Marsden fund grant, March 2021 - February 2024
Antarctica has been surrounded by ocean for tens of millions of years, and many researchers have assumed that its unique species and ecosystems evolved largely in isolation. Antarctica’s terrestrial and marine ecosystems have high levels of endemism, and the strong, circumpolar winds and oceanic thermal fronts of the Southern Ocean are widely thought to have blocked passive dispersal of organisms southward into the Antarctic. Indeed, apart from migrating seabirds and marine mammals, and some recent anthropogenic incursions, there is little evidence of Holocene movement into and out of the Antarctic. Although phylogenetic analyses indicate a handful of marine and terrestrial lineages have traversed the Southern Ocean in the >40 million years since Antarctica broke from its last Gondwana connection, there has been little evidence of any such dispersal events in more recent times, supporting the long-held view that physical isolation remains a key factor protecting Antarctic ecosystems.
Tantalising new discoveries are changing our understanding of the evolution and vulnerability of Antarctic ecosystems. For example, in 2017, two pieces of an exotic, cool-temperate bull kelp (Durvillaea) species were found on beaches in Antarctica. Our high-resolution genomic analyses, drawing on thousands of samples previously collected from throughout the species’ range, revealed that each drift individual had travelled tens of thousands of kilometres from its northern source population. Such journeys, traversing presumed oceanic ‘barriers’, were thought at the time to be essentially impossible. Our oceanographic simulations indicated, however, that prior dispersal models were missing key physical parameters – particularly Stokes drift (horizontal transport by wind-driven surface waves) – and that passive dispersal of buoyant objects across the Southern Ocean to Antarctica is both possible and frequent.
With parts of Antarctica among the most rapidly warming regions on Earth, and increasing evidence that the Antarctic is becoming hospitable to diverse taxa from lower latitudes, there is a pressing need to reassess the extent of Antarctica’s biological isolation.
Kelp rafts transport diverse invertebrates (including crustaceans, echinoderms and molluscs) and other taxa (including non-buoyant seaweeds) across oceans, and we now suspect that Antarctic coastlines are bombarded by thousands of such rafts every month. These widely dispersing species have presumably failed to establish in the past because of the extreme environmental conditions in Antarctica – conditions that are rapidly becoming less harsh. Our discovery of non-Antarctic kelp rafts drifting to Antarctica raises critical questions that must be addressed if we are to project how Antarctic ecosystems will change into the future.
At what point, and under what conditions, might these kelp-associated communities be able to settle and establish in Antarctica?
Our research brings together interdisciplinary approaches – genomic, ecological, physiological, and oceanographic / sea ice modelling – to build a comprehensive picture of the scale of biological incursions to Antarctica via rafting.
Specifically, our research targets the following three key objectives:
Objective 1: Empirical genomic data will resolve sources of kelp rafts (Durvillaea and Macrocystis) reaching Antarctica.
Objective 2: Oceanographic and ice modelling will resolve predominant incursion patterns.
Objective 3: Manipulative experiments will resolve which taxa could establish in Antarctica in the future.
Principle Investigator: Ceridwen Fraser
Associate Investigators: Adele Morrison, Andy Hogg, Miles Lamare, Fabien Montiel, Jonathan Waters
Key collaborators: Erasmo Macaya, Huw Griffiths, Cath Waller, Pat Langhorne
Masters: Frances Perry
A postdoctoral fellow will soon be appointed.
We warmly welcome enquiries from prospective research students interested in this project.