Structural diversity and environmental impacts of Cladophora mats in a large plateau brackish lake

Filamentous algal blooms (or algal mats) are increasingly recognized as a growing threat to clear lakes worldwide, particularly in the context of climate change and lake eutrophication. Nevertheless, knowledge about filamentous algal mats and their environmental consequences is still limited. In this study, we investigated the structural characteristics and environmental impact of filamentous algae (Cladophora) mats in the brackish water of Qinghai Lake on the Tibetan Plateau. Our results classify the development of Cladophora blooms into three distinct stages: the attachment stage (May to July), the floating stage (August to September), and the decomposition stage (October to November), corresponding to attached, floating, and decaying mats, respectively. The attached mats consist of single layer, while the floating and decaying mats exhibit more complex structures, with two-layer and three-layer formations, respectively. Each layer displays distinct physiological states in the vertical direction, highlighting their structural diversity. The layered structure enables Cladophora mats to better adapt to environmental changes, ensuring long-term stability in the lake ecosystem through the synergistic effects of upper-layer protection, middle-layer growth, and bottom-layer decomposition. Notably, the water surrounding the decaying mats showed significantly elevated concentrations of nitrogen, phosphorus, and dissolved organic matter. Partial Least Squares Path Modeling analysis further revealed that Cladophora mats have a substantial influence on dissolved organic carbon and fluorescent dissolved organic matter, with path coefficients of 0.84 and 0.65, respectively. These findings significantly enhance our understanding of the dynamics of filamentous algal blooms and their environmental impacts, and are crucial for the conservation of lakes with high water quality.