Obtaining spores for the production of Saccharina latissima: seasonal limitations in nature, and induction of sporogenesis in darkness

Abstract

When cultivating the kelp Saccharina latissima, knowledge on the availability of seeding material for the production is essential. Applying a spore seeding approach requires spores from the reproductive organs of the fertile sporophytes (sori). As sori are generally not present during the time of seeding in late summer, the production of spores (sporogenesis) can be artificially induced by removing the meristematic part of the sporophyte and keeping the sporophyte under short day, temperate, and nutrient-replete conditions. Only limited information is available on the effect of light intensities including darkness on the sporogenesis of S. latissima. This study examined the natural pattern of sporogenesis in S. latissima from Middelfart, Denmark, and the effect of four different light regimes (0, 20, 60, or 120 μmol photons m−2 s−1) on the artificial induction of sporogenesis in S. latissima. Natural reproductivity and availability of spores in Denmark peaked in early winter, with 86% of the population being reproductive in November. Reproductive material was available from October until late spring, but with a variable spore release from 11 × 103 to 1.2 × 106 spores cm−2 sori. The artificial induction of sporogenesis was optimal in darkness with > 90% of sporophytes developing sori after 49 days, with an average spore release density of 1.15 ± 0.38 × 106 spores cm−2 sori. The results confirmed that S. latissima in Denmark follows the general pattern of reproduction of S. latissima in North Atlantic regions and demonstrated for the first time that sporogenesis in S. latissima can be efficiently induced in darkness.

Optimising the zoospore release, germination, development of gametophytes and formation of sporophytes of Ecklonia radiata

“…Kelp species are widespread in temperate regions, which are characterised by strong seasonal variation in daylength, light intensity and temperature (Lüning 1993). In general, growth and reproduction of kelps show clear seasonal patterns (Kain 1979;Novaczek 1984a; Lee and Brinkhuis 1988;Fairhead and Cheshire 2004;Bartsch et al 2008;Miller et al 2012;Boderskov et al 2021) and the reproduction of sporophytes (formation of sorus) is driven by short daylengths (Lüning 1988;Pang and Lüning 2004;Boderskov et al 2021) and occurs during periods of low or no growth (Kain 1979). Similarly, daylength is the trigger for the reproduction of gametophytes in kelps, although the requirements for the formation of antheridia and oogonia (gametogenesis) are species-specific (Choi et al 2005;Nelson 2005).…”

Upscaling cultivation of Saccharina latissima on net or line systems; comparing biomass yields and nutrient extraction potentials

“…For all seeding events, a minimum of 10 sporophytes was used for spore extraction. The sporophytes were collected during May -July 2018 and 2019, and artificially induced to produce spores in darkness in an intermediate bulk container (IBC) of 1000 L with up to 50 sporophytes per tank, according to Boderskov et al (2021b). The spores were released from fertile tissue, and counted in a Thoma hemocytometer counting chamber prior to seeding.…”

The sugar kelp Saccharina latissima II: Recent Advances in farming and applications

“…Sporogenesis in S. latissima can also be induced efficiently out of season in total darkness (Boderskov et al 2021).…”

“…The seeding methods did not affect the biomass's protein content when harvested. A Danish study compared biomass yield and quality between direct seeding and traditional spore seeding on twine and two substrates, including three deployment times at three different cultivation sites (Boderskov et al 2021). The main findings showed that the direct seeding method gave yields comparable to the traditional seeding method with spores at the most exposed site, whereas at the sheltered sites, the highest biomass yield was achieved using the traditional spore seeding method.…”