Anja Murray: Seaweed is a deep-sea treasure — when it's growing, and when it washes up on shore

In recent years, the nutritional value of seaweeds is gaining recognition and now it is considered one of the most sustainable opportunities for food production in a future where food security is increasingly in jeopardy. Picture: Denis Minihane

The storms have left their mark on the shores of Connemara. Dramatic gales blowing over the coast have left the sandy intertidal zone strewn with masses of washed-up seaweed. These great linear piles are as much as a metre deep in places — a gigantic squelch of tangled, slippery kelp.

The big flat, blades of kelp are a brownish, olive-green colour, attached to long stipes, or stems, that are like big rubbery sticks. Some are more than a metre long and as thick as my wrist. The kelps that have been washed ashore in such abundance here are strapweed, oarweed, and sugar kelp — all species of the family Laminaria, the kelps.

Out below the low tide, these kelps can grow as tall as four metres. When lots of them grow together, as they do, they are sometimes called ‘kelp forests’. Like terrestrial woodlands, dense forests of kelp are host to many creatures, from tiny worms and shimmering blue-rayed limpets to big fish and even seals. Kelp provides delicate seahorses with useful hiding places to avoid enemies and to capture unsuspecting prey. 

It is a rich habitat for crustaceans such as crabs and lobsters. Brightly-coloured sea anemones grow around the rugged base. Brittlestars and other starfish live among the kelp forests too. Some species of sharks, skates and rays tie their little egg cases, known as mermaid’s purses, to the kelp, where the embryo inside spends months developing. Many fish species find shelter from rough weather amongst the fronds of kelp and also lay their eggs in among the kelp beds too. Kelp beds are well-recognised as fish nurseries, without which many fisheries would be much the poorer.

More than 500 types of seaweed grow in the waters around Ireland, their uses have long been appreciated by coastal communities, mainly as food and fertiliser

Huge heaps of knotted wrack, serrated wrack and bladderwrack are washed up too, all along the top of the shore where the high tide has deposited them. The latter is easily recognisable by the air-filled 'bladders' that run down the length of each frond. Locally, the wracks are considered best for conditioning the soil to grow potatoes and vegetables. Late winter and early spring is when it is traditionally gathered from the shore after a storm, or harvested from shallow water in small boats to be let break down on vegetable beds.

Amid the great mounds of kelp and wrack are lots of other seaweeds too. My favourite is the bright pink dulse — also known as dillisk — that grows among the shelter of kelp and other big seaweeds. Dulse has always been the tastiest of seaweeds to eat, people would gather it up in autumn and keep a supply to chew on through the winter. There are clumps of dark green, aptly named tubes of ‘velvet horn’ scattered about the shore. Shiny shards of bright green eelgrass add a streak of vivid colour too, itself the basis of whole marine ecosystems.

The seaweed Palmaria palmata (common name Dulse) — and also known as dillisk

More than 500 types of seaweed grow in the waters around Ireland, their uses have long been appreciated by coastal communities, mainly as food and fertiliser. In recent years, the nutritional value of seaweeds is gaining recognition and now it is considered one of the most sustainable opportunities for food production in a future where food security is increasingly in jeopardy. But the wider value of seaweed and the marine habitats where it grows is also gaining recognition. Marine habitats also make a massive contribution to climate change mitigation and adaptation.

When all these seaweeds are growing in the shallows beyond the shore, they are not only crucial habitats for ocean wildlife, but they also help protect the shore from the force of stormy seas. Kelp forests, for example, buffer against the damaging impacts of storm surges by ameliorating wave energy. As a result, coastal erosion is reduced. With the intensification of severe storm events as a result of climate change, kelp forests and other marine habitats are a crucial ally in climate change adaptation, helping to protect coasts from damaging impacts of rising sea levels and more frequent storms.

Seaweed used as a mulch in the vegetable garden

On a much wider scale than seaweed, ‘blue carbon’ refers to the carbon captured and stored by the totality of marine life. A whole array of underwater habitats across the world’s oceans, including seaweeds and eelgrass, actively capture carbon from the atmosphere and help sustain vast reservoirs of marine carbon. In recent years, scientists have come to understand and quantify the dynamics of these carbon stores, and with this understanding, they are also recognising that the health of marine life is intrinsically connected to the wellbeing of all living creatures, including us humans.

Over the course of many millennia, vast quantities of carbon have accumulated in underwater habitats and seafloor sediments. Long overlooked, these carbon stores are now being assessed to better understand the processes of how the carbon is retained and how it is released to the atmosphere after disturbance. Bottom-trawling has been identified as having enormously negative impacts on climate, as it disturbs these stores of carbon-rich sediment. A recent study has found that bottom-trawling releases hundreds of millions of tonnes of carbon dioxide into the atmosphere each year.

The vital role of marine ecosystems is finally gaining prominence in climate change policy. As we recognise just how much these previously overlooked areas are for biodiversity, climate mitigation and adaptation, we cannot continue to consider them only in terms of what we can take from them. The only logical response is to safeguard the areas where these habitats occur and curtail damaging activities such as bottom trawling. Recognising the urgency with which emissions reductions are necessary, and the far-reaching value of marine habitats for all of earth’s systems, stronger action is needed.

Marine Spatial Planning and Marine Protected Areas (MPAs) are a major part of part of how this protection is carried out. This Government undertook to implement new legislation for Marine Protected Areas — promised by the end of 2023 — but it has not yet materialised. This cannot be allowed to fall by the wayside.