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Document Type:Latin Dissertation
Language of Document:English
Record Number:55572
Doc. No:TL25526
Call number:‭3212712‬
Main Entry:Toby Westberry
Title & Author:Satellite remote sensing of Trichodesmium spp. and its relation to atmospheric dust depositionToby Westberry
College:University of California, Santa Barbara
Date:2005
Degree:Ph.D.
student score:2005
Page No:155
Abstract:This dissertation focuses on Trichodesmium spp., a N 2-fixing cyanobacterium that can alter the supply of nutrients to the ocean. For this reason, its abundance has been linked to local dynamical processes, regional elemental cycling, and global climate patterns on glacial-interglacial timescales through its modulation of the global nitrogen and carbon cycles. Despite its potential significance in earth system processes, information regarding their spatial and temporal distribution is sparse. In this work, patterns of Trichodesmium blooms are assessed from an ocean color satellite (SeaWiFS) using a globally tuned bio-optical algorithm. The algorithm correctly predicts 76-92% of bloom observations in training and validation datasets. Application of the model to the first six years of SeaWiFS data (1998-2003) shows a mixture of patterns consistent with historical and anecdotal observations of blooms, as well as previously unobserved patterns. The most prominent features are large blooms in the Arabian Sea which persist for ∼35% of the time examined, possibly in response to the winter monsoon and extensive areas in the central and eastern tropical Pacific which are appear >30% of the time. Seasonal and interannual variability is observed these quantities in all ocean basins. In addition, we can also estimate global rates of N2 fixation due to the observed Trichodesmium bloom frequency using physiological values from literature. This number is relatively low (∼10 Tg N yr-1) compared to total pelagic N2 fixation (∼110 Tg N yr-1), but not insignificant. Environmental forcing of blooms can be related sea-surface temperature, wind speed, mixed layer depth, and dust deposition rates. However, regional analysis shows that these relationships change strength and timing from place to place. Cross-correlation and conditional probability distributions are used to diagnose preferred conditions for growth and accumulation of blooms. Blooms are found to be rare at wind speeds >10 m s-1, and mixed layer depths >100 and are most probable at wind speeds of 4 m s-1, mixed-layer depth of ∼20m, and sea surface temperature of ∼26.8C. Relationships with dust are more complicated as they require information on the pre-conditioning of the water column.
Subject:Earth sciences; Algal blooms; Atmospheric dust; Nitrogen fixation; Trichodesmium; Biogeochemistry; 0425:Biogeochemistry
Added Entry:D. Siegel
Added Entry:University of California, Santa Barbara