Plastic waste interferes with chemical communication in aquatic ecosystems

B Trotter,A F R M Ramsperger,P Raab,C Laforsch,J Haberstroh

doi:10.1038/s41598-019-41677-1

Abstract

Environmental pollution with plastic waste has gained increasing attention, as the contamination of aquatic habitats poses a challenge to these ecosystems. Plastic waste has direct negative effects on animals such as reduced growth rate, fecundity or life span. However, the indirect effects of plastic waste, which has the ability to sorb chemicals from the surrounding media, on chemical communication have yet to be investigated. Chemical communication is crucial for aquatic organisms, e.g., to avoid predation. The planktonic water flea Daphnia (Crustacea), an important link between trophic levels, relies on info-chemicals (kairomones) to assess its current predation risk and to form inducible defences. We show that plastic waste, composed of high-density polyethylene (HDPE) and polyethylene terephthalate (PET) interferes with the formation of inducible defences in Daphnia longicephala when exposed to a combination of kairomones of Notonecta glauca and plastic waste. D. longicephala shows a reduction in all defensive traits, including body length, crest width and time until primiparity, compared to exposure to solely kairomone conditioned media. Plastic waste in the absence of kairomones had no effect on defensive traits. Since it is vital to adjust these defences to the current predation risk, any misperception can have far-reaching ecological consequences. Therefore, plastic waste can have indirect effects on organisms, which may manifest at the community level.

Highlights

Humans have substantially influenced and modified ecosystems in the past by introducing anthropogenic pollutants and waste into these systems
D. longicephala were exposed to a single piece of high-density polyethylene (HDPE) or polyethylene terephthalate (PET) as macroplastic waste in combination with kairomones released by Notonecta glauca (I + HDPE and I + PET; see Fig. 1 for schematic experimental setup)
Further controls were: i, one treatment lacking kairomones and plastics (C); ii, one treatment with D. longicephala being solely exposed to HDPE (C + HDPE) or iii; PET (C + PET)

Summary

Introduction

Humans have substantially influenced and modified ecosystems in the past by introducing anthropogenic pollutants and waste into these systems. Plastics leach chemicals out of their matrices and adsorb and accumulate a multitude of organic substances onto their surfaces, forming a so-called eco-corona[7,8]. This condition leads to the question of whether semiochemicals, used in chemical communication among aquatic organisms, can adsorb to plastics. In Daphnia it has been shown that contaminants such as copper are interfering directly with the olfactory system, reducing the prey’s ability to detect the kairomone[15] It is not clear whether particulate anthropogenic litter, such as plastic waste, interferes with chemical communication as well by adsorbing chemical substances to its surface. This condition would result in the reduced formation of inducible defences as the process of the formation of these phenotypically plastic defences follows a dose response curve, as shown in studies by Tollrian et al.[10], Laforsch et al.[16] and Elert and Pohnert[17]

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