On a planetary scale, the measurement of Sea Surface Temperatures (SSTs) are important for understanding how the oceans interact with the atmosphere, which is crucial for predicting weather patterns as well as indications of climate change.
On a more local level, the temperature of the surface of the coastal waters has a bearing on marine ecosystems in general, particularly in the changing distributions of species, in determining when the process of reproduction might take place, and for indicating when food supplies are likely to become more plentiful or be restricted in some way or other.
The marine life at Lundy includes many species whose centres of distribution lie well to the south of the British Isles and some species close to the northern limits of their recorded distributions.
The first record of surface sea water temperatures at Lundy from October 1972 to October 1973 (after Hiscock & Dymond, 1973). 
Attaching a temperature logger to the f’w’d steps of the MV Robert, 9th June 1995 © Paul Kay 
The same logger after 12 months in situ, overgrown by keelworms, saddle oysters, and encrusting bryozoans. Sadly, upon recovery, this unit was found to have flooded. © Robert IrvingRegular recordings of sea surface temperatures were initiated in 1972-73 at Lundy by the warden at the time Nick Dymond. Recordings were made in the Landing Bay at approximately fortnightly intervals from October 1972 to October 1973 using a mercury thermometer. A plot of these temperatures (right) shows the minimum temperature during this period as being 8.4°C on 11th March 1973 and the maximum being 17.5°C on 19th August 1973. The winter of 1972/73 was a mild one with sea water temperatures not expected to have fallen to their mean winter level (Hiscock & Dymond, 1973).
Regular recordings of sea water temperatures were not attempted again until 1995 when compact digital temperature recorders, which could register every 4 hours for up to 12 months ,were available for use under water. Two of these were positioned on the wreck of the MV Robert at 18 m depth (below chart datum). Sadly, upon recovery a year later, both units were found to have flooded with none of the data recoverable.
Successful daily sea water temperature recordings have been made since, albeit on an irregular basis, as devices have been unable to be re-located or have purposely been removed without permission. The plot below shows recordings from a device attached to one of the piles supporting the jetty (at approximately 1 m BCD) from October 2018 to January 2020. The maximum temperature recorded during this period was 18.8°C in the second half of August 2019; and the minimum was 8.4°C in the send half of March 2019.
Sea water temperature recordings from an automatic logger attached to the jetty, from October 2018 to January 2020.
