Food Shortage Amplifies Negative Sublethal Impacts of Low-Level Exposure to the Neonicotinoid Insecticide Imidacloprid on Stream Mayfly Nymphs

• Published in: Water (Basel) Vol. 11; no. 10; p. 2142
• Main Authors: Hunn, Julia G., Macaulay, Samuel J., Matthaei, Christoph D.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.10.2019
• Subjects: Agriculture; Algae; Anthropogenic factors; Appendages; Availability; Biodiversity; Competition; ecotoxicology; Experiments; Exposure; Food; Food availability; Food chains; Food chains (Ecology); Food processing; Food webs; Fresh water; freshwater ecology; Freshwater organisms; Human influences; Imidacloprid; Insecticides; Invertebrates; Laboratories; Metabolism; multiple stressors; Organisms; Pesticides; Population density; resource limitation; Risk assessment; Runoff; Starvation; Sublethal effects; synergism; Toxicity; Twitching; Water pollution effects; Water, Underground; New Zealand; North America
• ISSN: 2073-4441; 2073-4441
• DOI: 10.3390/w11102142

Interactions of pesticides with biotic or anthropogenic stressors affecting stream invertebrates are still poorly understood. In a three-factor laboratory experiment, we investigated effects of the neonicotinoid imidacloprid, food availability, and population density on the New Zealand mayfly Deleatidium spp. (Leptophlebiidae). Larval mayflies (10 or 20 individuals) were exposed to environmentally realistic concentrations of imidacloprid (controls, 0.97 and 2.67 μg L−1) for nine days following five days during which individuals were either starved or fed with stream algae. Imidacloprid exposure had severe lethal and sublethal effects on Deleatidium, with effects of the lower concentration occurring later in the experiment. The starvation period had delayed interactive effects, with prior starvation amplifying imidacloprid-induced increases in mayfly impairment (inability to swim or right themselves) and immobility (no signs of movement besides twitching appendages). Few studies have investigated interactions with other stressors that may worsen neonicotinoid impacts on non-target freshwater organisms, and experiments manipulating food availability or density-dependent processes are especially rare. Therefore, we encourage longer-term multiple-stressor experiments that build on our study, including mesocosm experiments involving realistic stream food webs.