Climate Change Effects on Harmful Algal Blooms
Summary
Climate change is reshaping the frequency, distribution and toxicity of harmful algal blooms (HABs) worldwide. Rising sea surface temperatures accelerate metabolic and growth rates of many bloom-forming algae, while elevated atmospheric CO₂ leads to ocean acidification that alters inorganic carbon speciation in coastal and open-ocean waters. Increased thermal stratification reduces vertical mixing, favouring the retention and intensification of surface blooms. Concurrent eutrophication driven by agricultural runoff and changing precipitation patterns supplies nutrients that can fuel more frequent and severe HAB events. Interactions among warming, acidification, deoxygenation and nutrient loading produce non-linear, species- or strain-specific outcomes in bloom dynamics, community succession and toxin production. As a result, blooms are emerging in regions previously unaffected, posing risks to human health, fisheries, aquaculture and ecosystem function. Understanding the combined effects of these climate drivers is essential for developing predictive tools and mitigation strategies that protect coastal economies and biodiversity.
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Climate Change Effects on Harmful Algal Blooms publication trend
The graph below shows the total number of articles in climate change effects on harmful algal blooms across all publications each year (not limited to Nature Index journals).
Technical terms
Harmful algal bloom (HAB): A rapid proliferation of toxin-producing algae that can harm aquatic life, human health and coastal economies.
Ocean acidification: The decrease in seawater pH and alteration of carbonate chemistry due to absorption of anthropogenic CO₂.
Carbon-concentrating mechanism (CCM): Physiological adaptations in phytoplankton that increase the efficiency of inorganic carbon uptake under low CO₂ conditions.
Eutrophication: Enrichment of aquatic systems with nutrients, often nitrogen and phosphorus, leading to excessive algal growth.
Partial pressure of CO₂ (pCO₂): A measure of CO₂ concentration in air or water, influencing the availability of dissolved inorganic carbon for photosynthesis.
References
- Meta‐analysis reveals enhanced growth of marine harmful algae from temperate regions with warming and elevated CO2 levels. Global Change Biology (2019).
- Harmful algal blooms: A climate change co-stressor in marine and freshwater ecosystems. Harmful Algae (2019).
- Dynamic CO2 and pH levels in coastal, estuarine, and inland waters: Theoretical and observed effects on harmful algal blooms. Harmful Algae (2019).
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