I just googled "science mastodon" and found plenty of results, including this reddit thread with some listed[0] and this list of academics on Mastodon[1]

[0] https://old.reddit.com/r/Mastodon/comments/yy71wh/is_there_a...

[1] https://github.com/nathanlesage/academics-on-mastodon

Although, of course, you can follow any account you like from whatever instance you choose to use (assuming that instance doesn't block it.) A lot of people you may be interested in are on universeodon.com, although typically you'll discover things on Mastodon by searching hashtags, not people.