Colonies of Montastrea annularis live near La Parguera, Puerto Rico, and maybe 799 years old. Time series from 1964 to 1982 of delta 13C and delta 18O from a continuous core of these corals are compared to an adjacent environmental record. At the intraannual level, delta 18O correlates well with water temperature. Changes in the amplitude of the delta 18O signal between 1967 and 1976 are attributed to sampling frequency but may be also due to environmental changes such as salinity. Average annual delta 18O, delta 13C and sea surface temperature show similar trends of the period from 1964 to 1982 but expecially from 1969 onwards. Changes in average annual values during this time interval are most likely due to water mass changes brough about by interannual variability of the North Atlantic circulation. Since water temperature at La Parguera are representative of changes occurring in the wider Caribbean, the isotope record from La Parquera corals could be used as a proxy for large-scale environmental changes beyond the historical record through the Little Ice Age.