摘要
To study the effect of hydrographic factors on the spatial distributions of chlorophyll a （Chl a）, an investigation was carried out in the tropical eastern Indian Ocean （80 –100 E along 7 S, and 7 –18 S along 80 E） in December 2010. The fluorescent method was used to obtain total Chl a and size-fractioned Chl a at the 26 stations. The results show that surface Chl a concentration averaged at （0.168 ± 0.095） mg/m 3 s.d. （range： 0.034–0.475 mg/m 3 ）, concentrations appeared to be higher in the west for longitudinal variations, and higher in the north for latitudinal variations. Furthermore, the surface Chl a concentration was lower （0.034–0.066 mg/m 3 ） in the region to the south of 16 S. There was a strong subsurface Chl a maximum layer at all stations and the depth of the Chl a maximum increased towards to the east and south along with the respective nitracline. The spatial variation of Chl a was significant： correlation and regression analysis suggests that it was primarily affected by PO 3 4 , N（NO 3 –N＋NO 2 –N） and temperature. Size-fractionated Chl a concentration clearly showed that the study area was a typical oligotrophic open ocean, in which picophytoplankton dominated, accounting for approximately 67.8% of total Chl a, followed by nanophytoplankton （24.5%） and microphytoplankton （7.6%）. The two larger fractions were sensitive to the limitation of P, while picophytoplankton was primarily affected by temperature.
To study the effect of hydrographic factors on the spatial distributions of chlorophyll a （Chl a）, an investigation was carried out in the tropical eastern Indian Ocean （80 –100 E along 7 S, and 7 –18 S along 80 E） in December 2010. The fluorescent method was used to obtain total Chl a and size-fractioned Chl a at the 26 stations. The results show that surface Chl a concentration averaged at （0.168 ± 0.095） mg/m 3 s.d. （range： 0.034–0.475 mg/m 3 ）, concentrations appeared to be higher in the west for longitudinal variations, and higher in the north for latitudinal variations. Furthermore, the surface Chl a concentration was lower （0.034–0.066 mg/m 3 ） in the region to the south of 16 S. There was a strong subsurface Chl a maximum layer at all stations and the depth of the Chl a maximum increased towards to the east and south along with the respective nitracline. The spatial variation of Chl a was significant： correlation and regression analysis suggests that it was primarily affected by PO 3 4 , N（NO 3 –N＋NO 2 –N） and temperature. Size-fractionated Chl a concentration clearly showed that the study area was a typical oligotrophic open ocean, in which picophytoplankton dominated, accounting for approximately 67.8% of total Chl a, followed by nanophytoplankton （24.5%） and microphytoplankton （7.6%）. The two larger fractions were sensitive to the limitation of P, while picophytoplankton was primarily affected by temperature.
基金
China Ocean Mineral Resources R & D Association under contract No. DY125-13-E-01
the Scientific Research Fund of the Second Institute of Oceanography, State Oceanic Administration under contract No. JG1024
