A refined model of Gambierdiscus growth and abundance in the coastal waters of Hawaii.
Michael L. Parsons1, Paul K. Bienfang2, and Chelsie J. Settlemier3
1
Florida Gulf Coast University, Fort Myers, FL
2
University of Hawaii, Honolulu, HI
3
University of Hawaii at Hilo, Hilo, HI
Gambierdiscus is a circumtropical, benthic dinoflagellate that produces toxins known to cause
ciguatera, a reef fish-borne food poisoning. Ciguatera may be the most common form of
seafood poisoning globally, yet the conditions and causal factors leading up to ciguatera
outbreaks remain speculative. In an effort to better understand the population dynamics of
Gambierdiscus in relation to changing environmental conditions, an intensive sampling effort
was undertaken around the Big Island of Hawaii to determine what factors appear to most
influence the abundance of Gambierdiscus in Hawaii reef environments. Over 150 samples
were collected from two leeward and two windward sites on a monthly basis over a three-year
period and analyzed. A new growth-limitation model was constructed using sinusoidal
simulations of the environmental data from the windward sites coupled with growth curve data
obtained from culture-based studies of Gambierdiscus isolated from the same waters.
Following model calibration and stabilization using the windward data, the model was confirmed
with the leeward environmental data, resulting in good predictability of Gambierdiscus seasonal
abundance (r2 = 0.89; p<0.0001; slope = 0.88). The model parameters were then modified to
simulate environmental perturbations to trigger a Gambierdiscus bloom, which would
hypothetically lead to a ciguatera flare-up. Results of these manipulations will be discussed.