Plant Cuttings

This is the second (of three) posts that make the connection between phytoplankton free-floating in the ocean [see the preceding post] and earth-bound rice plants [see next post]?

This image of Karenia brevis from the Florida Fish and Wildlife Conservation Commission is in the public domain.

Of the many types of phytoplankton (e.g. diatoms (David Mann), coccolithophores, green algae (Sagar Aryal, Richard McCourt et al.), and cyanobacteria), one of the most intriguing are the dinoflagellates (Mona Hoppenrath & Juan F Saldarriaga). Famously, dinoflagellates (when they’ve lost their flagella… ) are the resident photosynthetic partners of coral polyps (Alexis Wiktorowicz-Conroy). Termed zooxanthellae in this association, it is their presence that is largely responsible for the existence and persistence of coral reefs (Sam Couch) (and maybe contribute to the success of heart cockles). That mutually beneficial – mutualistic – symbiotic relationship represents the ‘good side’ of these algae.

Dinoflagellates also have a ‘dark side’ too as one of the organisms that cause the phenomenon known as a red tide (also known as a harmful algal bloom [HAB]). Red tides (and brown tides) are so-called because the concentrations of these individually minutely-pigmented microscopic algae in these aquatic aggregations are so high that the water appears to be ‘stained’ red (or brown) with their massed pigmentation.

Whilst red tides may look spectacular they are generally bad news for many forms of marine life because the algae produce a range of toxic compounds that can cause harm to organisms that consume the algae. Particularly vulnerable in this respect are filter-feeding molluscs (Brian Morton) because large volumes of algae-contaminated water flow through their bodies as they filter out water-borne food particles. In this way the microscopic algae can be accumulated in shellfish bodies (P Ciminiello & Ernesto Fattorusso, 2006; Federica Farabegoli et al., 2018) to concentrations that can poison the mussel, clam, scallop or whatever unfortunate enough to have internalised the harmful algae (Alejandra Goya et al., 2020). Whilst that’s clearly an issue for the mollusc, it can also become problematic for any animal that may consume the shellfish. Since an animal, such as a seal, will likely consume several shellfish at a meal, the process of biomagnification of the toxins continues as more and more of the harmful microscopic plankton are consumed and their compounds accumulate within the predator’s body. And so on up the food-chain.

But the danger and damage doesn’t stop in the ocean food web. If toxin-contaminated shellfish are harvested and consumed by humans then people can be badly affected. For example, they may develop conditions such as paralytic shellfish poisoning [PSP] (Vernon Ansdell), which can – in extreme cases – lead to death (Federica Farabegoli et al., 2018; Alejandra Goya et al., 2020).

Although their existence, and knowledge concerning factors that contribute to development of red tides have been investigated for a long time (Donald Anderson et al., 2012), there is still much that is either not known or insufficiently well-understood, and debate continues. However, because of the dangers associated with HABs, any ‘early-warning’ of their occurrence – in time and place – would be of considerable benefit to the health and wealth of all involved in shellfish exploitation, management, and consumption – both human and non-human. In this regard, some potential good news may have been provided by the work of Shen Jean Lim et al. (2025) in the case of one particular red tide-forming organism, Karenia brevis (Jan Landsberg et al., 2009).

Red tides caused by Karenia brevis are a particular problem for the American state of Florida (Cynthia Heil & Amanda Lorraine Muni-Morgan, 2021), where they develop “almost annually along the coasts and offshore waters of the eastern Gulf of Mexico*” (Lim et al. (2025). The dinoflagellate produces compounds known as brevetoxins (EFSA Panel on Contaminants in the Food Chain, 2010) that are not only toxic to fish directly, but also can accumulate in filter-feeding zooplankton and shellfish, from where they are transferred up the food chain (Lim et al. (2025). If consumed, brevetoxins can cause neurotoxic shellfish poisoning [NSP] (Vernon Ansdell; Sharon Watkins et al., 2008) in humans (Barbara Kirkpatrick et al., 2004).

Furthermore, brevetoxins can be aerosolized [dispersed from the ocean into the atmosphere] and transported onshore by winds, where they may trigger respiratory irritation in animals and humans (Barbara Kirkpatrick et al., 2004). Also, “K. brevis blooms can endure for a few months to a few years and can be localized to a single estuary, or span Florida’s Gulf and Atlantic coasts. … and ”The negative aesthetic, environmental, and health effects of K. brevis blooms lead to significant economic losses across the tourism, fisheries, and public health sectors” (Lim et al. (2025). With that as important background, it is understandable that early warning of a HAB event – whether from K. brevis or other organisms – is highly desirable, and may give sufficient time for action to be taken to avoid harm to health. And this is where the work by Lim et al. (2025) fits into the story.

Examining water samples from K. brevis blooms off southwest Florida, Lim et al. (2025) discovered the presence of several species of virus. Not only was this the first time that an association between K. brevis and viruses had been demonstrated, but one of the viruses was a new species with some similarity to a known virus from a coral dinoflagellate symbiont. Since several of the identified viruses are from groups known to infect other bloom-forming phytoplankton such as diatoms, it would be nice to think that some of the viruses found, and maybe the previously unknown species, may be capable of infecting Karenia brevis.

If so, that presents the possibility that viruses might be exploited as a form of biocontrol (Marieke Busson et al.) of such HABs. Although it will be essential to ensure that viruses that infect K. brevis do not also infect and kill non-HAB-forming blooming phytoplankton. Alternatively – and maybe additionally – increase in sea-water concentrations of any of those HAB-associated viruses might be employed as an indication that a red tide is about to form. Such an ‘early-warning’ system may give sufficient advance notice of the event so that necessary safety and avoidance measures can be put in place to protect lives and livelihoods. However, for that to be effective it will be necessary to monitor and sample the ocean for presence of the relevant virus(es), at the right time and place. Which is no mean feat, and, I imagine, may be likened to trying to find the needle before we know where the haystack is.

There is still some way to go to see if any of this is established, or whether biocontrol of K. brevis is feasible, but, as Lim et al. (2025) say, “The findings lay the groundwork for studying the effects of environmental drivers on K. brevis blooms and their associated viruses, as well as for exploring the roles of viruses in bloom dynamics and potential applications of viruses as biocontrol agents for K. brevis blooms”. Nevertheless, here’s hoping that this insight will help to turn the tide against HABs.

For more on this story, see here, here, here, Dyllan Furness, Jesse Mendoza, and Andrew Wulfeck.

From this post looking at the association of viruses with ocean-dwelling phytoplankton to one that looks at viruses and terrestrial angiosperms…[see the next – third and final one for this series – post]

* For the sake of completeness – and to alert readers to a possible name change – it should be mentioned that Donald Trump, 45^th and 47^th President of the United States of America, has decreed – by executive order – that the body of water known for many years as the Gulf of Mexico is to be renamed the Gulf of America (Jesse Mendoza). [Ed. – Since the scientific paper was accepted for publication by the journal before the date of the executive order it can presumably still refer to the Gulf of Mexico.]

Of direct relevance to this post, “The Florida Fish & Wildlife Conservation Commission will join the other Florida government agencies making hefty changes to government records to use the name “Gulf of America” in compliance with an executive order from President Donald Trump” (Jesse Mendoza). [Ed. – is this particular name change nomenclatural evidence that the gulf between the USA and the rest of the world appears to be widening..? Even more worrying, will historic American documents be changed retrospectively to reflect the new name? If so, suggestions of parallels with a certain 20^th century work of fiction – George Orwell’s Nineteen Eighty-Four (JN Fenwick) – could be made…]

REFERENCES

Donald M Anderson et al., 2012. Progress in understanding harmful algal blooms: paradigm shifts and new technologies for research, monitoring, and management. Ann Rev Mar Sci. 4: 143-76; doi: 10.1146/annurev-marine-120308-081121

P Ciminiello & Ernesto Fattorusso, 2006. Bivalve molluscs as vectors of marine biotoxins involved in seafood poisoning. Prog Mol Subcell Biol. 43: 53-82; doi: 10.1007/978-3-540-30880-5_3

EFSA Panel on Contaminants in the Food Chain (CONTAM), 2010. Scientific opinion on marine biotoxins in shellfish – emerging toxins: Brevetoxin group. EFSA Journal 8(7): 1677; doi:10.2903/j.efsa.2010.1677

Federica Farabegoli et al., 2018. Phycotoxins in marine shellfish: Origin, occurrence and effects on humans. Mar Drugs. 16(6): 188; doi: 10.3390/md16060188

Alejandra B Goya et al., 2020. Paralytic shellfish toxins and associated toxin profiles in bivalve mollusc shellfish from Argentina. Harmful Algae 99: 101910; https://doi.org/10.1016/j.hal.2020.101910

Cynthia Heil & Amanda Lorraine Muni-Morgan, 2021. Florida’s harmful algal bloom (HAB) problem: Escalating risks to human, environmental and economic health with climate change. Front. Ecol. Evol. 9: 646080; doi: 10.3389/fevo.2021.646080

Barbara Kirkpatrick et al., 2004. Literature review of Florida red tide: implications for human health effects. Harmful Algae 3(2): 99-115; https://doi.org/10.1016/j.hal.2003.08.005

JH Landsberg et al., 2009. Karenia brevis red tides, brevetoxins in the food web, and impacts on natural resources: Decadal advancements. Harmful Algae 8(4): 598-607; https://doi.org/10.1016/j.hal.2008.11.010

Shen Jean Lim et al., 2025. Diverse ssRNA viruses associated with Karenia brevis harmful algal blooms in southwest Florida. mSphere: e01090-24; https://doi.org/10.1128/msphere.01090-24

Sharon M Watkins et al., 2008. Neurotoxic shellfish poisoning. Mar. Drugs 6(3): 431-455; https://doi.org/10.3390/md6030431