Optimization of culturing conditions for toxicity testing with the alga Oophila sp. (Chlorophyceae), an amphibian endosymbiont

Screening Salamanders for Symbionts

Microbial symbionts are broadly categorized by their impacts on host fitness: commensals, pathogens, and mutualists. However, recent investigations into the physiological basis of these impacts have revealed nuanced microbial influences on a wide range of host developmental, immunological, and physiological processes, including regeneration. Exploring these impacts begins with knowing which microbes are present. This methodological pipeline contains both targeted assays using PCR and culturing, as well as culture-independent approaches, to survey host salamander tissues for common and unknown microbial symbionts.

Lichen microalgae are sensitive to environmental concentrations of atrazine

The identification of new organisms for environmental toxicology bioassays is currently a priority, since these tools are strongly limited by the ecological relevance of taxa used to study global change. Lichens are sensitive bioindicators of air quality and their microalgae are an untapped source for new low-cost miniaturized bioassays with ecological importance. In order to increase the availability of a wider range of taxa for bioassays, the sensitivity of two symbiotic lichen microalgae, Asterochloris erici and Trebouxia sp. TR9, to atrazine was evaluated. To achieve this goal, axenic cultures of these phycobionts in suspension were exposed to a range of environmental concentrations of the herbicide atrazine, a common water pollutant. Optical density and chlorophyll autofluorescence were used as endpoints of ecotoxicity and ecophysiology on cell suspensions. Results show that lichen microalgae show high sensitivity to very low doses of atrazine, being higher in Asterochloris erici than in Trebouxia sp. TR9. We conclude that environmental concentrations of atrazine could modify population dynamics probably through a shift in reproduction strategies of these organisms. This seminal work is a breakthrough in the use of lichen microalgae in the assessment of micropollution effects on biodiversity.

Aquatic hazard assessment of MON 0818, a commercial mixture of alkylamine ethoxylates commonly used in glyphosate-containing herbicide formulations. Part 2: Roles of sediment, temperature, and capacity for recovery following a pulsed exposure

A series of toxicity tests with MON 0818, a commercial surfactant mixture of polyoxyethylene tallow amines, were performed: 1) in the presence of sediment for benthic invertebrates and fish: 2) to examine the recovery capacity of Daphnia magna and 4 primary producers after a pulsed (24-h) exposure; and 3) to examine the potential effect of increased water temperature on toxicity of MON 0818 to 2 cold-water fishes. In the presence of sediment, no acute (24-h) mortality was observed for 3 of the 5 species up to 10 mg L-1 . The median effective concentrations for the other 2 species were significantly greater than for water only tests. The EC50 at 15 °C for Salvelinus alpinus was statistically lower than that at 10 °C. Latent effects of a 24-h exposure (1 mg L-1 ) were observed for Rhabdocelis subcapitata and Chlorella vulgaris, as indicated by delayed growth during recovery phase; however, both cultures were able to recover, as indicated by a lack of changes in maximum absolute growth rates. No significant effects of a 24-h exposure to MON 0818 were observed for Oophila sp. (1.5 mg L-1 ) or Lemna minor (100 mg L-1 ). Latent mortality after a 24-h exposure to 5 mg L-1 was observed during the recovery phase for D. magna; however, reproduction endpoints on surviving individuals were not altered. The results indicate that quick dissipation of MON 0818 in the presence of sediment can reduce the effects on exposed organisms, and that full recovery from 24-h exposures to concentrations of MON 0818 equal to, or greater than, those expected in the environment is possible. Environ Toxicol Chem 2017;36:512-521. © 2016 SETAC.

Aquatic hazard assessment of MON 0818, a commercial mixture of alkylamine ethoxylates commonly used in glyphosate-containing herbicide formulations. Part 1: Species sensitivity distribution from laboratory acute exposures

The sensitivity of 15 aquatic species, including primary producers, benthic invertebrates, cladocerans, mollusks, and fish, to MON 0818, a commercial surfactant mixture of polyoxyethylene tallow amines, was evaluated in standard acute (48-96-h) laboratory tests. In addition, the potential for chronic toxicity (8 d) was evaluated with Ceriodaphnia dubia. Exposure concentrations were confirmed. No significant effects on any endpoint were observed in the chronic test. A tier-1 hazard assessment was conducted by comparing species sensitivity distributions based on the generated data, as well as literature data, with 4 exposure scenarios. This assessment showed moderate levels of hazard (43.1% of the species exposed at or above median effective concentration levels), for a chosen worst-case scenario-unintentional direct over-spray of a 15-cm-deep body of water with the maximum label application rate for the studied formulations (Roundup Original, Vision Forestry Herbicide; 12 L formulation ha-1 , equivalent to 4.27 kg acid equivalent [a.e.] ha-1 ). The hazard decreased to impairment of 20.9% of species under the maximum application rate for more typical uses (6 L formulation ha-1 , 2.14 kg a.e. ha-1 ), and down to 6.9% for a more frequently employed application rate (2.5 L formulation ha-1 , 0.89 kg a.e. ha-1 ). Finally, the percentage (3.8%) was less than the hazardous concentration for 5% of the species based on concentrations of MON 0818 calculated from maximum measured concentrations of glyphosate in the environment. Environ Toxicol Chem 2017;36:501-511. © 2016 SETAC.