Completed on 26 Jan 2018 by Udo Nitschke. Sourced from https://www.biorxiv.org/content/early/2018/01/05/243410.
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This is a very interesting study and the findings certainly have merit. I would like to make
some general comments on the manuscript as presented. The authors state that Laminariales are the most efficient iodine accumulators (p. 3, l. 69). Latest findings suggest that this is not entirely true. For example, we showed that Fucus vesiculosus (Fucales) is more efficient in iodine accumulation than Laminaria digitata (Nitschke et al. 2018, J. Phycol., doi: 10.1111/jpy.12606). In addition. Laminaria digitata is probably the strongest, as opposed to the most efficient, iodine accumulator (Küpper et al. 1998, Planta 207:163–71; Ar Gall et al. 2004, Bot. Mar. 47:30–7) with iodine levels averaging about 1% dw. By contrast, other Laminariales such as Saccharina spp. and Alaria esculenta contain on average “only” 0.5% dw and 0.05% dw, respectively. Iodine concentrations of many algal species vary greatly among seasons (Ar Gall et al. 2004, Bot. Mar. 47:30–7; Nitschke et al. 2018, J. Phycol., doi: 10.1111/jpy.12606) and thallus parts (Nitschke & Stengel 2015; Food Chem. 172:326–34). The results for intra-thallus variation of iodine levels for kelps are, however, inconsistent: Küpper et al. (1998, Planta 207:163–71) reported that iodine levels in a blade of one Laminaria digitata specimen were higher in distal parts than towards the meristem. By contrast, we observed that iodine levels increase from distal towards basal blades and further to stipes in Laminaria digitata, Laminaria hyperborea and Saccharina latissima (Nitschke & Stengel 2015; Food Chem. 172:326–34). The latter is consistent with the translocation of iodine within algal thalli as documented for Saccharina latissima (Amat & Srivastava 1985, J. Phycol. 21:330–3). Thus, the authors should check their statement on p. 14, l. 379-380. Furthermore, the authors state on
p. 12, l. 344 that iodine contents of kelps increase with seawater depth. Published findings do not support this statement; for example, Laminaria hyperborea usually occurs at greater depths than Laminaria digitata, but Laminaria hyperborea has lower iodine levels than Laminaria digitata. In general, iodine contents are species-specific and, to my knowledge, the proof of the effect of water depth is still missing.
The authors report the expression of vHPOs in gametophytes of Saccharina japonica (p. 10-11, l. 283-290). Küpper et al. (1998, Planta 207:163–71) showed that gametophytes of Saccharina latissima do not take up iodine. Do the authors have any possible explanation for this?
If would be great, if the authors presented iodine contents along with their findings.