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Title: Biogeochemical investigation of caves within Bahamian carbonate platforms
Author: Schwabe, Stephanie Jutta
ISNI:       0000 0001 3556 9721
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 1999
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The Bahamas are thousands of islands stretching along the coast of Florida and south to the tropic of cancer. An aerialv iew, spectaculaar s it is, shows only a small part of the islands, a larger part is submerged and discernible only by the abundance of blue dots onshorea nd in the shallow water around the islands. The blue holes are entrancesto an underwater world wherein biology seems to have slowed down to offer a fascinating view of species rarely seen elsewhere, and of rock formations that tell a story of the subterranianw orld below the islands. My studies were inspired by curiosity and the desire to make a contribution to the preservationo f this unique and irreplaceablew indow into the pastf or geologistsa nd biologists alike. Important questions as to how the caves formed and when and what the role of cavel ife might havep layed in the excavationp rocessesa re addressedin this thesis. As a result of these studies bacteria must be considered as possibly active participantsi n the formation processesa fter the time when the rising watertablef looded all the Bahamian caves. The layering, often in hypersharp zones of biological material, matches or is perhaps caused by, equally dramatic changes in hydrogen ions and acetate and sulphate concentrations. In both caves, pH profiles were observed that varied sharply over very short distances. In all three study sites it could be shown that, vertically and horizontally, the geochemical perimeters varied dramatically. Organically mediated processes are a dominant control on dissolution within the fresh, mixing, and saline zone. The combined generationof C02 results, known from earlier studies, and 112S and other bacterially measured activity, supports this finding. Retention of suspended organic matter was directly proportional to the salinity gradient. Elevated levels of DOC, POM, and acetate at the two major density interfaces confirm this finding. In the results, generated from CHN&S methods, wall rock material was found to contain residual carbon for potential microbial use, and large bacterial populations were identified through the SEM method in excess of what was measured within the water column. Significant lepidocrocite deposits (dimorphose iron oxihydroxide) were identified as a fraction of the cave sediment, and material known as "mung7, based on amino-acid analysis, was shown to be proteinaceous. This mung appears to be unique to caves in the Bahamas. In a sense the cave system is an underground geo-biosphere wherein the peculiar water flow patterns foster a specific, sometimes rich and unusual, fauna and flora that is a treasure for science and a sight for humans to enjoy.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Bahamas ; Bacteria ; Blue holes