Biological and water quality characteristics of anchialine resources in Kaloko-Honokohau National Historical Park

Brock, Richard E.
Kam, Alan K.H.
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Cooperative National Park Resources Studies Unit, University of Hawaii at Manoa, Department of Botany
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This study was undertaken to examine the status of biological and water quality resources in the anchialine pools, fishponds and nearshore marine waters of the Kaloko-Honokohau National Historic Park (KAHO) over a 3-year period. The study identified 82 anchialine pools and pool complexes in and adjacent to the present Park boundaries. Routine monitoring of water quality and biota was carried out in 16 anchialine pool, 8 fishpond, 10 marine and 3 coastal well sample sites. Water chemistry studies show that the water quality in the ground, anchialine, fishpond and nearshore marine waters fronting the KAHO are typical of the West Hawaii coast. Presently, there is no evidence of water pollution from anthropogenic sources in this system using the limits of detection available to this study. However the status of native anchialine species in the pools of the KAHO is poor. Sixty-four pools were examined within the Park's boundaries. Only 21 or 33% of these pools contained the most common and characteristic anchialine species the opae'ula or Halocaridina rubra and only 10 or 16% of these ponds was this species consistently present during daylight hours. In contrast, a study carried out in 1972 of some of these same pools noted that 75% contained the usual array of anchialine species including H. rubra. Concurrent with the decrease in native anchialine species has been the increase and spread of alien fish (primarily guppies, Poecilia reticualta) in these ponds. The alien fish are predators on several key anchialine species including the opae'ula. Halocaridina rubra is a keystone herbivorous species in Hawaiian anchialine systems, maintaining the ecological balance in the benthic communities. Its removal often leads to dramatic shifts in the benthic communities, which become dominated by a few macroalgal species and resulting in a decrease in the diversity of species in the system. The study recommends that an active management program be initiated to (1) promote a strong education program and permit limited cultural use, (2) protect existing "high value" pools and (3) undertake a pool restoration program. The restoration program would have the following elements: (1) curtail the spread of alien fish, (2) remove alien fish from selected pools, (3) restore the physical features of some pools by the removal of alien vegetation and accumulated sediments due to the input of leaf litter, (4) develop new anchialine pools in presently disturbed (bulldozed a'a) habitat but well-removed from the alien fish threat, (5) undertake the acquisition of additional anchialine resources presently outside of the Park's boundaries and (6) establish a monitoring program to insure that the management program meets its objectives. Anchialine resources in the US are only located in the Hawaiian Islands and the majority of these are along the West Hawaii coastline. Recent ecological work on the West Hawaii anchialine pools suggests that in excess of 95% of the resource has been contaminated by the invasion of alien fish. The spread of these exotics has occurred in the last 20 years. The KAHO is one of the few national parks where anchialine resources can be protected and viewed by the public. This fact in itself should be enough of an impetus to initiate a strong program to halt and reverse the loss of these precious resources. Without such a proactive approach, anchialine resources will probably disappear within the next two decades.
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Aquatic organisms -- Hawaii -- Hawaii Island., Kaloko-Honokohau National Historical Park (Hawaii), Tide pool ecology, Landlocked -- Hawaii -- Hawaii Island., Water quality biological assessment -- Hawaii -- Hawaii Island.
Brock RE, Kam AKH. 1997. Biological and water quality characteristics of anchialine resources in Kaloko-Honokohau National Historical Park. Honolulu (HI): Cooperative National Park Resources Studies Unit, University of Hawaii at Manoa, Department of Botany. PCSU Technical Report, 112.
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