Dissolved silicic acid (Si(OH)4) and biogenic silica (BSiO2) concentrations were measured on four different cruises in the Southern Ocean along 1700 W from late October 1997 to mid-March 1998. These data were used to construct a vertically integrated Si budget in the surface layer from 58° to 68° S. Throughout...
Nature is an inspirational source of silica structures that possess unique optical properties. A few classes of organisms fabricate metal oxides with nanoscale features by a bottom-up self assembly process. In particular, diatoms are a prolific class of single-celled algae that possess silica shells or “frustules” with intricate submicron scale...
A new technique for determining the amount of opal in deep-sea
sediments of any age is described. Using a normative calculation, a
portion of the analytical silica concentration of sediments is subtracted
as non-biogenic in proportion to the concentration of aluminum in the
sample. The ratio of SiO₂:Al₂O₃ used to...
The role of hypothalamic biogenic amines (norepinephrine,
dopamine and serotonin) in regulating the release of luteinizing
hormone (LH) in the ewe was investigated. Eleven experiments
utilizing mature crossbred or Hampshire ewes were conducted to
determine the ability of exogenous 17β-estradiol and various pharmacological
agents to alter the levels of hypothalamic...
The alteration of subseafloor volcanic glass from three locations is qualitatively attributed to biological
(biotic) or chemical (abiotic) reactions on the basis of microscopic morphology of the boundary between
the unaltered and altered glass. Eleven-element composition of fresh basalt glass (sideromelane) and its
alteration products were determined by electron microprobe....
Calcium carbonate percentages at five Ceara Rise sites were estimated at 1- to 2-k.y. intervals over the past 5 m.y., using
reflectance spectroscopy and magnetic susceptibility proxies. From these estimates and detailed correlations between sites, gradients
of calcite and terrigenous sediment accumulation rates in a depth transect of sites reveal...
Diatoms are a ubiquitous group of plankton responsible for 20-40% of oceanic
primary production, and a higher fraction of organic matter export to the ocean
interior. Diatoms actively transport dissolved inorganic silicon into their cells, and
through the process of silicification (i.e. biogenic silica production) they build tough
and intricate...
Algal chlorophyll and carotenoid distributions were measured periodically in the euphotic zone of Sta. ALOHA (22º45′N, 158º00′W) between February 1989 and October 1991 to document the variability in phytoplankton abundance and composition. The annual mean depth-integrated (O-200 db) concentration of Chl a displayed significant interannual variability. Seasonal patterns in Chl...
This thesis details my investigations of marine cyanobacterial natural products that resulted in the discovery of thirteen new secondary metabolites, the isolation of over fifteen previously reported metabolites and the biosynthetic investigation of two additional cyanobacterial compounds. Two novel lipopeptides were identified from a Lyngbya majuscula and Schizothrix sp. assemblage...