Nitrogen uptake rates and f-ratios in the Equatorial and Southern Indian Ocean

• Main Authors: Prakash, S, Ramesh, R, Sheshshayee, MS, Mohan, R, Sudhakar, M
• Format: Article in Journal/Newspaper
• Language: English
• Published: Indian Academy of Sciences 2015
• Subjects: oceanography; Antarctic; Indian; Southern Ocean; The Antarctic; Antarc*
• Online Access: http://moeseprints.incois.gov.in/1969/; http://moeseprints.incois.gov.in/1969/1/Nitrogen%20uptake.pdf; http://www.currentscience.ac.in/php/cissue.php

We report data on nitrate, ammonium and urea uptake rates from the Equatorial and Southern Indian Oceans. Productivity (0.81–2.23 mmol N m–2 d–1) over the Equatorial Indian Ocean was low, but the f-ratio (0.13–0.45) was relatively high. In the Southern Indian Ocean total N-uptake rate varied from 1.7 to 12.3 mmol Nm–2 d–1; it was higher in the Antarctic coast (69S) and lower over most of the Southern Ocean, the lowest being at 58S. The f-ratio also showed significant spatial variation, but was higher compared to values at the Equatorial Indian Ocean. The mean f-ratio in the Southern Indian Ocean was 0.50. The nitrate-specific uptake rates and f-ratios appear to have increased significantly in the recent past relative to earlier estimates. While productivity in the Southern Ocean is comparable to that in the Equatorial Indian Ocean, higher f-ratios in the former underscore its importance in the uptake of CO2