Published Study Documents Shift in Diet of Kaneohe Bay Green Turtles

A research paper recently published in the peer-reviewed journal Pacific Science describes a 28-year study of dietary shifts in green turtles in the Kaneohe Bay region of Oahu, Hawaii. The paper was co-authored by PIFSC scientist George Balazs and colleague Dennis Russell of the University of Sharjah, United Arab Emirates.

Balazs and Russell analyzed data from 1977–2005 and found that Kaneohe Bay green turtles have modified their feeding behavior to include the increasing abundance of nonnative algae growing in the greater Kaneohe Bay area of Oahu. Changes in the diet are correlated with an increase in abundance of seven species of nonnative algae during the 28-year span. During this period, the abundance of green turtles has increased throughout the Hawaiian Islands.

The average frequency (Adj %) of nonnative algae in the diet of Kaneohe Bay green turtles (diamonds; solid lines) increased during 1978–2005 while the frequency of native algae (squares; dashed lines) decreased.

The analysis showed that green turtles in Kaneohe Bay ate 130 species of marine vegetation. Most common were three nonnative species Acanthophora spicifera, Hypnea musciformis, and Gracilaria salicornia. These species are now an important part of the turtle diet in addition to native species found in and near Kaneohe Bay. Green turtle foraging behavior shifted to include the new seaweeds within 10 years of their introduction to the region. The turtles have also gradually included four less-prolific, slow-growing nonnative algal species in their diet (Eucheuma denticulatum, Gracilaria tikvahiae, Kappaphycus striatum, and Kappaphycus alvarezii), but over a longer time interval, 20–30 years, after the seaweeds were introduced.