Saturday, 4 April 2020

I is for Intertidal

Please remember! We ask that people do not visit the Reserve particularly if you have to travel. All car parks on Holy Island are closed to visitors until government restrictions are lifted. Many residents on Holy island fall into the vulnerable category. Please adhere to these guidelines for the health and safety of yourself and others during this time

Lindisfarne National Nature Reserve covers some 3,500 hectares but the majority of this gets covered twice a day by the sea, cutting off Holy Island to the outside world for a few hours at a time. To some the intertidal areas look like blank canvases of empty land but nothing could be further from the truth. These areas are teeming with life both above and below ground. Twice a day the ebb and flow of the tide bathe thousands of acres of the Reserve in the nutrient rich waters of the North Sea providing the life blood for millions of worms, winkles and mussels filtering their food through the tidal current. It is these animals that draw thousands of waders to the Reserve to feed. Armies of birds can be seen marching in and out with the tide, furiously feeding, with each species having a different bill shape adapted to poke into the thick mud to reach their favoured quarry.
Waders feeding on the tideline ©JJD
As well as the mud and sandflats the intertidal area includes the salt marsh. The variation in the frequency and length of time of tidal inundation creates a zoning of salt marsh species adapted to different conditions. The lower salt marsh contains the plants that are most tolerant of the briny water. Plants such as Glasswort and Spartina can be found here. This moves in a sliding scale to the upper saltmarsh which is full of plants that are less resilient of salt. The harsh conditions allow a diverse range of plants to bloom without being outcompeted by another.

Photo showing upper to lower Salt marsh ©JJD
Aside from nutrients and food being bought in on the tide the water can also bring and take away sediment and sand, sculpting the shape of the coastline, although the Reserve is largely accreting. This gives the Reserve a very dynamic and transient feel, never the same, always constantly changing.

Sunsetting over the intertidal area at Lindisfarne National Nature Reserve ©JJD


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