Space Partition within Aquatic Ecosystems

(HNF) , autotrophiC nanoflagellates, clhated Protozoa and mlcroalgae) and autotrophic and heterotrophic Because of difficulties related to sampling methods, activIties III a moderately aCid and humiC lake III central fixatIOn and taxonomic IdentificatIOn (Gates, 1984), It France the Lake of Vasslvlere IS only III the last decade that the Importance of the microbial loop III the transfer of energy and matter III pelagic marIne (Azam et al , 1983) and freshwater Materials and methods ecosystems (Porter, 1988, Stockner & Porter, 1988, Bermnger et ai, 1991) has been clearly demonstrat- The phYSico-chemical charactenstIcs of the lake of ed The microbial loop IS a part of a larger microbial Vasslvlere (Central maSSif of France) are summanzed food web Illcludlllg both autotrophiC and heterotroph- III Table 1 It IS a brown-colored humiC lake moderately IC pro-and eukaryotIc umcellular orgamsms (Sherr & aCidiC (pH values ranged between 5 1 and 7 5) A total Sherr, 1988, Weisse, 1991), which can be of paramount of 28 samples were collected from the end of Apnl to Importance III the recychng of orgamc matter (Fenchel, the middle of October at several depths (1, 5, 10 and 1987) More precisely, recent studies have suggest- 15 m) III the deepest area of the lake (20 m) Samples ed that Protozoa are Illvolved III the microbial loop were taken With a Van Dorn bottle and pre-filtered onto III predatIOn and control of bactenal and autotroph- a 160 p,m pore size filter, except those which were used