State studies water quality impact of oysters in Pearl Harbor

Photo: Department of Land and Natural Resources


For more than a decade, oysters have been improving the water quality at Chesapeake Bay on the East Coast.

Now, the Hawaii Department of Land and Natural Resources hopes the same can be done for Pearl Harbor.

Oysters are known as filter feeders. They eat phytoplankton, or microscopic algae, which improves water clarity and light penetration for other species to thrive, and helps prevent oxygen depletion.

The harbor once supported abundant native oyster populations (Pinctada radiada) and an introduced species (Crassostrea virginica) in 1860s to 1920s. It is the largest natural estuary in Hawaii, and historically has been an important fishery and breeding area for many species of fish and other forms of aquatic life, including oysters.

Officials say excessive dredge harvesting during the times of the Hawaiian monarchy and sediment-laden runoff from changing land use during the mid-1900s severely comprised the oyster settlement capability and survival. Modern-day challenges for oyster survival in the bay include the accumulated sediments, petrochemicals, and heavy metals.

To increase their numbers, DLNR will use cages to suspect the oysters, which will allow them to grow without exposure to predators or harmful sediments. Officials will track their growth rate, impact on water quality, and any possible accumulation of metals in the oysters’ tissue.

“Basically the effort is to determine whether or not oysters are able to thrive, grow, and survive in waters of the modern-day Pearl Harbor,” said Dr. Paul Bienfang, president of Analytical Services. “The dream is to establish a project for natural bioremediation of sections of the harbor through the establishment of viable oyster populations in the harbor. We are talking about clarification of the water. With the clarification, there comes an increase in water transparency, and the ability of reestablishment of the habitats that once were here.”

In addition to measuring oyster growth and survival, the state will also consider the feasibility of scaling up the project for future bioremediation efforts.

Photo: Department of Land and Natural Resources

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