Winter 2004

The Strandline - Just a load of old rubbish?

Article by Paul Wisse, Information Officer, Coastal Defence Sefton Council

Natural debris left on to the shore by the tide, the strandline, can appear lifeless and unattractive. However, hidden within the debris is a hectic community of scavengers, predators and parasites.

The strandline can change day by day and include anything that occurs in the sea and along coastlines, but most commonly seaweed. Unfortunately the tide may bring up litter and other human refuse that we carelessly dispose of.

A well-formed strandline can become home to a varied community of organisms. This complex community feeds on the materials making up the strandline, each other and are themselves preyed upon by higher organisms such as birds and mammals. Beetles, woodlice, centipedes, spiders, flies, other insects and nematode worms are all common inhabitants. However, it is often dominated by a few specialised invertebrate species such as the sand hoppers, which jump erratically when the strandline is disturbed, and seaweed flies, which can swarm in large numbers. These specialists are normally endemic to the strandline.
Sand hopper, Talitrus saltator. Copyright Paul Wisse
Sand hopper, Talitrus saltator, one of the dominant species in the strandline on the Sefton Coast. Actual size 15mm - 20mm.

A natural strandline can have many benefits to the shoreline upon which it is deposited. This stranded material can be a major source of nutrients for the beach fauna and flora. On coastal dune systems it is thought that the strandline can act as a precursor to the formation of embryo dunes by providing nutrients, protection from the wind, waves and thermal stresses for young plants.

The habitat is important along the Sefton Coastline, as many species come to feed on the stranded material and the inhabitants of the strandline. Wading birds such as oystercatcher, ringed plover, dunlin and knot are frequent visitors. The nationally scarce natterjack toad visits in late summer to feed up for its winter hibernation. One of the best place to explore the strandline is at Ravenmeols, Cabin hill, and Birkdale Beach.

The inhabitants have to cope with a variety of stresses including habitat disturbance, desiccation (water loss), thermal stresses and predation. The amazing sand hoppers have developed a number of physical and behaviours characteristics to help them survive in this habitat. They have only relatively recently left the seas and their major stress is desiccation. They have a thick waxy cuticle to reduce water loss, they are nocturnally active (only active at night) when its cooler and during the day burrow into sand until they reach a moist layer or remain hidden under strandline debris.

Sand hoppers also use a variety of universal cues such as the sun, moon, magnetic compass, polarized light and local cues such as landscape, wave action and slope to navigate across the shore to find their food and their way back to safe burrowing areas.
Sand hopper, Talorchestia deshayesii. Copyright Paul Wisse
A male sand hopper, Talorchestia deshayesii, one of the other species in the strandline on the Sefton Coast. Actual size 10mm-15mm.