Rothera Oceanographic and Biological Time Series (RaTS) in Antarctica began in 1997 and involves regular sampling of the water column undertaken by CTD (conductivity, temperature and depth) casts with associated collection of discrete water samples and the deployment of four moorings. The RaTS site is located in Marguerite Bay, approximately 4 km from shore and over a water depth of approximately 520 m. Marguerite Bay is enclosed by Adelaide Island to the north, Alexander Island to the south and the Antarctic Peninsula to the east. When optimal conditions are not available a secondary site is occupied. In times when fast ice prevents sampling at both the primary and secondary site, a third site is utilised close to the Rothera Research Station. However, only a water sample is collected during this time as the water is too shallow to allow for a cast to be conducted. An upper ocean CTD cast is made every five days in the summer and every seven days in the winter, except when weather, ice or logistic constraints intervene. A CTD unit is lowered from an inflatable boat by use of a hand-cranked winch during summer months and through a hole in the ice during the winter. As well as conductivity, temperature and depth other variables measured from the CTD cast include fluorescence and down-welling irradiance. Measurements are typically binned to 1 metre increments with a varying maximum depth typically ranging between 200 and 500 metres. Subsequent data processing involves the calculation of salinity from the conductivity channel (applying the UNESCO 1983 algorithm), calculation of chlorophyll from raw fluorescence and calibration, plus calculating depth from the pressure output. Discrete water samples are taken from a depth of 15 m using a Niskin bottle closed with a brass messenger. Water samples collected are measured for macronutrients (nitrate, nitrite, phosphate, ammonia and silicate), chlorophyll (both whole and size fractionated), dissolved oxygen isotopes, dissolved organic carbon and microbial community analysis. There are two extended periods during which no data could be collected. August to December, in both 2000 and 2001. In 2000, there was an unusually extended period of unfavourable ice conditions which were too heavy for boat operations and unsafe for sledge operations. Then in the period during 2001 a fire occurred which resulted in loss of use of the laboratory at Rothera. It was not possible to restart observations until replacement equipment arrived with the relief of the Rothera Research Station the following December. The mooring deployments took place in January 2005 (13 months), February 2006 (10 months) and December 2006 (4 months). A further mooring was deployed in the Marguerite trough in January 2005 for approximately 13 months. Mooring instrumentation included current meters, acoustic Doppler current profilers (ADCP), temperature and depth recorders, a CTD and a sediment trap. These sensors were strung out from the surface down to approximately 390 m (sediment trap). Data was collected in 15 minute intervals from the ADCP and once every hour from all the other sensors. Data processing included calibration of the pressure, conductivity and pressure channels and calculation of salinity (from conductivity channel) and depth (from pressure channel). This time series is continuously monitored by the British Antarctic Survey in an attempt to gain a suite of oceanographic data which provide an environmental background to aid interpretation of the near-shore marine ecology and to test a series of broad hypothesis concerned with pelagic-benthic coupling and environmental forcing of the near-shore oceanographic environment. The project has previously been managed by Prof. Andrew Clarke and Prof. Mike Meredith. At present (November 2021), the project and dataset is directed and managed by Mr. Hugh Venables of the British Antarctic Survey and data are available on request from the British Oceanographic Data Centre.