Morphology and microhabitat preferences of benthic foraminifera from the northwest Atlantic Ocean

Abstract

The distribution of Rose Bengal stained calcareous benthic foraminifera was determined in six ☐ cores raised from water depths between 200 and 3000 m on the Nova Scotian continental margin and Gulf of Maine. The taxa can be separated into four microhabitats within the surficial sediments. Epifaunal taxa are generally found in the top cm, intermediate infaunal taxa are found from about 1 to 4 cm and deep infaunal taxa are found at > 4 cm sediment depth in at least one ☐ core. A fourth group, shallow infaunal taxa, is found in the top 2 cm and is inferred to be infaunal based on wall porosity characteristics and test shapes similar to infaunal taxa. The epifaunal, shallow infaunal and intermediate infaunal taxa maintain their positions within the sediments from core to core, whereas the deep infaunal taxa are found at progressively shallower sediment depths in cores within increasing organic carbon contents from shallower water depths. Each microhabitat category has distinct morphological characteristics. Epifaunal taxa have plano-covex or biconvex cross sections, trochospiral coiling and large pores absent or found on only one side. Shallow infaunal taxa have uniserial, triserial, or planispiral coiling, with surface ornamentation present on a number of taxa. The intermediate infaunal taxa have rounded peripheries, pores over the entire test and planispiral coiling, with the exception of Cibicidoides bradyi which has trochospiral coiling. The deep infaunal taxa have, in general, planispiral or triserial coiling with cylindrical or ovate shaped tests.