A microscopic pigment known as chlorophyll a is shedding new light on the complex relationship between severe tropical storms and marine ecosystems. Chlorophyll a, a vital pigment responsible for absorbing light to drive photosynthesis in algae, plants, and certain bacteria, acts as a biological indicator reflecting the health and productivity of aquatic environments. Fluctuations in chlorophyll a concentrations often signal disturbances in aquatic ecosystems, making it a critical proxy for evaluating the impacts of extreme weather events, particularly typhoons.
Typhoons, characterized by their sustained hurricane-force winds over oceanic and coastal regions, are notorious for agitating marine waters and triggering drastic ecological changes. While the effects of single typhoon occurrences on chlorophyll a dynamics have been extensively documented, the cumulative impact of successive typhoons remains an area ripe for deeper exploration. Researchers from China have now unveiled pioneering findings that highlight the compounded influences of back-to-back typhoon events on chlorophyll a concentrations, advancing our understanding of estuarine ecosystem responses under extreme environmental stressors.
The January 2026 publication in Ocean-Land-Atmosphere Research details an innovative study led by Shaojing Guo, a doctoral candidate at Sun Yat-sen University and the Southern Marine Science and Engineering Guangdong Laboratory. Guo’s team focused their investigation on the Pearl River Estuary, a critical marine interface where freshwater from China’s second-largest river converges with the South China Sea. Spanning more than 490,000 square kilometers with an average annual discharge exceeding 10,000 cubic meters per second, the Pearl River and its estuary represent a dynamic and highly productive ecosystem modulated by variable freshwater inputs and coastal hydrodynamics.
Central to this study is the concept of the river plume: a distinct region where freshwater outflow and nutrient-rich discharge from the river create favorable conditions for phytoplankton productivity, indicated by elevated chlorophyll a levels. However, the summer of 2021 experienced an anomalously low runoff period, with only 46% of the climatological average discharge entering the estuarine system—a record low for over two decades. This unique hydrological backdrop provided an extraordinary natural laboratory for the research team to dissect the nuanced ecological interactions triggered by successive typhoons in an environment under hydrological stress.
The two typhoons, Cempaka and Lupit, struck the Pearl River Estuary region on July 19 and August 3, 2021, respectively. Utilizing a multidisciplinary approach that integrated direct field observations, comprehensive water sampling, and sophisticated computational modeling, the researchers mapped the three-dimensional distribution and temporal evolution of chlorophyll a in response to these successive storms. Intriguingly, their findings revealed a sharp decline in chlorophyll a concentrations with the approach and passage of each typhoon, followed by a rebound in the upper water layers of the main estuarine sub-region, Lingdingyang. Contrastingly, the subsurface waters exhibited a sustained decrease post-Cempaka and an almost complete disappearance of chlorophyll a after Lupit.
This vertical stratification in chlorophyll a response underscores the complex interplay between physical hydrodynamics and biological processes during extreme weather events. The strong mixing induced by storm-driven currents, upwelling, and altered freshwater inflow reshapes nutrient availability and light conditions within the water column, leading to spatially heterogeneous phytoplankton responses. The researchers’ coupled ecological-hydrodynamic model demonstrated high fidelity in replicating these observed patterns, confirming its robustness for simulating the biophysical consequences of successive typhoons.
Further analysis elucidated that different physical mechanisms governed chlorophyll a dynamics across various spatial domains and typhoon phases. While the upper estuarine zones experienced transient blooms fueled by nutrient entrainment and reduced stratification post-typhoon, bottom layers and nearshore regions showed more pronounced depletion. This divergent behavior highlights the importance of resolving three-dimensional processes rather than relying on surface observations alone when assessing ecological impacts in such complex coastal systems.
The study’s implications extend beyond the immediate context of the Pearl River Estuary. With anthropogenic climate change intensifying ocean warming and increasing the frequency and severity of extreme climate phenomena, the likelihood of successive typhoons and fluctuating freshwater discharges affecting coastal ecosystems may rise globally. Understanding the cumulative effects of these compound disturbances is thus imperative for accurately forecasting ecosystem health, managing fisheries, and preserving biodiversity in vulnerable estuarine and marine environments.
Guo advocates for enhanced future research efforts focusing on refining high-resolution physical-ecological models that integrate multiple stressors and feedbacks. Such improved predictive capacities will be critical for designing adaptive management strategies in the face of accelerating environmental variability. Additionally, the coupling of continuous in situ monitoring with satellite remote sensing and modeling will be instrumental in capturing the spatially and temporally complex responses of marine primary productivity to successive extreme weather events.
This pioneering work is also notable for its multidisciplinary collaboration, incorporating expertise from institutions such as the National Marine Environmental Forecasting Center and Shandong University, ensuring a comprehensive approach to tackling the multifaceted challenges posed by typhoon-driven ecosystem disturbances. Funding support from the Southern Marine Science and Engineering Guangdong Laboratory, the National Natural Science Foundation of China, and the Ocean Negative Carbon Emissions Program facilitated the integration of advanced computational techniques with empirical data collection, setting a benchmark for future oceanographic and ecological research in the region.
By providing a deeper mechanistic insight into how successive tropical cyclones affect phytoplankton dynamics and thus the foundational productivity of coastal ecosystems, this study offers a crucial framework to understand and mitigate the ecological consequences of a rapidly changing climate. As oceanographic research increasingly intersects with climate science, hydrology, and ecology, such interdisciplinary studies are indispensable for protecting the resilience and sustainability of the world’s aquatic environments.
Subject of Research:
Not applicable
Article Title:
Notable Variations in Chlorophyll a in Response to Successive Typhoons in and near the Pearl River Estuary
News Publication Date:
27-Feb-2026
Web References:
https://doi.org/10.34133/olar.0134
Image Credits:
Shaojing Guo et al. / Ocean-Land-Atmosphere Research
Keywords:
Oceanography, Marine biology, Marine ecology
