Acanthococcus J.D.Hooker & Harvey, 1845 (additional source)
Acanthococcus antarcticus Hooker f. & Harvey, 1845 (basis of record)
Acanthococcus antarcticus Hooker f. & Harvey, 1845 (additional source)
Acanthocorbis asymmetrica (Thomsen) Hara & Takahashi, 1984 (additional source)
Acanthocorbis unguiculata (Thomsen) Hara & Takahashi, 1984 (additional source)
Acanthoeca brevipoda W.Ellis, 1930 (additional source)
Acanthoeca spectabilis W.N.Ellis, 1930 (basis of record)
Acanthoeca spectabilis W.N.Ellis, 1930 (additional source)
Acanthoecaceae (basis of record)
Acanthoecopsis asymmetrica Thomsen (additional source)
Acanthoica quattrospina Lohmann, 1903 (additional source)
Acinetosporaceae Hamel ex J. Feldmann, 1937 (basis of record)
Acrosiphonia J.Agardh, 1846 (additional source)
Acrosiphonia arcta (Dillwyn) Gain, 1912 (additional source)
Acrosiphonia pacifica (Montagne) J.Agardh, 1857 accepted as Spongomorpha pacifica (Montagne) Kützing, 1854 (additional source)
Acrosiphoniaceae S. Jónsson, 1959 (basis of record)
Actinochloridaceae Korshikov, 1953 (basis of record)
Actinochloris Korshikov, 1953 (basis of record)
Actinochloris sphaerica Korschikov, 1953 (basis of record)
Actinomonadaceae Kent, 1881 (basis of record)
Actinotaenium (Nägeli) Teiling, 1954 (basis of record)
Actinotaenium cucurbita (Brébisson ex Ralfs) Teiling, 1954 (basis of record)
Actinotaenium cucurbita var. attenuatum (G.S.West) Teiling, 1954 accepted as Actinotaenium cucurbita (Brébisson ex Ralfs) Teiling, 1954 (basis of record)
Actinotaenium cucurbita var. rotundatum (Willi Krieger) Teiling, 1954 (basis of record)
Actinotaenium curtum (Brébisson ex Ralfs) Teiling ex Růžička & Pouzar, 1978 (basis of record)
Actinotaenium globosum (Bulnheim) Kreiger & Gerloff, 1969 accepted as Actinotaenium globosum (Bulnheim) Kurt Förster ex Compère, 1976 (basis of record)
Actinotaenium globosum (Bulnheim) Kurt Förster ex Compère, 1976 (basis of record)
Acutodesmus (Hegewald) Tsarenko, 2001 (basis of record)
Acutodesmus acuminatus (Lagerheim) P.M.Tsarenko, 2000 accepted as Tetradesmus lagerheimii M.J.Wynne & Guiry, 2016 (basis of record)
Acutodesmus obliquus (Turpin) Hegewald & Hanagata, 2000 accepted as Tetradesmus obliquus (Turpin) M.J.Wynne, 2016 (basis of record)
Adenocystis J.D.Hooker & Harvey, 1845 (additional source)
Adenocystis utricularis (Bory) Skottsberg, 1907 (basis of record)
Adenocystis utricularis (Bory) Skottsberg, 1907 (additional source)
Agitata Cavalier-Smith & D.Bass, 2009 (basis of record)
Agitata agilis (Moroff) Cavalier-Smith, 2011 (basis of record)
Agitatidae Cavalier-Smith & D.Bass, 2009 (basis of record)
Ahnfeltia Fries, 1836 (additional source)
Ahnfeltia plicata (Hudson) E.M.Fries, 1836 (basis of record)
Ahnfeltia plicata (Hudson) E.M.Fries, 1836 (additional source)
Alethocladus Sauvageau, 1903 accepted as Halopteris Kützing, 1843 (additional source)
Alethocladus corymbosus (Dickie) Sauvageau, 1903 accepted as Halopteris corymbosa (Dickie) Draisma, Prud'homme & H.Kawai, 2010 (additional source)
Alexandrium Halim, 1960 (additional source)
Alexandrium tamarense (Lebour) Balech, 1995 (basis of record)
Alexandrium tamarense (Lebour) Balech, 1995 (additional source)
Algirosphaera Schlauder, 1945 (additional source)
Algirosphaera oryza Lecal-Schlauder, 1945 (basis of record)
Algirosphaera oryza Lecal-Schlauder, 1945 (additional source)
Alisphaera Heimdal, 1973 (additional source)
Alisphaera unicornis Okada & McIntyre, 1977 (additional source)
Aliterellaceae J.Rigonato & al., 2016 (basis of record)
Allantion tachyploon Sandon (additional source)
Alphamonadaceae Cavalier-Smith (basis of record)
Alphamonas Alexeieff, 1918 (basis of record)
Alphamonas edax (Klebs) Alexieeff, 1924 (basis of record)
Althenia Petit, 1829 (basis of record)
Althenia cylindrocarpa (Koernicke) Ascherson, 1899 (basis of record)
Althenia preissii (Lehmann) Ascherson & Graebner, 1907 (basis of record)
Amallocystis Fage, 1936 (basis of record)
Amallocystis fagei Boschma, 1948 (basis of record)
Amastigomonas debruynei Saedeleer, 1931 (basis of record)
Amastigomonas debruynei Saedeleer, 1931 (additional source)
Ammatoideaceae Elenkin, 1949 (basis of record)
Amorphonostoc Elenkin, 1931 (basis of record)
Amorphonostoc paludosum (Kützing ex Bornet & Flahault) Elenkin, 1936 accepted as Nostoc paludosum Kützing ex Bornet & Flahault, 1886 (basis of record)
Amphibolis C.Agardh (basis of record)
Amphibolis antarctica (Labillardière) Sonder & Ascherson ex Ascherson, 1868 (basis of record)
Amphibolis bicornis C.Agardh accepted as Amphibolis antarctica (Labillardière) Sonder & Ascherson ex Ascherson, 1868 (basis of record)
Amphibolis griffithii (J.M.Black) Hartog, 1970 (basis of record)
Amphibolis zosterifolia C.Agardh accepted as Amphibolis antarctica (Labillardière) Sonder & Ascherson ex Ascherson, 1868 (basis of record)
Amphidinium Claperède & Lachmann, 1859 (additional source)
Amphidinium hadae Balech, 1976 (additional source)
Anabaena Bory de Saint-Vincent ex Bornet & Flahault, 1886 (basis of record)
Anabaena aequalis O.Borge, 1906 (basis of record)
Anabaena aequalis O.Borge, 1906 (additional source)
Anabaena antarctica F.E.Fritsch, 1912 accepted as Trichormus antarcticus (F.E.Fritsch) Komárek & Anagnostidis, 1989 (basis of record)
Anabaena constricta (Szafer) Geitler, 1925 accepted as Johanseninema constrictum (Szafer) Hasler, Dvorák & Poulícková, 2014 (source of synonymy)
Anabaena cylindrica Lemmermann, 1896 (additional source)
Anabaena oscillarioides Bory ex Bornet & Flahault, 1886 (basis of record)
Anacystis dimidiata (Kützing) Drouet & Daily, 1952 accepted as Chroococcus turgidus (Kützing) Nägeli, 1849 (basis of record)
Anacystis marina (Hansgirg) Drouet & Daily, 1948 accepted as Aphanocapsa marina Hansgirg, 1890 (basis of record)
Anacystis montana (Lightfoot) Drouet & Daily, 1952 accepted as Gloeocapsa atrata Kützing, 1843 (basis of record)
Anagnostidinema acutissimum (Kufferath) Strunecký, Bohunická, J.R.Johansen & J.Komárek, 2017 (basis of record)
Anagnostidinema amphibium (C.Agardh ex Gomont) Strunecký, Bohunická, J.R.Johansen & J.Komárek, 2017 (basis of record)
Anagnostidinema deflexum (West & G.S.West) Strunecky et al., 2017 (basis of record)
Anagnostidinema lemmermannii (Wołoszyńska) Strunecky, Bohunická, J.R.Johansen, Capková, Raabová, P.Dvořák & Komárek, 2017 (basis of record)
Anathece (Komárek & Anagnostidis) Komárek, Kastovsky & Jezberová, 2011 (basis of record)
Anathece clathrata (West & G.S.West) Komárek, Kastovsky & Jezberová, 2011 (basis of record)
Ancyromonadidae Cavalier-Smith, 1993 (basis of record)
Ancyromonas sigmoides Kent, 1881 (basis of record)
Ancyromonas sigmoides Kent, 1881 (additional source)
Anisonema Dujardin, 1841 (additional source)
Anisonema prosgeobium Skuja, 1939 (additional source)
Anisonematidae Kent, 1880 (basis of record)
Ankistrodesmus Corda, 1838 (basis of record)
Ankistrodesmus acicularis (Braun) Korshikov, 1953 accepted as Monoraphidium griffithii (Berkeley) Komárková-Legnerová, 1969 (basis of record)
Ankistrodesmus antarcticus Kol & E.A.Flint, 1968 (basis of record)
Ankistrodesmus falcatus (Corda) Ralfs, 1848 (additional source)
Ankistrodesmus falcatus var. acicularis (A.Braun) G.S.West, 1904 accepted as Monoraphidium griffithii (Berkeley) Komárková-Legnerová, 1969 (basis of record)
Ankistrodesmus gracilis (Reinsch) Korshikov, 1953 accepted as Messastrum gracile (Reinsch) T.S.Garcia, 2016 (basis of record)
Ankistrodesmus tatrae Kol, 1927 accepted as Koliella tatrae (Kol) Hindák, 1963 (basis of record)

English ant-like flower beetles for Anthicidae Latreille, 1819
English black siphon weed [from synonym] for Polysiphonia fucoides (Hudson) Greville, 1824
English bushy berry wrack [from synonym] for Cystoseira baccata (S.G.Gmelin, 1768) P.C.Silva, 1952
Swedish fjäderslick [from synonym] for Polysiphonia fucoides (Hudson) Greville, 1824