What is the meaning of "Mah Rabu Ma'asecha"?
Radak #1: They are great, like "Al Kol Rav Beiso" (Esther 1:8).
Radak #2: They are many - "Mal'ah ha'Aretz Kinyanecha."
Malbim: Hashem created many species.
Lev Eliyahu (Shemos p.79, citing the Akeidah): After all the creations mentioned in this Mizmor, that are great in quality and quantity, we see that all of them announce 'we are Your deeds'!
Why does it say "Kulam b'Chachmah Asisa Mal'ah ha'Aretz Kinyanecha"?
Radak: We recognize the greatness of Hashem's deeds; everything is done with Chachmah. Nothing is chance. There is no place where Hashem's acts are not seen.
Malbim: You prepared for each species the means to survive; one does not swallow its colleague. You prepared for weak beings an abode and shelter from the strong ones. All species persist, and are not eradicated. Individuals multiply as needed, until the land is full.
What is "Kinyanecha"?
Rashi: Your acquisition, like "Kone Shamayim va'Aretz" (Bereishis 14:19). Everything is acquired to You!