Abstract
Biennial variations of marine palynomorph concentrations mirrored oceanographic conditions in the Magdalena Basin, Baja California Sur (Mexico), in the period from 1811 to 1907 (common era, CE), for which the sea surface temperature index (SSTI) showed predominantly negative anomalies. We analyzed 49 samples of laminated sediments taken from a core extracted at a water depth of 520 m. Changes in dinoflagellate assemblages and copepod egg abundances were compared to SSTI records and to El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) reconstructions. Copepods were the most abundant and showed a significant correlation with SSTI. Among the dinoflagellates, heterotrophs were the most abundant and did not correlate with SSTI. The lowest concentration of autotrophs showed a significant and inverse correlation with SSTI. The canonical correlation analysis also indicated that copepods and autotrophs were modulated by variations in SSTI. Dinoflagellate richness and concentrations and copepod egg concentrations were low, indicating low productivity, and these values coincided with the negative SSTI anomalies. In contrast, the increase in concentrations from 1881 to 1907 CE coincided with positive SSTI anomalies. Also, even when marine palynomorphs showed no significant correlation with either ENSO or PDO, their concentrations increased during age intervals with combined negative conditions (La Niña, negative PDO) and decreased during combined warm conditions (El Niño, positive PDO).
Highlights
Two major climate events occurring in the northeastern Pacific Ocean have been studied, namely El Niño/Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO)
The ENSO phenomenon exhibits interannual periodicity, is significantly associated with sea surface temperature (SST) anomalies, and presents phases that range from positive, or warm (El Niño), to negative, or cold (La Niña)
We aim to elucidate primary productivity and temperature conditions in the southern continental margin of the Baja California Peninsula (Mexico) during the 19th century. The hypothesis, to this end, is that during the 1811–1907 CE period, abundances of autotrophic and heterotrophic dinoflagellates and of copepods were associated with oceanographic conditions and regional forcings such as ENSO and PDO in the Magdalena Basin, Baja California Sur
Summary
The ocean floor provides an excellent sedimentary record that can help us recognize and understand paleoceanographic and paleoclimatic changes (Esparza-Álvarez 1999). The biogenic component in these sediments is important because it is largely represented by phyto- and zooplankton (Aguirre 1989) It provides a record of the dominant organic productivity and the sedimentological and climatological conditions in the basin where it settled (Emery and Hülsemann 1961). 96 living species (6% of the total) produce resistant organic cysts (Zonneveld and Pospelova 2015). Marine planktonic copepods belonging to the order Calanoida produce diapausing eggs when environmental conditions (temperature, salinity, light, etc.) are not suitable for a dormant state (Fernández-de-Puelles 2015). These eggs are so resistant that they have been described in pre-Holocene marine sediments (Uye et al 1979). López-Velázquez et al.: Biennial variations of marine palynomorph concentrations been used as a biological indicator of the effects of climate phenomena such as El Niño (Jiménez-Pérez and Lara-Lara 1988)
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