Phytoplankton growth and new production in the Weddell Sea marginal ice zone in the .austral spring and
Rates of primary production, N03- uptake, and NH,l uptake by phytoplankton were measured in the marginal ice zone of the Weddell Sea in austral spring 1983 and autumn 1986. In spring Chl concentrations averaged 3 pg liter-‘, primary productivity 490 mg C m-2 d-l, and surface phytoplankton growth rat...
| Main Authors: | , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
1990
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.506.4035 http://www.aslo.org/lo/toc/vol_35/issue_4/0809.pdf |
| Summary: | Rates of primary production, N03- uptake, and NH,l uptake by phytoplankton were measured in the marginal ice zone of the Weddell Sea in austral spring 1983 and autumn 1986. In spring Chl concentrations averaged 3 pg liter-‘, primary productivity 490 mg C m-2 d-l, and surface phytoplankton growth rates 0.30 doublings d-l. In autumn these rates were all much lower, av-eraging 0.14 pg liter- l, 126 mg C m-2 d-l, and 0.14 doublings d-l. During both seasons NH,+ was consistently the preferred source of N, but because of the much greater availability of N03- in the euphotic zone (21-28 PM NO,- vs.-0.4 yM NH,+ during both seasons), N03- uptake rates generally equaled or exceeded those of NH, +. Vertically integrated&ratios (the ratio of NO3- uptake to the sum of NO,- plus NH,+ uptake) averaged 0.52 (range from 0.35 to 0.70) in spring and 0.72 (range from 0.60 to 0.84) in autumn. In 1983 we observed sharply elevated relative preference indices for NH,+ whenever the ambient NH,+ concentration was ~0.3 PM, which we interpret as evidence that Antarctic phytoplankton growing at NH.,+ concentrations CO.3 PM have the ability to increase their rate of NH,+ uptake rapidly in response to increased availability. We estimate the new production of the marginal ice zone to be at least 49 g C m-2 yr-1 for the November- |
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