Toxic effect of copper on marine picophytoplankton populations isolated from different geographic locations

Abstract

In an approach to understand more about copper toxicity effects on marine microalgae, 72-h growth inhibition toxicity tests were followed on natural picophytoplanktonic populations belonging to different coastal and oceanic geographic locations (Mediterranean Sea and Atlantic Ocean) covering, at an approximate longitude of 30ºW, latitudes from 32º14´S to 29º10´N. Analyses of samples established different predominant populations for different locations. Copper toxicity tests showed a group of cyanobacteria isolated from coastal samples that were the most sensitive, and a second group of picoeukaryotes collected from the Atlantic Ocean surface, which were more tolerant to copper. The use of flow cytometry for studying copper toxic effects provided a variety of information on cell parameters in addition to cellular density. In particular, an established increase in copper tolerance with increase of cell size was observed in cyanobacteria, but it was not clearly followed in picoeukaryotes. This study aims to relate copper tolerance to the geographic location sites of sampling collection. The results obtained establish that other factors such as cell size, proximity to the coast and copper concentration in situ are considered to have a greater influence than the fact of belonging to a determined location site.