Decoding the spatial spread of cyanobacterial blooms in an epilimnion

TL;DR

This paper develops a spatially explicit PDE model based on ecological stoichiometry to understand cyanobacterial bloom spread in lakes, highlighting the roles of lake shape, wind, and nutrients in bloom dynamics.

Contribution

It introduces a novel spatial PDE model incorporating GIS and wind data to analyze cyanobacterial blooms, advancing beyond simpler models.

Findings

Lake shape and size significantly affect bloom patterns.

Light attenuation and intensity are primary drivers of bloom variation.

Water movement influences early bloom stages, while nutrients impact later stages.

Abstract

Cyanobacterial blooms (CBs) pose significant global challenges due to their harmful toxins and socio-economic impacts, with nutrient availability playing a key role in their growth, as described by ecological stoichiometry (ES). However, real-world ecosystems exhibit spatial heterogeneity, limiting the applicability of simpler, spatially uniform models. To address this, we develop a spatially explicit partial differential equation model based on ES to study cyanobacteria in the epilimnion of freshwater systems. We establish the well-posedness of the model and perform a stability analysis, showing that it admits two linearly stable steady states, leading to either extinction or saturation. We use the finite elements method to numerically solve our system on a real lake domain derived from Geographic Information System (GIS) data and realistic wind conditions extrapolated from ERA5-Land. Our numerical results highlight the importance of lake shape and size in CB monitoring, while global sensitivity analysis using Sobol Indices identifies light attenuation and intensity as primary drivers of bloom variation, with water movement influencing early bloom stages and nutrient input becoming critical over time. This model supports continuous water-quality monitoring, informing agricultural, recreational, economic, and public health strategies for mitigating CBs.