Benthic algal blooms (e.g., Codium isthmocladum) have become increasingly common on reefs and hardgrounds of Southeast Florida. The contribution from possible responsible nutrient sources, including natural upwelling and local pollution, has not been quantified. In an attempt to differentiate each potential source, lattice-bound barium concentrations in the skeletons of two common Southeast Florida stony coral species (Montastraea faveolata and Solenastrea bournoni) were measured by isotope dilution inductively coupled mass spectrometry (ICP/MS). Specimens were collected offshore between 26˚01'-57'N at shallow (10m) and deep (20m) reefs. X-rays of skeletal slabs revealed annual density bands which guided annual and subannual chemical sampling over 20 years. Selected specimens were analyzed for oxygen and carbon isotope content to gauge water temperature and salinity. Results demonstrate historical Ba levels in corals and variability among species, seasons, years, and sites.