Found on strandline beside Strangford Narrows - very fast tidal currents. Glove is 28 cm long
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...edit and move to plants (all seaweeds are plants) - you will get more help from the right group area and the correct carousel pictures :)
... for iSpot purposes, not all algae fall within even the widest concept of plant as currently accepted by taxonomists. Red and green algae do, but brown and golden algae don't.
The narrowest conception of plants includes land plants (and derived forms like sea grasses) only; the intermediate conception adds green algae; and the broadest additionally adds red algae and glaucophytes.
This may change if it turns out that Archaeplastida turns out to be paraphyletic.
Did your local algologist say what particular features s/he based the ID on? I believe the stipe of L. digitata is oval in cross section while that of S. latissima is round. ISpot can be very useful to others when such details are given. Did s/he have an answer to your own question about the warty surface of the frond?
I've asked her to get involved here, rather than my trying to be a go-between. She sent me a photo of another local L. digitata (cape form). It's at https://www.dropbox.com/s/9yxio4b14wvwgxg/Laminaria%20digitata%20cape%20...
....still see the fingers in your friend's pic :)
I wonder if there are two species here?
Picture 1 certainly looks to me like Sugar kelp (under any Latin name).
Photo 2 does not seem to contain the palmate fronds shape of oar weed, but it is not spread out. It certainly does not seem to have the length of Sugar kelp but maybe it is new growth.
I note that the glove seems to change position in the photos
Great photo from you friend, Isobel. What an interesting topic this ID is becoming. I would like to add this to the discussion from the excellent book, Bunker, Brodie, Maggs & Bunker 2010 Seasearch guide to seaweeds of Britain & Ireland Marine Conservation Society.
"In sheltered situations the frond of S. latissima expands width-ways into a broad cape form that can be virtually indistinguishable from L.hypoborea, especially in sheltered sea lochs. L. digitata can be distinguished from these other two species by the oval shape of its stipe."
And still no agreements.
This is a complex case and probably deserves even more consideration (than mine) but the lack of dimples (though you mention 'warty') on the frond, even length of stalk suggest to me that this may not be Sugar Kelp.
There's a lovely pictures of 'capes' here http://en.wikipedia.org/wiki/Saccharina_latissima but one can still see the dimples.
And yet none (well, nearly none) of the hundreds of Google images of Laminaria digitata show single fronds.
Picture two almost certainly shows one or other of the main Laminaria (kelps).
So yes, the post has two species (I think) and one might be of slightly unusual Sugar kelps (Saccharina latissima).
I now have a little, but intensive, experience of round vs oval stems and I have found that round ones are often flattened (more oval) near the frond! One has rough stems, the other smooth (it says in books) but roughness often appears in stranded examples, sometimes created by abrasion. The converse is also true that rough ones become smoothed by the tumbling action on the beach. Such helpful prose eh?! Sorry.
>>A SEAWEED PROJECT UK<<
A SEAWEED PROJECT UK
Lat/Lng: 54.3797, -5.5708
OS grid ref: NW682041
On strandline beside Strangford Narrows