A multi-year study of summer diatom blooms in the North Pacific Subtropical Gyre

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Title: A multi-year study of summer diatom blooms in the North Pacific Subtropical Gyre
Author: Brown, Colbi Gabrielle, 1984-
Abstract: In the North Pacific Subtropical Gyre , a nearly -annual phytoplankton bloom forms near the subtropical front at ~30° N . Mixed communities of nitrogen -fixing diatom symbioses (diatom -diazotroph associations ) increase 10² -10³ fold in these blooms . In July 2008 (31 .46˚N 140 .49˚W ) and August 2009 (25 .18 °N 154 °W ) , two blooms were sampled to determine diatom -diazotroph association species composition , physical , and chemical characteristics of the water column . In both 2008 and 2009 , the dominant diatom -diazotroph association was the Hemiaulus hauckii -Richelia intracellularis symbiosis . The 2009 subtropical front bloom was missed ; however , another bloom closer to Hawaii was sampled where diatom -diazotroph association abundance was 10 -fold lower (10² cells Lˉ¹ ) than 2008 despite surface chlorophyll a values that were 3 times greater . Both blooms showed substantial changes in phytoplankton size structure with the >10 μm size chlorophyll a fraction increasing from 10 to 40 % in 2008 . In the 2009 bloom , the non -symbiotic pennate diatom Mastogloia woodiana numerically dominated ( >150 ,000 cells Lˉ¹ ) and formed aggregates that resulted in substantially higher % of netplankton chlorophyll a fractions . Summer open ocean blooms from the two years share a common trend of Hemiaulus dominance of the diatom -diazotroph association population and size structure changes . However , non -symbiotic species can dominate the overall bloom , and diatom -diazotroph association species may not be responsible for the chlorophyll a increase . These two years may represent different types of blooms or temporal changes within summer diatom blooms . The increased biomass in the larger -size fraction suggests these blooms are potential sites for carbon export from the surface layer .
URI: http : / /hdl .handle .net /2152 /ETD -UT -2010 -08 -1757
Date: 2010-12-22

Citation

A multi-year study of summer diatom blooms in the North Pacific Subtropical Gyre. Master's thesis, University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /ETD -UT -2010 -08 -1757 .

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