Marine Samples (Environmental samples) and disk space

Hi team
I have almost finished my analysis (Marine water metagenome) using MetaphlAn3 and HuManN3.

I do need clarification

Can Metaphlan and humann be used for environmental samples (especially marine water)?

Both Kneaddata and humann produce temp life which occupies more disk space. Can I delete the files or do I have to keep them?

Thank you