A 14-ka Record of Dust Input and Phytoplankton Regime Changes in the Subtropical NE Pacific: Oceanic and Terrestrial Processes Linked by Teleconnections at Suborbital Scales
Por:
Arellano-Torres, Elsa, Alvarez-Covelli, Catalina, Kasper-Zubillaga J.J., Lozano-García M.D.S.
Publicada:
1 ene 2019
Ahead of Print:
1 ene 2019
Resumen:
We study shifts in phytoplankton proxies linked to terrigenous inputs
and teleconnections in a core from Soledad Basin, Gulf of Ulloa, NW
Mexico, spanning the end of the deglaciation and the Holocene. We used
biogenic opal (% opal), organic carbon (% total organic carbon
[TOC]), and inorganic carbon (% CaCO3) as proxies of productivity and
opal/TOC and CaCO3/TOC ratios as proxies of nutrient uptake and C-export
by siliceous and carbonate organisms. We reconstructed terrestrial
inputs and identified authigenic gypsum. Based on opal/TOC and CaCO3/TOC
ratios, we found periodic changes of similar to 0.5, 1.1-1.8 ka cycle in
phytoplankton proxies exporting siliceous and carbonate skeletal debris
to the sediments. An increase in carbonate organisms occurred during
14-8.7 ka, corresponding to reduced El Nino-Southern Oscillation
(ENSO)-like variability, in parallel to the northward displacement of
the Intertropical Convergence Zone (ITCZ) and an overall negative phase
of the Pacific Decadal Oscillation (PDO). An increase in siliceous
organisms occurred between 6 and 3 ka, coincident with strong ENSO-like
conditions, southern migration of ITCZ, and less intense but more
frequent positive PDO-hydrological variability. Grain size analyses show
significant amounts of fine fraction (dust <6.6 mu m) present during the
early- to mid-Holocene in agreement to extreme weather on land, with
episodes of eolian and fluvial transport to the sea. The ENSO-like
variations influenced biological C-export producers on a scale of
1.1-1.8 ka, but PDO-related variability is uncertain. We suggest that
Holocene drivers for phytoplankton successions are changes in
insolation, ITCZ migration, California Current upwelling, nutrient
inputs by advection, and terrestrial sources.
Plain Language Summary We worked on a marine core off SW Baja
California, Mexico, to study past changes in microscopic algal groups
(phytoplankton) over the last 14,000 years. We study the role of
nutrients from terrestrial and marine sources and investigate the role
of ocean currents and natural phenomena like El Nino-Southern
Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) along NE
Pacific margin. To reconstruct biological productivity, we analyzed the
remains of ancient organisms like silicon (opal), calcium carbonate
(CaCO3), and organic matter (TOC) content and determine the algal group
that grows more efficiently and deposits more organic matter in the
sediments. To reconstruct terrestrial sources, we measure the sediments'
grain size. We found cyclical periods that alternate siliceous versus
carbonate algae every 500, 1,100, and 1800 years. Carbonate
phytoplankton was more abundant between 14,000 and 8,000 years ago, and
siliceous phytoplankton was more abundant between 6,000 and 3,000 years
ago. Reconstructions of terrestrial climate suggest that during humid
periods land nutrients and carbonate phytoplankton increase in parallel,
whereas during the strength of the California Current, ocean nutrients
and siliceous phytoplankton grow together, proving that an important
connection exists between land climate, ocean circulation, and
biological productivity.
Filiaciones:
Arellano-Torres, Elsa:
Facultad de Ciencias, Departamento de Ecología y Recursos Naturales, UNAM. Circuito Exterior s/n, Ciudad Universitaria, Mexico City, Mexico
Univ Nacl Autonoma Mexico, Fac Ciencias, Dept Ecol & Recursos Nat, Circuito Exterior S-N,Ciudad Univ, Mexico City, DF, Mexico
Alvarez-Covelli, Catalina:
Facultad de Ciencias, Universidad El Bosque, Bogotá, Colombia
Univ El Bosque, Fac Ciencias, Bogota, Colombia
Kasper-Zubillaga J.J.:
Instituto de Ciencias del Mar y Limnología, Unidad Académica de Procesos Oceánicos y Costeros, UNAM. Circuito Exterior, Ciudad Universitaria, Mexico City, Mexico
Lozano-García M.D.S.:
Instituto de Geología, UNAM. Circuito de la Investigación, Ciudad Universitaria, Mexico City, Mexico
Univ Nacl Autonoma Mexico, Unidad Acad Proc Ocean & Costeros, Inst Ciencias Mar & Limnol, Ciudad Univ, Mexico City, DF, Mexico
Univ Nacl Autonoma Mexico, Inst Geol, Circuito Invest, Ciudad Univ, Mexico City, DF, Mexico
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