Seasonal change and subniche dynamics of three Alexandrium species in the Korea Strait

Some members of the dinoflagellate genus Alexandrium produce toxins responsible for paralytic shellfish poisoning, which causes environmental impacts and large economic losses worldwide. The Outlying Mean Index (OMI) and the Within Outlying Mean Index (WitOMI) were used to examine the ecological niches of three Alexandrium species identifying factors affecting their population dynamics in the Korea Strait (KS). Species niches were divided into seasonal subniches based on species' temporal and spatial patterns, with A. catenella being highest in the spring, A. pacificum in the summer, and A. affine in the autumn. These shifts in abundance are likely due to changes in their habitat preferences and resource availability, as well as the effects of biological constraints. A subniche-based approach, which considers the interactions between the environment and the biological characteristics of a species, was useful in understanding the factors shaping the population dynamics of the individual species. Additionally, a species distribution model was used to predict the phenology and biogeography of the three Alexandrium species in the KS and their thermal niches on a larger scale. The model predicted that, in the KS, A. catenella exists on the warm side of the thermal niche, while A. pacificum and A. affine exist on the cold side, indicating that these species may respond differently to increases in water temperature. However, the predicted phenology was incongruent with the abundance of the species as measured by droplet digital PCR. Overall, the WitOMI analysis and species distribution model can provide valuable insights into how population dynamics are influenced by the integrated interplay of biotic and abiotic processes.

Automated summary

Some members of the Alexandrium genus produce toxins that cause shellfish poisoning, causing global environmental impacts and economic losses. The OMI and WitOMI indices were used to examine the ecological niches of three Alexandrium species in the Korea Strait, identifying factors affecting their population dynamics. Species niches were divided into seasonal subniches, with shifts in abundance likely due to habitat preferences, resource availability, and biological constraints. A species distribution model predicted the phenology and biogeography of the species, indicating potential differences in response to water temperature. However, the predicted phenology did not align with measured species abundance. Overall, the WitOMI analysis and species distribution model provide valuable insights into the interplay of biotic and abiotic processes in population dynamics.