Phytoplankton group classification by integrating trait information and observed environmental thresholds

Assigning phytoplankton taxa to functional groups is essential for aquatic ecology models but challenging in systems with high taxonomic diversity. Without a clear framework, many models subjectively group phytoplankton at the phyla or class level, aggregating the substantial functional and trait diversity that occurs within these groups. However, this creates challenges for model parameterization and evaluation. To address this, we developed a data-driven approach to define phytoplankton functional groups, considering species trait information and occurrence data from a 12-year dataset of the Hawkesbury-Nepean River (Australia). Our framework reduces subjectivity by using multi-correlation and principal component analysis to identify key environmental factors. K-prototype was used to classify phytoplankton based on a priori species-level trait and observed threshold ranges across the factor gradients defined by threshold indicator taxa analysis. Five trait-threshold classified groups had statistically distinct environmental preferences and morphological and physiological characteristics and were more homogeneous than taxonomic-based groups. These groups were integrated into a 3D hydrodynamic-biogeochemical model (2017 – 2018), parameterized using their unique traits and ecological thresholds. The model successfully simulated historical conditions and captured group-level dynamics in chlorophyll-a and biomass, including bloom events. The insights gained from this study can be extended to other urban rivers, offering a practical approach to managing phytoplankton blooms.

Presentation Preference: Oral

Primary Presenter: Hoang Vuong Dang, The University of Western Australia (hoangvuong.dang@research.uwa.edu.au)

Authors:

Kermode Stephanie, WaterNSW, Parramatta, Australia  (stephanie.kermode@waternsw.com.au)

Peisheng Huang, Centre for Water and Spatial Science, UWA School of Agriculture and Environment, The University of Western Australia  (peisheng.huang@uwa.edu.au)

Cayelan Carey, Department of Biological Sciences, Virginia Tech, USA  (cayelan@vt.edu)

Matthew Hipsey, Centre for Water and Spatial Science, UWA School of Agriculture and Environment, The University of Western Australia  (matt.hipsey@uwa.edu.au)