Resumo

Picophytoplankton is a collection of photosynthetic cells, 1 to 3 µm of diameter, that inhabit the photic zone of the ocean, are integral members of marine ecosystems in terms of cell abundance, biomass, activity, and diversity playing crucial roles in food webs and biogeochemical cycles. picophytoplankton includes cyanobacteria, represented by Synechococcus & Prochlorococcus, and photosynthetic picoeukaryotes (PPEs), that can belong to a wide range of algal classes. Picoplanktonic populations can be controlled in terms of abundance and structure mainly by light availability and inorganic nutrients like nitrogen, phosphorus, silica and iron. Normally, the phytoplankton displays a fairly predictive annual cycle. Human activities have an important impact on marine ecosystems, particularly relevant in near-shore waters. The pressures exerted are diverse and result from many activities such as coastal engineering, urban development, maritime transport, oil extraction, industrial activities & mining. In northern Chile, at Chañaral Bay (26°15´S, 69°34´W), copper mine wastes discharged for more than 60 years have had direct effects on the biota and induced changes on the coast topography, including the formation of tailing beaches. In contrast with other contaminated coastal areas around the world, in Chañaral area there are no other anthropogenic wastes or natural inputs that could mask the effect of copper as a chronic and dominant pollutant. In this study, an in situ microcosm experiment was developed to evaluate the effect of copper addition on picophytoplankton community in a chronic copper impacted area. Measurements were focused on Synechococcus and PPEs cell counts, in vivo chlorophyll fluorescence and fingerprinting analysis of the PPEs community High copper concentration (250 µg/L) has a lethal effect on picophytoplaktonic community in microcosm experiment. In contrast, 25 µg/L of Copper treatment exert a differential effect on the two mainly picophotosyntetic organisms, while Synechococcus seems to be more sensitive to copper addition, PPEs have an increase in cell number compared with control conditions. These results show that PPEs tend to be more resistant to metal addition than the bacterial counterpart in a copper impacted area.