Effects of lake sediment contamination by PAHs on nutrients and phytoplankton in Vaca Muerta, Neuquén, Argentina

Aquatic sediments act as a source for nutrients as well as contaminants, among which there are polycyclic aromatic hydrocarbons (PAHs) such as phenanthrene (Ph), anthracene (An), pyrene (Py) and benz(a)anthracene (Ba). Phytoplankton can be an indicator of contaminants presence, thus, we decided to study it in Los Barreales reservoir (Neuquén Province, Argentina). Reservoir water and sediments were characterized, and additional samples were collected to perform assays. Bioassays were carried out by incubating sediments contaminated with increasing concentrations of PAHs and filtered lake water, with the addition of native phytoplankton: with the addition of Scenedesmus quadricauda (Turpin) Brébisson (reservoir native alga); and without sediments. The results showed that: (A) nutrient concentrations in water decreased for Ph, Py and Ba at concentrations from 500 ppm, (B) S. quadricauda abundance and chlorophyll a decreased with Ph treatments at 250 ppm (on incubation days 2 and 7), Py from 1000 ppm (on incubation day 2) and Ba from 50 ppm (on incubation days 2 and 7), and (C) that the effect of the PAHs used on algal growth was direct. Sediments contamination with Ph, Py or Ba modified nutrient concentrations in the water column and affected S. quadricauda growth.