Marine phytoplankton assays: Effects of detergents

Abstract Environmental impacts of an anionic detergent — sodium dodecylbenzene sulfonate (LAS) — a polyphosphate, and a largely employed commercial detergent powder containing methylene blue active substances (MBAS) were evaluated with cultures of the diatom Phaeodactylum tricornutum . Bioassays with natural phytoplankton from an estuarine region (Cananeia — SP) were also performed using the same commercial detergent powder. For P. tricornutum , LC 50 values of LAS were 1.94 and 1.90 mg/l after 48 and 96 h, respectively, and NOEC values were always below 0.50 mg/l. LC 50 values for the commercial detergent were 2.14 mg/l and 1.65 mg/l of its MBAS content after 48 and 96 h, respectively. NOEC values were 1.2 mg MBAS/l after 48 h, and less than 0.1 mg MBAS/l 96 h after the beginning of the experiment. The polyphosphate can be an effective source of phosphorus for cell growth. MBAS concentrations in Cananeia estuarine waters showed values ranging from 0.10 mg/l in surface waters, to 8.75 mg/l in a laundry effluent. The commercial detergent solution added to samples of natural phytoplankton (with or without nutrient enrichment) showed a significant change on chlorophyll-a content, primary production potential, and a drastic reduction in P. tricornutum cell density, at concentrations of 2.0 and 5.0 mg MBAS/l. Microphytoplankton diversity was not affected. The agreement found between field and laboratory experiments emphasized the need for toxicological tests in the monitoring of aquatic environments.