Phosphorus Deposition to Hawaii via Precipitation

Kilauea Volcano on the Big Island of Hawaii may be an important source of bioavailable phosphorus to the Hawaiian Island Chain. Because it has been hypothesized that these volcanic islands undergo a shift from nitrogen to phosphorus limitation over geologic time, atmospheric phosphorus deposition could play a considerable role in ecosystem processes, especially on the older, more highly weathered islands such as Kauai. We measured the soluble reactive phosphorus (S-PP flux in weekly rainwater samples collected on Kauai and the Big Island between December 1998 and July 2000. SRP fluxes were 0.14 and 0.27 ± 0.06 mg P m yr on the Big Island and Kauai, respectively. The small variability and low concentrations of arsenate (a gauge of volcanic activity) in the rainwater samples suggests weak and uniform levels of volcanic activity during the sampling period. Given the low atmospheric SRP flux and the lack of high SRP concentrations, we have determined that the volcanic influence on our samples is minimal. Noting the relatively constant volcanic activity during the sampling period, the small data set does not support or refute the hypothesis that Kilauea Volcano can be a significant source of P to the Hawaiian Island Chain.