• Ben Porter

Strandline seaweeds

I know what you're thinking: that doesn't sound like the most glamorous of autumn spectacles to witness whilst you're on Pen Llŷn! But read on - you'd be surprised!

Carrageen, also known as Irish Moss

Seaweeds (gwymon) are an overlooked, under-appreciated and yet vital component of our coastal ecosystems. Here on Pen Llŷn, a key part of our coastal habitats are the kelp 'forests' that flourish in our cold water and temperate seas; carpeting the seabed and rocky intertidal zone in a canopy of leafy fronds and harbouring an immense diversity of species. Anyone that has spent time diving or snorkelling amidst these remarkable habitats can attest to the hustle and bustle of life that most would associate with the colourful coral reefs of the tropics!


A Snakelocks Anemone sways in a gentle underwater current amidst the fronds of kelp off Bardsey Island (Ynys Enlli)


Like the leaf-fall of deciduous woodlands, many seaweeds like Kelp (Môr-wiail byseddog) shed their fronds in the autumn, ridding themselves of the overgrowth of marine life that burdens the fronds after a summer's growth, and making way for the fresh growth come spring. These fronds and seaweeds wash up in their tonnes around the beaches of Pen Llŷn, sometimes swept into immense mounds during fierce storms.


Seaweeds washed ashore on the rocky strand line of Porth Neigwl

These piles of seaweed and kelp provide a rich source of food for a whole plethora of invertebrates, which in turn are feasted upon by gulls, pipits, wagtails, starlings, crows and even Choughs! And it's not just the wildlife that has a field day when piles of this rich organic matter wash ashore: seaweed is sought after by gardeners to apply to gardens as a natural fertiliser and a mulch.

At a more aesthetic level, taking a look at the colours, patterns and structure of the seaweeds washed ashore can present just as dazzling a display as the colours of autumn leaves on deciduous trees! Species like the Carrageen seaweed, also known as Irish Moss, are particularly immaculate: the fan-like branching structure can appear in browns, reds, vivid pinks, whites, yellows and iridescent blues.



A bright pink Carrageen frond amidst the tougher fronds of kelp
A vivid array of colours erupts as some kelp and Irish Moss begins to decompose
Another whiter shade of Carrageen with other seaweed species thrown up on the strand line

So next time you're walking along one of Pen Llŷn's beaches in autumn and winter and stride past the piles of rotting seaweed, delve a bit deeper and appreciate the story these overlooked algae have to tell.

And so whilst the risk of rain, thundery showers, cold winds and seaspray might stem the enthusiasm to get out during autumn, the scenes rewarding those adventurous enough to venture out can be spectacular. I'd argue it's worth the downpours for the spectacles we're so lucky to enjoy in this amazing part of North Wales.