[A little precursor: the document was a beast to print. I use Illustrator, which is overpriced if you're only using it for game prototypes so I wouldn't suggest it. But I believe free software like Gimp offers excellent and easily learned solutions to card layout, design, and output.]
We had a little trouble with this one. After a third read of the rules, we understood what needed to be done. However, the flip-flop of "roles" confused gameplay. The way we understand it is only one player gets a true turn per round; the starting player simply applies negative effects to a kelp set in secret.
This needs a streamlining edit. A little anecdote: my fifth or sixth game design was a worker placement game set in high school. In the beginning, players could collect friends, attend class, go to study hall, be a delinquent, buy special items to put in their locker, have an after-school job, blah blah blah. It was too much. And it turned out there was only one way to play: perfunctory. Decisions were mandated by the game, not the player. I sat with it one day and asked myself, "Do players need money?" This was huge. I eliminated that currency and the game smoothed out tremendously.
So what does this mean for your game? It feels right now like there are a lot of "if this doesn't happen, then this" conditions. The game almost plays itself. Player decisions don't feel as rewarding as they should. For example, the bit about "if a playable card doesn't appear, keep drawing until one does" feels arbitrary. And I think that's because you've envisioned a way this game plays in your head. (Believe, I've been there and it's tough to break.) Give players more freedom.
Are the kelp forests already present and the players must fight to save them as they degrade? Drawing them from the deck to build them doesn't feel rewarding, it feels lucky. The events, however, feel almost as they should - bad stuff that happens seemingly at random to set players back. This is good, but shouldn't be a player's turn.
The strict "level 1 must come before level 2 must come before level 3" element was a bit underwhelming. Are there other ways cards can play to the table? We enjoyed the idea that there were costs to more powerful cards (gull needing to eat a crab). There's tough decision making inherent there. Consider exploring that.
For a future draft, consider making player reference for the roles (a week to build a game is nuts, right!?). It's slightly confusing that one player must be the sea otter, but sea otters are also cards in the deck. We either didn't use our powers or forgot we had them as a result.
I know the above might seem like a dump, but this game is a draft! You're getting ideas out there! Inside this draft there are genuinely interesting ideas. Explore them more. Straight up steal from games you think are similar for your next draft. Adjust from there. And repeat. You'll no doubt surprise yourself with a truly ingenious breakthrough soon enough.
I think your game's message is unique and under-represented. Bonus points for the possibility of cute artwork too! (Sea otters? Come on. Adorable.) I'm confident you know way more about kelp forests than I do, but could man-made damage be brought more to the forefront? Does that drive the great eco-friendly message home more or is that too much? I'm also confident you can take this idea and turn it into something great!
Cheers!