Seasonal Flux and Assemblage Composition of Planktic Foraminifera from the Northern Gulf of Mexico, 2008-2009

Abstract

The U.S. Geological Survey established a sediment trap in the northern Gulf of Mexico to collect time-series data on the flux and assemblage composition of live planktic foraminifers. This report provides an update of the 2008 time-series data to include results from 2009. Ten species, or varieties, of planktic foraminifers constitute >90 percent of the assemblage: Globigerinoides ruber (pink and white varieties), Gs. sacculifer, Globigerina calida, Globigerinella aequilateralis, Globorotalia menardii group, Gt. truncatulinoides, Pulleniatina spp., Orbulina universa, and Neogloboquadrina dutertrei. The mean daily flux is about 215 tests per square meter per day, with maximum fluxes of >800 tests per square meter per day during early February and minimum fluxes of <20 tests per square meter per day during early October. Globorotalia truncatulinoides shows a clear preference for the winter and continues to provide the greatest number of tests for 2009, consistent with data from 2008. Globigerinoides ruber (white variety) flux increased more than 3 orders of magnitude from an average of 3 tests per square meter per day in 2008 to 11 tests per square meter per day in 2009. However, though Gs. ruber (white) abundance increased from 1.5 percent in 2008 to 4.9 percent in 2009, it continues to be a minor contributor to the total assemblage composition, in contrast to assemblage records from nearby sediments that indicate Gs. ruber (white) typically comprises approximately 20-30 percent of the assemblage.