An invasive mussel is in trouble: How do glyphosate, 2,4-D and its mixture affect Limnoperna fortunei's survival?

Contamination and biological invasions are important factors that alter the functioning of freshwater systems. We carried out two experiments involving daily measurements of dissolved oxygen (DO) and Limnoperna fortunei mortality: 1) the impact of DO on mussel survival mediated by glyphosate, 2,4-D and their mixture was analysed in a 22-day indoor experiment (IE) under controlled conditions using microcosms with L. fortunei, with and without air supply; and 2) the effect of each herbicide and their mixture on mussel accumulated mortality was compared in a 18-day outdoor experiment (OE) using mesocosms without air supply, with and without L. fortunei. Results showed that glyphosate, alone or mixed affected L. fortunei survival both directly and indirectly. In IE we observed direct toxicity of glyphosate in treatments with air supply, with accumulated mortality of 20.0% for glyphosate and 10.0% for the mixture. In OE, L. fortunei deepened the changes in the patterns of DO fluctuations driven by the herbicides, which led to hypoxia in the system. The accumulated mortality was 46.7, 8.6 and 48.2% for glyphosate, 2,4-D and the mixture, respectively. This study contributes to the understanding of the mechanisms that control the invasion of L. fortunei in freshwater systems influenced by agrochemicals.

Comparative effects of technical-grade and a commercial formulation of glyphosate on the pigment content of periphytic algae.

We investigated the potentially different effects of one of the most commonly used glyphosate formulations in Argentina, Glifosato Atanor(®), and the technical-grade glyphosate on the pigment content, as biomass indicators of the algal fraction in a freshwater periphytic community. A laboratory bioassay was carried out in 250-ml beakers. Two treatments were used: technical-grade glyphosate acid and Glifosato Atanor(®) (isopropylamine salt of glyphosate 48 % w/v), which were at a concentration of 3 mg active ingredient per liter. Treatments and the control (without herbicide) were replicated in triplicate. The concentrations of chlorophyll a and b and carotenes were determined at 0, 2, 6, 10, 24, 48, 96 and 192 h after herbicide addition. A significant increase in pigment content was observed for both herbicides after a 2-day exposure. Moreover, the formulation had little or no effect compared to the active ingredient, suggesting that the additives of Glifosato Atanor(®) may not enhance glyphosate toxicity.