Phytoplankton Dynamics in Marine and Estuarine Ecosystems

Phytoplankton form the base of marine and estuarine food webs and drive critical biogeochemical processes that regulate the global carbon cycle. Their distribution and activity vary across temporal and spatial scales, influenced by light availability, nutrient supply and hydrodynamic forces. In open oceans, stratification, mixing and mesoscale circulation govern bloom initiation, community composition and vertical carbon flux, whereas in estuaries, steep gradients in salinity, turbidity and riverine nutrient input create hotspots of productivity and complex seasonal succession. Drivers such as upwelling, river discharge and climate oscillations interact to control phytoplankton growth, species turnover and export pathways. Recent advances in high-resolution observations, satellite hyperspectral imaging and trait-based ecosystem modelling have improved our understanding of phytoplankton phenology, diversity and their role in carbon export, informing global carbon budget assessments and management of coastal resources in a changing climate.

Research from Nature Portfolio

Recent multi-year observations in polar waters using autonomous sensors have concurrently tracked the activity of gravitational sinking and two particle injection pumps—namely the mixed layer pump and the eddy subduction pump—revealing how physical forcing and phytoplankton phenology determine seasonality and magnitude of downward carbon export. These findings refine estimates of biological carbon sequestration efficiency across contrasting Southern Ocean regimes. Complementing this, complex ecosystem modelling incorporating 35 phytoplankton types projects 21st-century shifts in community composition, size structure and turnover under warming scenarios. The analyses indicate an accelerating rate of community turnover and reduced ecological resilience, with potential knock-on effects for marine productivity and biogeochemical cycles.

Phytoplankton Dynamics in Marine and Estuarine Ecosystems publication trend

The graph below shows the total number of articles in phytoplankton dynamics in marine and estuarine ecosystems across all publications each year (not limited to Nature Index journals).

Technical terms

Biological carbon pump: Mechanism by which phytoplankton convert dissolved CO₂ into organic matter that sinks to the deep ocean, enabling long-term carbon storage.

Euphotic zone: Upper layer of the water column where sunlight penetration is sufficient to support photosynthesis by phytoplankton.

Mixed layer pump: Process in which turbulent mixing subducts organic particles from the surface mixed layer into deeper waters.

Eddy subduction pump: Downward transport of organic carbon along sloping density surfaces driven by mesoscale eddies.

Hyperspectral remote sensing: Technique using high-resolution spectral measurements of reflected light to distinguish phytoplankton groups based on pigment signatures.

References

1. Seasonality of downward carbon export in the Pacific Southern Ocean revealed by multi-year robotic observations. Nature Communications (2023).
2. Phytoplankton composition from sPACE: Requirements, opportunities, and challenges. Remote Sensing of Environment (2024).
3. The Western Channel Observatory: a century of physical, chemical and biological data compiled from pelagic and benthic habitats in the western English Channel. Earth System Science Data (2023).
4. Phytoplankton as Key Mediators of the Biological Carbon Pump: Their Responses to a Changing Climate. Sustainability (2018).
5. Phytoplankton primary production in the world's estuarine-coastal ecosystems. Biogeosciences (2014).
6. Future phytoplankton diversity in a changing climate. Nature Communications (2021).