Longhurst code refers to a set of geospatial four-letter geocodes for referencing geographic regions in oceanography.
The set of 56 geocodes represent biogeochemical provinces that partition the pelagic environment.
It is assumed that each province represents a unique set of environmental conditions.
[2] They are named after Alan R. Longhurst, the author of "Ecological Geography of the Sea", the textbook in which these codes are defined.
[3] These codes have also been used in bioinformatic databases such as IMG to represent sample origins for sequenced microbial genomes, as a supplement to latitude and longitude coordinate metrics.