• Abratopdinium cardioforme S.Mao & B.A.R.Mohr †: nanoplankton
• Abratopdinium kerguelense S.Mao & B.A.R.Mohr †: nanoplankton
• Abruptophycus compositus Vologdin, 1962 †: nanoplankton
• Acaciella angepena W.V.Preiss, 1972 †: nanoplankton
• Acaciella augusta W.V.Preiss, 1972 †: nanoplankton
• Acaciella australica (Howchin) M.R.Walter, 1972 †: nanoplankton
• Acaciella savoryensis K.Grey & M.R.Walter, 1994 †: nanoplankton
• Acanthina bullosa Korde, 1973 †: nanoplankton
• Acanthina multiformis Korde, 1973 †: nanoplankton
• Acanthodinium caryophyllum Kofoid, 1907: nanoplankton
• Acanthogonyaulax acanthosphaera (Sargeant) Sargeant †: nanoplankton
• Acanthogonyaulax paliuros (Sargeant) Sargeant †: nanoplankton
• Acanthogonyaulax spinifera (Murray & Whitting) H.W.Graham, 1942: nanoplankton
• Acaryochloris thomasi Partensky & al., 2018: nanoplankton
• Achomosphaera alcicornu (Eisenack) R.J.Davey & G.L.Williams, 1966 †: nanoplankton
• Achomosphaera antleriformis P.Schiøler †: nanoplankton
• Achomosphaera argesensis E.Demetrescu †: nanoplankton
• Achomosphaera gralliforme (Brosius) R.J.Davey & G.L.Williams, 1969 †: nanoplankton
• Achomosphaera hirundo (Eisenack) R.J.Davey & G.L.Williams, 1969 †: nanoplankton
• Achomosphaera improcera M.A.Islam, 1983 †: nanoplankton
• Achomosphaera linifera (Cookson & Eisenack) Stover & Evitt, 1978 †: nanoplankton
• Achomosphaera neptuni (Eisenack) R.J.Davey & G.L.Williams, 1966 †: nanoplankton
• Achomosphaera recurvata K.P.Jain, S.C.D.Sah & R.Y.Singh †: nanoplankton
• Achomosphaera sagena R.J.Davey & G.L.Williams, 1966 †: nanoplankton
• Achomosphaera triangulata (Gerlach) R.J.Davey & G.L.Williams, 1969 †: nanoplankton
• Achroonema articulatum Skuja, 1956: nanoplankton
• Achroonema gotlandicum Skuja, 1956: nanoplankton
• Achroonema inaequale Skuja, 1956: nanoplankton
• Achroonema macromeres Skuja, 1956: nanoplankton
• Achroonema simplex Skuja, 1956: nanoplankton
• Achroonema spiroideum Skuja, 1948: nanoplankton
• Achroonema splendens Skuja, 1956: nanoplankton
• Achroonema sporogenum Skuja, 1956: nanoplankton
• Actinodinium apsteinii Chatton & Hovasse: nanoplankton
• Actinophycus kordeae Vologdin, 1962 †: nanoplankton
• Actinophycus obrutschevii Korde, 1954 †: nanoplankton
• Actinophycus parvus Vologdin, 1962 †: nanoplankton
• Actinophycus ramosus Vologdin, 1962 †: nanoplankton
• Acuasiphonoria ordovica Lijing Liu, Yasheng Wu, H.J.Yang & Riding, 2016 †: nanoplankton
• Adrianema adriaticum (Ercegovic) G.De Toni, 1936: nanoplankton
• Aegeococcus anagnostidisii Konstantinou & Gkelis, 2020: nanoplankton
• Aegeococcus thuretii Konstantinou & Gkelis, 2020: nanoplankton
• Aerofilum fasciculatum Chakraborty & J.Mukherjee, 2021: nanoplankton
• Aerosakkonema funiforme Nanda Kyaw Thu & Watanabe, 2012: nanoplankton
• Aetokthonos hydrillicola S.B.Wilde & J.R.Johansen, 2014: nanoplankton
• Affixifilum floridanum Lefler, D.E.Berthold & Laughinghouse, 2021: nanoplankton
• Affixifilum granulosum (Caires, Sant'Anna & Nunes) Lefler, D.E.Bertholdt & Laughinghouse, 2021: nanoplankton
• Ailadinium reticulatum Saburova & Chomérat, 2014: nanoplankton
• Akashiwo sanguinea (K.Hirasaka) Gert Hansen & Moestrup, 2000: nanoplankton
• Alasphaera caudata H.Keupp, 1979 †: nanoplankton
• Alatosphaera hermosillae (Carbonell-Moore) Nézan, Carbonell-Moore, K.N.Mertens & Chomérat, 2023: nanoplankton
• Albertania alaskensis Strunecky, Raabova, Bernardova, Ivanova, Semanova, Crossley & Kaftan, 2019: nanoplankton
• Albertania obscura R.F.S.Luz, Kaštovský, J.R.Johansen & V.Gonçalves, 2023: nanoplankton
• Albertania pratii J.R.Johansen, Kaštovský & M.U. Akagha, 2023: nanoplankton
• Albertania skiophila Zammit, 2018: nanoplankton
• Alborzia kermanshahica Nowruzi & F.Soares, 2021: nanoplankton
• Albrightia roraimae Kastovský, Fucíková, Hauer & Bohunická, 2011: nanoplankton
• Albrightia tortuosa J.Copeland, 1936: nanoplankton
• Alcheringa narrina M.R.Walter, 1972 †: nanoplankton
• Algidasphaeridium minutum (Harland & Reid, 1980) Matsuoka & Bujak, 1988 †: nanoplankton
• Aliferia kharlamenkoi Selina, K.V., Efimova & Hoppenrath, 2023: nanoplankton
• Aliferia nikselinii Selina, K.V., Efimova & T.V.Morozova, 2023: nanoplankton
• Aliinostoc alkaliphilum Christodoulou, Economou-Amilli, M.Fiore & Sivonen, 2022: nanoplankton
• Aliinostoc bakau Merican, Abdul Rahim, Broady, Convey & Muangmai, 2023: nanoplankton
• Aliinostoc catenatum Kabirnataj, Nematzadeh, Talebi, Saraf, Suradkar, Tabatabaei & Singh, 2020: nanoplankton
• Aliinostoc magnakinetifex Kabirnataj, Nematzadeh, Talebi, Saraf, Suradkar, Tabatabaei & Singh, 2020: nanoplankton
• Aliinostoc morphoplasticum Bagchi, Dubey & P.Singh, 2017: nanoplankton
• Aliinostoc vietnamicum S.Maltseva, E.Kezlya & Y.Maltsev, 2022: nanoplankton
• Aliterella antarctica J.Rigonato et al., 2016: nanoplankton
• Aliterella chasmolithica P.Jung, Schermer, Mikhailyuk & Büdel, 2020: nanoplankton
• Aliterella compacta P.Jung, Büdel & Lakatos, 2021: nanoplankton
• Aliterella gigantea P.Jung, Büdel & Lakatos, 2021: nanoplankton
• Aliterella vladivostokensis Abdullin, A.Y.Nikulin, Bagmet & V.Y.Nikulin, 2021: nanoplankton
• Alkalinema pantanalense Vieira Vaz et al., 2015: nanoplankton
• Allocoleopsis franciscana Moreira-Fernandes, Giraldo-Silva, D.Roush & Garcia-Pichel, 2021: nanoplankton
• Alpinella graeca Dragastan, Gieslich, D.K.Richter, Grewer, Kaziur, Kube & Radusch, 1994 †: nanoplankton
• Alterbidinium compactum O.N.Vasilyeva, 2016 †: nanoplankton
• Alterbidinium nuculum O.N.Vasilyeva, 2016 †: nanoplankton
• Alterbidinium nummuliforme O.N.Vasilyeva, 2016 †: nanoplankton
• Alterbidinium pentangulare O.N.Vasilyeva, 2016 †: nanoplankton
• Alterbidinium prominens O.N.Vasilyeva, 2016 †: nanoplankton
• Alterbidinium pseudocirculum O.N.Vasilyeva, 2016 †: nanoplankton
• Alterbidinium saltanovae O.N.Vasilyeva, 2016 †: nanoplankton
• Alterbidinium simplex O.N.Vasilyeva, 2016 †: nanoplankton
• Altericista lacusladogae Averina, E.Polyakova, Senetskaya & Pinevich, 2021: nanoplankton
• Altericista variichlora Averina, E. Polyakova, Senatskaya & Pinevich, 2021: nanoplankton
• Altericista violacea Averina, E.Polyakova, Senatskaya & Pinevich, 2021: nanoplankton
• Alternantia geitleri J.Schiller, 1954: nanoplankton
• Alternantia quadriga J.Schiller, 1954: nanoplankton
• Alternantia ramifera J.Schiller, 1954: nanoplankton
• Alternantia serra J.Schiller, 1954: nanoplankton
• Alternantia tabularis J.Schiller, 1954: nanoplankton
• Alternella bianca (Raaben) Raaben, 1972 †: nanoplankton
• Alternella hyperboreica Raaben, 1972 †: nanoplankton
• Alternia silva Vologdin, 1962 †: nanoplankton
• Amazoninema brasiliense Genuário, W.R.de Souza, R.T.R.Monteiro, Sant'Anna & I.T.S.Melo, 2020: nanoplankton
• Amazonocrinis nigriterrae Alvarenga & al., 2021: nanoplankton
• Amazonocrinis thailandica Tawong, Pongcharoen, Pongpadung, Ponza & Saijuntha, 2022: nanoplankton
• Ambigolamellatus ovatus Maithy, 1979 †: nanoplankton
• Amiculosphaera umbracula R.Harland †: nanoplankton