Invertebrates on the edge
“The space between the shifting tide-marks, that intertidal zone that changes its character twice each day from land to sea, can be a harsh place to live. “Only the most hardy and adaptable can survive in a region so mutable”(Rachel Carson, The Edge of the Sea). One high tide is never the same as the next, especially in an estuarine environment like the Solway: the mix of saline and fresh water, the amount of sediment, the predators, parasites and planktonic food, will vary every time … and on the edges the plants, algae and animals are exposed variously to desiccatingly hot sun or wind, or rain, sleet or hail.”
In 1881, the plates of ice were so thick that when they were swept out on the ebbing tide, they damaged the Solway Railway Viaduct that crossed the Firth from Bowness to Annan: you can read the extraordinary story of the construction, damage and demolition of the SJR and the viaduct, and see many more images, on the Crossing the Moss website, a project that photographer James Smith and I carried out in 2017/18.
Many of the Solway’s shores are expanses of sand, stippled with rocky scaurs and occasional boulders deposited by glaciers. Where can you live if you are an intertidal animal? On or in the sand, amongst the rocks and pebbles, or attached; you can build your own home too (and for more about sand and shores, see my essay Sand in Little Toller’s The Clearing.
Allonby Bay Marine Conservation Zone is home to the honeycomb worms, Sabellaria alveolata, which construct fine tubes of sand grains around themselves, building reefs which trap pools of water where other animals and algae take up residence. (There’s some basic information about Sabellaria here, and more on tube-construction here – in addition to those articles cited in the Notes section of the book.)
The Upper Solway is edged predominantly by mudflats and saltmarshes, the former home to millions of invertebrate animals like the ragworm Hediste, the mudsnail Hydrobia and the mudshrimps, Corophium – as well as billions of microscopic invertebrates, and billions of micro-organisms (see Chapter 7, Mudlife)
‘What’s the point of them?’ someone once asked me, referring to the marine worms we had found. Are invertebrates merely fodder for animals higher up the food-chain? As top predators, we too eat invertebrates like winkles, whelks, scallops and scampi (for more on Sea-food, see Chapter 8). ‘What’s the point of us? someone replied (there might be an answer in Simon Armitage’s poem at the end of the book …).