Monsoon-induced changes in the size-fractionated phytoplankton biomass and production rate in the estuarine and coastal waters of southwest coast of India.
Changes in the autotrophic pico- (0.2-2 microm), nano- (2-20 microm), and microplankton (>20 microm) biomass (chlorophyll a) and primary production were measured in the estuarine and coastal waters off Cochin, southwest coast of India during the onset and establishment of a monsoon. During this period, the estuary was dominated by nutrient-rich freshwater, whereas the coastal waters were characterized with higher salinity values (>30 psu) and less nutrients. The average surface chlorophyll a concentrations and primary production rates were higher in the estuary (average 13.7 mg m(-3) and 432 mgC m(-3) day(-1)) as compared to the coastal waters (5.3 mg m(-3) and 224 mgC m(-3) day(-1)). The nanoplankton community formed the major fraction of chlorophyll a and primary production, both in the estuary (average 85 +/- SD 8.3% and 81.2 +/- SD 3.2%) and the coastal waters (average 73.2 +/- SD 17.2% and 81.9 +/- 15.7%). Nanoplankton had the maximum photosynthetic efficiency in the coastal waters (average 4.8 +/- SD 3.9 mgC mgChl a m(-3) h(-1)), whereas in the estuary, the microplankton had higher photosynthetic efficiency (average 7.4 +/- 7 mgC mgChl a m(-3) h(-1)). The heavy cloud cover and increased water column turbidity not only limit the growth of large-sized phytoplankton in the Cochin estuary and coastal waters but also support the proliferation of nanoplankton community during the monsoon season, even though large variation in nanoplankton chlorophyll a and production exists between these two areas.
Madhu
N V
NV
National Institute of Oceanography, Regional Centre, Kochi-18, Kerala, India. nmadhu@nio.org
Jyothibabu
R
R
Balachandran
K K
KK
D018533:Biomass; D002734:Chlorophyll / Q000032:analysis / Q000378:metabolism; D000077194:Chlorophyll A; D004784:Environmental Monitoring; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology; D007194:India; D010839:Phytoplankton / Q000254:growth & development* / Q000378:metabolism; D011891:Rain; D012621:Seasons; D012623:Seawater / Q000737:chemistry / Q000382:microbiology
D002734:Chlorophyll; D000077194:Chlorophyll A