iron supply and irradiance in the subantarctic Southern Ocean: Experimental results from the SAZ Project, Journal of Geophysical Research, 106, (C12) pp. 31573-31583. ISSN 0148-0227 (2001) [Refereed Article] http://ecite.utas.edu.au/22375 |
op_doi |
https://doi.org/10.1029/2000JC000348 |
container_title |
Journal of Geophysical Research: Oceans |
container_volume |
106 |
container_issue |
C12 |
container_start_page |
31573 |
op_container_end_page |
31583 |
_version_ |
1766207809749254144 |