Change Everything No 17: You had no idea of how amazing algae are

How Dinophysis gets to photosynthesise: a carnivore that gets more than nutrients from its prey

Apr 10, 2024

This slightly delayed edition contains reflections from The Lives of Seaweeds: A Natural History of Our Planet’s Seaweeds and Other Algae, by Julie Phillips. You might call it a review, but possibly more of a rave.

But first…

Book news

My diary is filling up with Change Everything events (but if you have a friendly local bookstore who might host one, please do suggest it). A couple to note from London:

On Monday morning, April 22, at SOAS, but all welcome (you don’t need to be a student), I will be in conversation with BBC journalist Divya Talwar.

And pleased to returning to an historic stomping ground, Housman’s Radical Booksellers, founded in 1945, beside Kings Cross station, on the evening of Friday May 10.

Picks of the week

Reading

I’ve been revisitng An Environmental History of the Caribbean: Sea & Land, which I read last year. Not the easiest of reads, dense, detailed and not very tightly edited, but containing a huge amount of important information. The current focus of the impact of the British Empire is - rightly - the human cost of slavery, but the environmental costs (and subsequent human impacts) were also deadly at scale.

“Barbados’s rapid conversion to a fully commercial sugar economy destroyed its forest cover within a generation.. sugar cultivation began in eanest in Barbados in the 1640s, and towards the end of the decade 40% of the island’s forests were gone; by the next decade, alarmed island authorities began restricting timber cutting; by then, it was too late. By the late 17th century, the island’s open landscape reverberated to the sound of turning windmills rather than burdsong… Soil erosion was such that one heavy downpour in 1668 carried hundreds of coffins from a local churchyard out to sea.”

Listening

Nests of complex networks, like our own bodies, are something we’re just beginning to understand how little we know about how they work. A couple of really clear ideas emerged for me from this rich episode of Big Biology with Rosemary Braun. One is that in thinking about systems and networks, we need to separate the concepts of robustness (ability to withstand shocks and not change) and resilience (ability to adapt to shocks). Which was something I hadn’t really thought about before. Robustness is good, of course, to a point, until it is exceeded. The other was the importance of temporality - how taking drug treatment at different times of day can have profoundly different impacts. But more about its impact on our immune system. Perhaps the single largest impact we could have in reducing cancer rates is ensuring people get enough sleep. Which could demands substantial changes. Ending all unnecessary shift work, maybe?

Thinking

Ambient levels of noise in the oceans have increase 20 decibels since 1950, within the memory of some whales, representing a 100-fold increase in the intensity of noise. Mathematicians have been thinking how whales might react, by seeking being less in company (hard to communicate with others in a nightclub, to put it in human terms), avoiding noisy areas, or getting confused. No real answers yet about what can, or will, happen if we keep polluting the seas with ever more noise, but useful framing to think about it.

No escape from the din. Photo by Rémi Boudousquié on Unsplash

Researching

The peer-reviewed research is not yet out, but I’ve got no doubt of the general conclusions from recent surveys of populations of hen harriers on these islands: about three-quarters of the wonderful birds who could be here are absent. And they are entirely missing from what should be the ideal habitats of the Peak District and North York moors. Why? Well 33 satellite-tagged hen harriers disappeared under suspicious circumstances in 2023 - a record number. As an RSPB spokesman said: “continuing illegal killing, typically associated with intensive grouse moor management, is stifling their full recovery”.

And now, amazing algae!

The text of The Lives of Seaweeds is, surely deliberately, very straight and unvarnished. It tells us about the evolution of algae and other related organisms, their morphologies, their life histories, ecology, and relationship with human animals. Taken on its own, it would be apparently rather dull.

What immediately brings this text tremendously, brilliantly, alive are the photographs and diagrams, which could classify this as an art book as much as a science text. This could serve as a reference book, but it is also a browser’s delight.

Take the richly alien microscopic Ceratium hirundinella, with a single apical horn pointing forward from the flagellate tail that gives the group its name, with three backward pointing horns, the whole covered with armoured plates, its photosynethic green clumped around a central void. It lives the life its image suggests – a mix of generating energy from light and absorbing it from the pond and lake water in which it lives. This all about 450 microns long, or rather small. It is beautiful, and magnificent, and it is humble pond scum. (p. 50)

But also gripping is the sheer amazingness of the information in the text, which for all its dryness reflects in its contents the brilliance of the pictures. The book starts at the beginning of course, 3.5 billion years ago, with the oldest cyanobacterial fossil, then skips past stromatolites, which had their peak around 2.3 billion years ago, and are still around today, testimony to the power and persistence of biofilms (although of course, inevitably, under threat from us.) The throwaway note that the oxygenation of the world (from 3.2 – 2.4 billion years ago) predates green algae (1.45 billion year old fossils of green algae that resemble modern prasinophytes, takes us on to the first known red algae, Bangiomorphia pubescens, just over a billion years ago, meaning primary endosymbiosis, must have occurred before that. That’s all on page 39!

It is the algae that – may be – the foundation also of multicellularity, fascinating Clamydomonas, which can live in colonies of up to 50,000 cells in Volvox, the number of cells pre-determined in each species by genetics. Colonies typically consist of cells embedded in a mucilage, with the two flagella of each cell protruding outwards. One example, Gonium, swims in two ways, four central cells producing a slow forward rotation, while a dozen flagella of 21 peripheral cells beat in parallel, producing a left turn. Such apparent simplicity producing amazing complexity.

So many different ways of living as algae appear, from the algal balls, formed by red, brown and green macroalgae, freegrowing, sometimes hugely numerous creations of photosynthesis, with one stranding in 1950 of soft philamentous Cladopora balls at Torbay estimated to number 7 million. Others are made by coraline red algae, which form hard and stony balls known by the French term maerl. They cover an estimated 700 square kilometres of the Mediterranean. And of course you knew it “threatened by large-scale human extraction for fertiliser, aquaculture facilities, sewage discharge and bivalve dredging”. (p. 220)

Although when thinking impressive algae, what probably comes to mind first is kelp forests, with the giant species Macrocystis pyrifera able to reach 50 metres in height, a perennial that can live up to eight years. Equally impressive in a different way is bull kelp, which can grow up to 14 cm a day, its hollow stipe (stalk) filled with a gas that can be 12% carbon monoxide, and provides buoyancy to lift the blades to the water surface for maximum light capture. That can reach more than 30 metres, which requires navigating a change in hydrostatic pressure from 4 to 1 atmospheres, but the internal pressure is kept at less than 1 atmosphere, which prevents buckling. Serious engineering.

Photo by Oleksandr Sushko on Unsplash

The biology can be equally sophisticated. The knotted wrack, Ascophyllum nodosum, which can survive for 40 years, and each year, in February and March in the Northern hemisphere, it fills reproductive structures, conceptacles that formed during the previous summer, on the thallus, with four eggs in each in the females and multiple spermatozoids in the males. “Once in the sea, the eggs secrete the chemical sex attractant finavarrene, which attracts the spermatazoids to swim to the eggs and fertilize then. After fertilization the zygotes sink, settle on to the substratum and germinate into new thali.” (p. 148)

But the algae, we learn, don’t have to live in water. About 800 green algae species are terrestrial, some living in the soil, others on trees, walls and rocks. An amazing picture from California shows Trentephalia flava, in this group but brilliantly orange in colour from the sunscreen beta-carotene it synthesises itself, growing on an old Monterey cypress trunks.

Lichens must also get an appearance, but so too do the lesser-known symbioses found in nutrient-poor tropical and subtropical oceans between cyanobacteria and colonial diatom species, neither of which can live alone. The diatoms provide buoyancy, keeping the cyanobacteria in the light, and are donated nitrogen by their hosts. They’re a major part of the productivity of oceanic food webs, we learn.

Of course so too are coral reefs, “supporting as many as 1.3 million species and more than 500 million people worldwide”, renamed by phycologists “coralgal reefs”, given the importance of the algae within them, more than 85% of the biomass of the Pacific Einwetok reef, for example. Yet the most famous zooxanthellae are generally only 20% of the algal biomass, macroalgae 6% and the algal turfs endolithic algae and algal crusts 73%, with the seaward edge typically dominated by encrusting coralline algae (p. 182). It is the turf algae that in nutrient-poor seas that are the main primary producers – not how we think generally think of reefs – with the cyanobacteria, the bulk, also fixing nitrogen. Yet they’re not dominant in our pictures of a healthy reef, because most of their thali are consumed by grazing fish and invertebrates.

Look beyond coral and colourful fish Photo by SGR on Unsplash

Nor, when we think of the White Cliffs of Dover do their creators often get a look-in; calcareous red and green algae that more than 63 million years ago locked dissolved carbon dioxide into calcium carbonate, depositing that on the sea floor after their death to form limestone. Let’s not get into the mess that human geoengineering might create, but at the centre of the world’s sulphur cycle are more algae, phytoplankton that emit dimethyl sulfide into seawater, having used it to regulate osmotic pressure, as an antioxidant and an antifreeze. That’s thought to play a major role in global cooling, with light forming sulfate aerosols that both scatter solar radiation and seed cloud formation. (pp. 234-5) The Antarctica Ocean, making up 6% of world’s oceans, is thought to contribute 10-30% of global emissions. (Which makes the state of the place particularly concerning.)

About those carnivorous photosynthesisers

So many wonders are being described, but the one that really got me amazed was the story of the dinoflagellate genus Dinophysis, only grown in a lab for the first time in 2006. No wonder, given it is a predator that relies on capturing photosynthesising plastids from ciliate prey. But in turn, they had grabbed these from algal prey. A full-page microscopic image brings this amazing transaction to life in stages, the Dinophysis caudata sucking through its feeding tube the protoplast of the spherical Myrionecta rubra, possibly injecting a poison that causes it to shed its cilia and become immobile. The transfer of the red plastids is clearly visible, the emptied-out ciliate becoming entirely colourless. But this can only happen with the intermediate step; the dinoflagellate can’t take the plastids directly from the algae. (p. 224) (more here)

The relationship of algae and humans feels by scale a minor part of this book – we might be being hugely destructive, but most algae are no doubt going about their lives with little sense of the dangers we’re presenting – but the Japanese relationship with seaweed does inevitably form a memorable part of the text, particularly the story of Dr Kathleen Drew, who solved the mystery of how nori reproduced in 1949, her contribution recorded at a Shinto shrine, where every year since 1963 fishermen have assembled to pay homage. Another female scientist to celebrate!

This is labelled as a “natural history”, and a reminder of the emerging revival of that term – as in the GCSE course that is due to start in 2026 – the study of nature based more on observation than experiment. The format and approach would be familiar to Maria Sibylla Merian or Elizabeth Twining.

When so many courses in foundational sciences, from botany to zoology, are under threat, with the applied approach at risk of overwhelming the basic knowledge that underlies it, the book not only has the potential to introduce many to the truly spectacular wonders of the more than three-quarters of this planet covered in water, of which our understanding is so rudimentary, but also to encourage more such ventures in publishing texts that had gone out of favour.

Almost the end

I’m trying to keep up-to-date a list of upcoming Change Everything events (and also podcasts and other related material) here. See if I’m coming to visit near you.

What did you think?

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