Acanthophora J.V.Lamouroux, 1813 (additional source)
Acanthophora muscoides (Linnaeus) Bory de Saint-Vincent, 1828 (basis of record)
Acanthophora muscoides (Linnaeus) Bory de Saint-Vincent, 1828 (additional source)
Acanthophora nayadiformis (Delile) Papenfuss, 1968 (basis of record)
Acanthophora spicifera (M.Vahl) Børgesen, 1910 (additional source)
Acetabularia J.V.Lamouroux, 1812 (additional source)
Acetabularia caliculus J.V.Lamouroux, 1824 (basis of record)
Acetabularia subg. Acicularia (basis of record)
Acinetospora Bornet, 1891 (additional source)
Acinetospora crinita (Carmichael) Sauvageau, 1899 (additional source)
Acinetosporaceae Hamel ex J. Feldmann, 1937 (basis of record)
Acrochaetium Nägeli, 1858 (additional source)
Acrochaetium balticum (Rosenvinge) Aleem & Schulz, 1952 (additional source)
Acrochaetium catenulatum M.Howe, 1914 (basis of record)
Acrochaetium catenulatum M.Howe, 1914 (additional source)
Acrochaetium codicola Børgesen, 1927 accepted as Colaconema codicola (Børgesen) Stegenga, J.J.Bolton & R.J.Anderson, 1997 (basis of record)
Acrochaetium codicola Børgesen, 1927 accepted as Colaconema codicola (Børgesen) Stegenga, J.J.Bolton & R.J.Anderson, 1997 (additional source)
Acrochaetium densum (K.M.Drew) Papenfuss, 1945 accepted as Acrochaetium catenulatum M.Howe, 1914 (basis of record)
Acrochaetium densum (K.M.Drew) Papenfuss, 1945 accepted as Acrochaetium catenulatum M.Howe, 1914 (additional source)
Acrochaetium kylinii Hamel, 1927 (basis of record)
Acrochaetium kylinii Hamel, 1927 (additional source)
Acrochaetium leptonema (Rosenvinge) Børgesen, 1915 accepted as Colaconema leptonema (Rosenvinge) Alongi, Cormaci & G.Furnari, 2017 (basis of record)
Acrochaetium leptonema (Rosenvinge) Børgesen, 1915 accepted as Colaconema leptonema (Rosenvinge) Alongi, Cormaci & G.Furnari, 2017 (additional source)
Acrochaetium mahumetanum Hamel, 1927 (basis of record)
Acrochaetium mediterraneum (Levring) Athanasiadis, 2003 (basis of record)
Acrochaetium mediterraneum (Levring) Athanasiadis, 2003 (additional source)
Acrochaetium microscopicum (Nägeli ex Kützing) Nägeli, 1858 (additional source)
Acrochaetium moniliforme (Rosenvinge) Børgesen, 1915 (additional source)
Acrochaetium robustum Børgesen, 1915 accepted as Colaconema robustum (Børgesen) Huisman & Woelkerling, 2018 (basis of record)
Acrochaetium robustum Børgesen, 1915 accepted as Colaconema robustum (Børgesen) Huisman & Woelkerling, 2018 (additional source)
Acrochaetium rosulatum (Rosenvinge) Papenfuss, 1945 accepted as Kylinia rosulata Rosenvinge, 1909 (basis of record)
Acrochaetium sargassicola Børgesen, 1932 accepted as Acrochaetium robustum Børgesen, 1915 accepted as Colaconema robustum (Børgesen) Huisman & Woelkerling, 2018 (basis of record)
Acrochaetium savianum (Meneghini) Nägeli, 1862 accepted as Colaconema savianum (Meneghini) R.Nielsen, 1994 (basis of record)
Acrochaetium savianum (Meneghini) Nägeli, 1862 accepted as Colaconema savianum (Meneghini) R.Nielsen, 1994 (additional source)
Acrochaetium secundatum (Lyngbye) Nägeli, 1858 (additional source)
Acrochaetium spathoglossi Børgesen, 1937 (basis of record)
Acrochaetium subpinnatum Bornet ex Hamel, 1927 (basis of record)
Acrochaetium subpinnatum Bornet ex Hamel, 1927 (additional source)
Acrochaetium subseriatum Børgesen, 1932 (additional source)
Acrocladus Nägeli, 1847 accepted as Lychaete J.Agardh, 1846 (basis of record)
Acrocladus herpesticus (Montagne) Boedeker, 2016 accepted as Lychaete herpestica (Montagne) M.J.Wynne, 2017 (basis of record)
Acrosorium Zanardini ex Kützing, 1869 (additional source)
Acrosorium ciliolatum (Harvey) Kylin, 1924 (basis of record)
Acrosorium venulosum (Zanardini) Kylin, 1924 (basis of record)
Acrosorium venulosum (Zanardini) Kylin, 1924 (additional source)
Acrothamnion J.Agardh, 1892 (additional source)
Acrothamnion preissii (Sonder) E.M.Wollaston, 1968 (basis of record)
Acrothrix Kylin, 1907 (additional source)
Acrothrix gracilis Kylin, 1907 (additional source)
Actinomonadaceae Kent, 1881 (basis of record)
Aegagropila Kützing, 1843 (basis of record)
Aegagropila brownii (Dillwyn) Kützing, 1854 (basis of record)
Aegagropila linnaei Kützing, 1843 accepted as Aegagropila brownii (Dillwyn) Kützing, 1854 (basis of record)
Agardhiella F.Schmitz, 1897 (additional source)
Agardhiella subulata (C.Agardh) Kraft & M.J.Wynne, 1979 (basis of record)
Agarophyton Gurgel, J.N.Norris & Fredericq, 2018 (basis of record)
Agarophyton vermiculophyllum (Ohmi) Gurgel, J.N.Norris et Fredericq, 2018 accepted as Gracilaria vermiculophylla (Ohmi) Papenfuss, 1967 (basis of record)
Aglaothamnion Feldmann-Mazoyer, 1941 (additional source)
Aglaothamnion feldmanniae Halos, 1965 (additional source)
Aglaothamnion halliae (Collins) Aponte, D.L.Ballantine & J.N.Norris, 1997 (basis of record)
Aglaothamnion halliae (Collins) Aponte, D.L.Ballantine & J.N.Norris, 1997 (additional source)
Aglaothamnion tenuissimum (Bonnemaison) Feldmann-Mazoyer, 1941 (additional source)
Aglaozonia Zanardini, 1843 accepted as Cutleria Greville, 1830 (basis of record)
Aglaozonia Zanardini, 1843 accepted as Cutleria Greville, 1830 (source of synonymy)
Aglaozonia parvula (Greville) Zanardini, 1843 accepted as Cutleria multifida (Turner) Greville, 1830 (basis of record)
Ahnfeltiopsis P.C.Silva & DeCew, 1992 (additional source)
Ahnfeltiopsis devoniensis (Greville) P.C.Silva & DeCew, 1992 (additional source)
Ahnfeltiopsis flabelliformis (Harvey) Masuda, 1993 (additional source)
Ahnfeltiopsis furcellata (C.Agardh) P.C.Silva & DeCew, 1992 accepted as Asterfilopsis furcellata (C.Agardh) M.S.Calderon & S.M.Boo, 2016 (basis of record)
Ahnfeltiopsis furcellata (C.Agardh) P.C.Silva & DeCew, 1992 accepted as Asterfilopsis furcellata (C.Agardh) M.S.Calderon & S.M.Boo, 2016 (additional source)
Alaria Greville, 1830 (additional source)
Alaria esculenta (Linnaeus) Greville, 1830 (additional source)
Alexandrium Halim, 1960 (additional source)
Alexandrium acatenella (Whedon & Kofoid) Balech, 1985 accepted as Alexandrium catenella (Whedon & Kofoid) Balech, 1985 (additional source)
Alexandrium affine (H.Inoue & Y.Fukuyo) Balech, 1995 (basis of record)
Alexandrium affine (H.Inoue & Y.Fukuyo) Balech, 1995 (additional source)
Alexandrium andersonii Balech, 1990 (additional source)
Alexandrium angustitabulatum F.J.R.Taylor, 1995 accepted as Alexandrium minutum Halim, 1960 (additional source)
Alexandrium catenella (Whedon & Kofoid) Balech, 1985 (additional source)
Alexandrium concavum (Gaarder) Balech, 1985 (additional source)
Alexandrium fundyense Balech, 1985 accepted as Alexandrium catenella (Whedon & Kofoid) Balech, 1985 (additional source)
Alexandrium kutnerae (Balech, 1979) Balech, 1985 (additional source)
Alexandrium leei Balech, 1985 (additional source)
Alexandrium margalefii Balech, 1994 (additional source)
Alexandrium minutum Halim, 1960 (basis of record)
Alexandrium monilatum (J.F.Howell) Balech, 1995 (additional source)
Alexandrium ostenfeldii (Paulsen) Balech & Tangen, 1985 (additional source)
Alexandrium peruvianum (Balech & Mendiola) Balech & Tangen, 1985 accepted as Alexandrium ostenfeldii (Paulsen) Balech & Tangen, 1985 (additional source)
Alexandrium pseudogonyaulax (Biecheler) Horiguchi ex K.Yuki & Y.Fukuyo, 1992 (basis of record)
Alexandrium pseudogonyaulax (Biecheler) Horiguchi ex K.Yuki & Y.Fukuyo, 1992 (additional source)
Alexandrium tamarense (Lebour) Balech, 1995 (basis of record)
Alexandrium tamarense (Lebour) Balech, 1995 (additional source)
Alexandrium taylorii Balech, 1994 (basis of record)
Amphidinium Claperède & Lachmann, 1859 (additional source)
Amphidinium carterae Hulburt, 1957 (basis of record)
Amphiroa J.V.Lamouroux, 1812 (additional source)
Amphiroa rigida J.V.Lamouroux, 1816 (additional source)
Anadyomene J.V.Lamouroux, 1812 (additional source)
Anadyomene howei D.S.Littler & Littler, 1991 (basis of record)
Anotrichium Nägeli, 1862 (additional source)

Mediterranean Sea Area for Caulerpa racemosa var. cylindracea (Sonder) Verlaque, Huisman & Boudouresque, 2003  (origin: alien)

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