Size-ftactioned photoautotrophic production in a shallow Bay.

Abstract

CO2 assimilation measurements werecarried out in Concepción Bay (36"40'S, 73"0rW), toevalúatesizefractioned and total primary production in HC incubations. The P-I curve shows an assimilation nuinber of 3.82 mgC (mgChl-a)-1 h~1 and an a valué of 0.0076 (mgC(mgChl — a)'1 h~‘)/uE m-2 s-1, both parameters were used to estimate primary production in the water column using the Hermán & Platt model (1983). Integrated production was calculated as 0.97 gC m-2 d-1, four times higher than previous estimations reponed off the Chilean coast. At low irradiance (1= 109 uE m~2 s" ’). picoplankton and nanoplankton were responsible for 9.5% and 12.5% of the non-normalized production. whereas the net phytoplankton accounted for 64.6% of the photosynthetic assimilation.The chlorophyll normalized photosynthetic rate (productivity Índex) was higher for smaller than larger fractions, size dependant relationship with ecological significance at low light irradiances.