Exposure to a common antidepressant alters crayfish behavior and has potential subsequent ecosystem impacts

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Abstract

Abstract Pharmaceuticals are ubiquitous in aquatic environments, yet little is known regarding their impacts on ecological processes. Selective serotonin reuptake inhibitors (SSRIs) are frequently prescribed human antidepressants and have been shown to alter crayfish behavior. These behavioral alterations are particularly relevant as crayfish play a central role in freshwater ecosystems and often reach high biomass in anthropogenically influenced environments commonly exposed to pharmaceutical contamination. Using a 14‐d artificial stream experiment, we exposed spinycheek crayfish ( Faxonius limosus ) to citalopram, a common SSRI, at an environmentally realistic concentration (0.5 µg/L). We used a Y‐shaped flume to quantify the effects of SSRI exposure on crayfish behavior and food/conspecific preference. We also tested the interacting effects of citalopram and crayfish on habitat‐specific and whole‐stream ecosystem functions and biomass. Crayfish exposed to SSRIs exhibited increased boldness (time to emerge from shelters; P < 0.05) and spent more time orienting to food resources than nonexposed crayfish. Crayfish increased water column chlorophyll a ( P < 0.01) and benthic organic matter ( P = 0.03). Furthermore, crayfish potentially increased water column respiration ( P = 0.09) and potentially decreased nitrate uptake ( P = 0.05). SSRI exposure exhibited a potential effect of decreasing benthic chlorophyll a ( P = 0.07), but there were no significant CRAY+SSRI interactions. Neither crayfish nor SSRI treatments affected whole‐stream metabolism. These results suggest that citalopram has the potential to affect algal biomass but did not affect ecosystem functioning. However, alterations to crayfish behavior driven by SSRI exposure could lead to subsequent ecosystem‐level effects as crayfish did affect various response metrics. We were unable to detect the effects of altered crayfish behavior at the ecosystem scale during our study, likely due to the short time frame (2 weeks) of our experiment. Further work is needed to quantify longer‐term ecosystem consequences of sublethal effects of pharmaceuticals, but these results show that ecological responses to pharmaceuticals should consider the entire ecosystem.

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