Plankton and carbon sequestration
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Plankton Role in Carbon Sequestration: Key Mechanisms
Plankton, especially phytoplankton, are central to the process of carbon sequestration in aquatic ecosystems. Through photosynthesis, phytoplankton fix atmospheric CO2, converting it into organic carbon that can be transferred through the food web or exported to deeper waters, effectively removing it from the atmosphere for years to centuries 1278+1 MORE.
Phytoplankton Productivity and Environmental Influences
Phytoplankton productivity, which drives carbon fixation, is influenced by both internal factors (like community composition) and external environmental variables (such as nutrient availability). For example, green algae and diatoms contribute more to carbon sequestration than cyanobacteria, with their productivity being regulated by nutrients like nitrate and phosphate. Seasonal and spatial variations, such as higher productivity in upstream river sections or during autumn due to diatom blooms, also affect carbon sequestration potential .
Plankton Community Structure and Carbon Export
The efficiency of carbon export from surface waters to the deep ocean is closely linked to the size and composition of plankton communities. Larger plankton, such as diatoms and protists, tend to enhance carbon export due to their higher sinking rates, while smaller organisms like bacteria and cyanobacteria contribute less to deep carbon sequestration 3567. However, the relationship between plankton size spectra and export efficiency is complex, and recent studies suggest that both size structure and overall productivity are important for predicting carbon export 67.
Microbial Loop and Carbon Transformation
Microbial communities, including bacteria and viruses, play a crucial role in transforming and retaining carbon within aquatic systems. During phytoplankton blooms, bacteria process dissolved organic matter (DOM), producing refractory compounds that can immobilize carbon and contribute to long-term sequestration. The microbial loop can either retain carbon in the upper ocean or facilitate its export, depending on the stage of the bloom and the dominant microbial processes 510.
Pathways and Timescales of Ocean Carbon Sequestration
The ocean’s biological carbon pump operates through several pathways: gravitational settling of organic particles (mainly zooplankton fecal pellets and phytoplankton aggregates), active transport by migrating zooplankton, and physical mixing. Gravitational settling is the dominant pathway, responsible for about 70% of global carbon export, with sequestration times averaging 140–150 years. Regional differences exist, with the highest sequestration inventories in northern high latitudes and shorter timescales in subtropical gyres .
Plankton Networks and Oligotrophic Ocean Carbon Export
In nutrient-poor (oligotrophic) regions, specific plankton groups such as Radiolaria, Synechococcus, and their associated viruses are strongly linked to carbon export. The abundance of certain bacterial and viral genes can predict variability in carbon export, highlighting the importance of microbial networks in driving the biological carbon pump even in low-nutrient environments .
Inland Waters and Carbon Sequestration
Phytoplankton in lakes and reservoirs also contribute to carbon sequestration, with their abundance and chlorophyll-a concentrations serving as indicators of sequestration rates. These findings are important for developing strategies to enhance carbon sinks in freshwater systems . Additionally, factors like calcium concentration can regulate the interactions between DOM and planktonic bacteria, influencing the stability and sequestration of carbon in inland waters .
Conclusion
Plankton are fundamental to global carbon sequestration, with their community structure, productivity, and interactions with environmental variables shaping the efficiency and pathways of carbon export. Both marine and freshwater systems rely on the dynamic interplay between phytoplankton, bacteria, and environmental factors to regulate the long-term storage of carbon, making plankton a critical component in mitigating atmospheric CO2 and climate change 1235+5 MORE.
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Most relevant research papers on this topic
Response of plankton community respiration under variable simulated upwelling events
Planktonic community structure impacts community respiration and carbon sequestration in upwelling regions, with microplankton and nanoplankton dominating under extreme upwelling intensities and prokaryotic picoplankton contributing under other intensities and modes.
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