Abstract
For many types of seaweeds in Polar Regions, open questions remain about how their life cycle contributes to their overall adaptation to the extreme abiotic environment. This applies in particular to the major canopy-forming brown algae in much of the Antarctic Peninsula of the genus Desmarestia, which was investigated here. Diving surveys around Rothera Research Station (Adelaide Island, Antarctica) during December 2017–February 2018 revealed the widespread presence of a hitherto-unknown life form of Desmarestia sp. of a tender, feather-like morphology. Further studies explored whether this could be (1) a new, hitherto undescribed Desmarestia species (2) a new record for the region of a known Desmarestia species previously recorded elsewhere or (3) a so-far unknown life form of a species recorded for the region. Collections enabled the extraction of PCR-friendly DNA and sequencing of ITS1, which unambiguously showed that the samples belonged to Desmarestia menziesii, the only Desmarestia species presently recorded for the Adelaide Island/Marguerite Bay region. The presence of the juvenile morphology was subsequently confirmed throughout much of the natural range of D. menziesii during cruise-based diving surveys along the Western Antarctic Peninsula in 2019 and from collections at Anvers Island in 1989. Our collections thus constitute its juvenile morphology, which is not previously documented in the literature. The wider significance for the Polar seaweeds is discussed in the context of Taxonomy and Ecology.
Highlights
The Antarctic has some of the most extreme environments on planet Earth
The juvenile form of D. menziesii described in this paper was identified using a partial ITS1 sequence (MK506123) aligned with published sequences
Numerous sequences from other Desmarestiales, including all other Desmarestia species known from Antarctica, had previously been obtained
Summary
The Antarctic has some of the most extreme environments on planet Earth. Its marine environment is characterized by low temperatures rarely exceeding the range of − 1.8–2 °C (Barnes et al 2006). Pioneering studies of Antarctic seaweed biodiversity, taxonomy and biogeography were conducted over a century ago by Skottsberg (Skottsberg 1907), with a recent synopsis provided by Wiencke and Clayton (2002). Contrasting with tropical and temperate bioregions, Polar Regions typically show an intertidal zone which is almost devoid of macroalgae. The reason for this are the extreme environmental conditions in the intertidal zone—where temperature extremes range from − 50
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