Shore crab

Shore crab.

Plastic ingestion means less energy available for growth in shore crabs

A new study, led by Dr Andrew Watts at the University of Exeter, has shown that the ingestion of tiny plastic rope fibres by shore crabs leads to a reduction in food intake resulting in less energy available for growth.

Microplastics (< 5mm) are found in abundance along shorelines globally and comprise of either manufactured particles, such as microbeads found in cosmetic exfoliates or as fibres/fragments of larger pieces of plastic, degraded from exposure to the elements.

In the present study recently published in Environmental Science & Technology, the team investigated the effect of plastic ingestion on food consumption and energy allocation in the shore crab, Carcinus maenas.  Feeding trials exposed crabs to a diet consisting of homogenised mussels that contained up to 1% (by weight) polypropylene rope fragments, obtained by freezing and grinding rope to  replicate fibres found in the environment.  The plastic fed crabs consumed less food as the trial progressed driving a decreased scope for growth (the available energy after other metabolic costs have been deducted) by the end of the 4 week test period.   Dr Watts suggests that C. maenas may have the ability to preferentially choose non-contaminated food when the supply is high enough which could have resulted in the decreased overall consumption rate. However, other organisms with less discriminate feeding capabilities may be at greater risk of depleted energy reserves, potentially impacting on life history traits such as reproductive success, as has been reported in a previous study at Exeter on zooplankton.

The team also found that when passing through the gut and gastric mill of the crab, the physical properties of the fibres appear to alter, causing the breakdown and fracturing of the filaments.  This may make them bio-available to a greater range of organisms.

A wide range of marine organisms have already been reported to ingest microplastic particles, from zooplankton - the smallest creatures in the sea, to whales and whilst there is a growing body of evidence demonstrating plastic ingestion, the  potential biological consequences are just starting to emerge.

The full text can be found in the article below:

Watts, A. J. R., Urbina, M. A., Corr, S., Lewis, C. & Galloway, T. S. (2015) Ingestion of Plastic Microfibers by the Crab Carcinus maenas and Its Effect on Food Consumption and Energy Balance. Environmental Science & Technology, 49, 14597-14604.

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Article written by Rachel Coppock, Biosciences Press Gang.

Date: 11 January 2016

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