**3. Isolation, maintenance, and availability of cryptophytes**

Cryptophytes are inhabitants of still waters with a low trophic state, they reach maximal biomass near the summer chemocline [77], and vertically migrate as a mechanism for harvesting inorganic nutrients; they can grow in turbid waters with low light due to their efficient greenlight harvesting PBPs [64]. Nets of different kinds and sampling bottles can be used for collecting cryptomonads from the water column; sediments or mucilage should be placed in the water, so the cells can be motile while transporting them to the laboratory, and all samples should be placed at a low temperature [20, 77]. In the lab, the samples should be gently filtered (>30 μm–<200 μm) and cultured by enriching the water with one standard culture

media diluted (1:5–1:10), WARIS, and BBM (freshwater); ASP-12, ESM, f/2, and ASP (marine; check recipes on the CCAC, CCAP, CCMP, NIES, and SAG websites) [9, 78]. Cryptophytes do not grow in agar (only the palmella-forming taxa). Fluorescent light (20–50 μmol/m2 /s), 16:8 or 12:12 light:dark cycle, and 16–25 °**C***.*It is recommended that culture conditions should be the same or as close as possible to that of the sampling site. When cells establish a population, they can be isolated, and the method of choice is using a micropipette [9, 79]; another way is by dilution in a sterile 24-well microplate. The delicate cells do not resist the fixation with Lugol or formol, but glutaraldehyde 2% can be an option [9, 80, 81]. The cells can be identified as cryptophytes using a standard optical microscope, with respect to size, form, and movement. Photographs are difficult to obtain because of cell movement, but dark field, phase contrast, differential interference contrast (DIC), and fluorescence microscopy help identify some features of cells [9, 20]. For maintaining the isolated cells, low temperature and low light are recommended. With heterotrophic cryptophytes like *Goniomonas* and *Chilomonas*, an organic carbon source, like a sterilized wheat seed, pea, or lentil, in a soil-water media are typically provided. Some also grow in WARIS added with soil extract [9, 20]. Different strains of cryptomonads are available in collections around the world.
