Effects of malathion and nitrate exposure on the zooplankton community in experimental mesocosms

Abstract

Surface waters are likely to be contaminated by both pesticides and fertilizers. Such contamination can result in changes in community composition if there is differential toxicity to individual taxa. We conducted a fully factorial mesocosm experiment that examined the single and interactive effects of environmentally realistic concentrations of nitrate and malathion on zooplankton communities and phytoplankton productivity. Malathion significantly decreased the abundance of total zooplankton, cyclopoid copepods, copepod nauplii, and Ceriodaphnia, and increased the abundance of rotifers. Nitrate addition generally had no effect on zooplankton; however, Ceriodaphnia abundance was higher in control mesocosms than in nitrate-treated mesocosms. There was only one significant interaction between malathion and nitrate treatments: For Ceriodaphnia, the no malathion, no nitrate mesocosms had much higher abundances than all other combinations of treatments. Without nitrate addition, chl a levels were uniformly low across all malathion treatments, whereas in the presence of nitrate, there were differences among the malathion treatments. In conclusion, our results demonstrate that malathion contamination of aquatic ecosystems can result in changes in the abundance and composition of zooplankton communities. In contrast, nitrate contamination appeared to have much less potential impact on zooplankton communities, either on its own or in interaction with malathion. Our results reinforce the notion that the effects of contaminants on aquatic ecosystems can be complex and further research examining the single and interactive effects of chemical stressors is needed to more fully understand their effects.

Interactive effects of fish predation and sublethal insecticide concentrations on freshwater zooplankton communities

“…The decrease in cladocerans might have favoured the increase in rotifers, which were more tolerant to CLP, as previously demonstrated for other xenobiotics such as malathion and carbaryl (Hanazato and Yasuno, 1990;Relyea et al, 2005). Consistent with this, field studies found similar effects on species replacement after the application of CLP and other related insecticides (Kaushik et al, 1985;Chang et al, 2005;Smith et al, 2018).…”

“…2016). The effects of fish predation on zooplankton have been widely studied, as well as the impact of insecticides, with both factors individually having similar direct and indirect effects on community density, composition (species replacement), evenness, size and traits (Relyea and Hoverman, 2006;Laird et al, 2007;Iglesias et al, 2011;Smith et al, 2018).…”

Food in the Sea: Size Also Matters for Pelagic Fish

“…Oceanographic modifications, induced by global warming, coupled with pollution, are two potential candidates that may explain reduced prey sizes for sardines. Up to 77% of total marine pollution is from terrestrial sources (Williams, 1996) and contaminants such as pesticides, fertilizers, heavy metals and synthetic organic chemicals are all known to affect plankton communities, reducing their diversity and causing irreversible changes in marine ecosystems (Shahidul Islam and Tanaka, 2004;Pérez et al, 2011;Smith et al, 2018). For example, the insecticide Malathion and the herbicide Roundup R significantly decreased copepod abundance, but favored smaller and lower energetic zooplankton (Geyer et al, 2016;Smith et al, 2018).…”

Pesticide exposure enhances dominance patterns in a zooplankton community

“…There is currently a rich and growing body of literature on how pesticides affect individuals and species. Most studies to date have focused on single‐species approaches to assess the organismal responses to pesticide exposure (Delnat et al, 2019; Janssens & Stoks, 2020; Lal et al, 2013; Song et al, 2017; Thoré, Philippe, et al, 2021), or have relied on mesocosm experiments and field surveys to assess how pesticides affect biodiversity and community composition (Andrade et al, 2021; López‐Mancisidor et al, 2008; Mcmahon et al, 2012; Pestana et al, 2009; Smith et al, 2018). Pesticides may not only induce direct lethal (Delnat et al, 2020; Hua et al, 2013; Kafula et al, 2022) but also sublethal effects such as physiological and life history changes (Aliouane et al, 2009; Palma et al, 2009; Thoré, van Hooreweghe, et al, 2021).…”