Combined effects of the cyanobacterial toxin microcystin-LR and environmental factors on life-history traits of indigenous cladoceran Moina macrocopa

Abstract

Environmental factors are important in that they might interact with toxicants and could affect the concentration-response relationship of the toxicants in the water environment. Microcystins (MCs) produced by algal blooming are natural toxins that exert severe impacts on aquatic organisms. Despite the possibility of interaction effects between environmental factors and MCs, very few studies have been carried out to date. In the present study, the authors evaluated the effect of 3 environmental factors on chronic toxicity of MC-leucine-arginine (MC-LR; 0 µg/L, 0.8 µg/L, 4 µg/L, 20 µg/L, 100 µg/L, 500 µg/L) to the freshwater invertebrate Moina macrocopa. Three environmental factors were determined to reflect the reasonable worst conditions of the water body in South Korea: high water temperature (25 °C), the highest concentration of nutrients (ammonia-nitrogen [NH3 -N] = 3.8 mg/L; nitrate-nitrogen [NO3 -N] = 8.5 mg/L) during the occurrence of algal bloom, and 2 pH conditions of 7.0 and 9.0, which satisfy the test acceptance criteria for the Daphnia test. Among the various environmental factors being tested, high water temperature and NO3 -N elevated chronic toxicity of MC-LR, whereas NH3 -N reduced toxicity. Water pH did not influence chronic toxicity of MC-LR to M. macrocopa. This observation suggests that those environmental factors are responsible for changing the trend of MC-LR toxicity.

Combined effects of increased water temperature and cyanobacterial compounds exert heterogeneous effects on survival and ecological processes in key freshwater species

“…Such temperature-mediated toxicity could be responsible for the 50% decline observed in the survival of I. elegans exposed to high concentration of the crude extract at 25 °C in our study. Here, our finding supports the hypothesis on the combined effects of temperature and crude extract and corroborates earlier studies that demonstrated their combined effects on freshwater species (Kim et al 2014 ; Lamb et al 2019 ; Xiang et al 2017 ). Hence, the present study suggests that warming may co-occur with a much broad range of cyanobacterial metabolites following bloom senescence leading to impaired survival and feeding among important species (Paerl and Huisman 2008 ; Walls et al 2018 ).…”

“…Higher temperatures lead to increases in metabolic activity and accelerate the toxicokinetics of chemical stressors in ectotherms (Brown et al 2004 ; Noyes et al 2009 ). Increased metabolic activity at higher temperatures presumably elevated the rate of uptake, assimilation, and toxicity of the bioactive compounds in the crude extract (Buchwalter et al 2003 ; Kim et al 2014 ; Kozlowsky-Suzuki et al 2012 ). Such temperature-mediated toxicity could be responsible for the 50% decline observed in the survival of I. elegans exposed to high concentration of the crude extract at 25 °C in our study.…”

The Combined Effects of Toxic Microcystis aeruginosa and Thermal Stress on the Edible Clam (Corbicula fluminea): Insights into Oxidative Stress Responses and Molecular Networks

“…Although the individual effects of toxic CYBs and thermal stress on aquatic animals have been well characterized, there is a lack of information on the combined effects of toxic CYBs and elevated temperatures. Previous studies have assessed the toxicity of cyanobacteria at different temperatures in aquatic animals, including zebrafish (Danio rerio), mussels (Hyriopsis cumingii), freshwater daphnids (Moina macrocopa) and rotifers (Brachionus calyciflorus), indicating that the combined effects of temperature and cyanotoxins are complicated and species-specific [9][10][11][12][13]. Consequently, a comprehensive understanding of the combined impacts of toxic cyanobacteria and thermal stress on various aquatic organisms will provide a broader perspective on the sustainability of aquatic ecosystems.…”