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County: New study contradicts research that coral health is improving at Kahekili

By Staff | Nov 16, 2017

WAILUKU – According to the County of Maui, the authors of a recent study called “Vulnerability of Coral Reefs to Bioerosion From Land-Based Sources of Pollution” failed to address significant land-based sources of nutrients that easily find their way into the ocean.

An article about the study published in the Nov. 9 Lahaina News also didn’t emphasize that all groundwater in the islands eventually migrates to the ocean, county Spokesman Rod Antone noted.

Authored by Nancy G. Prouty, Anne Cohen, Kimberly K. Yates, Curt D. Storlazzi, Peter W. Swarzenski and Darla White, the study was accepted for publication in the Journal of Geophysical Research: Oceans, a journal of the American Geophysical Union. (Go to agu.org, then Publications, then Journals, then Oceans to find the study.)

The researchers concluded that local land-based pollution can make coral reefs even more vulnerable to ocean acidification by magnifying its effects.

They also contend that pollution in the form of treated wastewater from the Lahaina Wastewater Reclamation Facility in Honokowai has drastically weakened local coral reefs for more than ten years. Also, by increasing local seawater acidity and nutrient levels, the polluted water has instigated harmful bioerosion and inhibited coral reef growth.

Antone said the article referring to the research contradicts data from recent state studies that show that coral reefs fronting Kahekili Beach Park are actually getting healthier.

In the article “Hopeful signs of reef recovery emerging in North Kaanapali” (Lahaina News, Oct. 12, 2017), Russell Sparks of the state Department of Land and Natural Resources’ Division of Aquatic Resources wrote: “Since January of 2008, the State Division of Aquatic Resources has partnered with, first, the University of Hawaii, and then NOAA Pacific Islands Fisheries Science Center, to conduct comprehensive monitoring of the coral reef areas within what is now the (Kahekili Herbivore Fisheries Management Area). Those surveys involve detailed fish and habitat surveys conducted twice per year within the KHFMA, and in some nearby areas just outside of the reserve boundaries.

“Results of these assessments are very promising. At the end of 2016, seven years following the management area designation, there were clear signs that important grazing fishes are increasing in size and numbers.

“The good news, however, is that the earlier declines in coral cover have stopped, and there are signs of recovery. Corals grow relatively slowly, so recovery takes time, but the positive impacts of herbivore protection at the KHFMA have greatly improved conditions for local corals to thrive.”

According to the county, the authors of the study published in Oceans “failed to address significant land-based sources of nutrients that unfortunately and easily find their way into the ocean during rainfall and through natural groundwater migration, including fallow agricultural fields and roads, private cesspools and septic systems,” Antone noted in an e-mail.

“The article also glosses over the fact that all groundwater in the islands eventually migrates to the ocean, and when it reaches the ocean, there is a mixture of saltwater with the lower-pH fresh water. This is a natural hydrogeologic process. The saltwater-fresh water interface is extremely important, not only for its effects offshore but for the prevention of saltwater intrusion into our drinking water aquifers.”

Completed in May 2012, the study “Groundwater Availability in the Lahaina District, West Maui, Hawai’i” reported that model results indicate that injection of treated wastewater in Lahaina affects the groundwater flow system by creating a barrier to inflow of saltwater from the ocean.

Effects of wastewater injection on the nearshore ocean environment were not evaluated in this study.

Also released in 2012, the Maui Coral Reef Recovery Plan produced by the Maui Nui Marine Resource Council includes detailed information on the Kahekili Reef Recovery Priority Site.

The plan states: “Monitoring programs at this site documented declines in coral cover in the late 1990s with improvements in coral cover since 2006 (Hawaii Division of Aquatic Resources and Hawaii Coral Reef Initiative, 2008). Consequently this site has potential for coral recovery.”

The recovery plan also credits the county for wastewater treatment and reuse efforts that are “progressively environmentally friendly.”

The county did not yet provide its current rates (in millions of gallons per day) of treated wastewater used for irrigation or sent down injection wells at the Honokowai plant, as well as the source of foul odors generated by the facility recently.

Antone wrote, “The county remains committed to pursuing environmentally sustainable practices, and current efforts at the Lahaina Wastewater Reclamation Facility – which treats recycled water to the highest quality in the state – include increased irrigation reuse, as well as investigating a pilot project which could take the recycled water to drinking water standards and offer a possible solution to providing sufficient potable water to West Maui in the future.”