Abstract
Non-supervised artificial neural networks (ANN) and
hybrid evolutionary algorithms (EA) were applied to
analyse and model 12 years of limnological time-series
data of the shallow hypertrophic Lake Suwa in Japan.
The results have improved understanding of
relationships between changing microcystin
concentrations, Microcystis species abundances and
annual rainfall intensity. The data analysis by
non-supervised ANN revealed that total Microcystis
abundance and extra-cellular microcystin concentrations
in typical dry years are much higher than those in
typical wet years. It also showed that high microcystin
concentrations in dry years coincided with the
dominance of the toxic Microcystis viridis whilst in
typical wet years non-toxic Microcystis ichthyoblabe
were dominant. Hybrid EA were used to discover rule
sets to explain and forecast the occurrence of high
microcystin concentrations in relation to water quality
and climate conditions. The results facilitated early
warning by 3-days-ahead forecasting of microcystin
concentrations based on limnological and meteorological
input data, achieving an r2=0.74 for testing.
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