Influence of light quality and gassing on the vertical migration of diatoms inhabiting the Wadden Sea

Abstract

Diatoms inhabiting the Wadden Sea show a rhythmic migration pattern, which is superimposed by the tidal rhythm. In addition to light intensity, light quality has a pronounced influence on the upward-directed migration, thus giving some information on the nature of the relevant photoreceptors. Maximum diatom migration occurred when sediment surfaces were illuminated with blue light. The cell densities in blue light exceeded those of white light control experiments 1.8-fold. Furthermore, we registered a minor peak in the red light region, which reached approximately 60% of the white light controls. Cryptochrome and/or phototropin may thus be involved and act as photoreceptors for the vertical migration pattern. Flushing sediment surfaces of freshly mixed Wadden Sea sediments with air, O 2 , CO 2 or N 2 did not show a significant influence of O 2 on the upward migration. The disappearance of diatoms from sediment surfaces which were flushed with CO 2 is most probably caused by the acidification of the sediment bed.

Effect of Light Intensity and Light Quality on Diatom Behavioral and Physiological Photoprotection

“…A stronger migration response and diatom accumulation in blue light has been supported by Nultsch (1971) early work on Nitzschia communis as well as McLachlan et al (2009) on Navicula perminuta where wavelengths up to 540 µm induced positive phototropism while red wavelengths did not. Similarly, Wenderoth and Rhiel (2004) observed cell accumulations 1.8 times higher in blue compared to white light (low fluence rate 5 µmol.photons.m −2 .s −1 ). The cited studies were done at low light levels and are consistent with the absorptivity increases we observed in blue LL in comparison to green, red and dark (Figure 4), supporting the hypothesis that at low fluence rates blue wavelengths are more efficient at stimulating diatom movements.…”

“…However, these changes in light composition can affect diatom photo-protective capacity and photo-acclimation to high light intensities (Phaeodactylum tricornutum) (Schellenberger Costa et al, 2013a;Brunet et al, 2014). Light composition can also affect locomotion speed thereby affecting diatom vertical migration (Wenderoth and Rhiel, 2004;McLachlan et al, 2009). Spectral differences affect the relative proportion of photons available at each wavelength per unit area in a given time.…”

Sensing and Signalling in Diatom Responses to Abiotic Cues

“…Envionmental samples, G. fasciola, N. spartinetensis(Barnett et al 2020) upward migration in sediment Wadden sea populations(Wenderoth and Rhiel 2004) sinking rate T. weissflogii(Fisher et al 1996) photophobotaxis N. communis(Nultsch 1971) photophobotaxis Cryptochromes ? Aureochromes ?N.…”