Late Quaternary benthonic foraminifera in a bathyal core from the Leeward Islands, Lesser Antilles, NE Caribbean Sea

Abstract

The 3.13 m long bathyal piston core En20-2 from the northern Leeward Islands (17(49.9#N, 63(02.4#W, water depth 680 m) was sampled every 20 cm. The Pleistocene-Holocene boundary occurred at 107 cm, and the base of the core lay above the Atlantic extinction of Pulleniatina obliquiloculata (34 ka BP). The core yielded throughout both (a) a deep-water association (DWA) of middle bathyal benthonic foraminifera and (b) a shallow-water association (SWA; up to 56% of total recovery) comprising back-reef, epiphytal species. The environmental trends suggested by the two groups are compared.Although sea-levels during the Late Pleistocene and Early Holocene rose abruptly, there was no abrupt change in the DWA at the Pleistocene-Holocene boundary, but a gradual change from a higherproductivity fauna (Bulimina spp., Uvigerina spp.) at the base of the core to a lower-productivity fauna (Cassidulina spp., Globocassidulina spp.) at the top. Microhabitat preference changed from shallowinfaunal at the core base to primarily epifaunal at the top. Diversity and species dominance did not differ significantly between the Late Pleistocene and the Holocene.Percentage abundances of species were calculated separately for the DWA and SWA. Seventy significant correlations were found between the percentage abundances of individual DWA and SWA species, the two strongest correlations -both positive -being between (a) Neoconorbina terquemi and Uvigerina laevis, and (b) Amphistegina gibbosa and Cassidulina curvata. The percentage abundance of U. laevis decreased up-section, whereas the percentage abundance of A. gibbosa increased up-section, reflecting a change in the nutrient flux over time that impacted on both the DWA and the SWA. Positive correlations between the DWA low-productivity indicator Globocassidulina subglobosa and the SWA species Asterigerina carinata, Elphidium discoidale, Peneroplis bradyi and P. proteus suggests that these four SWA species comprise a guild.

Abundance Biozones and Community Structures in the Upper Quaternary of Odp Hole 994c (Blake Ridge, Western Atlantic Ocean) Compared With Marine Isotope Stages, Glacial Cycles, and Terminations

“…They found only subtle faunal changes at glacial-interglacial boundaries as defined using menardiform planktonic foraminifera, and noted that neither S nor H showed clear stratigraphic trends. Wilson (2008aWilson ( , 2011 did not find an abrupt community-level regime shift in benthonic foraminifera at the PleistoceneHolocene boundary (Termination I of Broecker & van Donk, 1970) in piston cores En20-2 and En20-10, taken from middle-bathyal depths in the eastern Caribbean Sea. He did, however, note that Trifarina bradyi Cushman and Hoeglundina elegans (d'Orbigny) were more abundant in the Holocene of En20-10, suggestive of species-level regime shifts.…”

“…Abrupt regime shifts have been inferred in bathyal (200-2000-m depth) and abyssal (.2000 m) foraminiferal community structures between glacials and interglacials in parts of the Atlantic Ocean and Gulf of Mexico (Streeter, 1973;Schnikter, 1974Schnikter, , 1980Streeter & Lavery, 1982;Denne & Sen Gupta, 2003) and in the eastern Caribbean Sea (Gaby & Sen Gupta, 1985;Sen Gupta et al, 1991;Wilson, 2008aWilson, , 2011. Although the strength of the shifts has rarely been quantified, it is apparent that, as in the ostracode and planktonic foraminiferal examples given above, this glacial-interglacial signal is not equally marked everywhere.…”

“…He did, however, note that Trifarina bradyi Cushman and Hoeglundina elegans (d'Orbigny) were more abundant in the Holocene of En20-10, suggestive of species-level regime shifts. In En20-2, there was a gradual change in fauna throughout the entire core (Wilson, 2008a). There is clearly a need to investigate the nature and occurrence of late Pleistocene community-level and species-level regime shifts and their relation to MISs, terminations, and glacial cycles.…”

Ontology Confounds Reproducibility in Ecology and Climate Science

“…The succession of abundance biozones differed between the three cores, although taken only ~150 km apart and from similar water depths, indicating that the region is one of considerable oceanographic complexity. This is reflected in the distinct benthonic foraminiferal associations found in these cores (Wilson 2011), which, once again, do not show any marked glacial-interglacial contrasts (Wilson 2008) but show that the organic flux in the northeast Caribbean Sea decreased gradually through the Late Quaternary. Wilson (2013) recorded a major regime shift during MIS 8-9 in the Upper Quaternary of ODP Hole 1006A (Santaren Channel, offshore western Bahamas), but otherwise found only weak evidence of Milankovich cycles, Globocassidulina subglobosa (Brady, 1881) and Cibicidoides aff.…”

Quantifying Assemblage Turnover and Species Contributions at Ecologic Boundaries

“…However, they suggested Nuttallides umbonifera , Bulimina buchiana dOrbigny and Chilostomella oolina Schwager to be rarer in the last glacial than in the two bounding glacials. Wilson [22], [23] examined the benthonic foraminifera in two bathyal piston cores near the northern Leeward Islands, eastern Caribbean Sea. He did not find any marked faunal changes at the Pleistocene-Holocene boundary, but showed that the organic flux in one core decreased gradually through the entire core.…”