GEOLOGIC PROBLEM SOLVING WITH MICROFOSSILS IV
EFFECTS OF INFAUNAL FORAMINIFERA ON SURFACE AND SUBSURFACE ASSEMBLAGES IN THE SOUTHWESTERN EVERGLADES, USA: BASELINE STUDY FOR PALEOENVIRONMENTAL ANALYSES
Published:January 01, 2019
ZOË R.F. VERLAAK, LAUREL S. COLLINS, LEE-ANN C. HAYEK, 2019. "EFFECTS OF INFAUNAL FORAMINIFERA ON SURFACE AND SUBSURFACE ASSEMBLAGES IN THE SOUTHWESTERN EVERGLADES, USA: BASELINE STUDY FOR PALEOENVIRONMENTAL ANALYSES", GEOLOGIC PROBLEM SOLVING WITH MICROFOSSILS IV, RICHARD A. DENNE, ALICIA KAHN
Download citation file:
This study investigated the extent to which deep-dwelling, infaunal foraminifera bias modern and fossil distributions in the subtropical mangroves of the Everglades (southwest Florida), and which sediment interval should be used as a modern analog for paleoenvironmental studies in this area. Typically, these studies are based on modern analogs from the upper 1 to 2 cm of sediments, as most benthic foraminifera live in the surface 1 cm, but in tropical mangrove environments, deep-dwelling infaunal foraminifera may be more common. The vertical distributions of live assemblages in cores from a mudflat and three mangrove sites were investigated. To examine the preservation potential of dead tests, distributions of wall types and inner test linings were recorded.
The living depths of benthic foraminifera showed a landward deepening from 1 to 3 cm in mudflats and low mangroves and from 7 to 10 cm in middle and high mangroves, possibly due to a landward increase in oxygenation of the subsurface sediments. Modern assemblages from the top 2 cm included species common in the deep infauna and contained, on average, 36% of the total standing crop. Additions to total assemblages at greater depths by subsurface production were negligible. Thus, the upper 2 cm of the sediment column would be sufficient as a modern analog for paleoenvironmental studies in the southwestern Everglades. Preservation of dead tests is influenced by a landward increase in the degradation of agglutinated taxa through oxidation/bacterial breakdown of organic cements. Fortuitously, calcareous taxa preserve well in the carbonate-buffered sediments of the Everglades.