The impact of the submarine volcano Kick ‘em Jenny on benthic foraminifera

Abstract

Nothing is known about the impact on marine meiofauna of submarine volcanic eruptions in the Grenada Basin. The benthic foraminiferal fauna is here examined in piston cores taken within ∼8 – 38 km of the crater of Kick ‘em Jenny (KeJ), decadal eruptions of which disseminate ash to the NW via the Caribbean Current. Piston core Gs29, taken ∼8 km W of the crater, consists of clay-rich material from the Globorotalia menardii Zone U, ∼500 ka old, probably exposed by slumping. The remaining cores (from proximal to distal: GC59, GC90, GC99 and GC100), taken between 1000 – 3000 m water depth, comprise volcanic ash and are of presumed Holocene age. Recovery from GC59, GC90 and GC99, the last taken 27.3 km NW of the crater, was poor and apparently reflects volcanic ash impact. Recovery from GC100, 38 km NW of the crater and from the basin floor, was rich. Thus, KeJ disrupts seafloor colonization by foraminifera up to 32 – 38 km from the crater. Bolivina spp., indicative of low dissolved oxygen concentrations, dominated the assemblage in proximal core Gs29. Cassidulina spp. dominated the distal core GC100 assemblage, indicating somewhat higher dissolved oxygen concentrations. This might reflect a long-term change in productivity in the area, or a nutrient-rich surface eddy to the lee of Grenada. Allochthonous, shallow-water foraminifera, recovered throughout cores Gs29 and GC100, were more abundant in the latter. This might indicate that Grenada protects nearshore foraminifera from disruptive hurricanes.