WAMSI 2 - KMRP Project 2.2.9: Historical Water Quality using sediment records

The remote Kimberley coast of north-western Australia is one of the few marine environments domains on earth largely unaffected by human use. However, the region is undergoing increasing economic importance as a destination for tourism and significant coastal developments associated with oil and gas exploration. The objective of the project was to reconstruct a timeline of inferred water quality changes from the sediment record for a selected set of sites in the Kimberley, Western Australia. \n\nThe project made use of palaeoecological approaches to reconstruct a chronology of change over the last approximately 100 years using a series of biogeochemical proxies for phytoplankton composition and biomass, temperature and terrestrial influences. Where possible these were matched to historical land/water use, meteorological or hydrological observational records. The project examined sediment cores from three coastal locations, Koolama Bay (King George River), Cygnet Bay and Roebuck Bay. Each sampling location provided a contrast with which to evaluate changes over either a spatial or temporal gradient of human or natural influence.\n\nSediment cores (up to 1.5 m) were obtained from each of these locations in the expectation that they would provide a time series for about the last 100 years. A set of parameters was measured along the core length (every 1-2 cm) for some or all cores depending on the particular focus for the location: 210Pb and 137Cs; 15N isotope; 13C isotope; Carbon/Nitrogen ratio; Sedimentation rate and grain size; Total Organic Carbon (TOC) and Total Nitrogen (TN); Biosilicate; Biomarkers; TEX86; long chain n-alkanes (C27+C29+C31); Elemental carbon (or black carbon). \n\nRainfall data was obtained from the Australian Bureau of Meteorology website (www.bom.gov.au). Stream flow data was obtained from the Western Australian Department of Water website (www.water.wa.gov.au). Historical bushfire data was obtained from the Western Australian Department of Parks and Wildlife.\nThe metadata record only relates to data generated as part of the sediment analysis.\n\nLineage: Sediment cores taken at each site (Koolama Bay [King George River], Cygnet Bay and Roebuck Bay) were obtained using a polycarbonate sleeve 6 cm in diameter within a 1.5m long steel casing. At each site, three or four replicate sediment cores with a length of approximately 1.0 – 1.4 meters each were collected. The cores were then frozen on board the ship in a vertical position and were later thawed as they stood vertically and were then sectioned into sub-samples at 1 cm intervals, weighed and freeze dried before being reweighed and then stored in a freezer at -20oC before being analysed.\n\nParameters measured:\n•\t210Pb and 137Cs isotopes – age of core, integrity of age structure in sediment;\n•\t15N isotope – a proxy for nitrogen source – anthropogenic or natural;\n•\t13C isotope – proxy for carbon source – land or marine derived carbon; \n•\tCarbon/Nitrogen ratio – can also be used to infer whether primary carbon source is marine or terrestrial;\n•\tSedimentation rate and grain size shows the variation of sedimentary environment (e.g. river input, sediment texture, other factors governing deposition and preservation);\n•\tTotal Organic Carbon (TOC) and Total Nitrogen (TN) indicate levels of productivity and deposition of organic matter;\n•\tBiosilicate indicates siliceous phytoplankton deposits (e.g. diatoms, silicoflagellates), enhanced productivity; \n•\tBiomarkers – sterols can be used as proxies for dinoflagellates (dinosterol), diatoms (brassicasterol) haptophytes (alkenones); TEX86 index for sea temperature; and long chain n-alkanes (C27+C29+C31) for terrestrial influence.\n•\tElemental carbon (or black carbon) – indicators of biomass burning (e.g. from bushfires) or hydrocarbon burning (fossil fuels).\n\nFor Full details, see KMRP 2.2.7 Final Report. \n\nRainfall data was obtained from the Australian Bureau of Meteorology website (www.bom.gov.au). Stream flow data was obtained from the Western Australian Department of Water website (www.water.wa.gov.au). Historical bushfire data was obtained from the Western Australian Department of Parks and Wildlife. \t\n

澳大利亚西北部偏远的金伯利（Kimberley）海岸是地球上少数几乎未受人类活动影响的海洋环境区域之一。然而，该区域作为旅游目的地以及与油气勘探相关的大型沿海开发项目的选址，其经济重要性与日俱增。本项目的目标是基于西澳大利亚金伯利地区选定采样点的沉积物记录，重建可推断的水质变化时间线。

本项目采用古生态学（palaeoecological）方法，利用一系列指示浮游植物（phytoplankton）组成与生物量、水温以及陆地影响的生物地球化学代用指标（biogeochemical proxies），重建了过去约100年的环境变化年表。在条件允许的情况下，将这些指标结果与历史土地与水资源利用、气象或水文观测记录进行了匹配。项目对三个沿海点位的沉积物岩芯（sediment cores）开展了研究，分别是库拉马湾（Koolama Bay，金乔治河）、天鹅湾（Cygnet Bay）与罗巴克湾（Roebuck Bay）。每个采样点位均设置了对照，用于评估人类或自然影响下的空间或时间梯度变化。

从上述各点位采集了最长可达1.5米的沉积物岩芯，以期获取过去约100年的时间序列数据。依据各点位的研究重点，沿岩芯长度方向（每1-2厘米间隔）对部分或全部岩芯测定了以下参数：210Pb与137Cs同位素、15N同位素、13C同位素、碳氮比、沉积速率与粒度、总有机碳（Total Organic Carbon, TOC）与总氮（Total Nitrogen, TN）、生物硅酸盐（biosilicate）、生物标志物（biomarkers）、TEX86指数（TEX86）、长链正构烷烃（C27+C29+C31）以及元素碳（或称黑碳）。

降雨数据源自澳大利亚气象局（Australian Bureau of Meteorology）官网（www.bom.gov.au）；径流数据源自西澳大利亚州水务局（Western Australian Department of Water）官网（www.water.wa.gov.au）；历史山火数据源自西澳大利亚州公园与野生动物管理部门。本元数据（metadata）记录仅涉及沉积物分析产生的相关数据。

采样流程：在每个采样点位（库拉马湾[金乔治河]、天鹅湾与罗巴克湾），使用直径6厘米的聚碳酸酯套管配合1.5米长的钢质套管采集沉积物岩芯。每个点位采集3至4根重复岩芯，单根岩芯长度约1.0至1.4米。岩芯采集后在船上以垂直状态冷冻保存，后续取出后仍保持垂直状态解冻，随后以1厘米间隔切割为子样本，称重后进行冷冻干燥，再次称重后置于-20℃冰箱中保存以待分析。

本次测定的参数详情如下：
• 210Pb与137Cs同位素：用于确定岩芯年代以及沉积物年代结构的完整性；
• 15N同位素：作为氮源的代用指标，可区分人为来源与自然来源；
• 13C同位素：作为碳源的代用指标，可区分陆地来源与海洋来源碳；
• 碳氮比：同样可用于推断初级碳来源为海洋还是陆地；
• 沉积速率与粒度：可反映沉积环境的变化，如河流输入、沉积物质地以及其他控制沉积与保存的因素；
• 总有机碳（Total Organic Carbon, TOC）与总氮（Total Nitrogen, TN）：可指示生产力水平与有机质沉积情况；
• 生物硅酸盐：可指示硅质浮游植物（如硅藻、硅鞭藻）的沉积量，反映生产力提升情况；
• 生物标志物：甾醇类物质可作为甲藻（甲藻甾醇）、硅藻（菜子甾醇）、定鞭金藻（烯酮类）的代用指标；TEX86指数用于表征海水温度；长链正构烷烃（C27+C29+C31）用于指示陆地影响；
• 元素碳（或称黑碳）：可指示生物质燃烧（如山火）或化石燃料燃烧产生的污染物。

详细内容请参见KMRP 2.2.7最终报告。

降雨数据源自澳大利亚气象局官网（www.bom.gov.au）；径流数据源自西澳大利亚州水务局官网（www.water.wa.gov.au）；历史山火数据源自西澳大利亚州公园与野生动物管理部门。