Assessing the threat to Antarctic shallow marine ecosystems from hitchhikers on non-native kelp

Human activity and shipping have long been considered the principal threats to the “biosecurity” of the remote and isolated shallow marine ecosystems of Antarctica (Chown et al., 2015). However, recent work has shown that the Southern Ocean’s strong, circumpolar winds, currents and fronts may not be a barrier to natural colonization from the north (Fraser et al., 2018). The sub-Antarctic (Patagonia, the Falkland Islands, New Zealand and the mid-latitude islands of the Southern Hemisphere) shallow water marine environment is often characterized by highly exposed shores on extremely remote islands (Griffiths & Waller, 2016). The ice-free coastlines are often dominated by dense beds of the kelp Durvillaea antarctica, Macrocystis pyrifera and other large macrophytes. Antarctic shallow coastal marine communities were long thought to be isolated from their subAntarctic neighbours by hundreds of kilometres of deep ocean and the Antarctic Circumpolar Current. 

According to the literature, over 70 million kelp rafts are afloat in the Southern Ocean at any one time (Smith, 2002). These living, floating islands can play host to a range of passenger species from both their original coastal location and those picked in the open ocean. Driven by winds, currents and storms towards the coast of the continent, these rafts are often cited as theoretical vectors for the introduction of new species into Antarctica and the sub-Antarctic islands.

Our discovery of non–native kelp and a wide range of “hitchhiking” passenger organisms washed up on Antarctic beaches led us to question the permeability of these barriers to species dispersal (Avila et al., 2020). This is the first evidence of non-native species reaching the Antarctic continent alive on kelp rafts. One passenger species, the bryozoan Membranipora membranacea, is found to be an invasive and ecologically harmful species in some cold-water regions, and this is its first record from Antarctica (Avila et al., 2020).

The successful applicant will investigate the communities found on floating and beached kelp from southern Chile, the Falklands, South Georgia and Antarctica using existing data and samples, opportunistic collections by scientific expeditions (including partners from University of Barcelona on the Spanish National Antarctic Expeditions), tourist vessels and previous expeditions. The candidate will be working with collaborators/partners in Chile (University of Magallanes) and the Falklands (South Atlantic Environmental Research Institute) and also the possibility to examine in situ kelp beds on a field campaign to the South Atlantic to quantify the potential hitchhikers for comparison. The candidate will investigate patterns in the species found using taxonomic and molecular methods and oceanographic models. Another aspect of the study could include cold tolerance experiments for some of the subAntarctic species to investigate their survival potential in Antarctica.

 

Refs:

Avila, C., et al. Invasive marine species discovered on non–native kelp rafts in the warmest Antarctic island. Sci Rep 10, 1639 (2020).

Chown, S. L. et al. The changing form of Antarctic biodiversity. Nature 522, 431–438 (2015).

Fraser, C. I. et al. Antarctica’s ecological isolation will be broken by storm-driven dispersal and warming. Nat. Climate Change 8, 704–708 (2018).

Griffiths, H. J. & Waller, C. L. The first comprehensive description of the biodiversity and biogeography of Antarctic and Sub-Antarctic intertidal communities. J. Biogeogr. 43, 1143–1155 (2016).

Smith, S. D. Kelp rafts in the Southern Ocean. Global Ecol. Biogeogr. 11, 67–69 (2002).