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USGS studying impacts of groundwater quality upon coral reef health

By Staff | Mar 17, 2016

Tubes collect water samples for reef research. PHOTO BY LIZ FOOTE.

KAANAPALI – This month, researchers from the U.S. Geological Survey will be here conducting fieldwork to study the impacts of groundwater quality upon coral reef health.

There will be an opportunity to meet the researchers in person and hear about their work and findings through an informal talk story gathering at 10 a.m. on Friday, March 25, at Kahekili Beach Park.

On-hand will be Nancy Prouty and Chris Gallagher from the USGS Pacific Coastal and Marine Science Center in Santa Cruz, California, and Kim Yates and Nate Smiley from the USGS Coastal and Marine Science Center in St. Petersburg, Florida.

The researchers also want the public to know that water sampling instrumentation will be deployed within the area of Kahekili Reef and should not be disturbed.

To address environmental concerns, scientists from the U.S. Geological Survey are working with local organizations to determine if groundwater quality is affecting coral reef health.

This month, researchers from the U.S. Geological Survey will be here in West Maui conducting fieldwork to investigate the impacts of groundwater quality upon coral reef health. Here, a USGS researcher inspects a groundwater seep. PHOTO BY THE WEST MAUI RIDGE-TO-REEF INITIATIVE.

Together with the state Department of Land & Natural Resources’ Division of Aquatic Resources on Maui, the National Oceanic and Atmospheric Administration’s Coral Reef Conservation Program, West Maui Ridge-to-Reef (R2R) Initiative, the U.S. EPA, and the Clean Water Branch of the state Department of Health, scientists are setting up instruments to analyze the composition of the seawater near the reefs close to shore.

Over a six-day period this month, USGS researchers will monitor seawater collected from the coral reefs at Kahekili Beach Park.

The water will be pumped through tubes leading from the reef to the beach. Every four hours, the scientists will take water samples and measure acidity and nutrient levels to calculate whether levels are higher than seawater further offshore.

An autonomous instrument will also be placed on the seafloor near the vent for the full six days to continuously measure the seawater composition. If residents or visitors see these instruments along the reefs, they are asked to not disturb them.

This research aims to discover whether a link exists between the quality of groundwater and the declining coral cover.

According to the agencies involved, a decline in the abundance of live coral and a rise in algal growth have been significant environmental concerns in West Maui since the late 1980s.

Too much algae can smother corals when competing for space, light and oxygen. Algae thrive when nutrients are abundant, but what boosts these nutrients levels?

Humans introduce a surplus of nutrients – such as phosphates and nitrates – into the environment when treating wastewater or using fertilizers in agriculture. These nutrients then trickle down through Maui’s porous volcanic rock, eventually mixing with the fresh groundwater below.

Underground streams of groundwater merge and run beneath the land and coastline until they eventually hit the ocean and bubble up through springs scattered on the seafloor called groundwater seeps.

Freshwater flowing from these seeps is more acidic (lower pH) and contains more nutrients than the surrounding seawater.

Corals living near these seeps appear to be more vulnerable to erosion by organisms such as urchins, bacteria and worms, which also flourish when an abundance of nutrients are in the water.