Odours from marine plastic debris induce food search behaviours in a forage fish

Abstract

Plastic pollution is an anthropogenic stressor in marine ecosystems globally. Many species of marine fish (more than 50) ingest plastic debris. Ingested plastic has a variety of lethal and sublethal impacts and can be a route for bioaccumulation of toxic compounds throughout the food web. Despite its pervasiveness and severity, our mechanistic understanding of this maladaptive foraging behaviour is incomplete. Recent evidence suggests that the chemical signature of plastic debris may explain why certain species are predisposed to mistaking plastic for food. Anchovy ( sp.) are abundant forage fish in coastal upwelling systems and a critical prey resource for top predators. Anchovy ingest plastic in natural conditions, though the mechanism they use to misidentify plastic as prey is unknown. Here, we presented wild-caught schools of northern anchovy () with odour solutions made of plastic debris and clean plastic to compare school-wide aggregation and rheotactic responses relative to food and food odour presentations. Anchovy schools responded to plastic debris odour with increased aggregation and reduced rheotaxis. These results were similar to the effects food and food odour presentations had on schools. Conversely, these behavioural responses were absent in clean plastic and control treatments. To our knowledge, this is the first experimental evidence that adult anchovy use odours to forage. We conclude that the chemical signature plastic debris acquires in the photic zone can induce foraging behaviours in anchovy schools. These findings provide further support for a chemosensory mechanism underlying plastic consumption by marine wildlife. Given the trophic position of forage fish, these findings have considerable implications for aquatic food webs and possibly human health.

The ecology of an olfactory trap

“…In the summer of 2015, I tested this question on Northern Anchovy (Engraulis mordax), an ecologically critical forage fish species and known plastic consumer (2). Anchovy responded to odors of food and plastic debris similarly, increasing clustering behavior and reducing school-wide rheotaxis in a manner that is characteristic of olfactory search (12). These behaviors are consistent with foraging in this species.…”

A Global Perspective on Microplastics

“…Savoca et al () hypothesized that the odor of dimethyl sulfide‐related chemicals that accumulated on plastics increased their consumption by sea birds. Savoca et al () later observed that aqueous leachates generated from weathered/biofouled polypropylene beads resulted in foraging behavior in the northern anchovy ( Engraulis mordax ) mimicking that observed when extracts of food were provided. Exposure to unfouled beads did not elicit such a response.…”

Micro‐by‐micro interactions: How microorganisms influence the fate of marine microplastics

“…Other studies have demonstrated that biofilm formation is not essential to increase the attractiveness of microplastic to marine grazers, such as copepods; microbeads spiked with DMS were sufficient to induce selective feeding in copepods (Procter et al ). In addition, olfactory mechanisms were also implicated to activate the ingestion of plastic debris by fish (Savoca et al ).…”