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THE DISTRIBUTION OF B-VITAMINS IN TWO CONTRASTING AQUATIC SYSTEMS, AND IMPLICATIONS FOR THEIR ECOLOGICAL AND BIOGEOCHEMICAL ROLES by Laila Pualani Barada A Dissertation Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (BIOLOGICAL SCIENCES) December 2013 Copyright 2013 Laila Pualani Barada
|Title||The distribution of B-vitamins in two contrasting aquatic systems, and implications for their ecological and biogeochemical roles|
|Author||Barada, Laila Pualani|
|Degree||Doctor of Philosophy|
|School||College of Letters, Arts And Sciences|
|Advisor (committee chair)||Capone, Douglas G.|
|Advisor (committee member)||
Fuhrman, Jed A.
Webb, Eric A.
Sanudo-Wilhelmy, Sergio A.
Wilcox, Rand R.
|Abstract||B-vitamins are recognized as important organic growth factors, although our knowledge regarding their concentrations and distribution in aquatic ecosystems is limited. We present the first direct measurements of the organic growth factors thiamin (B₁) and pyridoxine (B₆) in the North Atlantic Ocean that is influenced by Amazon river plume. This is an area known to have high productivity, di-nitrogen (N₂) fixation, and carbon (C) sequestration. The first directly measured vitamin B₆ and biotin (B₇) concentrations from an oligotrophic freshwater system, Lake Tahoe, are also presented. B-vitamins function as essential enzymatic co-factors for diverse biological reactions. Specifically, vitamins B₁ and B₇ are involved in carbon metabolism while vitamin B₆ is required for the metabolism of almost all amino acids. Therefore, vitamins B₁, B₆, and B₇ may play critical roles in both C and nitrogen (N) cycling in aquatic environments as many phytoplankton cannot synthesize these growth factors and need to acquire them from the environment. These studies draw attention to the potential roles of B-vitamins in ecosystem dynamics. ❧ Concentrations of vitamins B₁ and B₆ in the WTNA Ocean ranged from undetectable to 230 and 40 pM, respectively. Depth profiles in the photic zone of B₁ and B₆ varied with depth and salinity. Vitamin B₁ concentrations were significantly higher in the surface plume waters at some stations suggesting a possible riverine influence. Linear regression models were used to determine the influence of vitamins B₁ and B₆ on biologically mediated C and N fixation. The results indicated that the availability of these co-enzymes could affect the rates of these processes in the WTNA. Specifically, significant increases in C and N₂ fixation were observed with increasing concentrations of vitamin B₁ (low salinity and mesohaline stations 9.1 and 1, p value < 0.017 and < 0.03, respectively). A significant positive correlation was also observed between N₂ fixation and vitamin B₁ at station 1 (p value < 0.29) and vitamin B₆ at station 9.1 (p value < 0.017). This study suggests that a dynamic interplay is possible between these organic growth factors and biologically mediated C and N₂ fixation that ultimately affect global biogeochemical cycling. ❧ Concentrations of vitamins B₆ in Lake Tahoe ranged from undetectable to 3.17 and 3.67 pM at the West Lake Tahoe (WLT) and Mid Lake Tahoe (MLT) stations respectively. Vitamin B₇ concentrations ranged from 0.59 to 4.28 pM and 0.23 to 3.45 pM at the WLT and MLT stations, respectively. Other B-vitamins were below the detection limits suggesting that dissolved B-vitamin concentrations in the water column were very low during this study. Generally, the WLT station had higher trace metal concentrations compared to the MLT station suggesting a potential terrestrial source of trace metals to the lake. Depth profiles showed corresponding peaks in trace metals and B-vitamins, and correlation analysis showed a significant relationship of some trace metals and B-vitamins that tended to increase together. This suggests possible trace metal limitation or co-limitation of B-vitamin biosynthesis. ❧ Collectively these studies highlight the importance of B-vitamins to various aquatic systems because of their ability to affect rates of biologically mediated C and N₂ fixation, community structure, and ecosystem functioning. Multiple factors contribute to the abundance and distribution of B-vitamins, specifically species distribution and trace metal concentrations. However, further studies are required to determine the magnitude of the influence of B-vitamins on global biogeochemical cycling and other factors affecting their distribution in various aquatic habitats.|
|Keyword||B-vitamins; thiamin; biotin; pyridoxine; Amazon River Plume; Atlantic Ocean; Lake Tahoe; California; phosphonate; biogeochemical cycles; methane; Trichodesmium; trace metals|
|Part of collection||University of Southern California dissertations and theses|
|Publisher (of the original version)||University of Southern California|
|Place of publication (of the original version)||Los Angeles, California|
|Publisher (of the digital version)||University of Southern California. Libraries|
|Provenance||Electronically uploaded by the author|
|Legacy record ID||usctheses-m|
|Contributing entity||University of Southern California|
|Rights||Barada, Laila Pualani|
|Access conditions||The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given.|
|Repository name||University of Southern California Digital Library|
|Repository address||USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA|
|Contributing entity||University of Southern California|
|Full text||THE DISTRIBUTION OF B-VITAMINS IN TWO CONTRASTING AQUATIC SYSTEMS, AND IMPLICATIONS FOR THEIR ECOLOGICAL AND BIOGEOCHEMICAL ROLES by Laila Pualani Barada A Dissertation Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (BIOLOGICAL SCIENCES) December 2013 Copyright 2013 Laila Pualani Barada|