PELAGIC-BENTHIC COUPLING IN THE OLIGOTROPHIC CRETAN SEA (NE-MEDITERRANEAN) - CINCS. VERTICAL FLUX OF PHYTOPLANKTON, MICROZOOPLANKTON AND FAECAL PELLETS. PRELIMINARY RESULTS <B>PELAGIC-BENTHIC COUPLING IN THE OLIGOTROPHIC CRETAN SEA (NE-MEDITERRANEAN) - CINCS. VERTICAL FLUX OF PHYTOPLANKTON, MICROZOOPLANKTON AND FAECAL PELLETS. PRELIMINARY RESULTS</B> <HR><P> Ypma, J. E. & Wassmann, P.<BR> Norwegian College of Fishery Science (NCFS). University of Tromsø, N-9037 Tromsø, Norway</B><P><P> Primary production in the open ocean of the Cretan Sea is expected to be strongly coupled to pelagic heterotrophic organisms with little flux to deeper waters. To test this hypothesis PPS 3/3 Technicap sediment traps were deployed at 200 m and 1500 m depth at a deep sea station in the Cretan Sea. <P><P> The microscopical analysis of the collected material from November 1994 to May 1995 revealed that faecal pellets and amorphous material made up the bulk of organic matter. Faecal pellets were grouped in four size categories: cylindrical (250-2200 micrometer(s)), elliptical/ spherical pellets of large (250-400 micrometer(s)), medium (80-200 micrometer(s)) and small (30-75 micrometer(s)) size. In addition we observed that very large elliptical pellets (400-800 micrometer(s)) were present in the trap at 1500 m depth. The average faecal pellet flux was calculated to 0.242 mg C m<SUP>-</SUP><SUP>2</SUP> d<SUP>-</SUP><SUP>1</SUP> (s.d 129) and 0.291 mg C m<SUP>-</SUP><SUP>2</SUP> d<SUP>-</SUP><SUP>1</SUP> (s.d 88) at 200 m and 1500 m depth, respectively. Biovolume of faecal pellets was converted to carbon by using a conversion factor of 0.0268 pg C micrometer(s)<SUP>-</SUP><SUP>3</SUP> according to Urrere and Knauer (1981). <P><P> Diatom remains and skeletons of silicoflagellates were numerous, but very few intact cells were observed. Coccolithophorids and unidentified cells (probably cysts) made up the majority of phytoplankton carbon flux to deeper waters. The vertical flux of polycystine and phaeodarian radiolaria and foraminifera ranged between 0.2-5 10<SUP>3</SUP> and 2-8 10<SUP>3</SUP> cells m<SUP>-</SUP><SUP>2</SUP> d<SUP>-</SUP><SUP>1</SUP>, respectively. <P><P> Swimmers were present in all samples from 200 m depth. Copepodes were dominating, but pteropods (Thecosomata), polychaete larva, malacostracan larva and small fish larva were also present. <B><P><P> Material & Methods</B><P><P> Two Technicap PPS 3/3 cylindro-conical sediment traps with a collecting area of 0.125 m<SUP>2</SUP> were programmed with a collection sequence of 15 days interval which gave 12 consecutive samples from November 1994 to May 1995. The traps were deployed at 200 m and 1500 m at the deep sea station D7 in the Cretan Sea. See Tselepides <I>et al</I> (this volume) for exact location of the stations in the CINCS project. A volume split of 1/16 were analysed in a Leitz IML inverted light microscope at low magnification (40X). To count smaller pellets and organisms the material was diluted and a 1:10 subsample was taken out by a pipette and analysed. Faecal pellets are reported in five categories of cylindrical and spherical/oval forms. Biovolume of faecal pellets were calculated from linear dimensions. To convert faecal matter to carbon flux we used a factor of 0.0268 pg C micrometer(s)<SUP>-</SUP><SUP>3</SUP> according to Urrere and Knauer (1981). <B><P><P> Results & Discussion</B><P><P> Foraminifera and radiolarians were found with highest numbers in December with lower numbers in February and March. Only the phaeodarians among the radiolarians appeared to have intact protoplasma. The polycystine radiolarians (<I>Spumellaria</I> and<I> Nassellaria</I>) were always recorded as skeletons.<P><P> Two characteristics were evident when comparing the pellet flux at 200 m and 1500 m depth. The vertical flux increased with depth from December to February, but was reversed from March to May. Secondly, the presence of large elliptical pellets (400-800 micrometer(s)) at 1500 m depth. These pellets appeared very dense and are probably produced by bathypelagic or interzonal migrating zooplankton. Their contribution to the carbon flux ranged from 3.5-20 mg C m-2 d<SUP>-</SUP><SUP>1</SUP> or < 10% of total faecal flux at 1500 m. <B><P><P> References</B><P><P> Tselepides <I>et al</I>. (this volume). <BR> Urrere, M. A. & G. A. Knauer (1981). Zooplankton fecal pellet fluxes and vertical transport of particulate material in the pelagic environment. <BR> J. Plankt. Res. 3: 369-387<P><P>