Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Bibliography: leaves 198-220. / by Richard H. Burroughs, III. / Ph.D.

Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Vita. / by Edward P. Laine. / Ph.D.

Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Bibliography: leaves 154-158. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1982. / Microfiche copy available in Archives and Science / Bibliography: leaves 33-38. / by Marie Diane Schneider. / M.S.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Vita. / Includes bibliographies. / by Wilford D. Gardner. / Ph.D.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1982. / "November 1981." Vita. / Includes bibliographical references. / Radiolarians which settle through the oceanic water column were recovered from three stations (western Tropical Atlantic-Station E, central Tropical Pacific-P1 and Panama Basin-PB) using PARFLUX sediment traps in moored arrays at several depths. The taxonomic diversities of the radiolarian assemblages in the sediment traps were very high. A total of 420 taxa, including 23 newly identified taxa, were found at the three stations; of these, 208 taxa were found at station E. The polycystine radiolarians generally reach the sea floor with little change in abundance or species composition, although slight skeletal dissolution occurs throughout their descent. The phaeodarian radiolarians, on the other hand, are largely dissolved within the water column; only a few species reach the sea-floor and these dissolve rapidly at the sediment-water interface. Most radiolarian skeletons sink as individuals through deep water columns without being incorporated into large biogenic aggregates. Because significant numbers of nassellarian and phaeodarian species are deep-water dwelling forms the diversity index of radiolarians increases with increasing depth in the mesopelagic zone. The vertical flux of the total radiolarians arriving at the trap depths (in x 103 individuals/m2/day) ranged from 16-24 (E), 0.6-17 (Pl), and 29-53 (PB). Of these on the average 25 % and 69 % of the total radiolarian flux is transported by Spumellaria and Nassellaria, respectively, while 5 % is carried by Phaeodaria. The measured SiO2 content of the skeletons averaged 91, 98 and 71 % of measured weight for Spumellaria, Nassellaria and Phaeodaria, respectively. The supply of radiolarian silica (mg SiO 2 /m 2/day) to each trap depth ranged from 2.5-4.0 (E), 0.9-3.2 (P ), and 5.7-10.4 (PB). The Radiolaria appear to be a significantly large portion of the SiO2 flux in >63 pm size fraction and thus play an important role in the silica cycle. When the radiolarian fluxes at the three Stations are compared with Holocene radiolarian accumulation rates in the same areas it became apparent that several percent or less of the fluxes are preserved in the sediments in all cases and the rest is dissolved on the sea-floor. Estimated excess Si which is derived from SiO2 dissolution on the sea-floor is fairly small relative to advective Si in the western North Atlantic and thus it appears to be insignificant to show any deviation in a simple mixing curve of deep water masses. Weight, length, width, projected area and volume of 58 radiolarian taxa were measured. The density contrast of radiolarians, relative to seawater, generally falls between 0.01 and 0.5 g/cm33. The sinking speed of 55 radiolarian taxa, measured in the laboratory at 3*C, ranged from 13 to 416 m/day. Despite the wide variety of morphology between the species, sinking speeds were best correlated with weight/shell among all the possible combinations of the examined variables. The estimated residence times of these taxa in the 5 km pelagic water column ranged from 2 weeks to 14 months. Large phaeodarians reached the water-sediment interface relatively quickly and ultimately dissolved on the sea floor. Small-sized taxa dissolved en route during sinking. The standing stock of 26 examined abundant taxa is on the order of 1 to 100 shells/m3 . Total radiolarian standing stock ranges from about 450 shells/m3 at Stations P1 and E to 1200 shells/m 3 at Station PB. The rate of production of total Radiolaria is calculated to be 77 to 225 shells/m 3 /day. The turnover time for these species ranges from several days to one month depending on the species and the assumption of the depth interval used for the estimation. / by Kozo Takahashi. / Ph.D.

Organic molecules such as amino acids have long been considered the cause of some anomalous behavior of metals in the marine environment, with respect to concentration in the water and adsorption on the sediment. Many studies have investigated the adsorption of amino acids and amino acid complexes. This study investigates the adsorption of cobalt, amino acids, and cobalt amino acid complexes on both Na⁺-montmorillonite and Na⁺-birnessite (MnO₂). Amino acids were also adsorbed on Co²⁺-saturated montmorillonite and birnessite. The oxidation state and chemical nature of sorbed cobalt and the chemical nature of the amino acid amine groups were investigated using x-ray photoelectron spectroscopy (XPS). XPS enabled determination of the stoichiometry of the sorbed complexes. Electrophoresis revealed changes in the surface charge of the substrate upon interaction with cobalt, amino acids, and cobalt amino acid complexes. These changes provided insight into the reaction mechanisms and chemical species involved. Infrared and visible spectroscopy, x-ray diffraction (XRD), and quantitative analysis enabled further determination of the reactions that occurred between cobalt, amino acids, cobalt amino acid complexes and the sediment surfaces. Using XPS, it was found at pH values 4 to 7 that Co(II) adsorbed on montmorillonite as Co(II) and on birnessite as Co(III). The birnessite (MnO₂) surface was determined to be the oxidizing agent. XPS, XRD, and infrared spectroscopy indicated that amino acid adsorbed on montmorillonite by cation exchange, keying into octahedral sites, and by peptide formation. Increased adsorption was observed on Co²⁺-montmorillonite in solutions of both glycine and lysine and was attributed to coordination reactions. Both Co(gly)₃ and Co(lys)₃³⁺ complexes were observed in solution and were either formed on the clay surface and released, or desorbed cobalt was complexed in solutions. Co(lys)₃³⁺ was observed on the clay surface following interaction of Co²⁺-montmorillonite with lysine. It is proposed that dissolved oxygen oxidizes cobalt in the amino acid complexes. XPS and electrophoretic mobility measurements indicated that amino acids interact with birnessite by chelation of the surface manganese. Measurement of the Mn 3s splitting for amino acid saturated birnessite samples showed that the surface was reduced. It was inferred that the manganese dioxide surface oxidizes amino acids, but no proof of oxidized amino acids was obtained. Hydrolysis of complexes was observed on both the manganese dioxide and montmorillonite surfaces. Because these complexes are known to be relatively stable to hydrolysis in solution, it was proposed that the surface catalyzed the hydrolysis. The oxidation state and chemical nature of selected metals in Pacific manganese nodules were investigated using XPS. Analysis of binding energies, shake-up satellite features, and multiplet splittings revealed that the oxidation states for the metals in the nodules were Mn(IV), Fe(III), Co(III), Pb(II and IV), Cu(II), Ni(II), and Ti(IV). / Doctor of Philosophy

Little Lake Worth (LLW) (800 m x 200 m x 8« m) is an artificially deep, monomictic marine basin. Pigments and other water quality parameters (O2, pH, T, S, NO3 -. etc.) were utilized to characterize phototrophic communities and water quality. The water column is dominated by diatoms except in the hypolimnon during stratification events (late Summer) when strong anoxia and H2S favors abundant Chlorobium sulfur bacteria. Results indicate nitrate-enriched freshwater baseflow indicative of septic tank seepage during the wet season. This also appears to lead to the accumulation of concentrated organic matter in the sediment. LLW is a potential threat to the health of the ecosystem and the humans using it recreationally. More research is required to verify the effectiveness of restoration options. The spatial and temporal distribution of Chlorobium (phaeovibiroides tent.) and their Bacteriochlorophyll-e homologues is described and compared to similar studies. / by Keren Prize Bolter. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

Continental margin sediments play an important role in marine biogeochemical cycles, partly due to high primary production rates and efficient export of organic matter to sediments in margin environments. This thesis presents studies of solute exchange in fine-grained sediments representative of slope and rise environments, and carbon and nitrogen cycling in sandy sediments dominant in continental shelves worldwide. Results of these studies advance understanding of the role of benthic processes on marine ecosystems. In fine-grained sediments, solute exchange by diffusion, biological mixing and bioirrigation can be quantified using in situ flux chambers with inert tracer additions. Mechanistic models of chamber tracer transport across the seabed indicate that in organic-rich sediments, bioirrigation and mixing dominate over a wide range of bottom water oxygen levels, reflecting the patchiness and versatility of benthic macrofaunal communities. Positive correlations between benthic oxygen and tracer fluxes appear site-specific. Reliable chamber volume estimates derived from mechanistic models reveal that empirical fits to chamber tracer datasets may overestimate chamber volume and benthic solute fluxes. The biogeochemistry of sandy, highly permeable sediments that dominate continental shelves is largely unknown because of the difficulty in sampling and studying them under natural conditions. Novel sediment reactors were developed and used to mimic in situ porewater advection and natural sedimentary conditions. Compositional changes of natural seawater, with and without the addition of

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