Thanks, 75RR, fo the ID.
Regarding the moving dots, bacteria seem like a good possibility, but I don't know that the chlorophyll pattern indicates damage. Aside from the fact that it is symmetric, it appears that some Cosmarium sp. are like that, such as this one:http://www.digicodes.info/Cosmarium_gon ... gidum.html
The Wikipedia article on Desmids (https://en.wikipedia.org/wiki/Desmidiales
) mentions "characteristic crystals of barium sulphate at either end of the cell which exhibit a continuous Brownian type motion". Might this species have something like that not restricted to the ends of the cell? I could believe that the motion I saw was Brownian motion.