Great Barrier Reef Marine Monitoring Program for Inshore Water Quality - Physico-chemical and Nutrient Database

This metadata record describes physico-chemical and nutrient data collected through in situ monitoring by the Great Barrier Reef Marine Monitoring Program for Inshore Water Quality (MMP WQ). A full description of the MMP WQ and its associated datasets can be found in the parent metadata record linked above. Water quality sampling is conducted during both ambient conditions and river discharge events. Ambient monitoring refers to routine sampling during the wet and dry seasons outside of major flood events. Event-based monitoring occurs in response to major flood events to capture conditions within flood plumes; event-based monitoring occurs at the 55 routine site locations, plus 33 additional sites. The MMP WQ uses in situ sampling to measure 17 key parameters:    physico-chemical: salinity, temperature, Secchi depth, total suspended solids (TSS), and coloured dissolved organic matter (CDOM);    nutrient: ammonium (NH4), nitrite (NO2), nitrate (NO3), dissolved inorganic phosphorus (DIP), silicate (Si), particulate nitrogen (PN), particulate phosphorus (PP), total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), particulate organic carbon (POC), and dissolved organic carbon (DOC); and    biological: chlorophyll a (Chl-a).Discrete water samples are collected with Niskin bottles at each site. Samples are collected from the surface (~0.5 m below water surface) and bottom (~1 m above the seabed) of the water column; although, for some event-based sampling only surface water samples are collected. Samples from the Niskin bottles are taken in duplicate and are analysed for the suite of water quality parameters listed above. Detailed descriptions of analytical chemistry procedures can be found in the program's annual published QA/QC report (see link below in Related Information).Brief description of collection, storage and analysis method for parameters:    Salinity: 250 mL unfiltered sample, stored refrigerated at 4ºC in screw-top plastic bottle, analysed on Guildline Portasal Salinometer (temperature-compensated and calibrated using OSIL standard seawater as reference)    Temperature: Electronic reversing thermometer attached to Niskin    Secchi depth: The average of the vertical disappearance and reappearance depths of a Secchi disc    TSS: Filtered onto pre-weighed 47 mm 0.4 µm polycarbonate membrane filter, rinsed with deionised water, dried at 60ºC for 12 hours, gravimetric analysis    CDOM: 50 mL filtered sample (0.2 µm acrodisc), CDOM absorption coefficient at 443 nm calculated from absorbance measured by UV-visible absorption spectroscopy    NH4, NO3, NO2 and DIP: 10 mL filtered sample (0.45 µm minisart), stored frozen at -25°C, filtrate analysed on segmented flow analyser    Si: 10 mL filtered sample (0.45 µm minisart), stored refrigerated at 4ºC, filtrate analysed on segmented flow analyser (reported as Si)    PN and POC: 500 mL filtered onto 25 mm GF/F, stored frozen at -25ºC, analysed by high temperature combustion (Shimadzu TOC-L)    PP: 250 mL filtered onto 25 mm GF/F (0.7 µm), stored frozen at -25ºC, persulphate digestion of filter, colorific (molybdate blue) analysis on UV-Vis spectrophotometer    TDN and TDP: 10 mL filtered sample (0.45 µm minisart), stored frozen at -25ºC, persulphate oxidation/digestion with mixture of NaOH, boric acid and K2S2O8 in autoclave, analysed on segmented flow analyser    DOC: 10 mL filtered sample (0.45 µm minisart), acidified with 100 µL HCl, stored refrigerated at 4ºC, analysed by high temperature combustion (Shimadzu TOC-L)    Chl-a: 100 mL filtered onto 25 mm GF/F (0.7 µm), stored frozen at -25ºC, extraction into 10 mL of acetone, read on Turner Fluorometer using acidification methodData can be downloaded from AIMS' main water quality database (see link below in Data Downloads). This link allows users to restrict searches to only MMP data rather than the entire database. Data are presented as depth-weighted means calculated using surface and bottom samples. Water quality data are collected in conjunction with the Great Barrier Reef Marine Monitoring Program for Inshore Coral Reefs see link below in Related Information).

本元数据记录描述了由大堡礁近岸水质海洋监测计划（Great Barrier Reef Marine Monitoring Program for Inshore Water Quality, MMP WQ）通过原位监测采集的物理化学与营养盐数据。关于MMP WQ及其关联数据集的完整说明，请参阅上文链接的父级元数据记录。

水质采样在背景环境条件与河流径流事件期间均开展。背景监测指在大型洪水事件之外的湿季与干季进行的常规采样；基于事件的监测则针对大型洪水事件开展，以捕捉洪水羽流内的水体状况。基于事件的监测在55个常规采样点位，外加33个新增点位进行。

MMP WQ采用原位采样方法测定17项关键参数，分为三类：
1. 物理化学参数：盐度、温度、赛氏盘深度（Secchi depth）、总悬浮颗粒物（total suspended solids, TSS）以及有色溶解有机物（coloured dissolved organic matter, CDOM）；
2. 营养盐参数：铵态氮（NH₄）、亚硝酸盐（NO₂）、硝酸盐（NO₃）、溶解态无机磷（dissolved inorganic phosphorus, DIP）、硅酸盐（Si）、颗粒态氮（particulate nitrogen, PN）、颗粒态磷（particulate phosphorus, PP）、总溶解态氮（total dissolved nitrogen, TDN）、总溶解态磷（total dissolved phosphorus, TDP）、颗粒态有机碳（particulate organic carbon, POC）以及溶解态有机碳（dissolved organic carbon, DOC）；
3. 生物学参数：叶绿素a（chlorophyll a, Chl-a）。

每个点位均使用尼斯金采水器（Niskin bottles）采集离散水样，采样层为水体表层（距水面约0.5 m处）与底层（距海底约1 m处），但部分基于事件的采样仅采集表层水样。尼斯金采水器采集的水样均设置平行双样，并针对上述全套水质参数开展分析。分析化学流程的详细说明可参阅该项目年度发布的质量保证/质量控制（QA/QC）报告（详见下文"相关信息"板块的链接）。

各参数的采集、存储与分析方法简述：
- 盐度：取250 mL未过滤水样，置于螺旋盖塑料瓶中4℃冷藏保存，使用盖德琳Portasal盐度计（Guildline Portasal Salinometer）进行分析，仪器经温度补偿，并以OSIL标准海水作为参照进行校准
- 温度：通过安装于尼斯金采水器的电子倒转温度计测定
- 赛氏盘深度（Secchi depth）：取赛氏盘垂直消失与重现深度的平均值
- 总悬浮颗粒物（TSS）：水样经预称重的47 mm直径0.4 μm聚碳酸酯膜过滤，用去离子水冲洗后，于60℃烘干12小时，采用重量法分析
- 有色溶解有机物（CDOM）：取50 mL过滤水样（0.2 μm Acrodisc滤膜），通过紫外-可见吸收光谱法测定吸光度，计算得到443 nm处的CDOM吸收系数
- 铵态氮（NH₄）、硝酸盐（NO₃）、亚硝酸盐（NO₂）与溶解态无机磷（DIP）：取10 mL过滤水样（0.45 μm Minisart滤膜），置于-25℃冷冻保存，滤液采用分段流动分析法测定
- 硅酸盐（Si）：取10 mL过滤水样（0.45 μm Minisart滤膜），置于4℃冷藏保存，滤液采用分段流动分析法测定（结果以Si计）
- 颗粒态氮（PN）与颗粒态有机碳（POC）：取500 mL水样经25 mm GF/F滤膜过滤，置于-25℃冷冻保存，采用高温燃烧法（岛津TOC-L总有机碳分析仪，Shimadzu TOC-L）分析
- 颗粒态磷（PP）：取250 mL水样经25 mm GF/F（0.7 μm）滤膜过滤，置于-25℃冷冻保存，对滤膜进行过硫酸盐消解后，采用紫外-可见分光光度计进行钼蓝比色分析
- 总溶解态氮（TDN）与总溶解态磷（TDP）：取10 mL过滤水样（0.45 μm Minisart滤膜），置于-25℃冷冻保存，采用NaOH、硼酸与过硫酸钾混合体系在高压灭菌锅中进行过硫酸盐氧化/消解，随后采用分段流动分析法测定
- 溶解态有机碳（DOC）：取10 mL过滤水样（0.45 μm Minisart滤膜），加入100 μL盐酸酸化，置于4℃冷藏保存，采用高温燃烧法（岛津TOC-L总有机碳分析仪，Shimadzu TOC-L）分析
- 叶绿素a（Chl-a）：取100 mL水样经25 mm GF/F（0.7 μm）滤膜过滤，置于-25℃冷冻保存，用10 mL丙酮萃取后，采用酸化法在特纳荧光计（Turner Fluorometer）上读数

数据可从澳大利亚海洋科学研究所（Australian Institute of Marine Science, AIMS）的主水质数据库下载（详见下文"数据下载"板块的链接），该链接可让用户将检索范围限定为仅MMP数据，而非整个数据库。数据以表层与底层水样计算得到的深度加权平均值形式呈现。本水质数据与大堡礁近岸珊瑚礁海洋监测计划（Great Barrier Reef Marine Monitoring Program for Inshore Coral Reefs）联合采集，详见下文"相关信息"板块的链接。