Phytoplankton, nutrients and hydrography in the frontal zone between the Southwest Indian Subtropical gyre and the Southern Ocean |
| |
| Authors: | J. F. Read M. I. Lucas S. E. Holley R. T. Pollard |
| |
| Affiliation: | 1. Faculdade de Oceanografia, Rio de Janeiro State University, Rua São Francisco Xavier, 524, Maracanã, Rio de Janeiro CEP 20550-013, RJ, Brazil;2. Instituto de Biologia, Rio de Janeiro Federal University, Avenida Carlos Chagas Filho, 373, Ilha do Fundão-Cidade Universitária, Rio de Janeiro CEP 21941-902, RJ, Brazil;3. Departamento de Ciências do Mar. Campus Baixada Santista. Universidade Federal de São Paulo (UNIFESP), Av. Saldanha da Gama, 89, Ponta da Praia, CEP 11030-400 Santos, SP, Brazil;4. Centro de Ciências Marinhas, São Paulo University, Rodovia Manoel Hypólito do Rego, km. 131,5, Praia do Cabelo Gordo, São Sebastião, SP, Brazil. CEP.: 11600-000;1. Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia;2. National Institute of Water and Atmospheric Research, Wellington, New Zealand;3. Institute of Geological Sciences and Oeschger Centre for Climate Change Research, University of Bern, Switzerland;4. Central Science Laboratory, University of Tasmania, Hobart, Australia;5. Australian National University, Canberra, Australia;6. Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, New South Wales, Australia;7. ARC Centre of Excellence in Ore Deposits (CODES), University of Tasmania, Hobart, Australia |
| |
| Abstract: | A survey was made of the Southwest Indian Ocean frontal region between 30 and 50°E containing the Agulhas Return, Subtropical and Subantarctic Fronts. From CTD, SeaSoar and extracted samples the distribution of nitrate, silicate and chlorophyll a is shown to be strongly linked to the front and water mass structure, varying zonally and meridionally. Surface chlorophyll a concentrations were low to the north and south leaving a band of elevated chlorophyll between the Subtropical and Subantarctic Fronts. The low concentration of chlorophyll a to the north, in Subtropical Water, was clearly due to nitrate limitation. Between the Subtropical and Subantarctic Fronts, where the chlorophyll a concentrations were highest, the surface layer showed silicate depletion limiting diatom growth. South of the Subantarctic Front there were deep extending, low concentrations of chlorophyll a, but despite plentiful supplies of macro-nutrients and a well-stratified surface layer, high concentrations of chlorophyll a were absent. Changes from west to east were associated with the meandering of the Southern Ocean Fronts, especially the Subtropical Front, and their strength and proximity to each other. Concentrations of chlorophyll a peaked where the Agulhas Return, Subtropical and Subantarctic Fronts were in close proximity. Combined frontal structures appear to have particularly pronounced vertical stability and are associated with enhanced upwelling of nutrients and leakage of nutrients across the front. Light levels are high within the shallow stable layer. Such conditions are clearly favourable for biological growth and support the development of larger-celled phytoplankton communities. |
| |
| Keywords: | Hydrography Nutrients Phytoplankton Oceanic Fronts Southwest Indian Ocean 35– 45° S, 30– 50° E |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
