Lessons from Wetlands

UH group studies the science of Molokai wetlands.

By Arleone Dibben-Young

Coastal wetlands have received much less attention than terrestrial and marine ecosystems, but Dr. Greg Bruland of the University of Hawaii, Manoa, hopes to change that.

Scientists and students have been busy studying vegetation, soils, water quality and fish communities of wetlands across the Hawaiian Islands on a quarterly basis. Initially, 40 sites were tested, with 20 picked for the three-year project. Of the five sites originally sampled on Molokai, three wetlands were chosen for continued research – Ohiapilo Pond Bird Sanctuary, Koheo Wetland, and Ualapue Pond. September’s sampling focused on water quality and fish by three team members.

 “We are curious to know what kinds of fish live in Hawaii's wetlands and how many fish there are in these wetlands,”  explains Dr. Rich MacKenzie.

Caitlin Kryss adds, “When investigating Hawaiian wetlands, most researchers look at the birds, but very few have looked at the fish.”

MacKenzie and Kryss are part of the Forested Wetlands team. “Fish are important food sources for other fish, birds, and humans, so knowing how many fish are in a wetland and what kinds of fish are there is very useful,” articulates MacKenzie. “This information can show us how healthy a wetland is as well as how valuable a certain wetland might be to native birds and fish. The fish act as sentinels for the wetlands; any changes that we detect in the fish community usually indicates that something is wrong in the wetland.”

MacKenzie and Kryss have been using lift nets. “These are specially designed nets that allow us to determine how many fish there are in a certain area. Because we use the same type of nets in each of the wetlands, we can compare fish among the different sites,” says Kryss.

“When we lay our nets, we pick random places to lay them and never use bait as we don't want to attract fish, which would influence our catch. My favorite sites on Molokai are Koheo and Ualapue. I like them because we catch all different kinds of fish and shrimp that are native to Hawaii. Their presence suggests that these wetlands are in really good shape.” The team plans to keep sampling the same sites over the next year, but will be using different nets such as a seine and a throw net.

University of Hawaii team member Gwen DeMent is comparing the phosphorus sorption capacity of wetland soils.

“Coastal wetlands are valuable ecosystems, and are responsible for many important functions including the biogeochemical cycling of phosphorus,” she explains. “Too much phosphorus can lead to invasive species dominance and coral reef degradation.“

DeMent has found significant differences in soil properties of restored and created wetlands versus natural wetlands. “These differences influence plant growth and survivability as well as the retention of nutrients for wetland health.” The results of DeMent’s study will assist in developing management strategies for protecting and preventing degradation of valuable coastal wetlands.

Working under a grant from the U.S. Environmental Protection Agency titled Assessment and Monitoring of the Water Quality and Habitat Functions of Natural, Restored, and Created Wetlands of the Hawaiian Islands, Bruland and the team of grad students have partnered with the U.S. Department of Agriculture Forest Service’s Forested Wetlands, Hilo, U.S. Fish and Wildlife Service, Army Corps of Engineers, Pacific Coast Joint Venture, and Ducks Unlimited.

For an in-depth look at this project and other mauka-to-makai research go to
http://www.ctahr.hawaii.edu/brulandg/whatsnew/CTAHR_Research_News_May_08.pdf

If you would like to volunteer in December’s sample collection, call Arleone at 553-5992.