The marine algae of Lundy were most thoroughly described by Irvine et al. (1972) from fieldwork undertaken between 1968 and 1971. Their lists include almost all of the algae currently recorded around Lundy, although studies undertaken in the late 1970s added a further ten species, which brought the total to 316 species – a very rich flora. Since then, a few further species have been added, so the total is now around 320 species.
According to the first Marine Management Plan (Hiscock, 1983), some species very rarely encountered in the British Isles (as well as two species new to science) have been recorded.
The algal flora is distinctively south-western, with some Mediterranean-Atlantic species, such as golden kelp Laminaria ochroleuca and the brown foliose seaweed Carpomitra costata, present in large amounts and others, such as the red alga Schmitzia neapolitana, being listed as nationally rare.
Intertidal zonation
The intertidal zone (also called the littoral zone) is the area that’s exposed to the air at low tide and which is under water at high tide. At Lundy, this zone is dominated by rocky substrata, either as solid bedrock, boulders or cobbles/pebbles. The one patch of sand which occurs in the intertidal zone is close to low water level on the Landing Beach, derived from fragmented slate.
Where there are firm substrata available for organisms (both plants and animals) to attach to, those organisms will arrange themselves in horizontal bands across the shore, determined by the amount of exposure to the air they can tolerate. Those that can tolerate the most exposure will be found towards the top of the shore, whereas those that can tolerate the least will be close to the low water mark.
Certain brown seaweeds (which belong to a group only distantly related to the green and red seaweeds) dominate sheltered rocky shores, best exemplified at Lundy on the Devil’s Kitchen shore in the south-east of the island. Here can be seen an obvious band of channelled wrack Pelvetia canaliculata
at the top of the shore, giving way to bladderwrack Fucus vesiculosus
, then serrated wrack Fucus serratus
and thongweed Himanthalia elongata
(this last characterised by little mushroom-like holdfasts), as one progresses towards the lower shore. At low water, particularly on a spring tide, the large fronds of oarweed Laminaria digitata become apparent on the water surface, a seaweed whose stipe is particularly flexible and thus avoids being snapped by breaking waves.
The intertidal zone on the west coast of the island is completely different. Here, in rough weather, most foliose or leafy seaweeds would be ripped away so they are largely absent in the intertidal zone, though one, dabberlocks Alaria esculenta
, seems to be able to survive at around the low water mark. Here you’ll see much of the vertical granite rock covered by a layer of hard, pink, encrusting seaweed, toughened by its calcareous skeleton.
Algal species of conservation interest
The following species are listed in the Lundy Marine Management Plan (2017) or have been commented upon in recent Annual Reports of the Lundy Field Society (LFS AR).
- Tassel weed Carpomitra costata Batters, 1902 – a southern species found off the Channel Islands, south-west and western coasts of the UK, though recorded as far north as the Isle of Man, Donegal, Coll Island and St Kilda. Characterised by having little tufts of ‘hair’ at the tips of the fronds, it is regarded as being nationally scarce.
- Golden kelp Laminaria ochroleuca Bachelot de la Pylaie, 1824 – another southern species found off the south-west coast of England, including south Devon and Cornwall, the Isles of Scilly and Lundy, with Lundy being its most northerly location. As a kelp species, it has a light brown frond with a characteristic golden area at the base of the frond/top of the stipe. The stipe is round in cross-section and clean of any attached seaweeds (helping to distinguish it from hyperborea). It is found from low water spring tide level down to 20 m, mixed in with both L. digitata (in the shallows) and L. hyperborea (in deeper water). Between the years 2004 and 2010, the proportion of L. ochroleuca in kelp forests in Gannets’ Bay increased dramatically.
- Sea noodle Nemalion elminthoides (Velley) Batters 1902 – “Noted as abundant on the mid to upper shore at Devil’s Kitchen during the Marine Bioblitz in 2022. Described as generally distributed around Britain but mostly as small plants. At Lundy, described as ‘locally abundant’ in Irvine (1973) at locations all around the island and likely that it is a ‘Lundy speciality’.” (Hiscock, 2022 LFS AR)
- Brown Tuning Fork Weed Bifurcaria bifurcata – “Notable here because it was not recorded at Lundy in the late 1940s and early 1950s by Leslie and Clare Harvey (Harvey, 1952) or by Tregelles (1937) but was by Irvine et al. (1972). It is a warmer water species that has possibly extended its range since the 1940s. In July 2022, during the Marine Bioblitz, the Porcupine Marine Natural History Society team visited the upper mid-shore rockpool on the offshore rock south of the Lametor peninsula and observed that the percentage cover of the species (the mean of three estimates) was 28%, which was about that of the first assessment measured in 1984 of 27% (Hiscock, 1984).” (Hiscock, 2022 LFS AR)
- Bushy Rainbow Wrack Ericaria selaginoides (was Cystoseira tamariscifolia) – This species is noted for its iridescence in bright light conditions. “There has been one clump in a pool at Devil’s Kitchen for many years but no others in the Landing Bay and Rat Island area despite apparently suitable habitats being present. The Devil’s Kitchen plant was ‘infested’ with a Ceramium species in July. The species was found to be more abundant in pools south of the Lametor Peninsula during 2022. In discussion with phycologists on the Marine Bioblitz surveys, it was wondered if, for a likely long-lived species, there may have been collecting in the distant past and lack of recruitment.” (Hiscock, 2022 LFS AR)
