Water quality in pools and groundwater monitoring wells of the national parks on the west coast of the Island of Hawaiʻi: Summary report 2012–2014

Raikow, David; Farahi, Ann

This Natural Resource Data Series Report (NRDS) presents data collected from anchialine pools and a brackish waterbody in the four National Park units on the Kona coast of the island of Hawaiʻi. This is a “data report” as described in the Water Quality vital signs Monitoring Protocol for the Pacific Island Network Version 1.0, Natural Resource Report NPS/PACN/NRR-2011/418. This report is primarily focused on data presentation and a limited description of findings. The data presented in this report will be analyzed for the establishment of expected parameter value ranges and long-term trends in future reports published in peer-reviewed outlets such as the NPS Natural Resource Report (NRR) series or a scientific journal. The purpose of collecting data on vital signs is to provide park managers information on current conditions and temporal trends in ecosystem health. Two anchialine “fixed site” pools associated with the Ala Kahakai National Historic Trail were sampled quarterly from 2012 to 2014. Deterioration of the walls surrounding the pool at Kahaluʻu Beach Park (HA_Kahalu_001) were caused by large storm events in the winter of 2013-14 and led to changes in water chemistry and greater rates of sand deposition. Development of a permanent channel connecting HA_Kahalu_001 with the sea at high tide, along with changes in salinity, indicated that it began to resemble a tide pool rather than an anchialine pool. No major events were observed at the cave pool (HA_Puuwaa_002). In Kaloko-Honokōhau National Historical Park, four anchialine “fixed site” pools were sampled quarterly, and 14 “temporary site” pools were sampled one to three times, from 2012 through 2014. Pools were grouped geographically into three groups: north, central, and south. During the period of 2012-2014, no discrete major ecological events were detected in pools, aside from possible minor algal blooms in some pools primarily in the south group. Wide variation in phytoplankton biomass was observed in north and central pools, but it is unclear if these observations constitute algal blooms. This uncertainty is due to inconsistent corroboration by pH and dissolved oxygen values. At Puʻukoholā Heiau National Historic Site, three fixed sites were sampled within the park’s only waterbody, which is unnamed, quarterly from 2012 through 2014. Elevated total dissolved nitrogen was observed in the waterbody in 2012. The water body experienced an algal bloom during the summer of 2013, as indicated by chlorophyll, dissolved oxygen, pH, and turbidity. No notable events at this waterbody were observed in 2014. In Puʻuhonua o Hōnaunau National Historical Park, the pool (HA_Keokea_004) added to replace the pool dropped for safety reasons (HA_Kiilae_001) displayed characteristics very different than either underground or surface pools, including high total dissolved phosphorus (TDP) and relatively high turbidity. These observations were the result of organic soil and possibly animal feces present in the pool, as well as its shallowness which prevented full flushing caused by tides. High salinity values observed park-wide in 2014 were caused by high sea-wave events that inundated pools and the surrounding land.

Water quality in pools and groundwater monitoring wells of the national parks on the west coast of the Island of Hawaiʻi: Summary report 2012–2014

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