Can nutrients mask community responses to insecticide mixtures?
- 450 Downloads
The ecological effect of simultaneous exposure to two nutrient gradients, three insecticides and different predator intensities was investigated over a 3-week period in 80 outdoor, artificial streams using field-collected benthic invertebrates. The experimental design consisted of a 2 × 5 factorial structure with two nutrient levels (oligotrophic or mesotrophic) and five concentrations of the ternary insecticide mixture consisting of the insecticides (chlorpyrifos, dimethoate and imidacloprid). Equivalent toxic unit doses were summed to create a ternary insecticide dose (e.g., 0.1 + 0.1 + 0.1 = 0.3 TU) resulting in a range of ternary insecticide mixture toxicity (i.e., control groundwater, 0.3, 0.6, 0.9 and 1.2 TU). Two genera of insect predators, Gomphus spp. (Odonata) and Agnetina spp. (Plecoptera) were also added into each replicate stream, at densities and sizes comparable to those found at our collection site, to evaluate how the contribution of predators may change in nutrient limited (oligotrophic) versus amended (mesotrophic) systems. We describe a causal mechanism whereby the combined action of nutrients and insecticides reshaped aquatic community structure by interacting through multiple pathways. Specifically, mesotrophic conditions reduced the toxic effects of ternary insecticide mixtures for aquatic insects which, in some cases, appeared to increase abundance of aquatic insects. However, higher levels of insecticides in mesotrophic streams negated this effect and were even more toxic; for example, to aquatic insect grazers than the same insecticide doses in oligotrophic treatment levels. Effects of predators were only significant in oligotrophic streams. Evidence is provided as to how nutrient and contaminant interactions can greatly complicate the assessment of community level responses to insecticide mixtures due to direct and indirect effects of the resulting changes in the density of different genera and functional feeding groups within a community.
KeywordsNutrient masking Ternary insecticide mixtures Field collected benthic macroinvertebrate community Artificial streams Structural-equation model (SEM)
We thank Bob Brua for his thoughtful review of an early draft of the manuscript. Jon Bailey at NHRC (Saskatoon) who conducted the chemical analyses. Also, Dave Hryn provided invaluable technical expertise and assistance in conducting the experiment. The authors declare that they have no conflict of interest. This work was supported in part by the Pesticide Science Fund awarded to Culp, Baird, Cessna and Alexander and an NSERC (PGS-D3 #362641) to ACA.
- Alexander AC, Culp JM (2013) Predicting the effects of insecticide mixtures on non-target aquatic communities. In: Trdan S (ed) Insecticides development of safer and more effective technologies. Intech Open Publishers, Rijeka. http://www.intechopen.com/books/insecticides-development-of-safer-and-more-effective-technologies/predicting-the-effects-of-insecticide-mixtures-on-non-target-aquatic-communities
- Alexander AC, Heard KS, Culp JM (2008) Emergent body size of mayfly survivors. Fresh Biol 53:171–180Google Scholar
- Baekken T, Aanes KJ (1991) Pesticides in Norwegian agriculture. Their effects on benthic fauna in lotic environments (preliminary results). Int Ver Theor Angew Limnol Verh 24:2277–2281Google Scholar
- Carter JL, Resh VH, Hannaford MJ, Myers MJ (2006) Macroinvertebrates as biotic indicators of environmental quality. In: Hauer FR, Lamberti GA (eds) Methods in stream ecology, 2nd edn. Elsevier, Boston, pp 805–854Google Scholar
- Culp JM, Baird DJ (2006) Establishing cause-effect relationships in multi-stressor environments. In: Hauer FR, Lamberti GA (eds) Methods in Stream Ecology, 2nd edn. Elsevier, Boston, pp 835–854Google Scholar
- Dunn A (2004) A relative risk ranking of pesticides used in Prince Edward Island. Report EPS-5-AR-04-03. Environment Canada, Dartmouth, p 41Google Scholar
- EPA (2009) ECOTOX (ECOTOXicology) database, Version 4. U.S. Environmental Protection Agency, Office of Research and Development (ORD), and the National Health and Environmental Effects Research Laboratory’s (NHEERL’s) Mid-Continent Ecology Division (MED). http://cfpub.epa.gov/ecotox/. Accessed 1 June 2009
- European Commission (2003) Technical guidance document on risk assessment in support of commission directive 93/67/EEC on risk assessment for new notified substances and commission regulation (EC) No. 1488/94 on risk assessment for existing substancesGoogle Scholar
- Hall SR, Shurin JB, Diehl S, Nisbet RM (2007) Food quality, nutrient limitation of secondary production, and the strength of trophic cascades. Oikos 116:1128–1143Google Scholar
- Hoffman ER, Fisher S (1994) Comparison of a field and laboratory-derived population of Chironomus riparius (Diptera, Chironomidae) - biochemical and fitness evidence for population divergence. J Econ Entomol 87:320–325Google Scholar
- Luis AT, Alexander AC, de Almeida SFP, da Silva EAF, Culp JM (2013) Benthic diatom communities in streams from zinc mining areas in continental (Canada) and mediterranean climates (Portugal). Water Quality Res J Can 48:180–191Google Scholar
- Merritt RW, Cummins KW (1996) An introduction to the aquatic insects of North America. Kendall Hunt Pub, DubuqueGoogle Scholar
- Murphy C, Mutch JP, Reeves D, Clark T, Lavoie S, Rees H, Chow L, Nunn L, Hebb D (2006) Multi-media pesticide monitoring program in Prince Edward Island, New Brunswick and Nova Scotia. An Environment Canada Pesticide Science fund project final project report: 3 year monitoring report program—2003/04 to 2005/06. Environment CanadaGoogle Scholar
- Schulz R (2004) Field studies on exposure, effects, and risk mitigation of aquatic nonpoint-source insecticide pollution: a review. J Environ Qual 33:419–448Google Scholar
- Traas TP, van de Meent D, Posthuma L, Hamers T, Kater BJ, de Zwart D, Aldenberg T (2002) The potentially affected fraction as a measure of ecological risk (Chapter 16). In: Posthuma L, Suter GW, Traas TP (eds) Species sensitivity distributions in ecotoxicology. CRC Press, Boca Raton, pp 315–344Google Scholar
- Underwood AJ (2002) Experiments in ecology: their logical design and interpretation using analysis of variance. Cambridge University Press, New YorkGoogle Scholar
- Westfall MJ, Tennessen KJ (1996) Chapter 12, Odonata. In: Merrit RW, Cummins KW (eds) An introduction to the aquatic insects of North America, 2nd edn. Kendall Hunt, Dubuque, pp 164–211Google Scholar