The transient oasis : consequences of spatial and temporal variability in macronutrients and photosynthetic pigments on particle export in Hawaiian lee cyclones

Rii, Yoshimi M.
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Two cyclonic eddies were surveyed during the E-Flux I and III cruises in order to investigate the consequences of spatial and temporal variability in macronutrients and photosynthetic pigments on particle export. Cyclone Noah, a ~2.5-month-old eddy in the . 'decay' stage that was sampled during E-Flux I, exhibited modest increases in macronutrients and photosynthetic pigments at the center of the eddy. Cyclone Opal, sampled during E-Flux III and in the 'mature' stage at ~1 month old, exhibited sharp increases in macronutrient concentrations at the center of the eddy concurrent with a dramatic 2-fold increase in total chlorophyll a (TChl a) concentration in the deep chlorophyll maximum layer (DCML), comprised mainly of large diatoms. However, euphotic zone depth-integrated TChl a concentration for both eddies were indistinguishable between the center of the eddy and surrounding waters. During an eight-day time-series in the center of Opal, TChl a concentration in the DCML decreased by ~50% with a simultaneous decrease in diatom biomass, potentially triggered by silicic acid limitation. Despite the large diatom bloom, cyclone Opal did not produce the expected increase in particulate carbon and nitrogen export but a ~4-fold increase in silica export. This study represents a direct observation of two eddies at different stages in their biological life cycle, which is controlled by various factors on multiple time scales. Results suggest that controls on the life cycle of a Hawaiian lee cyclone are likely a combination of physical (eddy dynamics), chemical (nutrient limitation), and biological (growth and grazing imbalance) processes. Further investigation of recently studied cyclones in comparison with cyclones Noah and Opal yields speculation of a relationship with the spin-up duration of a cyclone and the resulting biological response. As Hawaiian lee cyclonic eddies may influence an area 100's of km in diameter in the subtropical North Pacific Ocean, it is clear from this study that variability in Hawaiian lee cyclones still remains an enigma.
Thesis (M.S.)--University of Hawaii at Manoa, 2006.
Includes bibliographical references (leaves 72-79).
x, 79 leaves, bound ill. (some col.) 29 cm
Eddies -- Hawaii, Eddies -- North Pacific Ocean, Cyclones -- Hawaii, Cyclones -- North Pacific Ocean
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Theses for the degree of Master of Science (University of Hawaii at Manoa). Oceanography; no. 4157
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