Light limitation helps stabilize the phytoplankton assemblage steady-state in a temperate and highly turbid, hypertrophic shallow lake (Laguna Chascomús, Argentina)

IACHETTI, CLARA; LLAMES, M.E.

HYDROBIOLOGIA

SPRINGER

Lugar: Berlin; Año: 2015 vol. 752 p. 33 - 46

0018-8158

We performed a 30-month field study in ahighly turbid, hypertrophic shallow lake from thePampa Plain (Argentina) in order to investigate theoccurrence of steady-state phases of phytoplankton,with an emphasis on the effect of subtle, but measurable,increase in light availability. The results revealedthat a steady-state condition prevailed during the first14 months, during which Aphanocapsa cf. delicatissimarepresented, on average, 91% of the total phytoplanktonbiomass. The statistical analyses providesupport for the hypothesis that low light availability inthe water column regulates the structure of the algalassemblage in this lake. Our results agree withpredictions of the light-limited growth theory (i.e.the observed increase in light supply promoted anincrease in algal density) and are also consistent withthe notion that environmental constraints influence thedominant morphological traits in phytoplanktonassemblages, particularly, that small organisms and/or attenuated forms are favoured under very poor lightconditions. Nevertheless, further work is needed to geta full understanding of the processes controllingphytoplankton dynamics in this lake, including carefulstudies of the ecophysiology of the colonies comprisingpico-sized cells of Aphanocapsa cf. delicatissimathat dominated the assemblage during all the studiedperiod.