E ola i ka wai: A survey of two microbial pathogens within Hawai’iʻs kahawai along the ahupua’a

The ahupuaʻa system was created during the 1400s in ancient Hawaiʻi that served as land divisions running from mauka (uplands) to makai (lowlands). Most notably, ahupuaʻa was known to contain a water source through kahawai (fresh water streams) that served as the most important component of ahupuaʻa. Following the industrialization of the Hawaiian islands in the 1800s, kahawai became vulnerable to fecal and industrial contamination through on-site septic tanks, wild animal feces, storm and agricultural run-off, and sewer spills. The purpose of this experiment was to determine the distribution and abundance of two indicator pathogens - Escherichia coli (E. coli), a fecal indicator, and Staphylococcus aureus (S. aureus), a ubiquitous human-related bacteria - in Hawaiʻi’s kahawai and characterize how physico-chemical parameters influence their distributions. Water samples were collected across four fresh water kahawai in diversely managed ahupuaʻa in Hawai’i from mauka, and following the stream path to makai.Water quality parameters were measured and E. coli and S. aureus were cultivated utilizing standard techniques. Results from the four kahawai tested displayed that the abundance of both S. aureus and E. coli significantly increased in concentrations from mauka to makai. This is likely due to the increasing amounts of human associated runoff as streams move makai. The abundance of E. coli and S. aureus was not correlated with physicochemical properties of water such as salinity. This research aims to help aid those managing an ahupua’a land and water, protecting both ourselves and theʻāina (land). Regularly testing water quality in our kahawai can reduce human health risks by determining sites of contamination.