Here for a Good Time or a Long Time?

For the goldfish in Cootes Paradise, there isn’t much of a choice.

In 2017, a study investigated the impacts of anthropogenic contamination in multiple sites downstream of a wastewater treatment plant (Simmons et al., 2017). This water discharges into Cootes Paradise Marsh, leaving it polluted with various pharmaceuticals and personal care products. Simmons et al. found that chronic exposure to the contaminated environment resulted in high neurotransmitter concentrations in goldfish plasma, with one of the most prominent being serotonin (Figure 1).

Figure 1: A graph showing the activity of goldfish at three different locations (Simmons et al., 2017). The red and orange bars indicate two sites along the Cootes Paradise Marsh and the green bar shows the control site used in the study. The control site is at Jordan Harbour, a conservation area in Lake Ontario. These results indicate that the goldfish in both locations at Cootes Paradise have significantly higher activity levels than at the control site.

Well-known for its ability to make you happy and feel good, serotonin is a neurotransmitter that controls a range of neuropsychological processes, including mood, perception, appetite, and attention (Berger, Gray and Roth, 2009). Selective serotonin reuptake inhibitors (SSRIs) are used to create medications for numerous psychological disorders to increase serotonin concentrations in the synaptic membrane (Nutt et al., 1999). In turn, this allows for therapeutic effects in conditions such as depression and obsessive-compulsive disorder. While helpful for humans, SSRIs pose a much greater risk for fish and other aquatic organisms.

SSRIs block presynaptic serotonin transmitters and prevent the expulsion of synaptic serotonin, which causes elevated concentrations in the plasma (Prasad, Ogawa, and Parhar, 2015). In fish, this is exhibited by higher activity and exploratory behaviours, indicating a reduced sense of anxiety (Simmons et al., 2017). However, the ability to estimate predation risk diminishes. Through increased activity, the fish abide less by the predator avoidance phenomenon, increasing their chances of being attacked (Brodin et al., 2014).

Fish with higher serotonin levels are also more prone to dispersal, which is detrimental to the schooling structure that fish tend to live in. Schooling provides protection against predators, giving these fish an evolutionary advantage (Kasumyan and Pavlov, 2018). Additionally, the school provides foraging, reproduction, and migration advantages providing them with an evolutionary advantage over other species. When this critical behaviour is impaired, it puts the species at much higher risk of predation and lowers fitness. This is because fish release a chemical from epidermal cells when facing predation threat (Scott and Sloman, 2004). In response, surrounding fish exhibit predator avoidance behaviours such as decreased swimming and increased schooling. However, the observed anxiety-reducing (anxiolytic) effect of serotonin can reduce the response to these signals. When coupled with their exploratory tendencies under elevated serotonin levels, the animal faces slim odds of survival.

Although more research is required in this field, the effects of pharmaceutical contamination, notably those with SSRIs, are clearly harmful to the aquatic environment. So while the fish may be enjoying their zen lives right now, it is short-lived and action needs to be taken by us to ensure their long-term survival.

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Works Cited

Berger, M., Gray, J.A. and Roth, B.L., 2009. The Expanded Biology of Serotonin. Annual review of medicine, 60, pp.355–366. https://doi.org/10.1146/annurev.med.60.042307.110802.

Brodin, T., Piovano, S., Fick, J., Klaminder, J., Heynen, M. and Jonsson, M., 2014. Ecological effects of pharmaceuticals in aquatic systems—impacts through behavioural alterations. Philosophical Transactions of the Royal Society B: Biological Sciences, 369(1656), p.20130580. https://doi.org/10.1098/rstb.2013.0580.

Kasumyan, A. and Pavlov, D., 2018. Evolution of Schooling Behavior in Fish. Journal of Ichthyology, 58, pp.670–678. https://doi.org/10.1134/S0032945218050090.

Nutt, D.J., Forshall, S., Bell, C., Rich, A., Sandford, J., Nash, J. and Argyropoulos, S., 1999. Mechanisms of action of selective serotonin reuptake inhibitors in the treatment of psychiatric disorders. European Neuropsychopharmacology: The Journal of the European College of Neuropsychopharmacology, 9 Suppl 3, pp.S81-86. https://doi.org/10.1016/s0924-977x(99)00030-9.

Prasad, P., Ogawa, S. and Parhar, I.S., 2015. Role of serotonin in fish reproduction. Frontiers in Neuroscience, 9, p.195. https://doi.org/10.3389/fnins.2015.00195.

Scott, G.R. and Sloman, K.A., 2004. The effects of environmental pollutants on complex fish behaviour: integrating behavioural and physiological indicators of toxicity. Aquatic Toxicology, 68(4), pp.369–392. https://doi.org/10.1016/j.aquatox.2004.03.016.

Simmons, D.B.D., McCallum, E.S., Balshine, S., Chandramouli, B., Cosgrove, J. and Sherry, J.P., 2017. Reduced anxiety is associated with the accumulation of six serotonin reuptake inhibitors in wastewater treatment effluent exposed goldfish Carassius auratus. Scientific Reports, 7(1), p.17001. https://doi.org/10.1038/s41598-017-15989-z.