BIOTIC Species Information for Ascophyllum nodosum
Researched byJacqueline Hill & Nicola White Data supplied byMarLIN
Refereed byDr Dagmar Stengel
General Biology
Growth formShrub
Feeding methodPhotoautotroph
Mobility/MovementPermanent attachment
Environmental positionEpifloral
Typical food typesNot relevant HabitAttached
BioturbatorNot relevant FlexibilityHigh (>45 degrees)
FragilityFragile SizeLarge(>50cm)
Height Growth Rate5 - 15 cm/year
Adult dispersal potentialNone DependencyIndependent
General Biology Additional Information
  • The species is very long lived and has low recruitment. Growth rate is very slow in germlings but increases as the plant ages. During the first year growth takes place at 0.2 cm per year, rising to 1.5 cm per year in the second year (Sundene, 1973). The first air bladder is formed in the fifth year, after which they are produced annually. The holdfasts of Ascophyllum nodosum are thought to persist for several decades from which new fronds regenerate.
  • Growth is apical. 90% of the apical elongation takes place in the 0 to 5mm zone behind the apex. Growth rate is maximal in the morning, followed by a continuous decline throughout the day (Strömgren & Nielsen, 1986). In Strangford Lough in Northern Ireland, Stengel & Dring (1997) observed growth to be highly seasonal with low growth rates during November and December, and highest growth rates in late spring and early summer. A decline in growth in mid-summer was observed at all shore levels.
  • Ascophyllum nodosum repeatedly sloughs its entire outer epidermis, a phenomenon not exhibited by other related seaweeds. (Filion-Myclebust & Norton, 1981). Despite its longevity Ascophyllum nodosum is remarkably free of epiphytes even when adjacent plants of other species of fucoid algae are heavily infested. Shedding activity appears to contribute to this difference. The authors frequently observed that when the outer layers are shed, potential epiphytes including spores and germlings of other algae that had settled on the surface were discarded with the epidermis. Only those epiphytes with deeply penetrating rhizoids, such as Polysiphonia lanosa (see below), are able to maintain a hold.
  • Polysiphona lanosa is an obligate epiphyte that occurs primarily on Ascophyllum nodosum. The rhizoids of Polysiphonia lanosa penetrate the host and obtain some nutrition from Ascophyllum nodosum. However, the quantity of carbon obtained is minimal and Polysiphonia is pigmented and can photosynthesize itself (Levin & Mathieson, 1991).
  • The thalli of Ascophyllum nodosum contain an endophytic fungus, the ascomycete Mycosphaerella ascophylli Cotton, that penetrates throughout the thallus (Fries, 1988). Garbary & MacDonald (1995) provided experimental evidence for an obligate mutualistic symbiosis where infected thalli were longer, had greater apical diameters and more apical hairs than non-infected thalli. Garbary & London (1995) also suggest that the fungus may protect Ascophyllum nodosum from desiccation.
Biology References Baardseth, 1970, Strömgren & Nielsen, 1986, Fish & Fish, 1996, Filion-Myclebust & Norton, 1981, Fries, 1988, Garbary & London, 1995, Garbary & MacDonald, 1995, Sundene, 1973, Chock & Mathieson, 1976, Gibb, 1957, Levin & Mathieson, 1991, Barton, 1892, Stengel & Dring, 1997,
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