Hyalo- means hyaline, white or transparent

-sira means chain (all chain-forming diatoms are "-sira": Melosira, Staurosira...)

And what do Melo- and Aulaco- sira mean?

As Saúl Blanco already mentioned,

hyalo- : hyaline, from the Greek word ὑάλινος (=glass-like, transparent)

-sira : again from the Greek word σειρά, which translates (among other things) to objects placed next to each other. In this case, a chain of diatoms.

Aulaco: with furrows, melo: file, row.