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A Review Of The Combined Stress From PH And Microplastic Derived Odours On The Carcinus Maenas Olfactory Capacity

Ohnstad, Hannah


Hannah Ohnstad



In recent years, a large amount of research has been done on climate change, which predicts ocean acidification (OA) will end up causing a significant drop in the pH of the oceans by the end of the 21st century. Research carried out looking at pH reduction in the oceans show that a drop as little as 0.5 units can cause issues with behaviour and detection of cues in crustaceans. This drop in pH (0.5 units) is predicted to have occurred by the end of this century.
Ocean acidification is causing a wide range of problems including, coral bleaching, warming oceans and shell calcification within certain calcifying species. Every marine species is facing slightly different challenges. While there is considerable data looking at the overall impact on calcifying organisms, relatively little research has been undertaken examining the impacting animal sensory systems (olfactory disruption), as it is considered an ‘invisible’ impact of ocean acidification.
The main objectives of this study are to investigate the impact of reduced pH and microplastic odour on the olfactory capacity of the Carcinus maenas, looking in detail at whether the combination of the stressors has a greater impact on olfactory capacity in this crab species.
The European shore crab (Carcinus maenas) is a globally invasive species, it originates in European waters but has now spread to foreign waters and can be found globally in places such as the Southeast USA, Australia and South Africa. Like many crustaceans, Carcinus utilise chemical cues to detect food and mating partners. The aim of this study is to obtain a greater understanding of how a combination of stressors (pH and microplastic derived odours) may impact the olfactory capacity of the Carcinus maenas and whether these stressors may influence the behaviours exhibited. Plastic odour, food cues and a female produced sex pheromone cue are the chemical cues being used in this study. Males and females will both be used within the study as females may respond to the pheromone for other reasons, such as a food source from a moulting female.
Uridine diphosphate (UDP) and Uridine triphosphate (UTP) make up the pheromone bouquets used, the food cue is made from Glutathione (GSH) and the plastic odour is created from Polyethylene (PE). All cues stated above were made into gels using carboxycellulose powder and then freeze dried. The Carcinus were exposed to all gels, in pH 8.2, 7.6 and 7.2.
The results from this study show that Carcinus maenas took longer to react to the odours in the reduced pH conditions, confirming low pH causes olfactory disruption. This finding was significant when comparing data from pH 8.2 and pH 7.2 (p=0.0017). The Carcinus maenas has also shown behaviour (burying etc) that indicates that the combination of low pH with the microplastic odour present worsens this effect on olfactory capacity.
The findings from this study show similar results to other studies carried out on the impacts of ocean acidifications on different marine species, backing up the theories of low pH causing olfactory disruption. Further research in the field would help to determine whether long-term exposure to these low pH levels could lead to adaptations within crustaceans and other marine species. It would also help to determine the long-term impacts of a combination of microplastics and reducing pH within the environment, and how this combination may affect food consumption and predator avoidance.


Ohnstad, H. (2022). A Review Of The Combined Stress From PH And Microplastic Derived Odours On The Carcinus Maenas Olfactory Capacity. (Thesis). University of Hull. Retrieved from

Thesis Type Thesis
Publication Date May 1, 2022
Deposit Date May 25, 2023
Publicly Available Date May 25, 2023
Keywords Biological sciences
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Thesis (2.2 Mb)

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© 2022 Hannah Ohnstad. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.

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