There was a very large seaweed 'sigil' across my path this morning. May I ask if there is a meaning?
It's alien writing. Although I haven't spent much time communicating with these aliens, my immediate impressions are that the symbol means: a language with no grammar.
The alien who wrote this feels like a juvenile from a race of miners that have been visiting Earth for millennia.✶ There are some tablets or petroglyphs in caves, left by them in Death Valley, as well at the headwaters of the White Nile in Africa.
I'm not sure that the purpose of the glyph goes beyond self-amusement. But if it does, it's giving us a clue of what language to use to communicate with them. (They originated the relevant language as a bridge of communication between humanity and themselves more than 12,000 years ago during the rise of one of the first empires of humanity in the land of Akkad.) The juvenile who drew the glyph with seaweed might have learnt about it as part of his education.
✶See: Aliens in the Vicinity