Research shows connection between watersheds, reefs

Hawaiian custom recognizes a connection between the watershed and the ocean, mauka and makai; and experts are also looking to the mountains to explain the declining health of coral reefs.

“Everybody has known for a long time this ridge to reef paradigm,” said Ku‘ulei Rodgers, coral reef biologist at Hawai‘i Institute of Marine Biology (HIMB). “The ahupua‘a system, for centuries it’s been the central element in Native Hawaiian land management.”

The ahupua‘a system, she said, is a land and reef management system that combines watersheds, streams, coastal regions and even some areas further out to sea as an interacting, connected ecosystem.

“They (ancient Hawaiians) had this holistic view. They believed what they did on land was going to affect their fishing and they were careful,” Rodgers said. “We have that same view today. The sustain abilities of the watershed are linked to the near shore environment.”

Though the concept is commonly accepted, it wasn’t until recently that a project between HIMB and the Hawaii Stream Research Center quantified the connection between the reefs and the watersheds on a large scale. The explanation of that connection can be found in the water cycle. Henrietta Dulai is a geochemist and associate professor in the Department of Geology and Geophysics (G&G) who studies submarine groundwater discharge.

“So I study the water cycle and how water from the land gets to the ocean,” Dulai said. “While the water itself is doing that, it carries dissolved material in it.” Sediment, excess nutrients, pharmaceuticals and personal care products, and pesticides are on the list of things that streams bring down from the mountains, and which are local stressors for coral.

Read more about it in The Garden Island.