Plant Cuttings

What is the connection between phytoplankton free-floating in the ocean and earth-bound rice plants? In answering that question, the following three posts indicate some of the ways in which divergent stories about photosynthesizing organism can be connected. In doing so, Mr Plant Cuttings is not giving away any secrets about his modus operandi [MO]*, but just showing the threads that can connect seemingly-disparate plant-relevant stories.

This image of diatoms as viewed through a microscope by Prof. Gordon T Taylor of Stony Brook University, is in the public domain.

Whenever we recognise many different species within a particular group of plants – e.g. Poaceae, the grass family, with between 11,500 and an estimated 13,000 species (Tim Forestell)  – we may rightly wonder how they all manage to exist. After all, if they’re all the same type of plant, presumably they are exploiting the same kinds of resources, and there’s only so much of those to go round. For a family such as the Poaceae, presence of different species in different habitats and locations across the globe, and maybe at different times of the year, may explain some of the variation that exists. But, what about species that seemingly occupy the same habitat, how can such a biodiversity be permitted and maintained?

In the oceans, this question is known as the ‘paradox of the plankton’ (Shovonlal Roy & J Chattopadhyay, 2007). Originally proposed, and specifically for phytoplankton – microscopic aquatic algae, by GE Hutchinson (1961)** (David Goldenberg; Sima Sidik). It was expressed thus, “The problem that is presented by the phytoplankton is essentially how it is possible for a number of species to coexist in a relatively isotropic or unstructured environment all competing for the same sorts of materials” (Hutchinson, 1961). More than 60 years after its formalisation, Daniel Muratore et al. (2025) propose a resolution.

Working in the Sargasso Sea in the Atlantic Ocean [Ed. – if you’re intrigued by the distinction between sea and ocean, see here], Muratore et al. (2025) uncovered evidence that different plankton species absorbed ‘phosphorus’ – a nutrient essential for their growth, that’s needed in relatively large amounts (Adrienne Hollister et al., 2020), and which tends to be hard to find in the ocean (Senjie Lin et al., 2016) – from the environment at different times of day.

In summary, and i ntheir own words, Muratore et al. (2025) identified “a diel cascade in phosphate transporter expression [of genes involved in uptake of phosphate from the ocean] starting with heterotrophic bacteria in the morning, eukaryotic phytoplankton during the day, and Cyanobacteria at dusk”. The rather technical term for this phenomenon is ‘temporal niche partitioning’, which has some parallels with the notion of staggered ‘sittings’ for meals amongst human societies.

Somewhat gratifyingly, this temporal difference in phosphorus usage in the Atlantic Ocean (Muratore et al., 2025) by different planktonic groups complements that previously reported by Daniel Muratore et al. (2022) for nitrogen  – another nutrient essential for phytoplankton growth, that’s needed in relatively large amounts (Adrienne Hollister et al., 2020), and which tends to be hard to find in the ocean – in the North Pacific Subtropical Gyre.

Taken together, the work of Muratore et al. (2025) and Muratore et al. (2022), support the view that timings of exploitation of resources by plankton can go – at least – some way towards resolving Hutchinson’ paradox of the plankton. In other words, “The results reinforce the generality of temporal niche partitioning as a mechanism of competition alleviation in open ocean microbial ecosystems” (Muratore et al. (2025).

Whether temporal niche partitioning is the whole of the story behind the phytoplankton paradox remains to be established***. But, one thing that is certain is that Hutchinson’s paper has inspired others over the decades since its publication to examine the phenomenon and undertake their own investigations that have helped to illuminate the issue and attempt to resolve the seeming paradox. Arguably, that ‘investigative legacy’ is the sign of a very influential scientific paper, and one of the best ways to honour and celebrate Hutchinson’s particular contribution to the debate.

For more on the Sargasso Sea research item (and its relevance to climate change concerns…), see here, and here. For more on the North Pacific research, see here.

From a post concerning the rich biodiversity of phytoplankton to one that concentrates on a specific group of phytoplankters (Kate Madin)… [see the next post]

* Ed. – because, believe me (I know!), Mr Cuttings appears to operate without any discernible method. Having said that the fact that unites all three of the posts is that they were items in the same eMailed alert from science news provider Phys Org, one of the sources that Mr Cuttings regularly scans for blog-worthy inspiration.

** Although posited as a paradox (Magedah Shabo), Hutchinson’s ‘phytoplanktonic paradox’ may not in fact be so paradoxical because, as shown by Kléparski Loïck et al. (2022), “Here, we characterize the ecological niche of 117 plankton species belonging to three different taxonomic groups and show that all species have a niche sufficiently distinct to ensure coexistence in a structured marine environment. We also provide evidence that pelagic habitats are, unsurprisingly, more diverse in space and time than Hutchinson imagined, the marine environment being neither unstructured nor stable in space and time. We, therefore, conclude that the niche theory, and its corollary the principle of competitive exclusion, apply as much for the plankton as for other forms of life, be they terrestrial or marine”. In other words, paradox removed – maybe.

*** However, although these findings indicate that different (phyto)plankters are obtaining phosphorus at different times from the same habitat, there is still the issue that there’s only a limited amount of phosphorus (or other nutrients) to go around. On the face of it, extracting the nutrient at different times won’t in itself change what’s available for extraction. Is it therefore the case that those organisms who ‘feed’ earlier in the day can tap into a larger pool of the resource, which can consequently sustain a denser population of those organisms? And those that acquire their phosphorus at later times of the day are drawing upon an increasingly-impoverished supply, which can therefore only sustain less-dense populations of those species, etc.? Presumably, for this mechanism [‘temporal niche partitioning’] to work in a sustainable way – and support the rich biodiversity of plankton that is the source of the paradox – there needs to be a mechanism for replenishment of the nutrient(s) between ‘sittings’ so that sufficient is available for consumption by different organisms at different ‘mealtimes’.

I couldn’t see this issue explicitly addressed in the paper by Muratore et al. (2025), but may have missed it during my reading of the work. Although Muratore et al. (2025), do mention in their Discussion that “early morning heterotrophic activity may be linked to overnight processes of cellular division and viral-induced lysis of picocyanobacteria (Iwona Jasser & Cristiana Callieri; Cristiana Callieri et al., 2022), which may liberate dissolved organic matter”. This may be one way in which nutrient levels are replenished to satisfy the nutritional requirements of the biodiverse phytoplankton species – at least overnight. But what about during the day?

Interestingly, a potential – if maybe only partial – resolution to the paradox by control of plankton populations with marine lytic viruses [read more here] provides another link between this post and the next. For more on the critical roles played by viruses in the structure and function of aquatic food webs, see Steven Wilhelm & Curtis Suttle (1999).

REFERENCES

Cristiana Callieri et al., 2022. The “dark side” of picocyanobacteria: Life as we do not know it (yet). Microorganisms 10: 546; https://doi.org/10.3390/microorganisms10030546

Adrienne P Hollister et al., 2020. Regeneration of macronutrients and trace metals during phytoplankton decay: An experimental study. Limnology and Oceanography 65(8): 1936-1960; https://doi.org/10.1002/lno.11429

GE Hutchinson, 1961. The paradox of the plankton. The American Naturalist 95(882): 137-145; https://doi.org/10.1086/282171

Senjie Lin et al., 2016. Phosphorus physiological ecology and molecular mechanisms in marine phytoplankton. J Phycol. 52(1): 10-36; doi: 10.1111/jpy.12365

Kléparski Loïck et al., 2022. How do plankton species coexist in an apparently unstructured environment? Biol. Lett. 1820220207; http://doi.org/10.1098/rsbl.2022.0207

Daniel Muratore et al., 2022. Complex marine microbial communities partition metabolism of scarce resources over the diel cycle. Nat Ecol Evol 6: 218–229; https://doi.org/10.1038/s41559-021-01606-w

Daniel Muratore et al., 2025. Diel partitioning in microbial phosphorus acquisition in the Sargasso Sea. Proc Natl Acad Sci USA 122(11): e2410268122; doi: 10.1073/pnas.2410268122

Shovonlal Roy & J Chattopadhyay, 2007. Towards a resolution of ‘the paradox of the plankton’: A brief overview of the proposed mechanisms. Ecological Complexity 4(1-2): 26-33; https://doi.org/10.1016/j.ecocom.2007.02.016

Steven W Wilhelm & Curtis A Suttle, 1999. Viruses and nutrient cycles in the sea: Viruses play critical roles in the structure and function of aquatic food webs. BioScience 49(10): 781–788, https://doi.org/10.2307/1313569