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Thesis: Ph. D., Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2016., Cataloged from PDF version of thesis., Includes bibliographical references., Characterizing global and regional climate variability and climate-carbon cycle interactions in the past provides critical context for evaluating present and future climate trends. In this thesis, I use stable isotope and radiocarbon analysis of vascular plant biomarkers in lacustrine and marine sediment cores to explore late Quaternary climate variability and connections between past climate change and terrestrial carbon cycling in tropical South America. I investigate temporal and spatial trends in South American Summer Monsoon precipitation by reconstructing hydrologic variability over the past 50,000 years at two sites: the Lake Titicaca drainage basin in the Central Andes and the Pantanal wetlands in the interior lowlands. Diverging hydrologic trends at these two sites during the last glacial period suggest altered monsoon circulation patterns under glacial conditions, while changes in summer insolation appear to be an important control of precipitation at both sites during the Holocene. I next assess the relationship between climate change and the age structure of terrestrial biospheric carbon exported from two tropical catchments over the past 20,000 years. Radiocarbon dating of leaf waxes in Cariaco Basin and Lake Titicaca sediment records indicates that waxes preserved in sediments are likely composed of a fresh component transported to sediments within decades of production by vegetation and an old component derived from aged soil organic matter with an average age on the order of millennia at time of deposition. Results from both sites show that past hydrologic variability had a significant impact on the mobilization and export of different pools of terrestrial biospheric carbon. In particular, results from Cariaco Basin suggest that wetter conditions in the past resulted in increased export of fresh biospheric carbon to the ocean, representing a potentially important climate feedback mechanism on geologic timescales., by Kyrstin L. Fornace., Ph. D.

Thesis: Ph. D., Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2016., Cataloged from PDF version of thesis., Includes bibliographical references., Characterizing global and regional climate variability and climate-carbon cycle interactions in the past provides critical context for evaluating present and future climate trends. In this thesis, I use stable isotope and radiocarbon analysis of vascular plant biomarkers in lacustrine and marine sediment cores to explore late Quaternary climate variability and connections between past climate change and terrestrial carbon cycling in tropical South America. I investigate temporal and spatial trends in South American Summer Monsoon precipitation by reconstructing hydrologic variability over the past 50,000 years at two sites: the Lake Titicaca drainage basin in the Central Andes and the Pantanal wetlands in the interior lowlands. Diverging hydrologic trends at these two sites during the last glacial period suggest altered monsoon circulation patterns under glacial conditions, while changes in summer insolation appear to be an important control of precipitation at both sites during the Holocene. I next assess the relationship between climate change and the age structure of terrestrial biospheric carbon exported from two tropical catchments over the past 20,000 years. Radiocarbon dating of leaf waxes in Cariaco Basin and Lake Titicaca sediment records indicates that waxes preserved in sediments are likely composed of a fresh component transported to sediments within decades of production by vegetation and an old component derived from aged soil organic matter with an average age on the order of millennia at time of deposition. Results from both sites show that past hydrologic variability had a significant impact on the mobilization and export of different pools of terrestrial biospheric carbon. In particular, results from Cariaco Basin suggest that wetter conditions in the past resulted in increased export of fresh biospheric carbon to the ocean, representing a potentially important climate feedback mechanism on geologic timescales., by Kyrstin L. Fornace., Ph. D.

Thesis: Ph. D., Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2016., Cataloged from PDF version of thesis., Includes bibliographical references., Characterizing global and regional climate variability and climate-carbon cycle interactions in the past provides critical context for evaluating present and future climate trends. In this thesis, I use stable isotope and radiocarbon analysis of vascular plant biomarkers in lacustrine and marine sediment cores to explore late Quaternary climate variability and connections between past climate change and terrestrial carbon cycling in tropical South America. I investigate temporal and spatial trends in South American Summer Monsoon precipitation by reconstructing hydrologic variability over the past 50,000 years at two sites: the Lake Titicaca drainage basin in the Central Andes and the Pantanal wetlands in the interior lowlands. Diverging hydrologic trends at these two sites during the last glacial period suggest altered monsoon circulation patterns under glacial conditions, while changes in summer insolation appear to be an important control of precipitation at both sites during the Holocene. I next assess the relationship between climate change and the age structure of terrestrial biospheric carbon exported from two tropical catchments over the past 20,000 years. Radiocarbon dating of leaf waxes in Cariaco Basin and Lake Titicaca sediment records indicates that waxes preserved in sediments are likely composed of a fresh component transported to sediments within decades of production by vegetation and an old component derived from aged soil organic matter with an average age on the order of millennia at time of deposition. Results from both sites show that past hydrologic variability had a significant impact on the mobilization and export of different pools of terrestrial biospheric carbon. In particular, results from Cariaco Basin suggest that wetter conditions in the past resulted in increased export of fresh biospheric carbon to the ocean, representing a potentially important climate feedback mechanism on geologic timescales., by Kyrstin L. Fornace., Ph. D.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2013., Cataloged from PDF version of thesis., Includes bibliographical references., Predicting the response of net community calcification (NCC) to ocean acidification OA and declining aragonite saturation state [Omega]a requires a thorough understanding of controls on NCC. The diurnal control of light and net community production (NCP) on NCC confounds the underlying control of [Omega]a on NCC and must be averaged out in order to predict the general response of NCC to OA. I did this by generating a general NCC-[Omega]a correlation based on data from 15 field and mesocosm studies around the globe. The general relationship agrees well with results from mesocosm experiments. This general relationship implies that NCC will transition from net calcification to net dissolution at a [Omega]a of 1.0 ± 0.6 and predicts that NCC will decline by 50% from 1880 to 2100, for a reef of any percent calcifier cover and short reef water residence time. NCC will also decline if percent calcifier cover declines, as evidenced by estimates of NCC in two Caribbean reefs having declined by an estimated 50-90% since 1880. The general NCC-([Omega]a relationship determined here, along with changes in percent calcifier cover, will be useful in predicting changes in NCC in response to OA and for refining models of reef water [Omega]a., by Whitney Nicole Bernstein., Ph.D.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2013., Cataloged from PDF version of thesis., Includes bibliographical references., Predicting the response of net community calcification (NCC) to ocean acidification OA and declining aragonite saturation state [Omega]a requires a thorough understanding of controls on NCC. The diurnal control of light and net community production (NCP) on NCC confounds the underlying control of [Omega]a on NCC and must be averaged out in order to predict the general response of NCC to OA. I did this by generating a general NCC-[Omega]a correlation based on data from 15 field and mesocosm studies around the globe. The general relationship agrees well with results from mesocosm experiments. This general relationship implies that NCC will transition from net calcification to net dissolution at a [Omega]a of 1.0 ± 0.6 and predicts that NCC will decline by 50% from 1880 to 2100, for a reef of any percent calcifier cover and short reef water residence time. NCC will also decline if percent calcifier cover declines, as evidenced by estimates of NCC in two Caribbean reefs having declined by an estimated 50-90% since 1880. The general NCC-([Omega]a relationship determined here, along with changes in percent calcifier cover, will be useful in predicting changes in NCC in response to OA and for refining models of reef water [Omega]a., by Whitney Nicole Bernstein., Ph.D.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2013., Cataloged from PDF version of thesis., Includes bibliographical references., Predicting the response of net community calcification (NCC) to ocean acidification OA and declining aragonite saturation state [Omega]a requires a thorough understanding of controls on NCC. The diurnal control of light and net community production (NCP) on NCC confounds the underlying control of [Omega]a on NCC and must be averaged out in order to predict the general response of NCC to OA. I did this by generating a general NCC-[Omega]a correlation based on data from 15 field and mesocosm studies around the globe. The general relationship agrees well with results from mesocosm experiments. This general relationship implies that NCC will transition from net calcification to net dissolution at a [Omega]a of 1.0 ± 0.6 and predicts that NCC will decline by 50% from 1880 to 2100, for a reef of any percent calcifier cover and short reef water residence time. NCC will also decline if percent calcifier cover declines, as evidenced by estimates of NCC in two Caribbean reefs having declined by an estimated 50-90% since 1880. The general NCC-([Omega]a relationship determined here, along with changes in percent calcifier cover, will be useful in predicting changes in NCC in response to OA and for refining models of reef water [Omega]a., by Whitney Nicole Bernstein., Ph.D.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2013., Cataloged from PDF version of thesis., Includes bibliographical references., Predicting the response of net community calcification (NCC) to ocean acidification OA and declining aragonite saturation state [Omega]a requires a thorough understanding of controls on NCC. The diurnal control of light and net community production (NCP) on NCC confounds the underlying control of [Omega]a on NCC and must be averaged out in order to predict the general response of NCC to OA. I did this by generating a general NCC-[Omega]a correlation based on data from 15 field and mesocosm studies around the globe. The general relationship agrees well with results from mesocosm experiments. This general relationship implies that NCC will transition from net calcification to net dissolution at a [Omega]a of 1.0 ± 0.6 and predicts that NCC will decline by 50% from 1880 to 2100, for a reef of any percent calcifier cover and short reef water residence time. NCC will also decline if percent calcifier cover declines, as evidenced by estimates of NCC in two Caribbean reefs having declined by an estimated 50-90% since 1880. The general NCC-([Omega]a relationship determined here, along with changes in percent calcifier cover, will be useful in predicting changes in NCC in response to OA and for refining models of reef water [Omega]a., by Whitney Nicole Bernstein., Ph.D.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2011., Cataloged from PDF version of thesis., Includes bibliographical references., Corals are increasingly threatened by warming sea surface temperatures and other anthropogenic changes. The delicate symbiosis between corals and their algal endosymbionts (zooxanthellae) is easily disrupted by thermal stress, leading to bleaching and eventual mortality. The use of lipid ratios as biomarkers of environmental conditions is well established. Coral biomass contains abundant lipids, and the potential of lipid parameters to diagnose thermal tolerance in zooxanthellae has been previously suggested. In this thesis, I explore the response of specific fatty acids, sterols, and thylakoid membrane lipids to thermal and disease stress in zooxanthellae grown in culture, as well as those isolated from living corals. I present the discovery of a bioactive thylakoid lipid within zooxanthellae cells, and show how this compound is selectively mobilized in thermally stressed cells. I present a plausible mechanism for the breakdown of this compound into products that may cause apoptosis and disrupt the coral-algal symbiosis, eventually causing bleaching. I present two new lipid biomarkers of thermal stress in zooxanthellae, the C18 fatty acid unsaturation ratio, and the fatty acid to sterol ratio. I calibrate the decline of these two parameters to levels of thermal stress comparable to those needed to cause bleaching. I further show that these parameters are sensitive to pathogen stress as well. In several case studies of diseased and thermally stressed corals, I demonstrate that these lipid biomarkers of coral stress may be applied to zooxanthellae isolated from environmental samples. I show that these same compounds are preserved within coral aragonite, which opens up the potential to retrieve lipid-based historical records of coral health from annual layers of coral skeleton. This work demonstrates the value of using lipid biomarkers to assess coral health and better understand the biochemical mechanisms of coral bleaching., by Jessie Mary Kneeland., Ph.D.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2011., Cataloged from PDF version of thesis., Includes bibliographical references., Corals are increasingly threatened by warming sea surface temperatures and other anthropogenic changes. The delicate symbiosis between corals and their algal endosymbionts (zooxanthellae) is easily disrupted by thermal stress, leading to bleaching and eventual mortality. The use of lipid ratios as biomarkers of environmental conditions is well established. Coral biomass contains abundant lipids, and the potential of lipid parameters to diagnose thermal tolerance in zooxanthellae has been previously suggested. In this thesis, I explore the response of specific fatty acids, sterols, and thylakoid membrane lipids to thermal and disease stress in zooxanthellae grown in culture, as well as those isolated from living corals. I present the discovery of a bioactive thylakoid lipid within zooxanthellae cells, and show how this compound is selectively mobilized in thermally stressed cells. I present a plausible mechanism for the breakdown of this compound into products that may cause apoptosis and disrupt the coral-algal symbiosis, eventually causing bleaching. I present two new lipid biomarkers of thermal stress in zooxanthellae, the C18 fatty acid unsaturation ratio, and the fatty acid to sterol ratio. I calibrate the decline of these two parameters to levels of thermal stress comparable to those needed to cause bleaching. I further show that these parameters are sensitive to pathogen stress as well. In several case studies of diseased and thermally stressed corals, I demonstrate that these lipid biomarkers of coral stress may be applied to zooxanthellae isolated from environmental samples. I show that these same compounds are preserved within coral aragonite, which opens up the potential to retrieve lipid-based historical records of coral health from annual layers of coral skeleton. This work demonstrates the value of using lipid biomarkers to assess coral health and better understand the biochemical mechanisms of coral bleaching., by Jessie Mary Kneeland., Ph.D.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2011., Cataloged from PDF version of thesis., Includes bibliographical references., Corals are increasingly threatened by warming sea surface temperatures and other anthropogenic changes. The delicate symbiosis between corals and their algal endosymbionts (zooxanthellae) is easily disrupted by thermal stress, leading to bleaching and eventual mortality. The use of lipid ratios as biomarkers of environmental conditions is well established. Coral biomass contains abundant lipids, and the potential of lipid parameters to diagnose thermal tolerance in zooxanthellae has been previously suggested. In this thesis, I explore the response of specific fatty acids, sterols, and thylakoid membrane lipids to thermal and disease stress in zooxanthellae grown in culture, as well as those isolated from living corals. I present the discovery of a bioactive thylakoid lipid within zooxanthellae cells, and show how this compound is selectively mobilized in thermally stressed cells. I present a plausible mechanism for the breakdown of this compound into products that may cause apoptosis and disrupt the coral-algal symbiosis, eventually causing bleaching. I present two new lipid biomarkers of thermal stress in zooxanthellae, the C18 fatty acid unsaturation ratio, and the fatty acid to sterol ratio. I calibrate the decline of these two parameters to levels of thermal stress comparable to those needed to cause bleaching. I further show that these parameters are sensitive to pathogen stress as well. In several case studies of diseased and thermally stressed corals, I demonstrate that these lipid biomarkers of coral stress may be applied to zooxanthellae isolated from environmental samples. I show that these same compounds are preserved within coral aragonite, which opens up the potential to retrieve lipid-based historical records of coral health from annual layers of coral skeleton. This work demonstrates the value of using lipid biomarkers to assess coral health and better understand the biochemical mechanisms of coral bleaching., by Jessie Mary Kneeland., Ph.D.

Thesis (Ph. D.)--Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2007., Includes bibliographical references., A 225-year old coral from the south shore of Bermuda (64°W, 320N) provides a record of decadal-to-centennial scale climate variability. The coral was collected live, and sub-annual density bands seen in x-radiographs delineate cold and warm seasons allowing for precise dating. Coral skeletons incorporate strontium (Sr) and calcium (Ca) in relative proportions inversely to the sea surface temperature (SST) in which the skeleton is secreted. [Delta]180 of the coral skeleton changes based on both temperature and the [delta]180 of sea water ([delta]Ow), and 6Ow is proportional to sea surface salinity (SSS). Understanding long-term climate variability requires the reconstruction of key climate parameters, such as sea surface temperature (SST) and salinity, in records extending beyond the relatively short instrumental period. The high accretion rates, longevity, and skeletal growth bands found in coral skeletons make them an ideal resource for well-dated, seasonal climate reconstructions. Growing between 2 and 6 mm/year and reaching more than im in length, slow-growing corals provide multi-century records from one colony. Additionally, unlike the fast growing (10-20 mm/year) species Porites, slow-growing species are generally found in both tropical and sub-tropical locations greatly expanding the geographical location of these records. A high resolution record (HRR, ~11 samples per year) was drilled for the entire length of the coral record (218 years). Samples were split and Sr/Ca, [delta]180, and [delta]13C were measured for each sample. Sr/Ca was used to reconstruct winter time and mean-annual SST. Oxygen isotopic measurements were used to determine directional salinity changes, in conjunction with Sr/Ca based SST reconstructions., (cont.) Winter-time and mean annual SSTs show SSTs -1.5 'C colder during the end of the Little Ice Age (LIA) relative to today. Simultaneously, SSS is fresher during that time. Sr/Ca based climate reconstructions from coral skeletons have been met with some skepticism because some reconstructions show temperature changes back in time that are 2-4 times greater than the reconstructions of other marine proxies. In this study, we show that when using bulk-sampled, slow-growing corals, two steps are critical to producing accurate reconstructions: 1) incorporating growth rate into multi-variant regressions with SST and Sr/Ca and 2) using multiple colonies that grew at the same time with varying average growth rates and Sr/Ca. Application of these novel methods over the period of the instrumental record from Hydrostation S (monthly since 1954, 32°10'N, 64°30'W) reduces the root mean square of the residuals between the reconstructed SST and the instrumental SST by as much as 1.52'C to 0.460C for three coral colonies. Winter-time SSTs at Bermuda are correlated to phases of the North Atlantic Oscillation (NAO), a meridional oscillation in atmospheric mass. Much uncertainty remains about the relationship between the NAO and the ocean, and one critical outstanding question is whether anthropogenic changes are perturbing the system. Using winter Sr/Ca as a proxy for temperature, we show strong coherence to the NAO at multi-decadal and inter-annual frequencies. These coral records show significant changes in variance in the NAO during the late 20th century compared to the cooler LIA, but limited changes in the mean phase (positive or negative) of the NAO, implying that climate change may be pushing the NAO to extremes but not to a new mean position., by Nathalie Fairbank Goodkin., Ph.D.