MICROFORAMINIFERA AND NANOFORAMINIFERA FROM ABYSSAL NORTHEAST ATLANTIC SEDIMENTS - A PRELIMINARY-REPORT

Rose Bengal stained benthic foraminifera which pass through a 63 mu m mesh (microforaminifera and nanoforaminifera) have been extracted by h andsorting the fine sieve residues (> 45 mu m, 31 mu m, 28 mu m, 20 mu m, 15 mu m) of abyssal sediment samples. The samples were collected u sing a multiple corer in four areas of the northeast Atlantic between 31 degrees N and 59 degrees N. The abundance of these minute foraminif era varied from 2 specimens per 1 cm(2) (Madeira Abyssal Plain) to > 1 10 per 1 cm(2) (BIOTRANS area). They include a variety of taxa, the mo st common being certain rotaliid species, hormosinaceans and other mul tilocular agglutinated forms, the unilocular agglutinated genus Lagena mmina, soft-bodied agglutinated sphaeres and flasks (saccamminids and psammosphaerids) and allogromiids. Some specimens are < 63 mu m in max imum dimension but others belonging to elongate taxa are longer. Two s amples taken 10 cm apart on the Porcupine Abyssal Plain suggest that m inute foraminifera may be patchily distributed on a small scale. One s ample, which was overlain by substantial amounts of phytodetritus, con tained > 100 stained specimens (> 30 per 1 cm(2)) while the other, in which much less phytodetritus was present, yielded only 10 specimens ( 2.9 per 1 cm(2)). This observation suggests that some micro- and nanof oraminifera may flourish in the presence of decaying organic matter, p erhaps consuming the associated bacteria. The presence of phytodetritu s may also explain why two of our samples from the Madeira Abyssal Pla in (MAP) contained an order of magnitude more stained tiny foraminifer a than two other MAP samples in which phytodetritus was absent.