Water Quality Evaluation and Analytical Method Equivalency Testing for Hawaiian Fishponds on Molokai

Oshiro, Hisato
Babcock, Roger W.
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Water Resources Research Center, University of Hawaii at Manoa
This thesis summarizes the activities of the Moloka’i Fishpond Restoration Water Quality Study conducted by the Water Resources Research Center (WRRC) at the University of Hawai’i at Mānoa. EPA-approved methods were utilized to analyze Moloka’i fishpond water samples and the data were compared with DOH criteria. The fishponds nearly always met the DOH water quality criteria for pH, dissolved oxygen, temperature, and salinity. Due to inadequate detection limits, it cannot be determined whether ammonia nitrogen, nitrate/nitrite nitrogen, and chlorophyll-a meet the criteria. The criteria for total nitrogen, total phosphorus, turbidity, dissolved oxygen, temperature, and salinity may have to be modified because they apparently are not achievable under natural/pristine conditions in the vicinity of the fishponds. There are no criteria for orthophosphorus, total suspended solids, and volatile suspended solids. The equivalency of simplified, ready-to-use Hach methods for total nitrogen, nitrate nitrogen, nitrite nitrogen, total phosphorus, and orthophosphorus were compared EPA-approved methods. The Hach total phosphorus and orthophosphorus methods are EPA-approved and were found to be statistically equivalent for seawater analysis. The Hach nitrite nitrogen method is EPA-approved, but was found to be statistically not equivalent. The Hach total nitrogen and nitrate nitrogen methods were found to be statistically not equivalent, maybe due to interference in the samples and different detection ranges between the methods. The Hach methods can be used to obtain a rough estimate of a parameter in seawater, usually for on-site analysis.
Oshiro H, Babcock RW. 1999. Water quality evaluation and analytical method equivalency testing for hawaiian fishponds on molokai. Honolulu (HI): Water Resources Research Center, University of Hawaii at Manoa. WRRC-99-02.
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