Variability in vertical distributions of planktonic foraminifera in the California Current: Relationships to vertical ocean structure

Abstract

[1] Geochemical records from planktonic foraminifera are among the few means available to infer past changes in the upper ocean, although interpretations can be confounded by variability in foraminifera habitat depths. The principal environmental factors affecting foraminiferal vertical distributions were examined through 28 vertically stratified plankton tows taken off southern California in winter, spring, and summer. Each species has a dynamic range of preferred habitat depth, from the mixed layer to the thermocline, characterized by a unique relationship with environmental properties. Globigerina bulloides, Neogloboquadrina pachyderma (dextral), and Neogloboquadrina dutertrei can live near the surface but frequently live deeper as stratification increases and a particular isotherm deepens. Globigerinoides ruber and Orbulina universa vary more closely with the depth of the thermocline than the depth of a given isotherm. The shifts in habitat depth are of sufficient magnitude to affect d18 O records. The effects of such shifts are observed for G. bulloides and N. pachyderma in Santa Barbara Basin sediments. Geochemical signatures from multiple species of foraminifera, each with a different predicted response to environmental change, can permit the detection of changes in habitat depth of a given species and thus more accurately indicate past changes in hydrographic structure.

Seasonality and depth distribution of a mesopelagic foraminifer, Hastigerinella digitata, in Monterey Bay, California

“…has a primarily shallow depth distribution, given the lack of mature Hastigerina in shallower waters (0-200 m) in previous studies (Bradshaw 1959;Field 2004). Similarly, we also think it unlikely that Hastigerina sp.…”

“…Furthermore, while we captured 14 Hastigerina sp. on four ROV sampling trips, no surface water H. pelagica are reported off Southern California by 28 depth-stratified plankton net tows across seasons from 2000 to 2002 (Field 2004), by 28 yr of blue-water diving for planktonic foraminifera in the Davidson Current (June-September; H. J. Spero pers. comm.…”

Encrustation and trace element composition of <i>Neogloboquadrina dutertrei</i> assessed from single chamber analyses – implications for paleotemperature estimates

“…N. dutertrei is a subtropical thermocline dweller (Bé and Tolderlund, 1971;Field, 2004), is nonspinose and bears symbionts (Gastrich, 1987). Intra-annual whole-test Mg/Ca and stable oxygen isotopes show considerable variability, but on average were suggested to reflect a depth habitat around 60 m depth, just below the surface mixed layer (Fallet et al, 2011;Bé and Hutson, 1977;Dekens et al, 2002).…”

Modeling seasonal and vertical habitats of planktonic foraminifera on a global scale

“…Planktonic foraminifera are found throughout the open ocean, where they inhabit roughly the top 500 m of the water column (Fairbanks et al, , 1982Kohfeld et al, 1996;Kemle-von Mücke and Oberhänsli, 1999;Mortyn and Charles, 2003;Field, 2004;Kuroyanagi and Kawahata, 2004;Bergami et al, 2009;Wilke et al, 2009;Pados and Spielhagen, 2014;Iwasaki et al, 2017;Rebotim et al, 2017). Their calcareous shells, preserved in ocean sediments, are widely used to reconstruct past climate 5 conditions.…”

“…To do so, information about their habitat including their horizontal and vertical distribution are needed. It is known from observational data that the prevailing environmental conditions, such as temperature, stratification, light intensity, and food availability, affect the growth and distribution of the individual planktonic foraminifera (Fairbanks et al, , 1982Bijma et al, 1990b;Watkins et al, 1996;Schiebel et al, 2001;Field, 2004;Kuroyanagi and Kawahata, 2004;Žarić et al, 2005;Salmon et al, 2015;Rebotim et al, 2017).…”