Hi @KQUB,
I'd like to point out an important point, as we highlight in our RESCRIPt tutorial, SILVA does not curate species labels, and we warn about this, under the drop menu "Species-labels: caveat emptor!"
I'd suggest that you fetch trustworthy sequences of these algal taxa from GenBank and place them into a single FASTA file. Then add some legitimate cyanobacteria too. Then add the sequences of the two potential algal taxa within that same file. From here I'd generate a sequence alignment and a phylogeny. What you should see is two main clades: 1) true cyanobacteria, and 2) chloroplasts. If your sequences land within the chloroplast clade then you can trust that your sequences are indeed chloroplasts and not mis-identified bacteria.
You can also submit your potential algal sequences to SILVA's ACT tool and see if those sequences do actually fall within an algal (chlroroplast) clade.
But I'd still be wary about making any over claims with out other data information.