• Abratopdinium cardioforme S.Mao & B.A.R.Mohr †: microplankton
• Abratopdinium kerguelense S.Mao & B.A.R.Mohr †: microplankton
• Abruptophycus compositus Vologdin, 1962 †: microplankton
• Acaciella angepena W.V.Preiss, 1972 †: microplankton
• Acaciella augusta W.V.Preiss, 1972 †: microplankton
• Acaciella australica (Howchin) M.R.Walter, 1972 †: microplankton
• Acaciella savoryensis K.Grey & M.R.Walter, 1994 †: microplankton
• Acanthina bullosa Korde, 1973 †: microplankton
• Acanthina multiformis Korde, 1973 †: microplankton
• Acanthodinium caryophyllum Kofoid, 1907: microplankton
• Acanthogonyaulax acanthosphaera (Sargeant) Sargeant †: microplankton
• Acanthogonyaulax paliuros (Sargeant) Sargeant †: microplankton
• Acanthogonyaulax spinifera (Murray & Whitting) H.W.Graham, 1942: microplankton
• Acanthostomella conicoides Kofoid & Campbell, 1929: microplankton
• Acanthostomella lata Kofoid & Campbell, 1929: microplankton
• Acanthostomella minutissima Kofoid & Campbell, 1929: microplankton
• Acanthostomella norvegica (Daday, 1887): microplankton
• Acanthostomella obtusa Kofoid & Campbell, 1929: microplankton
• Acaryochloris thomasi Partensky & al., 2018: microplankton
• Achomosphaera alcicornu (Eisenack) R.J.Davey & G.L.Williams, 1966 †: microplankton
• Achomosphaera antleriformis P.Schiøler †: microplankton
• Achomosphaera argesensis E.Demetrescu †: microplankton
• Achomosphaera gralliforme (Brosius) R.J.Davey & G.L.Williams, 1969 †: microplankton
• Achomosphaera hirundo (Eisenack) R.J.Davey & G.L.Williams, 1969 †: microplankton
• Achomosphaera improcera M.A.Islam, 1983 †: microplankton
• Achomosphaera linifera (Cookson & Eisenack) Stover & Evitt, 1978 †: microplankton
• Achomosphaera neptuni (Eisenack) R.J.Davey & G.L.Williams, 1966 †: microplankton
• Achomosphaera recurvata K.P.Jain, S.C.D.Sah & R.Y.Singh †: microplankton
• Achomosphaera sagena R.J.Davey & G.L.Williams, 1966 †: microplankton
• Achomosphaera triangulata (Gerlach) R.J.Davey & G.L.Williams, 1969 †: microplankton
• Achroonema articulatum Skuja, 1956: microplankton
• Achroonema gotlandicum Skuja, 1956: microplankton
• Achroonema inaequale Skuja, 1956: microplankton
• Achroonema macromeres Skuja, 1956: microplankton
• Achroonema simplex Skuja, 1956: microplankton
• Achroonema spiroideum Skuja, 1948: microplankton
• Achroonema splendens Skuja, 1956: microplankton
• Achroonema sporogenum Skuja, 1956: microplankton
• Actiniscus pentasterias (Ehrenberg) Ehrenberg, 1844: microplankton
• Actinodinium apsteinii Chatton & Hovasse: microplankton
• Actinophycus kordeae Vologdin, 1962 †: microplankton
• Actinophycus obrutschevii Korde, 1954 †: microplankton
• Actinophycus parvus Vologdin, 1962 †: microplankton
• Actinophycus ramosus Vologdin, 1962 †: microplankton
• Acuasiphonoria ordovica Lijing Liu, Yasheng Wu, H.J.Yang & Riding, 2016 †: microplankton
• Adriamonas peritocrescens Verhagen, Zölffel, Brugerolle & D.J.Patterson, 1994: microplankton
• Adrianema adriaticum (Ercegovic) G.De Toni, 1936: microplankton
• Aegeococcus anagnostidisii Konstantinou & Gkelis, 2020: microplankton
• Aegeococcus thuretii Konstantinou & Gkelis, 2020: microplankton
• Aerofilum fasciculatum Chakraborty & J.Mukherjee, 2021: microplankton
• Aerosakkonema funiforme Nanda Kyaw Thu & Watanabe, 2012: microplankton
• Aetokthonos hydrillicola S.B.Wilde & J.R.Johansen, 2014: microplankton
• Affixifilum floridanum Lefler, D.E.Berthold & Laughinghouse, 2021: microplankton
• Affixifilum granulosum (Caires, Sant'Anna & Nunes) Lefler, D.E.Bertholdt & Laughinghouse, 2021: microplankton
• Ailadinium reticulatum Saburova & Chomérat, 2014: microplankton
• Akashiwo sanguinea (K.Hirasaka) Gert Hansen & Moestrup, 2000: microplankton
• Alasphaera caudata H.Keupp, 1979 †: microplankton
• Alatosphaera hermosillae (Carbonell-Moore) Nézan, Carbonell-Moore, K.N.Mertens & Chomérat, 2023: microplankton
• Albatrossiella agassizi Kofoid & Campbell, 1929: microplankton
• Albatrossiella filigera (Laackmann, 1910) Kofoid & Campbell, 1929: microplankton
• Albertania alaskensis Strunecky, Raabova, Bernardova, Ivanova, Semanova, Crossley & Kaftan, 2019: microplankton
• Albertania obscura R.F.S.Luz, Kaštovský, J.R.Johansen & V.Gonçalves, 2023: microplankton
• Albertania pratii J.R.Johansen, Kaštovský & M.U. Akagha, 2023: microplankton
• Albertania skiophila Zammit, 2018: microplankton
• Alborzia kermanshahica Nowruzi & F.Soares, 2021: microplankton
• Albrightia roraimae Kastovský, Fucíková, Hauer & Bohunická, 2011: microplankton
• Albrightia tortuosa J.Copeland, 1936: microplankton
• Alcheringa narrina M.R.Walter, 1972 †: microplankton
• Alexandrium australiense Sh.Murray, 2014: microplankton
• Alexandrium balechii (Steidinger) Balech, 1995: microplankton
• Alexandrium cohorticula (Balech) Balech, 1985: microplankton
• Alexandrium compressum (Y.Fukuyo, K.Yoshida & H.Inoue) Balech, 1995: microplankton
• Alexandrium concavum (Gaarder) Balech, 1985: microplankton
• Alexandrium depressum (K.R.Gaarder) Balech & Tangen, 1985: microplankton
• Alexandrium diversaporum S.A.Murray et. al., 2014: microplankton
• Alexandrium foedum Balech, 1990: microplankton
• Alexandrium fragae S.Branco & M.Menezes, 2020: microplankton
• Alexandrium fraterculus (Balech) Balech, 1985: microplankton
• Alexandrium gaarderae L.Nguyen-Ngoc & J.Larsen, 2004: microplankton
• Alexandrium globosum Nguyen-Ngoc & J.Larsen, 2004: microplankton
• Alexandrium insuetum Balech, 1985: microplankton
• Alexandrium kutnerae (Balech, 1979) Balech, 1985: microplankton
• Alexandrium limii S.T.Teng, Tillmann, N.Abdullah, S.Nagai & Leaw, 2023: microplankton
• Alexandrium mediterraneum U.John, 2014: microplankton
• Alexandrium minutum Halim, 1960: microplankton
• Alexandrium monilatum (J.F.Howell) Balech, 1995: microplankton
• Alexandrium ogatae S.T.Teng, N.Abdullah, Tillmann, Leaw & P.T.Lim, 2023: microplankton
• Alexandrium ostenfeldii (Paulsen) Balech & Tangen, 1985: microplankton
• Alexandrium pseudogonyaulax (Biecheler) Horiguchi ex K.Yuki & Y.Fukuyo, 1992: microplankton
• Alexandrium satoanum K.Yuki & Y.Fukuyo, 1992: microplankton
• Alexandrium tamarense (Lebour) Balech, 1995: microplankton
• Alexandrium tamiyavanichii Balech, 1994: microplankton
• Alexandrium tamutum M.Montresor, A.Beran & U.John, 2004: microplankton
• Alexandrium taylorii Balech, 1994: microplankton
• Alexandrium tropicale Balech, 1985: microplankton
• Algidasphaeridium minutum (Harland & Reid, 1980) Matsuoka & Bujak, 1988 †: microplankton
• Aliferia kharlamenkoi Selina, K.V., Efimova & Hoppenrath, 2023: microplankton
• Aliferia nikselinii Selina, K.V., Efimova & T.V.Morozova, 2023: microplankton
• Aliinostoc alkaliphilum Christodoulou, Economou-Amilli, M.Fiore & Sivonen, 2022: microplankton
• Aliinostoc bakau Merican, Abdul Rahim, Broady, Convey & Muangmai, 2023: microplankton