Exploring How Plankton Capture CO2 and Feed in Warm Coastal Waters

Jim Crocker
8th March, 2024

Exploring How Plankton Capture CO2 and Feed in Warm Coastal Waters

Image Source: Natural Science News, 2024

Key Findings

  • Study in South China Sea finds plankton use diverse methods to turn CO2 into organic matter
  • Different plankton types vary in their carbon-fixing ability, influenced by environmental factors
  • Some plankton can consume other organisms, potentially boosting their carbon-fixing capacity
Understanding how marine plankton communities fix carbon—a process vital to the Earth's climate and ecosystems—is a complex task. Researchers from Xiamen University have taken a significant step in unraveling this complexity by examining the activities of different plankton lineages in the South China Sea[1]. Their study sheds light on how various environmental factors influence the carbon fixation potential of different plankton groups and introduces the role of mixotrophy and alternative energy sources in this critical ecological process. Plankton, which includes phytoplankton like algae and cyanobacteria, as well as various bacteria and archaea, are the ocean's primary producers. They convert carbon dioxide (CO2) into organic matter through carbon fixation. The most well-known pathway for this is the Calvin cycle, but there are also non-Calvin pathways that have received less attention until now. The study conducted by Xiamen University researchers used a method called whole-assemblage metatranscriptomic profiling. This technique allows scientists to analyze the gene expression of all organisms in a community, in this case, the plankton community. By looking at the expression of RuBisCO, an enzyme central to the Calvin carbon fixation (CCF) pathway, they could assess the CCF potential of different plankton lineages. They found that this potential varied among Bacillariophyta (diatoms), Chlorophyta (green algae), Cyanobacteria, and Haptophyta, and was influenced differently by environmental factors for each group. Interestingly, the expression of phagotrophy-related genes, which are indicative of a plankton's ability to consume other organisms, was found to have a complex relationship with CCF potential. In some cases, phagotrophy appeared to enhance CCF, while in others, it seemed to complement it. This finding aligns with earlier research showing that mixotrophic haptophytes adjust their feeding strategies based on environmental conditions[2], and that dinoflagellates can upregulate genes related to nutrient uptake and phagocytosis under nitrogen deficiency[3]. The researchers also discovered significant non-Calvin carbon fixation (NCF) potential within the community, marked by the active expression of genes involved in all five recognized NCF pathways. These were mainly contributed by bacteria from the orders Flavobacteriales, Alteromonadales, and Oceanospirillales. The NCF potential was positively correlated with the expression of proton-pump rhodopsin (PPR) in several bacterial orders, suggesting that PPR may provide the energy needed for NCF. This insight expands on previous studies that have indicated the importance of iron and nitrogen in regulating the physiology of phytoplankton communities and their responses to nutrient limitations[4]. The study's findings are critical because they provide a clearer picture of the diverse strategies plankton use to fix carbon in different environmental contexts. The data revealed that the potential for CCF and NCF varies among lineages and that mixotrophy—organisms using both photosynthesis and ingestion of prey—is widespread. This underscores the importance of a balanced and biodiverse ecosystem in maintaining healthy plankton communities, which are essential for preventing harmful algal blooms[5]. By identifying the major contributors to both CCF and NCF and their potential energy sources, the research from Xiamen University offers a new understanding of the trophic landscape in the ocean. It lays the groundwork for future studies to explore the intricacies of carbon fixation further and the role of marine plankton in global carbon cycling and climate regulation. This study represents a significant advancement in marine biology and ecology. It not only ties together earlier findings on the importance of nutrient acquisition and competition among plankton[2][3][4][5] but also opens up new avenues for research into the complex interplay between different carbon fixation pathways and the environmental factors that influence them.

BiochemEcologyMarine Biology

References

Main Study

1) In situ community transcriptomics illuminates CO2-fixation potentials and supporting roles of phagotrophy and proton pump in plankton in a subtropical marginal sea.

Published 5th March, 2024

https://doi.org/10.1128/spectrum.02177-23

Related Studies

2) Abiotic and Biotic Factors Affecting the Ingestion Rates of Mixotrophic Nanoflagellates (Haptophyta).

https://doi.org/10.1007/s00248-018-1249-2

3) Transcriptome profiling reveals versatile dissolved organic nitrogen utilization, mixotrophy, and N conservation in the dinoflagellate Prorocentrum shikokuense under N deficiency.

https://doi.org/10.1016/j.scitotenv.2020.143013

4) Nitrogen and Iron Availability Drive Metabolic Remodeling and Natural Selection of Diverse Phytoplankton during Experimental Upwelling.

https://doi.org/10.1128/msystems.00729-22

5) In Situ Molecular Ecological Analyses Illuminate Distinct Factors Regulating Formation and Demise of a Harmful Dinoflagellate Bloom.

https://doi.org/10.1128/spectrum.05157-22


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