Seaweed biodiversity around the Antarctic Convergence in the South Atlantic

Alexandra Mystikou

Subantarctic and Antarctic regions remain little explored in their seaweed diversity. Major gaps remain in the knowledge of the seaweed biodiversity of the Falkland Islands and South Georgia compared to southernmost South America, Antarctica. So far, coverage of these regions has been inadequate in order to compile a complete inventory. Inevitably, a number of questions still remain unresolved and more have arisen since the last complete inventory by Skottsberg in 1941. Numerous new records were anticipated because of the first-ever use of scuba diving in studying seaweeds of these regions within the framework of this study which faces logistical and safety challenges in such remote areas. All previous investigators relied on collections from the shore or occasionally by dredging and bottom grab, inevitably missing much of the deep-water flora. Also, phycology has adopted new techniques over the years - especially molecular methods, but also the availability of advanced algal culturing techniques.

PhD supervisors: Prof. Frithjof Kuepper (University of Aberdeen), Prof. Pieter van West (University of Aberdeen) and Dr Paul Brickle (SAERI)

Among the main objectives of Alexandra's Ph.D. research is a first-ever inventory of the macroalgal species of the Falkland Islands which are an underexplored hotspot of seaweed biodiversity. During the two research expeditions to the Falkland Islands (in January – March 2013 and November – December 2013), she obtained a large amount of seaweed specimens and samples (~ 500). For each sample, herbarium specimens were created accompanied by silicagel samples for further molecular analysis.

At this stage of her Ph.D. project, a peer-reviewed paper in an ISI-listed journal about the diversity of the seaweed species of the southwestern Antarctic Peninsula has been published (Mystikou et al. 2014, Polar Biology 37, 1607–1619). The diversity of seaweed species of the southwestern Antarctic Peninsula region is poorly studied, contrasting with the substantial knowledge available for the northern parts of the Peninsula. However, this is a key region affected by contemporary climate change. Significant consequences of this change include sea ice recession, increased iceberg scouring and increased inputs of glacial melt water, all of which can have major impacts on benthic communities. We present a baseline seaweed species checklist for the southern Adelaide Island and northern Marguerite Bay region, combining data obtained during a small number of surveys completed in 1973–1975 and a 6-week intensive diving-based field campaign in 2010 – 2011. Overall, with a total of 41 macroalgal species recorded (7 brown, 27 red, 6 green, 1 chrysophyte), the region is species-poor compared to the north of the Antarctic Peninsula, and even more so in comparison with the sub-Antarctic. The key canopy-forming species is Desmarestia menziesii, which is abundant in Antarctic Peninsula waters, but lacking in the sub-Antarctic. Himantothallus grandifolius, which is a common species further north in the Antarctic phytobenthos, was absent in our recent collections. This paper also reports the first record of Aplanochytrium sp. (Labyrinthulomycetes) from this part of Antarctica and in association with Elachista sp.

Another part of her work is currently submitted and reports several new records and reassessments of brown algae and pathogens affecting brown algae from the Falkland Islands, Patagonia and Tierra del Fuego. Subantarctic and Antarctic regions remain little explored in their seaweed diversity. This study, based upon collections in the early 1970s and 2007-2013 and supported by COI sequences, reports new records of seven brown algae (Colpomenia peregrina, Dictyota dichotoma, Hincksia ovata, Hincksia sandriana, Myriotrichia claviformis, Punctaria latifolia, Syringoderma australe), four red algae (Erythrotrichia carnea, Paraglossum salicifolium, Phycodrys antarctica, Plumariopsis eatonii), one green alga (Chaetomorpha aerea) and of the oomycete Anisolpidium ectocarpii. A number of 4 brown algal taxa (Cladothele decaisnei, Geminocarpus geminatus, Ectocarpus dimorphus, Halopteris obovata) from the region were reassessed. The species composition of seven Antarctic and Subantarctic areas was compared based upon records from previous and the current studies, suggesting that Tierra del Fuego and the Falkland Islands share most species of their brown algal flora.

Moreover, an enigmatic brown alga Cladochroa chnoosporiformis that had been collected only on one occasion by Carl Skottsberg in 1907 from Port Philomel, West Falkland, resulting in its formal taxonomic description. Due to the lack of reports since then, doubts had to remain about its existence and identity. Within the framework of this study, Cladochroa was rediscovered after 106 years at its type locality, confirming its existence and morphological features as described by Skottsberg.

In another line of research her Ph.D. project explores the ecology of the seaweed communities around the Falkland Islands and South Georgia. The structure of a community of species and their functional groups points out the ecological status of an area. This project is comparing the number of single species per genus and per family between the three studied areas (Jason Islands, Beauchene Island and South Georgia) where the temperature and the productivity are affected differently by the Antarctic Circumpolar Current. The evolutionary relationships among coexisting species may provide further indicators of the ecology of the habitat.

She has recently been awarded with the “Santander Mobility Award” and the “Interconnect Inspire Student Grant” from Equate Scotland - Women in Science in order to undertake a 2 month research project on population genetics of Lessonia species from the southern South Chile and the Falklands Islands at Pontificia Universidad Católica de Chile in Santiago de Chile with Prof. Sylvain Faugeron’s group.