IS THERE CHAOS IN PLANKTON DYNAMICS

A controversial issue in ecosystem modeling is whether the irregular fluctuations that one observes in nature are due solely to random environmental factors or whether, at least partially, a deterministic mechanism is responsible for the unpredictable behavior. This second alternative is called deterministic chaos and the issue in this paper is to decide if actual plankton time series can vindicate the hypothesis of chaotic dynamics. The near-neighbor forecasting method is a recent technique for detecting determinism in a time series and we apply it to measurements of phytoplankton and zooplankton biomass obtained at a single station in the Middle Atlantic Bight. Although the results do not conclude the presence of chaos, they do give some support to the idea that deterministic non-linear trophic dynamics may account for at least some of the variability that is seen in the data, particularly in terms of inferring zooplankton oscillations from those of phytoplankton.