This thesis contributes to the development of dinoflagellate cysts as indicators of past environmental change in the Northeastern Pacific coastal ocean, and investigates past variations in sea-surface temperature, salinity and primary productivity encoded in dinoflagellate cyst sedimentary records from the Santa Barbara Basin (SBB, southern California) and Effingham Inlet (Vancouver Island, British Columbia) over the last millennium. The dinoflagellate cyst records extracted from the SBB and Effingham Inlet predominantly laminated sediments and analysed at sub-decadal resolutions, constitute some of the most detailed records of cyst-producing dinoflagellate populations in the world.
A two year-long sediment trap study from the SBB documents the seasonality in dinoflagellate cyst production for the first time on the Pacific coast of the United States. The study shows that dinoflagellate cyst data can be used as indicators of changes in sea-surface temperature and primary productivity associated with seasonal upwelling in the SBB. In particular, several dinoflagellate cyst taxa such as Brigantedinium spp. and Lingulodinium machaerophorum are identified as indicators of “active upwelling” (typically occurring in spring and early summer) and “relaxed upwelling” conditions (fall and early winter) at the site, respectively.
Analysis of a dinoflagellate cyst record from the SBB spanning the last ~260 years at biannual resolution documents the response of cyst-producing dinoflagellates to instrumentally-measured warming during the 20th century, and reveals decadal scale variations in primary productivity at the site that are coherent with phases of the Pacific Decadal Oscillation (PDO). The cyst assemblages are dominated by cysts produced by heterotrophic dinoflagellates (in particular Brigantedinium spp.), but the turn of the 20th century is marked by an abrupt increase in concentrations of L. machaerophorum and Spiniferites ramosus, two cyst taxa of autotrophic affinity. Their increasing abundances during the 20th century are interpreted to reflect warmer conditions and possibly stronger stratification during summer and fall. The dinoflagellate cyst data suggest a warming pulse in the early 1900s and provide further evidence that persistently warmer and/or more stratified conditions were established by the late 1920s.
The dinoflagellate cyst record from Effingham Inlet, spanning the last millennium, is characterized by the proportionally equal contribution of cysts produced by autotrophic and heterotrophic dinoflagellates in most samples. The cyst data indicate variations in sea-surface temperature, salinity and primary productivity that are associated with local expressions of the Medieval Climate Anomaly (from the base of the record to ~1230), the Little Ice Age (from ~1230 to ~1900) and warming during the second half of the 20th century.
Both dinoflagellate cyst records reveal that since the beginning (in the SBB) and mid-20th century (in Effingham Inlet), autotrophic dinoflagellates contribute to a greater portion of the primary production in the region, whereas heterotrophic dinoflagellates, as indicators of diatom populations, decline. Variability in the dinoflagellate cyst data is coherent at both sites and suggest a reduced expression of decadal scale variability associated with the PDO during the 19th century. / Graduate / 0416 / 0427 / mbringue@uvic.ca
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/6407 |
| Date | 07 August 2015 |
| Creators | Bringué, Manuel Alain |
| Contributors | Pospelova, Vera |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web, http://creativecommons.org/licenses/by-nc-nd/2.5/ca/ |
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