A Perfect Storm of Factors in Decline of Maui Reefs

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The decline of coral cover in nearshore areas of Maui has been dramatic in recent years. The state Department of Land and Natural Resources’ Division of Aquatic Resources reported in 2006 that, since 1999, mean coral cover at nine reefs had declined by nearly a quarter, going from 35 percent coral cover to 27 percent.
In the particular case of the reef at Ma`alaea, the DAR reported “total system collapse.” In 1972, the DLNR noted, a survey of coral reefs there had reported corals as “striking in their diversity,” with several “rare coral species.” In 1993, estimates of coral cover at Ma`alaea were between 50 and 75 percent at the same spots where, in 2006, coral cover was barely 8 percent. 

“One consequence of severe loss of living coral is that degrading reefs change from being actively-growing and structurally complex habitats, into eroding and relatively flat areas which do not support abundant marine life,” the DAR wrote. “That process is well advanced at Ma`alaea, where fish stocks are now in very poor condition.” 

At Kahekili, near the Lahaina injection wells, coral cover went from 55 percent in 1999 to 33 percent in 2006.

The reasons for the decline amount to a sort of perfect storm of developments. There is the presence of invasive algae, which thrive on the nutrients that injection wells and agricultural practices dump into nearshore waters. There is also the volume of effluent, which, although declining slightly in the last two years (the result of fewer visitors to Maui, perhaps), has on the whole increased tremendously over the last two decades.

Then there is the removal of important marine grazing animals from the nearshore environment as a result of overfishing of parrotfish and surgeonfish. In another study, the DAR had found that statewide, reefs where herbivorous fishes were plentiful had much less seaweed (macroalgae) than reefs where they had been depleted.

In an effort to prevent what happened at Ma`alaea from happening at Kahekili, last year the DLNR established a Herbivore Fisheries Management Area offshore of the beach. Rules governing the management area prevent the taking of parrotfish, surgeonfish, rudderfish, and sea urchins.

DLNR administrator Laura Thielen described the decision to establish the reserve as “an immediate management action … to intervene in the rapid coral reef degradation that has been documented in this area.”

But DAR staffers themselves see a need for more action. Last August, at an Environmental Protection Agency hearing on renewal of the permit for the Lahaina sewage plant injection wells, Russell Sparks of the DAR pointed out that protecting herbivores addresses only part of the problem. “We do not expect the reef to come back if we’re not able to address this holistically,” he said. “And so we really do need measurable steps taken to reduce the factors that promote algae growth and degradation, i.e., land-based nutrient loads.”

Sparks pointed out another aspect of the injection wells that had not been discussed much to that point. “Although much concern has been placed on nutrient loads,” he testified, “marine scientists have also expressed concerns that high volumes of fresh water entering marine ecosystems can alter water chemistry and adversely affect coral reef health. This concern is especially important in areas where coral reefs have evolved in the absence of fresh water. Real short, you can change the chemistry of the water, change the pH, and adversely impact the way corals fix calcium and build the skeleton that supports them. Reefs off of Lahaina, or outside of the wastewater injection facility, are collapsing on themselves. We feel this could be one reason why.”

Sparks recommended that the EPA revise its protocols for the Underground Injection Control Program “so as to assess impacts to Hawai`i’s coastal waters.” “The Clean Water Act, in addition to the Safe Drinking Water Act, must be considered when regulating existing and future injection well permit applications,” he said.


Patricia Tummons


Volume 20, Number 11 — May 2010