71% of the Earth is covered by oceans, in which tiny plankton form the base of the marine food web. Impacting all other aquatic and terrestrial ecosystems, tiny plankton are crucial for ocean biology and climate. The study “Organic and inorganic nutrients modulate taxonomic diversity and trophic strategies of small eukaryotes in oligotrophic oceans” in FEMS Microbes characterises the environmental drivers that impact the physiology and composition of plankton communities. Naomi Villiot explains in a #BehindThePaper interview why we need to better understand the impact of climate change on these essential organisms. #FEMSmicroBlog
Can you summarise the significance of your paper for microbiologists outside of your field?
In the open ocean, vertical stratification controls the availability of resource for microbes and influences the composition of microbial communities. Ultimately, stratification further impacts the productivity and carbon storage capacity of the deep ocean. As a result of global warming, vertical stratification is expected to strengthen.
In our study “Organic and inorganic nutrients modulate taxonomic diversity and trophic strategies of small eukaryotes in oligotrophic oceans” in FEMS Microbes, we examined the taxonomic and trophic composition of small eukaryotic plankton communities in the stratified waters of the oligotrophic Sargasso Sea. We sampled natural microbial communities and incubated them under different nutrient regimes to draw conclusions of the effect of nutrient availability on taxonomic and functional composition.
We identified inorganic phosphorus as an important controller of biodiversity, while dissolved organic matter addition reduced microbial diversity. Importantly, we found that the nutrient conditions to which the communities were exposed to previously predicts the physiological responsiveness to changing nutrient regimes.
The taxonomic composition and nutritional mode of these communities responded to the addition of nutrients in identifiable and reproducible ways. This highlights the importance of the water column structure when modelling future responses of plankton communities.
What can policy makers learn from your research results?
Ocean biogeochemistry models require an understanding of the impact of environmental drivers on the oceanic metabolism and microbial community composition. This allows predicting plankton community dynamics in oceans depending on climate change as well as reliably estimating oceanic primary productivity and nutrient fluxes.
Our results demonstrate the importance of testing the effects of nutrient availability at the community-level. These results significantly differ from laboratory observations and
generate different mechanistic hypotheses than those currently used to build biogeochemical and ecological models.As oligotrophic areas expand and vertical stratification strengthens, the patterns described in our study will drive the spatial and temporal dynamics of plankton communities in oligotrophic waters more significantly. Future studies will need to consider the water column structure and microbial community history when approaching similar experiments or modelling future responses of plankton communities.
Why are your results important for society or non-scientists?
Half of the oxygen we breath is produced by plant-like plankton. Hence, changes in the composition of plankton communities and their productivity can significantly impact the Earth’s biodiversity, fisheries, the human food supply and the pace of global warming.
Characterising the impact of environmental drivers on plankton community physiology has become an urgent need as we seek to predict their behaviour in future oceans and to understand the controls of and fate of their production.
Scientists aim to build accurate ecological and biogeochemical models of oceanic plankton community composition and dynamics. Many of these models predict that the warming of ocean surface waters will lead to increasingly stratified water columns, resulting in declined productivity of plankton.
Our results provide new insights into the impact of nutrient availability on the plankton community composition and behaviour in warm and stratified waters. Around 80 percent of the surface ocean is nutrient-limited with “low-nutrient oceanic deserts” like the Sargasso Sea, where our study took place.
Understanding the impact of nutrient availability on microbial communities is important to predict how productive they are and what might happen when inorganic nutrient availability declines. We hope that our conclusions can help model plankton behaviour in future oceans and refine current models.
What fascinates you about oceanic plankton communities?
I have always been amazed by how important microorganisms are, despite their tiny size. They sustain Earth and they have huge potential for applications ranging from biofuel and human nutrition to cosmetics and cancer treatments. Preserving the biodiversity of microbial communities is crucial to our planet’s health and requires us to improve our knowledge on their structure and dynamics at the community-level.
Why did you choose the transparent peer-review process for your publication?
I believe that an open peer-review process through transparency is the way forward. For the public to trust research findings and reports, we need to ensure that the peer-review and journals’ decision-making process is credible and accurate.
Open peer review facilitates accountability by authors, reviewers and editors and recognition for reviewers who contribute greatly to improving the quality of the published manuscripts. I believe that transparency can lead to more thoughtful reviews, open conversations and lead to potential collaborations that might otherwise not occur.
- Read the paper “Organic and inorganic nutrients modulate taxonomic diversity and trophic strategies of small eukaryotes in oligotrophic oceans” by Villiot et al. (2022) in FEMS Microbes.
Naomie Villiot graduated from the University of La Rochelle, France, with a European MSc Degree in Blue Biotechnology. Keen to undertake further research training and continue a research career, she completed a PhD degree in Marine Microbiology at Heriot-Watt University in Edinburgh, UK, on the physiological ecology of marine calcifying microalgae- coccolithophores. Her research interests include Marine Biotechnology, the elucidation of Ecological Processes as well as Phytoplankton Diversity and Physiology. In her free time, she likes travelling, drawing and jump roping.
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