In a recent short communication titled ‘First mesophotic Ecklonia radiata (Laminariales) records within the iSimangaliso Wetland Park marine-protected area, east coast, South Africa’ by Qwabe et al. (Reference Qwabe, Samaai, Harris, Palmer and Kerwath2023), the assertion of discovering a mesophotic population of kelp in the iSimangaliso Wetland Park is made by the authors. However, contrary to this claim, published literature has long recognized the presence of a mesophotic population of Ecklonia radiata in the extreme northeast of South Africa, where the iSimangaliso Wetland Park is situated.
Ecklonia radiata has been confirmed to have a widespread distribution throughout the Indo-West Pacific, as reported by Coleman et al. (Reference Coleman, Reddy, Nimbs, Marshell, Al-Ghassani, Bolton, Jupp, De Clerck, Leliaert, Champion, Pearson, Serrão, Madeira and Wernberg2022). Its populations typically occur in deeper water environments, with the exception of South Africa. There, coastal populations have been documented from De Hoop to Port Edward, alongside deeper water populations. Qwabe et al. (Reference Qwabe, Samaai, Harris, Palmer and Kerwath2023) make a sweeping claim that the species is recorded for the first time north of its recognized range, erroneously citing Port Edward as the eastern distribution limit for the species in southern Africa. Bolton and Anderson (Reference Bolton and Anderson1987) posit that pinpointing the eastward range limit of E. radiata in South Africa is challenging, based on observations in deeper waters off Natal (now Kwa-Zulu Natal). Additional details regarding these little-known deep-water populations, including their occurrence at 40 m, a depth considered mesophotic, were subsequently published in Bolton and Anderson (Reference Bolton, Anderson and Akatsuka1994). Stegenga et al. (Reference Stegenga, Bolton and Anderson1997) note the occurrence of the species at depths of 30–40 m in Zululand, the municipal district within which the iSimangaliso Wetland Park falls. Further references to these mesophotic populations of E. radiata are available in De Clerck et al. (Reference De Clerck, Bolton, Anderson and Coppejans2005), who mention occurrences up to 60 m at Sodwana Bay (within the extent of the iSimangaliso Wetland Park). This information is also reiterated in Anderson et al. (Reference Anderson, Stegenga and Bolton2016), a user-friendly, publicly available online resource for local seaweeds. It is worth noting that Qwabe et al. (Reference Qwabe, Samaai, Harris, Palmer and Kerwath2023) cite a chapter from De Clerck et al. (Reference De Clerck, Bolton, Anderson and Coppejans2005), but appear not to have consulted it thoroughly, as the pertinent information is clearly present in the cited literature.
Beyond two published field guides (Stegenga et al., Reference Stegenga, Bolton and Anderson1997; De Clerck et al., Reference De Clerck, Bolton, Anderson and Coppejans2005), an online resource (Anderson et al., Reference Anderson, Stegenga and Bolton2016), a book chapter (Bolton and Anderson, Reference Bolton, Anderson and Akatsuka1994), and a published article (Bolton and Anderson, Reference Bolton and Anderson1987), more substantial support for the existence of this population is also available. This evidence encompasses a herbarium record (NU0094006), published photographs (PSSA, 2019), and a DNA barcode (OM650132). Notably, a herbarium specimen deposited at the Bews Herbarium (NU) of E. radiata (as Ecklonia biruncinata) from St Lucia, part of the iSimangaliso Wetland Park, dates back to 1967. In 2018, the identity of the mesophotic kelp in the iSimangaliso Wetland Park was confirmed for the first time using DNA and published in a review by Wernberg et al. (Reference Wernberg, Coleman, Babcock, Bell, Bolton, Connell, Hurd, Johnson, Marzinelli, Shears and Steinberg2019). Details of the DNA barcodes, based on specimens collected from Cape Vidal within the iSimangaliso Wetland Park, were formally published in Coleman et al. (Reference Coleman, Reddy, Nimbs, Marshell, Al-Ghassani, Bolton, Jupp, De Clerck, Leliaert, Champion, Pearson, Serrão, Madeira and Wernberg2022) under the accession number: OM650132. Qwabe et al. (Reference Qwabe, Samaai, Harris, Palmer and Kerwath2023) proceed to formulate hypotheses regarding the dispersal history and origin of the supposedly newly discovered population, relying on mtDNA barcodes as published in Coleman et al. (Reference Coleman, Reddy, Nimbs, Marshell, Al-Ghassani, Bolton, Jupp, De Clerck, Leliaert, Champion, Pearson, Serrão, Madeira and Wernberg2022). While mtDNA is valuable for evolutionary hypotheses, it is typically employed in conjunction with other genes to reinforce such hypotheses. A notable drawback of relying solely on mtDNA for evolutionary hypotheses is its limited capacity to detect hybridization, a phenomenon well-documented in kelps, and indeed observed under laboratory conditions for E. radiata and Ecklonia maxima (Bolton and Anderson, Reference Bolton and Anderson1987). Coleman et al. (Reference Coleman, Reddy, Nimbs, Marshell, Al-Ghassani, Bolton, Jupp, De Clerck, Leliaert, Champion, Pearson, Serrão, Madeira and Wernberg2022) exercise caution when discussing hypotheses on the dispersal and origin of E. radiata in their work for these reasons.
Additionally, the study by Qwabe et al. (Reference Qwabe, Samaai, Harris, Palmer and Kerwath2023) is marked by numerous inaccuracies, with many instances where source information is incorrectly cited. Facts are often misattributed, and sources are either incorrectly cited or do not cite the primary literature. For instance, Graham et al. (Reference Graham, Kinlan, Druehl, Garske and Banks2007) serve as a reference for the species composition of a typical coastal kelp forest in South Africa. Although the focal point of Graham et al. (Reference Graham, Kinlan, Druehl, Garske and Banks2007) is in fact mesophotic kelp, their predictive models are limited to a region between 20′N and 20′S, excluding South Africa altogether. Another concern surfaces with the incomplete distribution map (Figure 1; Qwabe et al., Reference Qwabe, Samaai, Harris, Palmer and Kerwath2023) which omits Ecklonia muratii, a species considered part of E. radiata complex and for which herbarium records exist. Finally, it is worth questioning the contention that E. radiata is the most extensively distributed kelp in the Southern Hemisphere. This claim is debatable, especially when considering the broad distribution of Macrocystis pyrifera (Macaya and Zuccarello, Reference Macaya and Zuccarello2010). Confirmed records indicate that E. radiata occurs in the Indo-Pacific (Coleman et al., Reference Coleman, Reddy, Nimbs, Marshell, Al-Ghassani, Bolton, Jupp, De Clerck, Leliaert, Champion, Pearson, Serrão, Madeira and Wernberg2022), whereas M. pyrifera is present along all major continental coastlines in the Southern Hemisphere, encompassing numerous islands in the region (Macaya and Zuccarello, Reference Macaya and Zuccarello2010). These seemingly semantic discrepancies could have been easily avoided through consultation with active researchers in the field.
While it might appear that the foundation of the article rests on potentially overlooked information, this is not the case. Prior to submission of the article, the corresponding author and I engaged in discussions regarding the mesophotic kelp population in the iSimangaliso Wetland Park. He was therefore aware that the population was not new as the article claims and that a DNA barcode from Cape Vidal (iSimangaliso Wetland Park) by Coleman et al. (Reference Coleman, Reddy, Nimbs, Marshell, Al-Ghassani, Bolton, Jupp, De Clerck, Leliaert, Champion, Pearson, Serrão, Madeira and Wernberg2022), which confirmed the species’ identity had been published. What becomes strikingly evident from this article is the need for more systematic evaluation of deep-water kelp populations in southern Africa. Qwabe et al. (Reference Qwabe, Samaai, Harris, Palmer and Kerwath2023) through their innovative use of remotely operated vehicles contribute to this by assessing the extent of underwater kelp forests in South Africa. This is particularly valuable, especially when considering the role of kelps as a potential source of blue carbon. However, such studies should be conducted in a way that ensures the dissemination of accurate information.
