Abstract:
Thetemporalandspatialvariationsinthehiomassandphotosyntheticproductionof
phytoplanktoninrelationtosomephysico-chemicalenvironmentalfactorswere
investigatedattwo(offshoreandnear-shore)stationsinLakeChamofromAugust,
2003toMay,2004.Inorganicnutrientsvariedtemporally,withtheirlowandhigh
concentrationlevelsgenerallycorrespondingtothedryandrainyperiods
respectively.Lake'stransparencywasalwayslow(Zsd<40cm).Because
phytoplanktonhiomasswashighthroughoutthestudyperiod,itscontrihutiontothe
extinctionofunderwaterlightisexpectedtoheconsiderahle.Phytoplanktonhiomass
measuredaschlorophyllavaried43to95(mean=77.2)and47to108(mean=69.4)
mgChiam'^atthenear-shoreandcentralstations,respectively.Thevertical
distrihutlonofphotosyntheticactivitywasofatypicalpatternforphytoplanktonwith
light-inhihitiononallsamplingdates.Thelight-saturatedrateofphotosynthesis(Amax)
rangedfrom721to1789mgO2(~224.95to558.17mgC)m'^h'^atthecentral
stationandtfrom543to1803mg02(»169.42mgC)m'^h'^atthenear-shore
station.Lackofcorrespondencehetweenphytoplanktonhiomassand
Amaxwas
evident.Bipmass-specificrateofphotosyntheticproductionatlight-saturation,
photosyntheticcapacity(<Pmax)rangedfrom9to34mgO2(mgChia)'''h'^atthenearshorestationandfrom10to34mgO2(mgChia)'''h'''atthecentralstation.An
inverserelationshiphetweenphotosyntheticcapacityandphytoplanktonhiomasswas
alsoohserved.Hourlyintegralphotosynthesisrangedfrom0.36to1.72gO2("0.11
to0.54gC)m'^h'^atthecentralstationandfrom0.47to1.8gO2(^0.15to0.56g
C)m'^h'^atthenear-shorestation.Theproductionrateperunitareaseemstohave
heeninfluencedhythelight-saturatedrateofphotosynthesisasthestrongand
positivecorrelationhetweenthetwo(r=0.77)suggests.Thetemporalvariationsin
phytoplanktonhiomassandprimaryproductioninrelationtoenvironmentalfactors
arediscussed
