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

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.

本数据集为ASAC项目2914的元数据记录，有关该项目的公开详情可查阅下方链接。

动物能否借助漂浮海藻实现跨国漂流？本研究旨在借助先进的遗传工具解答这一问题。通过比对动物的线粒体DNA（mitochondrial DNA），我们可以判断不同种群间的基因流（gene flow）强度；借此可探明新西兰某一物种的个体是否与智利同种个体产生了生殖隔离。若二者并未隔离，它们又是如何维持基因交流的？已知南大洋中存在数以百万计的漂浮海藻团块，这些海藻或可为多种小型无脊椎动物提供跨洋迁徙的途径。

项目目标：
本项目的核心目标是借助遗传工具，探明漂流是否为南大洋周边固着及半固着生物的有效扩散途径。

为实现核心目标，本项目设立如下次要目标：
—— 探究南大洋周边牛海带（bull kelp，Durvillaea antarctica）及其固着器（holdfast）附着生物的生物地理学格局
—— 对南大洋内的多种大型藻类（macroalgal，俗称海藻）物种开展遗传分析，以评估两个问题：其一，历史上海域海冰的分布范围是否确实比此前认知的更偏北；其二，历史冰蚀作用对南大洋岛屿产生了怎样的生态与进化影响
—— 明确南大洋周边南极墨角藻（Durvillaea antarctica）固着器中最常见且分布最广泛的无脊椎动物类群
—— 在多个空间尺度上，对比该海带自身及其固着器中选定的无脊椎动物类群的种群遗传结构：
—— 固着器尺度的遗传变异：同一物种的个体（以等足类动物（isopod）Limnoria stephenseni为例）在单个固着器内是否具有较近的亲缘关系？
—— 样地尺度的遗传变异：同一物种的个体（以南极墨角藻自身为例）在同一样地内是否具有较近的亲缘关系？此处的“样地”指单个潮间带岩滩。
—— 国家尺度的遗传变异：沿智利海岸及新西兰南岛周边区域，是否存在物种间显著的生物地理分隔，或是单一物种出现明显的遗传分化？
—— 大洋尺度的遗传变异：南大洋各陆块间的物种是否存在明确的（基因流介导的）遗传连通性？本研究关注的陆块包括：智利、新西兰，以及生长有南极墨角藻的亚南极岛屿。

* 本项目拟重点研究的分类群包括：等足类动物（isopod）团水虱属（Limnoria）；端足类（amphipod）Parawaldeckia kidderi；石鳖（chiton）Onithochiton属；多毛类蠕虫（polychaete worm）蛰龙介科（Terebellidae）和裂虫科（Syllidae）；钟螺类（topshell）；双壳类（bivalve）；藤壶（barnacles）。

项目目标完成进展：
本项目自2006年启动以来，核心目标已取得显著进展。我们已从南大洋周边多个采样点（包括麦夸里岛、戈夫岛、马里恩岛、凯尔盖朗岛、克罗泽群岛、奥克兰群岛、安蒂波德斯群岛、坎贝尔岛、福克兰群岛等亚南极岛屿；以及新西兰与智利沿岸）采集（或获赠）并分析了牛海带（Durvillaea antarctica）及其附着的固着器无脊椎动物样本。截至目前，研究结果不仅证实了漂流可促进这些原本固着的分类群实现长距离扩散，还表明末次冰期的海冰对亚南极潮间带生态系统产生了显著影响。相关研究结论已发表于多篇高影响力期刊论文。

针对核心目标的次要目标完成进展如下：
—— 探究牛海带（Durvillaea antarctica）及其固着器附着生物的生物地理学特征：该目标已基本完成，相关研究结果已发表。
—— 对南大洋内多种大型藻类（海藻）物种开展遗传分析：本项目的这一部分工作仍在进行中，将使用在南半球夏季从麦夸里岛（及南半球其他区域）采集的样本。目前所有样本均已采集完毕，正在实验室中进行处理。
—— 明确牛海带固着器中最常见且分布最广泛的无脊椎动物类群：该目标已部分完成（详见Nikula等人2010年的研究），但相关研究仍在继续。
—— 在多个空间尺度上对比海带自身及其固着器中选定无脊椎动物类群的种群遗传结构：该目标已部分完成（关于团水虱属与Parawaldeckia kidderi的遗传研究结果详见Nikula等人2010年的研究），但针对这些类群及其他分类群的后续研究仍在进行。

下载文件包含一份Excel表格，详细记录了麦夸里岛采集样本的采样地点与采集编号。下载文件中还包含一份文本文档，列出了本项目使用的非南极相关样本的采集编号。数据质量说明：本次提供的时间与空间覆盖范围数据仅为近似值。

本段内容摘自2009-2010年度项目进展报告：

野外工作进展：
2009/2010年度科考季期间，驻留麦夸里岛的James Doube博士及其他澳大利亚南极署（AAD）工作人员成功采集了我们所需的大型藻类样本。采样工作在基地附近的两个点位开展：一处位于东海岸（花园湾，57F 0496283 3960990），另一处位于西海岸（科斯雷岩，57F 0495752 3960973）。本次野外工作从麦夸里岛的岩滩上采集了潮间带海藻（大型藻类）的小型样本。样本用乙醇保存后，通过快递寄往我们位于奥塔哥大学的实验室。这批样本于2010年5月14日签收，目前正在实验室中进行处理。

本项目整体的野外工作仍在持续——不过在2009/2010年夏季，我们已从以下区域采集（或获赠）样本：
—— 福克兰群岛
—— 智利中部
—— 智利南部（峡湾地区）
—— 新西兰亚南极区域（坎贝尔岛、奥克兰群岛、斯奈尔斯群岛、安蒂波德斯群岛与邦蒂群岛）
—— 凯尔盖朗岛
—— 马里恩岛
—— 戈夫岛
—— 澳大利亚塔斯马尼亚州

项目面临的困难：
并非所有采样点（包括麦夸里岛及其他区域）都能采集到目标海藻物种——但总体而言，我们已从多个亚南极区域采集到了大部分目标分类群的样本。

澳大利亚南极数据中心（AADC）2018年8月3日备注：
原始数据表已重新格式化，以符合OBIS/GBFI/IPT Biodiversity.AQ标准。新数据表"KelpRafts.csv"包含麦夸里岛样本的数据集，字段包括数据集ID（datasetID）、发生记录ID（occurrenceID）、事件日期（event date）、十进制纬度（decimal latitude）、十进制经度（decimal longitude）。经与世界海洋物种登记册（WoRMS，World Register of Marine Species）匹配后，将可确定的物种最低分类阶元予以标注。由于本数据集基于遗传鉴定生成，因此同时提供关联序列（associatedSequence）与关联参考文献（associatedReferences）信息。