2. 2 to 5 liters of water were filtered through a nylon bolting cloth 

 of 45 microns mesh size. The plankton and larger detritus 

 particles were formalin preserved. 



3. 2-liter-samples were filtered through an ignited and weighted 

 Whatman GF/C glasfiber filter, which as a pore size of 1 - 1 

 microns. Using a Millipore filtration apparatus and a vacuum 

 pump the seston was carefully removed. The dried filters were 

 stored airtight. 



The counted phytoplankton cells were grouped according to their size and 

 systematic categories. Applying the known relations between cell volume and 

 organic carbon content the phytoplankton biomass was calculated in terms of 

 carbon. 



Further differentiation of more species and their possible heterogenous 

 distribution as well as their frequency at day and night have still to be 

 worked out. Furthermore, size and frequency determinations of detritus 

 particles and chemical analyses of the sedimentated material which was 

 sampled from a variety of bottom surfaces for comparison are not yet available 

 at this time. 



The dried (70° C) glasfiber filters were reweighted using a Cahn electro- 

 balance. From the obtained total particulate matter (seston dry weight) the 

 carbonate was removed by treatment with fumes of hydrochloric acid. After 

 drying, the weight of the carbonate-free seston was determined (see table, 

 column 2) . The same filters were analyzed for organic carbon and nitrogen by 

 dry combustion in an Hewlett Packard carbon-hydrogen-nitrogen analyzer Mod, 185 

 (column 5 and 6 in table), 



RESULTS 



The seston distribution and quality were fairly uniform in the water column 

 observed and there was little change during the investigation time. The 

 seston weight at the bottom was slightly higher (1.76 and 1.75 mg/1, see table, 

 column 1) than at 5 m above it 1.67 mg/1). The carbonate content of the seston 

 was highest at 5 m above the bottom (48.4%, column 3) and lowest at the reef 

 bottom (42.67=), 



The biomass values as evaluated from phytoplankton counts (column 4) were the 

 same at 5 m above the sand bottom (13 ra of water depth, 41 micrograms carbon 

 per liter) as over the reef (14 m of water depth). Little more (44 ug carbon 

 per liter) was found near the sand bottom in 18 m water depth. 



The organic carbon content of the seston as determined by combustion (column 5) 

 however was higher at 5 m above the bottom and over the coral reef (68 and 71/ ug 

 carbon/1) than near the sand bottom (63 /ug carbon/1). 



The percentage of the direct determined carbon from total seston weight 

 (column 8) was slightly higher near the sand and coral bottom (4.1%) than at 

 5 m above the sand (3.8%). 



VI-276 



