If something looks kind of seaweedy, is there a "safe" identification?

I am very unknowledgeable about seaweed-like things, but I hang out in Unknown and give things coarse IDs so that the right eyes land on them.

Seaweed is a mystery to me. If something looks seaweedy, is there a coarse identification I can apply that will help it to get seen by the right people?


Most seaweeds (most that people would post pictures of on here, anyways) are either “red algae”, “brown algae”, or “green algae”. I tried typing those into the species search bar and those common names do lead to the appropriate groups. But if you aren’t sure which of those it is, “plants” is as small as you can go if you think it’s either red or green algae but aren’t sure which. Brown algae (kelp) is in a completely different kingdom (Chromista) along with diatoms, foraminifera, and other things, so just leave it at “brown algae”.


Ugh. I have been doing unknowns too and I have this problem a lot. The unknown bin for my county is largely shots of tidepools, and even if the photographer managed not go get glare off the water surface, there is almost always too many possible subjects/no obvious kingdom. Honestly I’ve started skipping them all. If only there was a (taxonomically irrelevant) “marine life” search category.


Amy: For the multiple subjects photos, any luck asking people to point out which thing they intend to be identified? I’ve run into a few that seem to have uploaded pictures of multiple things (including multiple pictures, each with different subjects), then forgot about the site altogether. But mostly the people I’ve encountered are good about responding with which one they want IDed.

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I don’t remember any responses regarding subject confusion, so far. Nor any luck asking people to split photos of obviously different taxa into multiple observations. I remember one person whose obs photo was a photo of a computer screen, and when I asked if she really saw the organism, she replied yes. However I started with oldest unknowns first, so stuff I’ve been through so far is from 2 years old down to 3 months. Maybe more recent observers would be more responsive .

some animals (ex. some Hydrozoans and Bryozoans) might look seaweedy, if you’re not aware that these kinds of things exist.

I’ve often wished for the same thing. While filtering by place could serve some of that purpose, in my area (the Pacific Northwest Coast), the place boundaries are heavily biased in favor of terra firma. There is a feature request for implementing standard marine places, though I’m not sure that includes the shorelines.

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It would be nice if there was a coarse ID for seaweeds but I’m not aware of one.

Seaweeds are tough because they are polyphyletic:

  1. Brown Algaes (such as Leathesia) are in the Class Phaeophyceae within the Kingdom Chromista
  2. Blue-Green Algae (such as Nostoc) is Phylum Cyanobacteria within the Kingdom Bacteria
  3. Red Algae (such as Halosaccion) is Phylum Rhodophyta within the Kingdom Plantae
  4. Green Algae (such as Dictyosphaeria) is Phylum Chlorophyta within the Kingdom Plantae

These algaes can all appear seaweedy depending on your acumen.

  • Identification conflicts between Red and Green Algaes will move the ID to Kingdom Plantae
  • Identification conflicts between Red or Green Algaes and Blue-Green Algaes will move the ID to State of matter Life
  • Identification conflicts between Red or Green Algaes and Brown Algaes will move the ID to State of matter Life
  • Identification conflicts between Blue-Green Algae and Brown Algaes will move the ID to State of matter Life

Observations that remain within the Kingdoms usually are filtered for and may be reviewed by novices and experts within that taxon.

Observations that move to State of matter Life may not be as likely to be reviewed by experts within that taxon. (if you are unaware of the topic of State of matter Life, you can see some of the issues here https://forum.inaturalist.org/t/state-of-matter-life-limbo/2870 )

Conflicting Phylums seem to become harder to move to Research Grade.

I think it is great to identify seaweeds. My one recommendation is that if you do, try to monitor those identifications so that you can modify a conflicting identification that you have made if a well supported alternate identification has been made.

1.Brown Algae
2.Blue-Green Algae
3.Red Algae
4.Green Algae


Also, if you “get it wrong”, don’t worry, because the taxa you put it to likely has identifiers that would know what it is, and get it heading in the right direction!


It helps to add a tag or description to the observation stating it is seaweed/algae. I have sometimes tried to find nonseaweed freshwater algae to ID by searching for terms like Pond, Algae, etc. You could also try adding them to a traditional project just for seaweeds, which I’m sure already exists.

I’m going to confess I use this easy approach -

I just put it up as one of the taxa discussed above - brown/red/green algae etc.- depending on what I think it looks like (I put in a little more effort than just the colour, though!) Sometimes I’m wrong, and then an identifier for the entered taxon moves it out of that taxon (and into the right one, or into a broad category).

I now tend to have some idea about what I’m entering my seaweed observations as. But earlier, when I was clueless, I used the exact same approach, and it did get me and my observations on the right track.

As far as I know, there is really no parent taxon for ‘seaweeds’ that is safe to enter and simultaneously get noticed by identifiers. This is true for certain other taxa as well (including animals), and I see this method as the only way to get it going somewhere. Since data with coarse-level IDs will hardly ever be relied upon for serious use, I think this is a low-risk route.


Thank you everyone! I definitely don’t feel confident to categorise seaweedy things accurately now, but I do feel reassured that I can make my best guess and it’s better that someone with more knowledge than me will see it and recategorise it. :)


@cas4moss iNat is as much about learning and communicating about nature as it is in creating datapoints, so don’t let the complexity of that branch put you off having a go! If you always make your best “educated” guess and push a little past your comfort zone, you WILL get some wrong, but that is itself a GOOD thing! others will let you know what they are (even by way of a corrected ID, but hopefully with some guidance on why you were wrong), and before you know it you will be looked at as the expert! If it seems too daunting, challenge yourself to at least make a comment on the observation as to what you think it is. For me, when I force myself to “commit” to a position like this it kind of makes me think a bit harder about it, and I find I “learn” them faster! Also, others see that you are giving it a go and will often chime in with helpful tips on how to differentiate. I add “maybe” or “possibly”, or even just a question mark after my guess, so that others know I am just guessing. And in some cases my comment has been wrong, but sparked off the line of enquiry that eventually came to the solution, so even a wrong guess can be helpful!


Amy: please don’t despair when it comes to tidepools. iNat actually has an excellent tide pool taxa ID database and the AI can help as well.

Ocean Sanctuaries has been running very successful tide pool bioblitzes here in California–it’s a major location of marine indicator species and every contribution helps–regardless of what coast you’re on.


Should I be adding some kind of tag? Or adding them to your project? What if they are poor image quality?

Hi, yes, please feel free to add any tide pool photos to our TP projects (links given above). If the image is poor quality, we can still ask for help with identification. Thanks!

You can always try under ‘Algae,’ as a top level identifier and then, let the experts take it from there. Don’t worry: things like algae, marine sponges and worms are specialized fields, which require specialists to ID. They are not the province of your average lay person. I’ve been diving for nearly 20 years and I still have to ask for help with these type of taxa. ;-)


You can always try under ‘Algae,’ as a top level identifier and then, let the experts take it from there.

That is where I get stuck! There’s no top level “algae”, you have to pick brown, green and red! I get nervous that I’ll pick the wrong one. :D Is picking the wrong one better than leaving something totally uncategorised, or is that just annoying?

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Annoying or not, it may help getting a correct ID faster:



Ha! Good point! :D