Underestimation of primary production as indicated by measurements with size-fractionated phytoplankton in Lake Maarsseveen I (The Netherlands)

Abstract

Primary productivity of four size classes of phytoplankton ( <150/~m, < 50/Jm, < 20/~m and ,~ 5/~m) was measured from March through October 1986 in Lake Maarsseveen I with an inbubator technique. The mean column production was approximately 400 mg C.m-2.day -1, with a range of values between 150 and 750 mg C.m-2.day-1. The mean contribution of the size fractions < 50 #m, < 20/~m and < 5 #m to the size fraction <. 150/~m was 80 %, 60 % and 35 %, respectively. During their appearance the grazing impact of small herbivorous zooplankton, e.g. rotifers, can give an underestimation of the size fraction <. 150/Jm. An indication of this phenomenon is given.