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Red Alga Invasive Species Information

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What Is Red Alga - (Grateloupia doryphora)?

Habitat: prefers to live in shallow, protected subtidal waters, and likes to attach itself to hard substrates. It can survive water temperatures between 4 and 28° C, and salinities between 12 and 52 parts per thousand. 
Distribution in Ireland: Coastal Areas 

Status: Unknown
Family name: Grateloupia

Reproduction: Spores develop giving rise to filaments and blades.

Red Alga - Grateloupia doryphora

Red Alga - Grateloupia doryphora

Red Alga leaves

How To Identify Red Alga?

Colour: Red, olive green, brown

Size: The ribbon-like blades of this seaweed can reach a size of 100 cm by 20 cm, but are usually much smaller.

Red alga prefers shallow, protected subtidal waters attaching itself to hard substrates.

Red Alga - grateloupia doryphora ID Guide

Red Alga - Grateloupia doryphora ID Guide

Why Is Red Alga A Problem?

Where Red Aga co-exists, it usually out competes the other non-native species.

It can invade the habitat of a native seaweed, Chondrus crispus, aka: "Irish Moss", and crowd it out. Irish moss is used commercially to manufacture carigeen, and also provides an important winter food source for local marine invertebrates.


Additionally, the long blades of Red Alga can shade out other local species of algae and prevent them from growing nearby. 

European Communities (Birds and Natural Habitats) Regulations 2011 non-native invasive plant species A-Z (Updated 2017)

There are currently 35 invasive plant species listed in the European Communities (Birds and Natural Habitats) Regulations (annex 2, Part 1)...


Click on a species from the following list to find out more regarding non-native species subject to restrictions under Regulations 49 and 50.

  1. American Skunk-CabbageLysichiton americanus

  2. Brazilian Giant-RhubarbGunnera manicata

  3. Broad-Leaved RushJuncus planifolius

  4. Cape PondweedAponogeton distachyos

  5. Cord-GrassesSpartina (all species and hybrids)

  6. Curly Waterweed - Lagarosiphon major

  7. Dwarf Eel-GrassZostera japonica

  8. FanwortCabomba caroliniana

  9. Floating PennywortHydrocotyle ranunculoides

  10. Fringed Water-LilyNymphoides peltata

  11. Giant HogweedHeracleum mantegazzianum

  12. Giant KnotweedFallopia sachalinensis

  13. Giant-RhubarbGunnera tinctoria

  14. Giant SalviniaSalvinia molesta

  15. Himalayan BalsamImpatiens glandulifera

  16. Himalayan KnotweedPersicaria wallichii

  17. Hottentot-FigCarpobrotus edulis

  18. Japanese KnotweedFallopia japonica

  19. Large-Flowered WaterweedEgeria densa

  20. Mile-a-Minute WeedPersicaria perfoliata

  21. New Zealand PigmyweedCrassula helmsii

  22. Parrots FeatherMyriophyllum aquaticum

  23. Red AlgaGrateloupia doryphora

  24. RhododendronRhododendron ponticum

  25. SalmonberryRubus spectabilis

  26. Sea-Buckthorn Hippophae rhamnoides

  27. Spanish Bluebell Hyacinthoides hispanica

  28. Three-Cornered LeekAllium triquetrum

  29. WakameUndaria pinnatifida

  30. Water ChestnutTrapa natans

  31. Water FernAzolla filiculoides

  32. Water LettucePistia stratiotes

  33. Water-PrimroseLudwigia (all species)

  34. WaterweedsElodea (all species)

  35. WireweedSargassum muticum

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