How light and biomass density influence the reproduction of delayed Saccharina latissima gametophytes (Phaeophyceae)

Alexander Ebbing; Ronald Pierik; Tjeerd Bouma; Jacco C Kromkamp; Klaas Timmermans

doi:10.1111/jpy.12976

How light and biomass density influence the reproduction of delayed Saccharina latissima gametophytes (Phaeophyceae)

J Phycol. 2020 Jun;56(3):709-718. doi: 10.1111/jpy.12976. Epub 2020 Feb 28.

Authors

Alexander Ebbing^{1

2}, Ronald Pierik³, Tjeerd Bouma^{1

2}, Jacco C Kromkamp^{1

2}, Klaas Timmermans^{1

2}

Affiliations

¹ Department of Estuarine and Delta Systems, NIOZ Royal Netherlands Institute for Sea Research, PO Box 140, 4401 NT, Yerseke, The Netherlands.
² Department Ocean Ecosystems, University of Groningen, PO Box 72, 9700 AB, Groningen, The Netherlands.
³ Department of Biology, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.

Abstract

Kelp life-cycle transitions are complex and susceptible to various (a)biotic controls. Understanding the microscopic part of the kelp's lifecycle is of key importance, as gametophytes form a critical phase influencing, among others, the distributional limits of the species. Many environmental controls have been identified that affect kelp gametogenesis, whose interactive effects can be subtle and counterintuitive. Here we performed a fully factorial experiment on the (interactive) influences of light intensity, light quality, and the Initial Gametophyte Density (IGD) on Saccharina latissima reproduction and vegetative growth of delayed gametophytes. A total of 144 cultures were followed over a period of 21 d. The IGD was a key determinant for reproductive success, with increased IGDs (≥0.04 mg DW · mL^-1 ) practically halting reproduction. Interestingly, the effects of IGDs were not affected by nutrient availability, suggesting a resource-independent effect of density on reproduction. The Photosynthetically Usable Radiation (PUR), overarching the quantitative contribution of both light intensity and light quality, correlated with both reproduction and vegetative growth. The PUR furthermore specifies that the contribution of light quality, as a lifecycle control, is a matter of absorbed photon flux instead of color signaling. We hypothesize that (i) the number of photons absorbed, independent of their specific wavelength, and (ii) IGD interactions, independent of nutrient availability, are major determinants of reproduction in S. latissima gametophytes. These insights help understand kelp gametophyte development and dispersal under natural conditions, while also aiding the control of in vitro gametophyte cultures.

Keywords: Saccharina latissima; Gametophyte; Initial Gametophyte Density; Interaction; Kelp; Lifecycle control; Light intensity; Light quality; Photosynthetically Usable Radiation; Reproduction; Vegetative growth.

MeSH terms

Biomass
Germ Cells, Plant
Kelp*
Phaeophyceae*
Reproduction