Kelp rafts in the Southern Ocean: intercontinental travel for sessile and semi-sessile organisms 2010

Brief description

Metadata record for data from ASAC Project 2914
See the link below for public details on this project.

Can animals raft between countries on floating seaweed? We aim to answer that question using powerful genetic tools. We can tell whether gene flow is strong between populations of animals by comparing their mitochondrial DNA; this could show us whether animals from one species in New Zealand are isolated from individuals of the same species in Chile. If they are not isolated, how are they managing to maintain gene flow? We know there are many millions of clumps of floating seaweed in the Southern Ocean, and these might provide a means of intercontinental travel for a range of small invertebrates.

Project objectives:
The primary objective of the project is to determine the effectiveness of rafting as a dispersal mechanism for sessile and semi-sessile organisms around the Southern Ocean using genetic tools.

The secondary objectives, by which the primary objective will be addressed, are:

- to examine the biogeography of bull kelp (Durvillaea antarctica) and its holdfast fauna around the Southern Ocean

- to undertake genetic analysis of a wide range of macroalgal (seaweed) species throughout the Southern Ocean to assess 1) whether sea ice indeed extended further north than previously believed, and 2) the ecological and evolutionary impacts of historic ice scour on Southern Ocean islands.

- to determine which holdfast invertebrates are the most common and ubiquitous in holdfasts of Durvillaea antarctica around the Southern Ocean

- to compare the genetic structure of populations of both the kelp itself, and select invertebrate taxa* from its holdfasts, on a number of spatial scales:
--- genetic variation at HOLDFAST level: are members of a single species, e.g., the isopod Limnoria stephenseni, closely related within a single holdfast?
--- genetic variation at SITE level: are members of a single species, e.g., Durvillaea antarctica itself, closely related at one site? In this case, a 'site' means a single intertidal rock platform.
--- genetic variation at NATIONAL level: are there distinct biogeographic separations of species, or does a single species show distinct genetic disjunction, along the Chilean coastline and around the south island of New Zealand?
--- genetic variation at OCEAN level: are species clearly connected (by gene flow) between Southern Ocean landmasses? The landmasses of interest are: Chile, New Zealand, and the subantarctic islands on which Durvillaea antarctica grows.

* The proposed taxa that this project will focus on are: the isopod genus Limnoria; the amphipod Parawaldeckia kidderi; the chiton genus Onithochiton; the polychaete worm families Terebellidae and Syllidae; a topshell; a bivalve; barnacles.

Progress against objectives:

Considerable progress has been made against the primary objective since the start of the project in 2006. We have collected (/ been sent) and analysed samples of bull-kelp (Durvillaea antarctica) and its associated invertebrate holdfast fauna from numerous sites around the Southern Ocean (subantarctic islands including Macquarie, Gough, Marion, Kerguelen, Crozet, Auckland, Antipodes, Campbell, Falkland Islands; along the coasts of New Zealand and Chile). Our results thus far have allowed us to determine not only that rafting facilitates long-distance dispersal of these otherwise sedentary taxa, but also that sea ice during the last ice ice likely had significant impacts on subantarctic intertidal ecosystems. Our conclusions have been published in several papers in high-impact journals.

The secondary objectives, by which the primary objective will be addressed, are:

- to examine the biogeography of bull kelp (Durvillaea antarctica) and its holdfast fauna - these objectives have now largely been achieved, and results published.

- to undertake genetic analysis of a wide range of macroalgal (seaweed) species throughout the Southern Ocean - this part of the project is ongoing, and will make use of samples collected over the austral summer from Macquarie Island (and other locations around the southern hemisphere). all samples have now been collected and are being processed in the laboratory.

- to determine which holdfast invertebrates are the most common and ubiquitous - this objective has been partially achieved (see Nikula et al. 2010), but research is ongoing.

- to compare the genetic structure of populations of both the kelp itself, and select invertebrate taxa from its holdfasts, on a number of spatial scales - this objective has been partially achieved (see Nikula et al. 2010 for results of Limnoria and Parawaldeckia genetic research) but additional research on these and other taxa continues.


The download file contains an excel spreadsheet detailing collection locations and accession numbers for the samples collected on Macquarie Island. A text document providing accession numbers for non-Antarctic related samples used in this project is also part of the download file. Quality: The figures provided in temporal and spatial coverage are approximate only.

Taken from the 2009-2010 progress report:

Field work:
During the 2009/2010 season, Dr James Doube and other AAD personnel based at Macquarie Island were able to collect the macroalgal samples we requested. Field work was undertaken at two sites close to the Base: one on the east coast (Garden Cove, 57F 0496283 3960990) and one on the west coast (Cosray Rocks, 57F 0495752 3960973). Fieldwork involved collection of small samples of intertidal seaweeds (macroalgae) from rock platforms at Macquarie Islands. Samples were preserved in ethanol, and couriered to our department at the University of Otago. These samples were received on 14 May 2010, and are now being processed in the laboratory.

Field work for the broader project is ongoing - however, during the 2009 / 2010 summer, we collected (or were sent) samples from:
- the Falkland Islands
- central Chile
- southern Chile (fiordland)
- the New Zealand subantarctic (Campbell, Auckland, Snares, Antipodes and Bounty Islands)
- Kerguelen Island
- Marion Island
- Gough Island
- Tasmania, Australia

Difficulties affecting project:
Not all target species of seaweed were obtained from all collection sites (both at Macquarie Is and elsewhere) - however, on the whole we have obtained most of our target taxa from a broad range of subantarctic locations.

Note from AADC, 2018-08-03:
The original datasheet was reformatted to fit OBIS/GBFI/IPT Biodiversity.AQ standardS. The new datasheet "KelpRafts.csv" provides the dataset from Macquarie Island samples. Contains datasetID, occurrenceID, event date, decimal latitude, decimal longitude. The lowest taxonomical rank of the species identified that could be determined is provided, after matched in WoRMS (World Register of Marine Species). As the data is genetics identification the associatedSequence and associatedReferences are provided.