Diurnal patterns of airborne algae in the Hawaiian Islands: a preliminary study

Abstract

Although the literature on the diversity of airborne algal communities in various locations around the world is increasing, little is known about their temporal and spatial patterns. We compared airborne algal communities from Honolulu, Hawai‘i, USA, over three 24-h sampling periods to examine diurnal patterns in diversity and abundance. Using a culture-based approach, 192 algal colonies were characterized and identified as 31 operational taxonomic units. A combination of microscopy and Sanger sequencing (of the UPA marker) was used for characterizations. More airborne algal colonies were identified from nighttime collections (127 of 192 colonies) than daytime collections (65 of 192 colonies) (p < 0.0001). Similarly, 95% of the daytime collections were Cyanobacteria, and 87% of the nighttime collections were Chlorophyta, and the trends of more Cyanobacteria being collected during the day and more Chlorophyta at night were significant (p < 0.0001). Meteorological analyses for the sampling periods indicated that air masses sampled during the three trials consistently arrived in the Hawaiian Islands on a northeast trade wind pattern, but with different origins in the Pacific Ocean, and that low-to-trace levels of rain fell during the sampling periods. Land breeze and sea breeze effects, which are common temperature-driven phenomena on tropical islands, may have played a role in the diurnal pattern observed in the current study.