HR: 1400h
AN: PP43B-03    [Abstracts]
TI: Last Century Patterns of Sea Surface Temperature and Diatom Variability in the Southern California Current
AU: * Esparza-Alvarez, M
EM: mesparza@cicese.mx
AF: Oceanología, CICESE, Km 107 Carretera Transpeninsular, Ensenada, BC 22850, Mexico
AU: Herguera, J
EM: herguera@cicese.mx
AF: Oceanología, CICESE, Km 107 Carretera Transpeninsular, Ensenada, BC 22850, Mexico
AU: Lange, C
EM: clange@udec.cl
AF: Universidad de Concepcion, FONDEP-COPAS, Concepción, Chile
AB: A time series reconstruction for the last 100 years of the variability of diatoms from laminated sediments off the southern Baja California margin shows the sensitivity of this phytoplankton group to oceanographic variability in the California Current on different timescales. Here we show that cool (warm) years are associated with higher (lower) diatom accumulation values, a proxy for their export production from the water column to the seafloor. There is a clear direction in the changes of the larger opaline flora community structure throughout the past century that parallels the observed trend towards higher SSTs in the southern part of the California Current. The diatom succession is reflected in three types of assemblages that show a clear progression from cool spring to early summer bloom species in the earlier part of the century towards alternating cool California Current and warm subtropical waters during the mid-century, to subtropical and tropical assemblages reflecting more stratified oligotrophic conditions during the latter part of the last century. This association between opaline floral succession and the SST anomaly trend implies a long term change that cannot be explained by the same mechanisms that are commonly associated with the typical interannual or interdecadal oceanographic variability. A small group of diatom species appears to follow the periodic swings of the large scale Pacific Decadal Oscilation index. The Coscinodiscus argus/radiatus and Coscinodiscus decrescens/marginatus complexes, commonly found in the California Current waters, closely follow the inter-decadal variability patterns over the Pacific, although with a decreasing amplitude after the mid 1970s shift.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4817 Food webs, structure, and dynamics (0491)
DE: 4944 Micropaleontology (0459, 3030)
DE: 4950 Paleoecology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Joint Assembly