Abstract. During the 1997-98 E1 Nifio event, the temperature and oxygen contents of the coastal waters off northern Chile were noticeably higher than during non-E1 Nifio conditions, but phytoplankton and zooplankton biomasses were not dramatically altered. In contrast, the herbivorous copepod Calanus chilensis, which showed a limited tolerance to low-oxygen conditions, exhibited greater abundances, higher growth rates, and a significant reduction in adult body size. These results indicate a positive effect of the changes in oceanographic conditions due to E1 Nifio on zooplankton growth and production, and provide evidence for lack of food limitation on secondary production in the coastal region during this period.

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We report for the first time the presence of filamentous fungi in the water column and sediment in the coastal upwelling ecosystem off central Chile, using molecular tools and epifluorescence microscopy. Positive amplifications of SSU 18s rDNA with specific fungal primers were obtained for surface waters and sediments of this coastal ecosystem. Molecular richness obtained from denaturing gradient gel electrophoresis showed a higher number of fungal genotypes in nearshore than offshore sites and in summer than winter. Fungal structures identified by epifluorescence microscopy in the water column were present as individual filaments or as aggregates of hyphae. We show for the first time vertical water column profiles of fungal biomass in the marine ecosystem. Fungal biomass reached up to 5 µg C Lin surface waters during summer and their vertical patterns agreed with those of chlorophyll-a and with the general distribution of microplankton biomass in the ocean. The presence of viable fungi in the coastal ocean encourages us to decipher their role in the processing of marine organic matter and to evaluate their inclusion in the actual paradigm of the microbial loop and in the biogeochemistry of the oceans.

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