Assessment of relative phosphorus limitation of Trichodesmium spp. in the North Pacific, North Atlantic, and the north coast of Australia
Trichodesmium spp. is a colonial diazotrophic cyanobacterium that occurs in the oligotrophic tropics and subtropics. Because of its ability to fix atmospheric N2, it is likely to be growth limited by P or Fe, and it has been hypothesized that limitation differs among different ocean basins. Two assa...
| Main Authors: | , , |
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| Format: | Text |
| Language: | English |
| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.297.249 http://www.aslo.org/lo/toc/vol_53/issue_6/2495.pdf |
| Summary: | Trichodesmium spp. is a colonial diazotrophic cyanobacterium that occurs in the oligotrophic tropics and subtropics. Because of its ability to fix atmospheric N2, it is likely to be growth limited by P or Fe, and it has been hypothesized that limitation differs among different ocean basins. Two assays used as indices of P limitation or stress in Trichodesmium spp. are uptake of 33 PO 3{ 4 to determine maximal P uptake (Vmax) and hydrolysis of P from methylumbelliferone phosphate to estimate alkaline phosphatase activity (APA). The kinetics of PO 3{ 4 uptake were determined for Trichodesmium spp. colonies in the North Pacific, North Atlantic, and in waters north of Australia, whereas APA was determined in the North Pacific and North Atlantic. Trichodesmium spp. Vmax was significantly greater (,fourfold or more) in the North Atlantic compared with the North Pacific and waters north of Australia when normalized to both chlorophyll a content and number of trichomes per colony. APA in the North Atlantic was also greater than in the North Pacific. The half-saturation constant for PO 3{ 4 uptake (Ks) was not significantly different among the three locations. These data indicate that Trichodesmium spp. is more |
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