The role of fungi in processing marine organic matter in the upwelling ecosystem off Chile

In a study that spanned from March 2007 through November 2009, we report high fungal biomass and over 90% of extracellular enzymatic activity occurring in the size classes dominated by fungi during periods of high autotrophic biomass in surface waters of the upwelling ecosystem off central-southern Chile (36A degrees 30.80'S-73A degrees 07.70'W). Fungal biomass in the water column was determined by the abundance of hyphae and was positively correlated with the concentration of the fungal biomarker 18:2 omega 6. High fungal biomass during active upwelling periods was comparable to that of prokaryotes (bacteria plus archaea) and was associated with an increase in phytoplankton biomass and in extracellular enzymatic hydrolysis in waters from the depth of maximum fluorescence. We show fungi as a new microbial component in the coastal upwelling ecosystem of the Humboldt Current System off central Chile. Our results suggest that the temporal pattern in fungal biomass in the water column during a year cycle is a reflection of their capacity to hydrolyze organic polymers and, in consequence, fungal biomass and activity respond to a seasonal cycle of upwelling in this ecosystem.