LIVING FORAMINIFERA AND TOTAL POPULATIONS IN SALT-MARSH PEAT CORES - KELSEY MARSH (CLINTON, CT) AND THE GREAT MARSHES (BARNSTABLE, MA)

Common species of intertidal agglutinated benthic foraminifera in salt marshes in Massachusetts and Connecticut live predominantly at the ma rsh surface and in the topmost sediment (0-2.5 cm), but a considerable part of the fauna lives at depths of 2.5-15 cm. Few specimens are ali ve at depths of 15-25 cm, with rare individuals alive between 25-50 cm in the sediments. Specimens living between the sediment surface and 2 5 cm deep occur in all marsh settings, whereas specimens living deeper than 25 cm are restricted to cores from the lower and middle marsh, a nd have an irregular distribution-with-depth. Lower and middle marsh a reas are bioturbated by metazoa, suggesting that living specimens reac h these depths at least in part by bioturbation. High-marsh sediments in New England consist of very dense mats of Spartina patens or Distic hlis spicata roots and are not bioturbated by metazoa. In this marsh r egion bioturbation by plant roots and vertical fluid motion may play a role in moving the foraminifera into the sediment. The depth-distribu tion of living specimens varies with species: living specimens of Troc hammina inflata consistently occur at the deepest levels. This suggest s that species have differential rates of survival in the sediment, po ssibly because of differential adaptation to severe dysoxia to anoxia, or because of differing food preferences. There is no simple correlat ion between depth-in-core and faunal diversity, absolute abundance, an d species composition of the assemblages. It is therefore possible to derive a signal of faunal changes and thus the environmental changes t hat may have caused them from the complex faunal signal of fossil asse mblages. (C) 1998 Elsevier Science B.V. All rights reserved.