This dataset aggregates and summarises the water quality data collected by researchers from the Australian Institute of Marine Science from 1974 until the present. AIMS' biological oceanographers have studied the physical, chemical, and biological properties of seawater around northern Australia using a variety of methods including in situ sampling, moored sensors, and vertical profiles. This dataset contains in situ water quality information (list of analytes shown below) from northern Australia, with a large volume of data from the Great Barrier Reef, Queensland. It also contains an historical dataset transcribed from the reports of the Low Islands Expedition 1928-29 led by C.M. Yonge. This dataset contains biogeochemical data from many research expeditions (the majority led by Dr. Miles Furnas) as well as records from water quality monitoring programmes. Some data in this record were collected as part of the Great Barrier Reef Marine Monitoring Program for Inshore Water Quality (MMP WQ), which has collected in situ water quality data, along with time-series of temperature, salinity, fluorescence, and turbidity since 2005. More information about the MMP WQ can be found on its metadata record (see link below in Related Information). Each water sample occurs at a unique combination of geographic location, time, and date. In the AIMS database, samples are assigned a unique alphanumeric identifier (called a ‘station’), which is comprised of a 3-letter area code and a 3-digit station number (e.g. WQM324). Using this code, water chemistry information can be linked to other associated data, such as vertical profiles of the water column (i.e., CTD casts), which can be retrieved from AIMS’ CTD database (link below). Variables in this database include: depth, silicate (Si), ammonium (NH4), nitrite (NO2), nitrate (NO3), dissolved inorganic phosphorus (DIP), dissolved organic carbon (DOC), temperature (Temp), salinity (Sal), particulate nitrogen (PN), particulate phosphorus (PP), particulate organic carbon (POC), total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), Chlorophyll-a (Chl), phaeophytin (Phaeo), suspended solids (SS), Secchi depth, and coloured dissolved organic matter (CDOM). All analytes may not be available at every station. Brief description of collection, storage and analysis method for parameters: SAL: 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) TEMP: Electronic reversing thermometer attached to Niskin SECCHI_DEPTH: The average of the vertical disappearance and reappearance depths of a Secchi disc SS: 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 NH4_INSITU: Unfiltered 20 mL sample, processed immediately, OPA fluorescence method (post 2005) SI: 10 mL filtered sample (0.45 µm minisart), stored refrigerated at 4ºC, filtrate analysed on segmented flow analyser (reported as Si) PN_SHIM 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_PER and TDP_PER: 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