Interactions between the Rates of Production of a Freshwater Macrophyte and Phytoplankton in a Pond

Abstract

In a gravel pit in N.E. England the annual production (for 1967) of phytoplankton (1100 g carbon/M2) was measured with the 14C technique, and the gross production of the macrophyte Ceratophyllum demersum (600 g carbon/M2) with the diurnal oxygen method. Over the year the two communities were complementary, and high productivity by the macrophyte in summer succeeded high productivity by phytoplankton in spring. A second pond, in which macrophytes were scarce, contained more phytoplankton in summer but on an annual basis its phytoplankton production (500 g carbon/M2) was less than in the first pond. Ceratophyllum was found to cause greater shading of the phytoplankton beneath it than Potamogeton natans. Some observations were made on the vertical distribution of chlorophyll and phytoplankton productivity. Pe3loMe B BogoeMe B ceBepO-BOCTO'IHOil AHriirn ro,wiqam fpOAYKIUHR COCTaB1S1a B 1967r. llOOr C/M2. (143MepeHHq rPOBOAHJIHCb C ripH;MCeHeHHeM C14). BanIOBas IIPOAYKXHA MaKpO4ITTOB Ceratophyllum demersum, H3MepeHHaq CyTO'qHbIM KHCJIOPOAHbIM MeTOAOM, COCTaBjiqJia 600r C/M2. B TeieHRe roxAa HccneJAoBaHbI ,oiioJiHHTeJi]HO eri~e )asB KOMnJIeKCa MaapO4HTOB. lIx BbICOKaR IIpOAYKTHBHOCTb IIeTOM IBjiqeTCA CJIieJCTBHeM BbICOKOA IIPOXYKTHBHOCTH 4HITOrIJIaHKTOHa BeCHOA. BTOPOll npya, rAe MaKpo4HTbI 6buIR HeMHoro'HCjieHHbI, cogepwaii 6oJibmee KO3IIIeCTBO 4DHTOiaiiaHKTOHa JIeTOM, HO B TeqeHRe roxga ero HPOAYKIIHR COcTaBJIssia 500r C/M2 MeHBIIIe, 'IeM B iTePBOM BOaOeMe. YCTaHOBJIeHO, tITO Ceratophyllum cHJIiHee noAaBI5eT 4IHTOnIiaHKTOH, ieM Potamogeton natans. npoBeaeHBI HeKOTOpbIe Ha6fnioeHHA BepT1IKaJThHOrO pacnpeAejieHHR xnopowRina R HpOAYKTHBHOCTH UHTOnjiaHKTOHa. Manuscript accepted April 1969.