Unlike macroalgae, which were clearly viewed as plants, microalgae were frequently considered animals because they are often motile.
ʌnlˈaɪk mˈækɹəˌælɡiː, wˌɪtʃ wɜː klˈɪɹli vjˈuːd æz plˈænts, mˈaɪkɹoʊˌælɡiː wɜː fɹˈiːkwəntli kənsˈɪdɚd ˈænɪməlz bɪkˈʌz ðeɪ ɑːɹ ˈɔfən mˈoʊɾaɪl.