A Walk Along the Shore

It is March!

I know that the best seaweed foraging months are between March and October, so here I am — an early bird down at the beach, scanning the rocks for the first signs of spring growth. I can’t help myself.

Strapped to my chest in a sling is my 14 month old, fast asleep as I walk slowly along the shoreline. His head is tucked against my jumper, warm and oblivious to the cold morning air.

One of the quiet pleasures of walking the shoreline is how it connects us to the cycle of the seasons. Each year when the foraging season begins again, I am transported back twelve months — to where I was and what I was doing at this same moment the year before.

“This time last year, you were only weeks old,” I whisper to the baby.
 “We’ve really got some catching up to do.”

He snores softly in response.

We arrive at the beach about one hour before low tide, on a full moon.

The sea has already pulled far out, revealing wide stretches of wet sand, rockpools, cliff faces and exposed rocky shelves that only an hour earlier were underwater.

Before long, I spot something familiar.

A small patch of pepper dulse, tucked into a rocky crevice where I find it every year. I nibble a tiny piece while the baby sleeps peacefully through the moment.

Pepper dulse thrives here in a north-facing crevice, sheltered beneath a small patch of bladderwrack in the middle intertidal zone.

He notices none of this, of course. He is in a deep sleep now.

 

Seven things worth noticing ...

So ... If you and I were to talk a walk along the beach together and you said to me - tell me about seaweed foraging ...  then I would say ... well, the first step is to start noticing and paying attention.

Then, I would walk you through seven short lessons to help you begin to understand how the shoreline works.

And I'd hope you are paying attention and an active listener. Because my small baby is going to snore sleep through this entire walk.

 

Lesson 1. Find the High Tide Line

The high tide line is the highest point the sea regularly reaches.

We can usually spot it easily.

Walk along the beach and look for a line of debris along the beach — fragments of seaweed, shells, driftwood and, sadly, these days, pieces of plastic rope or litter.

This line marks the boundary where the sea reaches during the highest tides.

Everything above this line is rarely submerged. Everything below it is influenced by the tide.

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Lesson 2. Look for the Low Tide Line

The low tide line marks the furthest point the sea retreats during low tide.

Most of the time this area is underwater. It only becomes visible for a short period each day when the tide goes out.

During spring tides, which occur around the full moon and new moon, the sea retreats even further and exposes more of the shoreline.

This is when many of the deeper seaweeds become visible.

 

“Around the Irish coast tidal ranges vary from around 1.75 metres on the southeast coast of Ireland to an average of 4.5 metres on the west coast.”

 

Lesson 3. Observe the Expanse of the Intertidal Zone

The area between the high tide line (that distinct line of dried seaweed) and the low tide line (most likely submerged in water) is called the intertidal zone.

You may also hear it called the foreshore.

Over the course of a typical 12-hour tidal cycle, this area experiences dramatic changes.

At low tide, it may be exposed to wind and sunlight. A few hours later, the same rocks may be completely submerged beneath cold seawater.

Seaweeds and marine animals that live here must survive these constant shifts in temperature, moisture and salt levels.

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Spiralled wrack, bladderwrack, and eggwrack grow in the upper areas of the shoreline. When we find these “wracks” growing abundantly, it is an indicator of a sheltered area of shoreline.  

In a more exposed area of rock face, on the same beach, we find much less seaweed cover.

Lesson 4. Notice the Three Levels of the Shore

Within the intertidal zone there are three broad levels, each supporting different species.

Upper Shore

The upper shore sits closest to the high tide line.

This area is covered by water only during the highest tides and spends most of its time exposed to air.

Hardy species live here such as:

• barnacles

• limpets

• mussels

• channelled wrack

Channelled wrack has small grooves along its fronds that help it hold moisture when the tide goes out.

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Middle Shore

The middle shore is covered and uncovered by the tide twice each day.

Because conditions here are less extreme, it supports a greater variety of life.

Here you may find:

• bladderwrack

• sea lettuce

• pepper dulse

• anemones

• small crabs

This is often the most interesting zone for beginner seaweed foragers.

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Lower Shore

The lower shore is underwater most of the time and only exposed briefly during low tide.

Here you will find many of the larger seaweeds, including:

• dulse

• nori

• carrageen

• sea velvet

During particularly low tides you may even reach the edges of kelp forests, where species such as sugar kelp, oarweed and Atlantic wakame grow.

These kelp forests create important underwater habitats for fish, invertebrates, seabirds and marine mammals. 

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Upper Shore: At low tide, you might notice stripes of colour across a cliff face or rocks.

Upper Shore: Intertidal zonation marks like those in the image above are a reminder of the changing sea levels across the tide and across the month.  

Upper Shore: Note in the upper part of this image is the 'splash zone’ - here we can see some lichens alongside some dried out sea campions. Late in the year this section of the rock face will be fluttering with flowers. 

Upper Shore: The distinctive channelled shape of channelled wrack is said to allow this seaweed to trap water for longer and so allow it to thrive in the drier upper reaches of the intertidal zone.

Middle Shore

The lower shore is virtually always underwater except during low tides. Here you will find dulse, nori, sea velvet, and carrageen in the upper reaches and in the lower sections of the lower shore, accessible on a Spring tide, you will find sugar kelp, oarweed, and alaria.

The subtidal zone is below mean low tide and is rarely, if ever, exposed. 

Lesson 5. Look for Hard Surfaces

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Seaweeds do not have roots like land plants.

Instead, they attach themselves to rocks using a structure called a holdfast.

The holdfast is the small, gnarly base that anchors the seaweed to hard surfaces.

Because of this, seaweeds usually grow where there are:

• rocks

• boulders

• cliff faces

• rock platforms

Even on sandy shores, seaweeds may grow if there are shells or stones available for them to attach to.