A nutrient manipulation experiment was undertaken in eight 11m(3) meso
cosms designed to give rise to selective development of different alga
l groups. The experiment was successful in that a silicate-controlled
toggle enabled a switch between flagellate (Emiliania huxleyi dominate
d) and diatom communities. The present account details the general man
agement and sampling of the enclosures and reports as a background the
results of the basic chemical and biological parameters. No attempt i
s made to undertake a detailed analysis of the results. (C) 1998 Acade
mic Press Limited.