Published Studies Investigate Carrying Capacity of Hawaii Green Turtle Habitats

PIFSC scientists George Balazs and Stacy Hargrove, members of the Marine Turtle Research Program (MTRP), joined colleague Manjula Tiwari of the Southwest Fisheries Science Center in publishing an article in the peer-reviewed journal Marine Ecology Progress Series (MEPS). The paper "Estimating Carrying Capacity at the Green Turtle Nesting Beach of East Island, French Frigate Shoals" describes a simulation study of green turtle nesting at East Island, a principal nesting beach for the Hawaiian green turtle population and location of annual monitoring efforts by the U.S. Fish and Wildlife Service and MTRP. The study concludes that the carrying capacity of the nesting beach at East Island is well above current turtle nesting levels. Moreover, it would likely remain so even if the beach nesting area were diminished by rising sea level to the degree predicted by climate change experts.

In December 2010, MEPS published another article on Hawaii green turtles co-authored by Colette Wabnitz (University of British Columbia), MTRP scientists Stacy Hargrove and George Balazs, research colleagues Karen Bjorndal Alan Bolten (University of Florida), and others. Entitled "Ecosystem Structure and Processes at Kaloko-Honokohau, Focusing on the Role of Herbivores, Including the Green Sea Turtle Chelonia mydas, in Reef Resilience", the paper resulted from a chapter of Wabnitz' PhD dissertation, which was sponsored jointly by MTRP and the Center's Ecosystems and Oceanography Division. Using ECOPATH/ECOSIM numerical models, Dr. Wabnitz demonstrated that green turtle carrying capacity of Kaloko-Honokohau has been reached by the aggregation of green turtles foraging there. Kaloko-Honokohau is a key MTRP study site for long-term monitoring on the Kona Coast of the Island of Hawaii. Many other green turtle aggregations sampled by the MTRP along this 100 km coastline are similar to the Kaloko-Honokohau turtles in their slow somatic growth and heavy cropping of algal forage.

The carrying capacity of Kaloko-Honokohau for green turtles was determined in the context of the 
            turtles' role as herbivores in the biological community, as depicted in this diagrammatic representation 
            of the Kaloko reef ecosystem.  Numbers and horizontal grey lines denote trophic levels. Other grey lines 
            represent trophic links between ecosystem components. (Illustration © M. Bailey)
The carrying capacity of Kaloko-Honokohau for green turtles was determined in the context of the turtles' role as herbivores in the biological community, as depicted in this diagrammatic representation of the Kaloko reef ecosystem. Numbers and horizontal grey lines denote trophic levels. Other grey lines represent trophic links between ecosystem components. (Illustration © M. Bailey)