The data set comprises measurements of temperature, salinity, nutrients chlorophyll, oxygen and phytoplankton from two locations near Port Erin (Isle of Man, Irish Sea). Sea surface temperature measurements began to be recorded from the breakwater in Port Erin in 1904. Between 1904 and 2006 SST was recorded twice daily and salinity also measured at this location between 1965 and 2006. Recordings continue at this location via a digital temperature logger attached to the lifeboat slip in Port Erin Bay. A second station the so-called 'Cypris' station located approximately 5km due west of Port Erin Bay was adopted as an offshore monitoring station in 1954 The Cypris data have been collected at frequencies ranging from weekly to monthly depending on season, boat availability and weather, and comprise measurements of temperature at 0, 5, 10, 20 and 37m since 1954; salinity, dissolved oxygen and phosphate at 0 and 37m since 1954; silicate at 0 and 37m since 1958; nitrate and nitrite and 0 and 37 m since 1960; Chlorophyll a at 0 m since 1966; ammonia at 0 and 37m since 1992; total dissolved nitrogen at 0 and 37m from 1996-2005; and total dissolved phosphorus at 0 and 37m from 1996-June 2002.
At the Cypris station water samples were collected with either a Nansen-Pettersen or an NIO bottle from 1954-2005. Phytoplankton counts have been undertaken on surface samples since 1996. The Nansen-Pettersen bottle was used in conjunction with an insulated thermometer, while the NIO bottle was used in conjunction with a mercury reversing thermometer. From 2006 onwards an RTM 4002 X digital deep sea reversing thermometer has been used with an NIO bottle. Salinity was determined by titration against silver nitrate until 1965, thereafter using inductively coupled salinometers (Plessey 6230N until June 1998; Guildline Portasal from July 1998). Nutrients are estimated colorimetrically and dissolved oxygen is determined by the Winkler technique. Until 2006 Chlorophyll a was estimated using the trichromatic methods recommended by SCOR-UNESCO Working Group 17. Since that year the spectroscopic methods of Aminot & Rey (2002) have been used. Dissolved nitrogen and phosphorus were measured using the persulphate digestion method adapted from Valderama (1981). The Cypris station data are frequently split into the Cypris I (D. John Slinn) data set comprising data from 1954-1992 and the Cypris II data set from 1992-present.
Data from the Port Erin and Cypris stations are sometimes known collectively as the `Port Erin Bay data set . Data from Port Erin Bay form part of the Isle of Man GAL Coastal Monitoring Sites network. . The data were collected by the Port Erin Marine Laboratory (part of the University of Liverpool) until its closure in 2006. Sampling has since been taken over by the Isle of Man Government Laboratory (Department of Environment, Food and Agriculture).