Chlorophyll diagenesis in the water column and sediments of the Black Sea

King, Linda L.

doi:10.1575/1912/2987

Cited by 18 publications

(10 citation statements)

References 64 publications

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“…cholesteryl While this problem may not be significant in recent sediments, it could become more significant in sediments heavily affected by diagenesis. [4] Recent studies of zooplankton grazing and senescence-induced changes [Harradine et al, 1996;King and Wakeham, 1996;7libot et al, 1999a, 1999b have confirmed the finding of King andRepeta [ 1991, 1994] that CSEs are formed during zooplankton herbivory when the sterols produced by phytoplankton become esterified to pyropheophorbide-a, a chlorin. Several studies suggest that the conversion of sterols to CSEs occurs nonselectively during the grazing process [King and Repeta, 1991;Harradine et al, 1996;Talbot et al, 1999a].…”

Section: Future Directionsmentioning

confidence: 88%

“…[5] After their formation in the water column, CSEs and other chlorins arrive at the seafloor via fecal pellets [King, 1993;Talbot et al, 1999a]. Within sediments, CSEs exhibit enhanced preservation relative to both other chlorins [Talbot et al, 1999a, and references therein] and free sterols [King and Repeta, 1991, 1.994;Talbot et al, 2000].…”

Section: Formation Of Cses In the Marine Environmentmentioning

confidence: 99%

“…Within sediments, CSEs exhibit enhanced preservation relative to both other chlorins [Talbot et al, 1999a, and references therein] and free sterols [King and Repeta, 1991, 1.994;Talbot et al, 2000]. The enhanced preservation of CSE sterols relative to free sterols has been inferred from stanol/stenol ratios of the two groups of compounds [King andRepeta, 1991, 1994;Pearce et al, 1998], which provide an estimate of the amount of degradation each type of compound has experienced [Wakeham, 1989]. CSE sterols have a low stanol/stenol ratio relative to free sterols, which indicates that they are less affected by microbial degradation [King andRepeta, 1991, 1994;Pearce et al, 1998].…”

Section: Formation Of Cses In the Marine Environmentmentioning

confidence: 99%

“…The enhanced preservation of CSE sterols relative to free sterols has been inferred from stanol/stenol ratios of the two groups of compounds [King andRepeta, 1991, 1994;Pearce et al, 1998], which provide an estimate of the amount of degradation each type of compound has experienced [Wakeham, 1989]. CSE sterols have a low stanol/stenol ratio relative to free sterols, which indicates that they are less affected by microbial degradation [King andRepeta, 1991, 1994;Pearce et al, 1998]. While several studies have now noted 2( the enhanced preservation of CSE sterols relative to free sterols, a definitive mechanism for this phenomenon has not yet been demonstrated.…”

Section: Formation Of Cses In the Marine Environmentmentioning

confidence: 99%

“…While several studies have now noted 2( the enhanced preservation of CSE sterols relative to free sterols, a definitive mechanism for this phenomenon has not yet been demonstrated. As a result of their enhanced preservation, the distribution of CSE sterols in sediments reflects the distribution of water column sterols more closely than the sedimentary free sterol distribution does [King andRepeta, 1991, 1994;Pearce et al, 1998]. Although CSEs do degrade once they reach the seafloor, the best available evidence suggests that the distribution of esterified sterols does not change during degradation; that is, there is no preferential degradation of a given CSE [Talbot et al, 2000].…”

Section: Formation Of Cses In the Marine Environmentmentioning

confidence: 99%

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Tropical climate variability from the last glacial maximum to the present

Dahl¹

2005

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This thesis evaluates the nature and magnitude of tropical climate variability from the Last Glacial Maximum to the present. The temporal variability of two specific tropical climate phenomena is examined. The first is the position of the Intertropical Convergence Zone (ITCZ) in the Atlantic basin, which affects sea surface temperature (SST) and precipitation patterns throughout the tropical Atlantic. The second is the strength of the Indian Monsoon, an important component of both tropical and global climate.Long-term variations in the position of the ITCZ in the Atlantic region are determined using both organic geochemical techniques and climate modeling. Upwelling in Cariaco Basin is reconstructed using chlorin steryl esters as proxies for phytoplankton community structure. We find that the diatom population was larger during the Younger Dryas cold event, indicating that upwelling was enhanced and the mean position of the ITCZ was farther south during the Younger Dryas than it is today. A climate simulation using an ocean-atmosphere general circulation model confirms these results by demonstrating that the ITCZ shifts southward in response to high-latitude cooling.The climate of the Arabian Sea region is dominated by the Indian Monsoon. Results from modern sediments from a suite of cores located throughout the Arabian Sea suggest that wind strength is well represented by the accumulation rate and carbon isotopic composition of terrestrially-derived plant waxes in sediments. Arabian Sea SST patterns, reconstructed from a suite of sediment cores representing four time slices utilizing the Mg/Ca SST proxy, suggest that both the summer and winter monsoons were enhanced 8,000 yr BP relative to today while the summer monsoon was weaker and the winter monsoon stronger at 15,000 and 20,000 yr. These results are confirmed by a time-series reconstruction of SST on the Oman Margin that reveals that SST at this site is sensitive to both regional and global climate processes. The results of this thesis demonstrate that tropical climate, as evaluated by a number of different proxies as well as climate models, has varied substantially over the past 20,000 years and is closely coupled to climate at high-latitudes. sharing ideas, opinions, and enthusiasm. Dan Repeta was the first to offer me the opportunity to come to WHOI and for that opportunity I will always be grateful. This thesis would have taken me double the time if not for the help of many assistants.

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