Country diary: sandhoppers are nature’s refuse workers

Langstone Harbour, Hampshire: As they break down rubbish on the strandline, the tiny crustaceans may however be contributing to the spread of secondary microplastics

With my back to the sea, I paced out a five-metre-wide transect and began methodically surveying the shore, working my way up the exposed shingle towards the high-tide mark. I was taking part in the Big Seaweed Search – a citizen science project that aims to investigate whether sea temperature rise, ocean acidification and the spread of non-native species is affecting the distribution and abundance of 14 indicator seaweeds.

The seaweed was growing in an uninterrupted three-metre-wide band that arced around the bay. Long skeins of pea-green gutweed were interwoven with flattened, tawny-coloured fronds of bladderwrack and spiralwrack, and an unfamiliar species that had tiny, spherical air bladders clustered along its wiry branches. According to my field guide, it was Japanese wireweed, an invasive alien.

The weed deposited along the strandline was sun-bleached and studded with marine detritus – dead crabs, cuttlebones, spongy balls of common whelk egg-cases and the ubiquitous litter of single-use plastics. Peeling back the mat of vegetation, I exposed a pulsing mass of sheltering sandhoppers (Orchestia gammarellus). With their semi-translucent segmented bodies and oversized hind legs, they looked like composite creatures – part shrimp, part woodlouse, part flea. They can jump up to 30cm by rapidly flexing and releasing their abdomen and telson (a flap-like tail), and I could feel them ricocheting off my shins as they leapt for cover.

An adult sandhopper (Orchestia gammarellus). Photograph: Steve Trewhella/FLPA/Rex/Shutterstock

Omnivorous scavengers, sandhoppers are nature’s refuse workers, helping to break down the vast quantities of dead and decaying material washed up on our shores. However, research undertaken by the University of Plymouth in 2017 revealed that these amphipods may actually be contributing to the spread of secondary microplastics within the marine environment. By monitoring them in the laboratory and on the shoreline, scientists discovered that they could shred a single plastic carrier bag into 1.75m microscopic fragments, with microplastics subsequently being found in their faecal matter.

It’s a sobering thought, considering that, by the time I reached the top of the beach, I had picked up a takeaway coffee cup lid, a tattered supermarket bag, a sandwich wrapper, two deflated balloons, three disposable drinks bottles, a shotgun cartridge case and a sheaf of straws and cotton-bud sticks.


Claire Stares

The GuardianTramp

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