Environmental conditions influencing growth rate and stalk formation in the estuarine diatom Licmophora flabellata (Carmichael ex Greville) C. Agardh

Submerged natural and artificial marine substrata can rapidly become covered by biofouling organisms, of which diatoms are the early algal colonisers. Licmophora flabellata is an estuarine stalk-forming diatom that strongly adheres to substrata via a compound-branching polysaccharide stalk. In the present study, the effects of light, nutrients, temperature and turbulence were examined in laboratory cultures to determine how they affected stalk formation and growth rates. Growth rates in multiwell plates were estimated using in vivo fluorescence in a plate reader. Low light intensities (50, 100 and 150 µmol photons m⁻² s⁻¹) produced no or poor growth, whereas growth rates of 0.24–0.42 divisions per day were achieved at 233 µmol photons m⁻² s⁻¹. High growth rates coincided with long stationary growth periods (21–36 days) and long branching stalks (800–3500 µm). N, P and Si nutrients had no effect on growth or stalks, whereas high turbulence (from an orbital shaker) reduced stalk length but not growth. The results call for species-specific approaches towards mitigating the impact of fouling diatoms.