This seaweed is renowned for its shimmering hues, which can shift between blue, green, and bronze in bright light. Its delicate, branching fronds create a safe haven for small marine creatures like crustaceans and juvenile fish. Around Lihou, you might spot it in wave-exposed pools where oxygen-rich waters support its vivid, iridescent display.

This invasive seaweed, introduced from the Pacific, forms dense tangles that can entangle marine life or foul boat propellers. Its wire-like stems and tiny floats make it easy to identify once you know what to look for. Around Lihou, large patches may appear in calm, shallow pools, potentially outcompeting native seaweeds for space and light.

These dark green, spongy fronds have a velvety surface and retain water well, making them soft to the touch even when exposed. Often referred to as “Green Sponge Finger,” it is sometimes found in calmer waters. Around Lihou, you may discover patches of Velvet Horn in deeper pools at low tide, feeling surprisingly squishy if gently squeezed – careful not to cause damage.

Eelgrass is a true flowering plant adapted to life underwater, in contrast to seaweeds which are algae. Its meadows provide important nursery grounds for fish and invertebrates, stabilise sediments, and can store large amounts of carbon, potentially slowing climate change. Around Lihou, these seagrass beds help maintain water quality and serve as havens for young marine life seeking shelter from predators.

This kelp has a distinct midrib and wing-like fronds, with reproductive “sporophylls” near its base. It thrives in turbulent waters and can form dense patches, providing shelter for fish and invertebrates. Around Lihou, you might see it in the more exposed areas of the shoreline where waves stir the water vigorously, helping it remain well-oxygenated.

Laver is recognisable by its delicate, dark-purple or brownish-green fronds, which can become crisp when dried. It is traditionally eaten in Wales as “laverbread” and is also the basis for Japanese nori. On Lihou’s rocky shore, you may spot these translucent sheets clinging to stones at low tide, easily overlooked unless you look closely at the tide line.

Coralline algae deposit calcium carbonate in their tissues, making them firm and often pinkish-white when dried. These algae create miniature reef-like structures that shelter small invertebrates and help stabilise the surrounding habitat. Look for their rigid, branching forms in Lihou’s tidepools, where they may appear as clusters of pinkish “twigs” on rocks.

Irish Moss has a slightly translucent appearance and contains carrageenan, a natural thickener used in foods like ice cream and desserts. For centuries, people have harvested it for culinary and medicinal purposes. Around Lihou, small clumps might be tucked in shaded crevices of rockpools, especially at lower tides.

Dulse has a tougher texture than many seaweeds and a deep red-purple hue, making it easy to spot. It is sometimes eaten as a snack or used in cooking, and coastal communities have collected it for centuries. Near Lihou’s lower shore, you might find dulse mixed among kelp forests, offering a burst of colour in more sheltered areas.

Gutweed has bright green, hollow fronds that trap bubbles of oxygen, causing it to float near the water’s surface. In calm or nutrient-rich areas, it can form large floating patches, making it quite noticeable. If you explore Lihou’s upper pools at low tide, you might see clumps of gutweed bobbing or clinging to rocks.

Sea Lettuce is one of the easiest seaweeds to recognise, with its bright green, translucent fronds. It can thrive in high-nutrient conditions, sometimes forming large blooms. On Lihou, look for sheets of sea lettuce draped over rocks at low tide or floating in pools.

This kelp has slightly ruffled edges and is known for its mild sweetness when dried, hence the name “sugar kelp.” It is sometimes used in soups or as a wrap in cooking. Around Lihou’s lower shore, you might find it attached to rocks or larger boulders where conditions are not too rough.

Oarweed forms underwater “forests” where many small creatures find food and protection. Its stout, flexible stipe keeps it anchored, even in strong currents. Off Lihou’s rocky coasts, it can be seen when the tide is out far enough to expose its long, fingered fronds. You can also find detached fronds washed up on the beaches around Lihou after storms.

Thongweed begins as a small, button-shaped disc before growing into thin, ribbon-like “strings.” Some people refer to it as “sea spaghetti” because it is edible and has been used in certain coastal cuisines. On Lihou, look for it in deeper rockpools or attached to submerged rocks, especially during low tide when its long fronds may become more visible.

Recognised by its solitary, egg-like air bladders, Knotted Wrack can form extensive wrack beds crucial for coastal ecosystems. It offers shelter for juvenile fish and invertebrates, helping them avoid strong currents or predators. Around Lihou’s quieter coves, you may see dense patches of this wrack at mid-tide, providing feeding and hiding spots for marine life.

The fronds have a clearly toothed edge that makes Serrated Wrack easy to identify among seaweeds. It thrives in lively waters around Lihou, appearing darker brownish-green when out of the sea. By forming dense stands, it helps reduce wave impact on the shore, offering shelter to smaller organisms dwelling beneath.

Recognised by pairs of air-filled bladders along its fronds, Bladder Wrack floats upright in the water and shelters small crustaceans and snails. Around Lihou, its drifting fronds can form dense mats, providing both cover and feeding opportunities for marine life. Its presence signals relatively sheltered conditions, though it also tolerates moderate wave action.

Named for the slight twist in its fronds, Spiral Wrack has a flattened, forked structure and often forms bands along the upper shore. Around Lihou, it clings to rocks regularly exposed to air, tolerating fluctuating moisture between tides. It bears small swollen tips (receptacles) containing reproductive cells, ensuring its continued spread on wave-washed coasts.

Channel Wrack’s narrow fronds curl into a channel shape, helping them retain moisture during low tide. This resilience allows it to thrive higher on the shore than most other wracks. On Lihou, you can spot it forming small, dark patches on exposed rocks that receive little direct splash, highlighting its tolerance of harsh, drying conditions.