Research sheds light on diatom bloom formation


Scientists have described how diatoms (a type of eukaryotic algae) can sense phosphorus, demonstrating a new role for calcium ion signalling in eukaryotes for the first time. 

Researchers at the Marine Biological Association (MBA) in collaboration with scientists at PML and the University of Warwick have shed light on how diatoms sense the availability of phosphorus, a vital macronutrient which controls diatom growth and productivity in the oceans.

The research, which has been published in the journal Current Biology, demonstrated a new role for calcium ion (Ca2+) signalling in eukaryotes, for phosphate sensing, which has not previously been described.

Diatoms are responsible for 20% of global primary productivity, equivalent to that of terrestrial rainforests combined. The work showed that phosphorus-starved diatoms used Ca2+-dependent signalling to perceive and coordinate rapid recovery responses to phosphorus resupply. The researchers also demonstrated that one of the first adaptations to phosphorus resupply is substantial enhancement of the uptake of another essential nutrient, nitrogen.

This rapid crosstalk between phosphorus and nitrogen metabolism, coordinated by the novel phosphorus-Ca2+ signalling pathway, enhances diatom competition for two critical nutrients. As major bloom formers, this work provides vital insight into how diatoms are so successful in rapidly responding to environmental cues such as nutrient supply, to dominate algal bloom formation.

Dr. Katherine Helliwell, first author and a NERC Independent Research Fellow at the MBA and the University of Exeter, said: “This work provides important new insight into how one of the most abundant marine phytoplankton groups is able to thrive in feast-famine nutrient regimes. Our study helps us to understand the cellular mechanisms employed by diatoms at the very early stages of bloom formation.

As diatoms sustain coastal fish populations and marine food webs, gaining understanding of what drives the ecological success of diatoms is important to all of us, especially those who enjoy the pleasures of coastal ecosystems, from swimming in the sea, to eating fish and seafood. The Helliwell Group studies environmental drivers regulating phytoplankton productivity, from understanding environmental signalling mechanisms to exploring the interactions between microbes, and their impact on marine microbial communities."

During this project the nutrient biogeochemistry team at PML combined forces with the MBA’s phytoplankton physiologists to investigate a previously unidentified process, specifically the role played by calcium in detecting and responding to the essential nutrient phosphorus by marine Diatoms.

PML senior scientist and biogeochemist Dr Andy Rees, an author on the paper, said: "My colleagues at the MBA used state-of-the-art procedures to detect this novel process. Following our discussions around this phenomenon we designed an experimental investigation where we were able to show how these groups of diatoms were able to detect and respond to changing levels of phosphorus and that signalling within the diatom cells also controlled the uptake of nitrogen.

Diatoms are algal cells which play a key role in the productivity of our oceans and also in the uptake of atmospheric CO2. By understanding  how these key phytoplankton groups control their response to variable levels of essential nutrients will enable us to better forecast how coastal and ocean ecosystems might respond to a changing environment.”

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