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Underwater data sensor monitors water quality at Maalaea Harbor

A new underwater data sensor is being used at Maalaea Harbor to collect more information every five minutes on water temperature, salinity, turbidity, chlorophyll and ocean depth.

Nonprofit Maui Nui Marine Resource Council is borrowing the device through the Pacific Islands Ocean Observing System Water Quality Sensor Partnership Program to boost its ocean water quality monitoring efforts in Maalaea.

“We are grateful to PacIOOS for the use of this data sensor that will help us learn more about the effects of tides, swell, rain events and runoff on water quality within Maalaea Harbor and to monitor water quality variability over time,” Amy Hodges, the marine council’s programs and operations manager, said in a news release Wednesday.

The data sensor is under the supervision of Margaret McManus, chairwoman of the University of Hawaii at Manoa’s Department of Oceanography. The PacIOOS program supports scientists and natural resource managers to collect water quality data for research, conservation, planning and resource management projects in the U.S. Pacific Islands region, according to the news release.

Divers from the marine council mounted the device about 3 to 6 1/2 feet below the ocean’s surface to be used in Maalaea Harbor through 2021.

The PacIOOS data sensor will help the organization with data collection for its watershed management plan for the 4,000-acre Pohakea watershed adjoining Maalaea Bay. The plan aims to reduce sediment and pollutants in the bay and harbor.

“In recent decades, declining ocean water quality has led to significant deterioration of Maalaea Bay’s reefs,” Hodges said. “Monitoring by the community-based program Hui O Ka Wai Ola — which was co-founded and is co-managed by Maui Nui Marine Resource Council, The Nature Conservancy and West Maui Ridge to Reef Initiative — using ocean water samples grabbed from the ocean’s edge has shown turbidity (sediment) and excessive nitrogen as primary causes of impaired water quality.”

In addition to Hui O Ka Wai Ola, marine council staff also assist with collecting ocean water samples from the shore. Sampling provides water quality data from five to 10 sites in Maalaea Harbor every three weeks.

These water quality management projects follow a string of efforts by the marine council, including the oyster bioremediation project and the organization’s use of the Manta data sonde, which was purchased with a grant from Lush cosmetics, to gather water quality data in the harbor.

The sonde is towed behind a kayak and records real-time data as it is pulled through the water at varying depths.

The organization has also been testing nitrogen isotope ratios in macroalgae, or limu, to determine the possible sources of nitrogen pollution in the harbor and the bay, according to the news release.

Other ongoing testing in Maalaea Bay conducted by the marine council includes drift analysis studies, underwater coral cover and fish transects, and stormwater sampling.

“The progress of our projects to clean up Maalaea Bay’s water quality will be measured by resulting data from the PacIOOS data sensor and our other monitoring methods,” said Hodges. “We to see evidence of improved ocean water quality, through reductions in sediment and excess nitrogen, an essential step in restoring coral cover and reef health in Maalaea Harbor and in the bay.”

To learn more about the PacIOOS Water Quality Sensor Partnership Program and to view data, visit http:// www.pacioos.hawaii.edu/water/sensor-maalaea/#about.

To learn more about nonprofit Maui Nui Marine Resource Council and other current projects, visit mauireefs.org.

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