Simple Summary
The European shore crab, Carcinus maenas, also known as the European green crab, uses its sense of smell to detect prey, predators, and mating partners. Here, we examined how such crabs behave in environmental conditions that simulate the changes predicted by climate change. Crabs were exposed to female sexual odours, food smells, and various types of plastic leach outs. A decreased pH altered the crab’s behaviour towards food (Glutathione) and sex odour, reducing the animal’s response levels and increasing reaction times. Most interestingly, the crabs were more attracted to polyethylene (PE) odour in future ocean conditions, whilst males’ responses to female sex cues were especially reduced significantly. Response-level changes vary between the sexes, highlighting that understanding the effects of climate conditions on animal behaviour and choices is complicated and difficult to predict. That crabs become more attracted to plastic raises the question of what the bioactive chemicals are in PE that induce such a response, and this could demonstrate how climate change potentially increases the risks associated with plastic pollution in future oceans.
Abstract
Ocean acidification (OA) associated with climate change is expected to lower the ocean’s pH by 0.5 units by 2100. Whilst associated effects such as coral bleaching and shell calcification are well documented, lesser-known impacts are the ‘invisible’ effects on animal sensory systems. Olfactory disruption impacts the behaviour towards chemical cues in many marine species, including crustaceans. We examine the effects of microplastic odour and additional stressors on the European green crab C. maenas. Using uridine diphosphate (UDP) and uridine triphosphate (UTP) as a sex pheromone bouquet, glutathione (GSH) as a food cue, and polyethylene (PE) as plastic odour, cues were mixed with carboxycellulose to create slow-release gels. Crabs were exposed to gels in seawater pH values of 8.2, 7.6, and 7.2. Crabs took longer to react to all odours in reduced pH conditions (pH 8.2 to pH 7.2, p = 0.0017). At a low pH, PE-exposed crabs exhibited attraction towards microplastic odour and changed behavioural responses by burying. The study confirms low pH as disruptive to olfaction and highlights that plastic derivatives can become more bioactive at reduced pH levels, potentially increasing the threat posed by microplastic pollution. Further research is required to determine the potential long-term impacts of the combined threat of microplastics and reduced pH in the environment.
Ohnstad H., Burnett J. & Hardege J. D., 2025. The effects of combined stress from pH and microplastic-derived odours on the European green crab Carcinus maenas’s olfactory behaviour. Animals 15(4): 464. doi: 10.3390/ani15040464. Article.
