WAMSI 2 - Dredging Node - Project 5.3 - Natural Dynamics

The Theme 5.3 study was undertaken to improve our understanding of the spatial and temporal patterns in seagrass composition, abundance and reproductive phenology in the Pilbara region. Key environmental parameters, especially light, that influence seagrass survival and can be altered by dredging were also characterised.

From August 2013 to March 2015 (18 months), surveys of seagrass abundance were undertaken in the Exmouth Gulf region. The locations surveyed (South Muiron Island, Bundegi and Exmouth Gulf) encompassed a range in water clarity from clear to turbid. Less frequent surveys were undertaken at other locations in the Pilbara: Thevenard Island, Rosemary Island and Balla. Measurements of seagrass abundance were also obtained from monitoring conducted as part of the dredging and dredge-spoil management plan for Chevron Australia's Wheatstone Liquefied Natural Gas (LNG) Project.

During each survey measurements were made in the field, photographs were taken or samples were collected in order to measure the following variables:
1. percentage cover of seagrass and other benthos;
2. above- and below-ground biomass, shoot density, leaf length, leaf width and number of flowers;
3. density of seagrass seeds;
4. sediment grain size;
5. stable isotope ratios (Ô13C and Ô15N) of seagrass leaf tissue; and
6. water quality (light, conductivity, temperature, salinity, nutrients, suspended particulate matter and chlorophyll).

本主题5.3研究旨在加深对皮尔巴拉（Pilbara）区域海草群落组成、丰度及繁殖物候的时空分布格局的认知，同时对影响海草存活、且可因疏浚作业发生改变的关键环境参数（尤其是光照）开展特征表征。

2013年8月至2015年3月（共计18个月），研究团队在埃克斯茅斯湾（Exmouth Gulf）区域开展海草丰度调查。本次调查覆盖南缪恩岛（South Muiron Island）、邦德吉（Bundegi）及埃克斯茅斯湾3个点位，其水体透明度覆盖从清澈到浑浊的梯度范围。此外，研究团队在皮尔巴拉区域的其他点位——瑟纳德岛（Thevenard Island）、罗斯玛丽岛（Rosemary Island）及巴拉（Balla）——开展了频次较低的补充调查。本研究还通过雪佛龙澳大利亚（Chevron Australia）惠斯通液化天然气（LNG）项目的疏浚及疏浚物管理监测计划，获取了海草丰度相关测量数据。

每次野外调查均开展现场测定，并通过拍摄照片或采集样本的方式测定以下变量：
1. 海草及其他底栖生物（benthos）的盖度百分比；
2. 地上、地下生物量，茎枝密度，叶长、叶宽及花数量；
3. 海草种子密度；
4. 沉积物粒径；
5. 海草叶片组织的稳定同位素比值（δ¹³C及δ¹⁵N）；
6. 水质指标：光照、电导率、温度、盐度、营养盐、悬浮颗粒物及叶绿素。