# Nonlinear Responses of Phytoplankton Communities to Environmental Drivers in a Tourist-Impacted Coastal Zone: A GAMs-Based Study of Beihai Silver Beach

## TL;DR

A three-year study in a tourist-impacted coastal area found that phytoplankton communities are strongly influenced by phosphorus and lead, with complex nonlinear relationships affecting their diversity and abundance.

## Contribution

The study introduces the use of Generalized Additive Models (GAMs) to reveal nonlinear environmental impacts on phytoplankton in a tourist-impacted coastal zone.

## Key findings

- Phytoplankton richness peaked in summer and was lowest in winter.
- Reactive phosphate was the primary driver with strong nonlinear effects on species richness and diversity.
- Lead concentration showed a positive correlation with species richness, indicating complex stressor interactions.

## Abstract

A three-year study in Beihai Silver Beach revealed that phytoplankton communities were consistently dominated by diatoms, with a major bloom of Skeletonema costatum occurring in autumn 2021. Species richness peaked in summer, while abundance hotspots were found near the Fengjia River estuary. Using advanced statistical models, phosphorus was identified as the primary driver, showing complex nonlinear relationships with both species richness and diversity. Surprisingly, lead concentration showed a positive correlation with species richness, revealing complex stressor interactions. These findings highlight the importance of phosphorus control and demonstrate the value of advanced modeling for coastal ecosystem management.

Based on multi-seasonal surveys (2020–2022) in Beihai Silver Beach, this study examined phytoplankton community dynamics and environmental drivers. Results showed persistent diatom dominance, with Skeletonema costatum as the predominant species and a major bloom in autumn 2021. Species richness peaked in summer and was lowest in winter, while abundance hotspots were associated with the Fengjia River estuary. Generalized Additive Models identified reactive phosphate as the primary driver, exhibiting nonlinear relationships with species richness (R2 = 0.91) and diversity (R2 = 0.436). Dissolved oxygen also had significant nonlinear effects. A counterintuitive positive correlation between lead concentration and species richness highlighted complex stressor interactions. This study emphasizes phosphorus control for eutrophication mitigation and demonstrates GAMs’ utility in detecting nonlinear ecological responses, supporting science-based management of coastal ecosystems.