My First (Almost) Extinction Event

Live periska.
Photo courtesy of Očuvanje plemenite periske u Jadranskom moru FB page.

I want to tell you about extinction, and I want to tell you about joy.

Pinna nobilis is a marine bivalve mollusc. The name does not evoke magic; it does not transport you to the Adriatic, to the feeling of breaking the surface for the first time, to the rush that—ever so slightly—verges on discomfort before you’re engulfed in the salty softness of the sea. The words plemenita periska—the name of this particular mollusc, a fan mussel or noble pen shell, in my first language—do.

Growing up holidaying on the Adriatic, I was vaguely aware that periske were special and not to be touched. Like the nobility their name refers to (plemenita means noble), we were to admire them from afar. ‘Strictly protected’ (strogo zaštićene in Croatian legislation) is what I knew about them, despite my parents not being particularly interested in either marine biology nor snorkelling. It was their majestic appearance that attracted me and made me wonder about the designation ‘strictly protected.’ As a child, I would occasionally glimpse them from a dušek, the inflatable device that supported adventures in depths otherwise inaccessible to not-so-confident young swimmers. I would hang on to this highly revered vessel of my childhood and stick my head in the water, a new world opening up to me even if I was not allowed to plunge into it.

Everyone knew, or so I thought, not to disturb them. But care and knowledge are precious currencies in the Adriatic. Other sea creatures, about whom we know and care less, were an easy target. I remember a particular attack on an equally protected, but apparently less majestic, species: the sea cucumber. I’m not sure which species of the thirty-six strange members of the Holothuroidea class was hurt that day, but I admit to have been part of a group of children that made a pile of them on the beach. Under the indifferent gaze of our parents and guardians, we collected dozens and let them dry on the beach. It must have been a horrible death and a difficult clean up. If morski krastavci are just not cute enough, imagine what happens to the protected sea urchins that are dangerous on top of being unattractive. When not eaten as a delicacy, they are seen as a threat: primed to ruin holidays with brittle spines that pierce human skin so easily, only to break off and become impossible to take out. I wonder who was responsible for cleaning up the mess of our violence on the beach that day. In these, more curious and careful days of my adulthood, I put effort into learning about these seemingly simple creatures. Morski krastavci made it onto the “endangered list” after they became a source of income (a delicacy in some parts of the world) in the years following the wars of the 1990s. Like sea urchins and so many mysterious habitants of the sea, we only learn to put them on our plates.

Even the occasional success of protected species is shrouded in salty mystery. In the Adriatic, periske have been protected since 1992. Then, in 2003, an unexplained decrease in predators played a key role in their reproductive success, and allowed me those glimpses from the inflatable. Periske fertilisation occurs via sea water in numbers reaching the millions, but very few larvae will descend and attach to the seabed after their few days of floating: they are a good source of food for various animals. For reasons unexplained, the 2003 fertilisation was an immense success and in 2005-2006 periske were everywhere. When they reached reproductive maturity in the 2010s, the future looked bright. As I grew older and upgraded my explorations with a mask and snorkel, I saw them occasionally, proudly sticking out of the seabed, immobile but free, fragile yet strong. The pinkish shell with ribbed edges can grow to the size of an arm: most are 30-50 cm long, but they can grow up to 120 cm.

Perhaps it is not surprising that the more time I spent outside of Croatia, the more wilfully I anchored myself in the Adriatic, a place of childlike possibility. During my postgraduate work in Wales, every summer would bring with it a calling, not to the Slavonian plains where I grew up, but to the Adriatic that I loved so much and knew so little about. But my romance with the Adriatic—one I think I share with millions who hold memories of salt drying on their skin during late sunsets—also changed: whilst I pined for it, I learned about the fraught future of the Mediterranean in a heating world. Missing it now also means fearing for its survival. Today, my research is also shifting, from focusing exclusively on humans to exploring the many ways in which plants, animals, and landscapes shape political lives. While my current project is land-locked and centred on the meaning that rocks and soils take on, outside of work I turn to periske to think about joy and extinction.

In 2019, I travelled to the island of Lastovo ready for the sea, morski krastavci and sea urchins included. The island is an enchanting place, especially for those who do not need holiday highlights beyond snorkelling and napping in a hammock. The whole archipelago is a nature park far removed from the mainland. The snorkelling was exciting: I spotted a baby octopus (chased by a cartoonishly evil speargun diver who made me finally expel hobotnica na salatu, octopus salad, from my diet), a crab devouring an unknown creature, a kaleidoscope of colourful fish, dozens of sea urchin skeletons, and haliotis shells (Petrova uha, or Peter’s ear), which I quickly introduced to my partner as a collector item.

Shells (callista chione or smooth clam) and sea urchin skeletons found on Krk island. Photo by the author.

Snorkelling in the Adriatic. Photo by Paul Blamire.

On Lastovo, I noticed a lot of periske. They fit into the narrative that I was quickly creating in my mind as I was falling in love with the archipelago: the sea is so clean, the currents so strong, the small islands so far from the buzzing of tourist rental boats that islands closer to the mainland have to endure. Lastovo was pure magic, and the periske that dotted its northwest seabed were both a logical result and a great addition to its splendour.

At the time, I did not know that I was swimming in a mass mortality event. Not many were “standing up,” and many were obviously dead: laying on the seabed and occasionally rolling with the currents rather than standing tall. Unstuck but empty. As the days passed and I closed in on the “strictly protected” treasures, I noticed that some of the ones standing were, in fact, not periske at all. I had a tried and tested system of “checking in” with my “strictly protected” friends, learned during my previous underwater escapades. You have to approach the periska without disturbing it. Without much movement (not an exactly straightforward feat underwater), you’d wave your hand just over the small gap between its two halves. The shell would react and close in a leave-me-alone kind of way. I always imagined it as a small act of annoyance, like blowing into a kid’s face. A fish could swim by and similarly move the water. Nothing to feel bad about.

But that summer on Lastovo, my little trick did nothing. I tried to peek inside the shell: could it be holding nothing at all? This was early into the vacation, so steeped in ignorance, it took me a while to try touching one to realize that the shells were indeed empty. What I saw on the seabed were the remains, the dead empty shells you can see decorating restaurant walls. I thought it strange, but I was still enchanted by the amount of periske around me. By the end of our stay on Lastovo, I saw so many huge specimens rolling on the seabed that I actually took one with me, packed it in a suitcase, checked it in on my flight, and relocated it to Wales. I could not resist its mother-of-pearl interior, the exclusivity of the forbidden  shell, the feeling of being connected to something special when I leave the warm Adriatic coast for one much colder. I’m not completely sure whether taking an empty shell was legal, but I guess it makes little difference now. Thousands are rolling with the waves.

In October of the same year, a group of scientists went to Lastovo Nature Park to monitor Pinna nobilis. They spent three days counting, found 550 shells, all of them dead. I don’t remember where I was when I read the news, but I remember it clicking in my mind, the moment that turned the shell I had with me in Wales into an artifact. I remember it as the official start of my very first extinction event. I knew and felt the Adriatic differently.

I now know that the Pinna nobilis mass mortality event started in Spain in 2016. It spread eastward faster than anyone paying attention could figure out what was happening. Initially, it was believed that death was caused by Haplosporidium pinnae, a cryptogenic—meaning scientists have no idea where it came from—parasite. Mortality rates were between 93% and 100%. It was first observed in southern Croatia in April 2019, a few months before my trip to Lastovo. From then on, the death reports moved steadily up the coast of thousand islands, an uninterrupted line. Because the parasite spreads in temperatures higher than 13.5 °C, and so is slowed down in the winter time when the sea cools down, the damage is counted in seasons: how many are killed and how many survive each long summer. Today, various bacteria are discussed alongside the Haplosporidium parasite as possible causes. It is unclear whether real extinction will happen; I have heard of ideas to freeze periske in order to reintroduce them in fifty to a hundred years, when the danger is over. I also collect news items of live specimens found.

I am not trained in biology, and the mysteries that surround beings that we take for granted still come as a shock. But I am trained to pay attention to the intersection of power and knowledge, and its echoes in political, social, and ecological relations. And “we” (humans) know surprisingly little about these, sometimes huge, creatures with whom we share our beloved sea. Even their life span is a guess: some estimates put life expectations to a hundred years, but no one really knows exactly how long they can survive. We do know, however, that they provide crucial “ecosystem services:” ways of supporting human wellbeing and quality of life that is difficult to measure. The ecosystems surrounding us are the providers, the services are keeping humans alive and happy. While feeding, one periska can filter up to 2000 litres of sea water per day, removing what it eats alongside additional organic matter. More than thirty-five other species live on its shell. A tiny crab and a tiny shrimp live inside the shell. Some sources say that they are responsible for spotting danger and then pinching the periska as a warning to close.

If these “services” are not enough to satisfy human needs, periske can give more. Their bodies were used for food, and the threads that hold them in the seabed for sea silk that covered pharaohs in Egypt and aristocrats in Venice. The huge shells can still be seen as ornaments, and they can also occasionally produce pearls. They were destroyed by anchors, disrupted by the building of marinas, beaches, and ports, hurt by pollution and devastated by invasive species. They and their habitats were endangered long before definite extinction came knocking.

I am no biologist, but I wonder what happens when this parasite enters the periska’s digestive system:

“In the first phase of the illness, individuals affected by this unknown disease are characterized by an anomalous slow closure of the valves after external stimulation. In the advanced phases, individuals are no longer able to completely close the valves, becoming highly vulnerable to predation. In the terminal stage, the mantle of the fan mussel detaches from the valves and moves down in the bottom of the shell, after which individuals cannot survive more than a few days (in the absence of predation).”

I cannot help but wonder how long it takes for the mantle to detach. What does it look like? Does it slide or float or collapse? Does the periska feel it’s dying? Next time I’m in the south Adriatic and I make my pilgrimage to fresh oysters, will I be able to identify the mantle before sliding “the individual” life down my throat, its saltiness only slightly softened by lemon? When I waved my hands in front of shells still vertical to the seabed in the early period of the “mortality event,” were some individuals trapped in them, unable to move because the mantle has detached? When does the crab living on the shell realise it’s over?

My curiosity is that of a lay person, my attachment of a sea romantic. But more serious people have formulated serious responses. Scientists all over the Mediterranean moved into action. First responses in Croatia came from biologists, divers, private institutions, and NGOs. The Pula Aquarium led the way in “ex-situ” preservation: live periske that were found and could possibly be healthy were moved to a sanctuary, a quarantine with closed conditions. The focus was on young specimens that might not have had contact with the parasite, but this seems an impossible task when the parasite travels by currents and can move over 300 kilometres in just one summer season. The water they use in their quarantine containers has to be carefully filtered, as every contact with the sea means potential contamination. It hurts to think of the beautiful blue as deadly.

Collectors were launched to capture larvae arriving with sea currents from Italy. Individuals must be numerous and in close proximity for reproduction, and the population around Venice is miraculously still large enough for successful reproduction. These are then manually picked from the potato nets onto which they latch and moved into controlled pools in the Pula Aquarium. The parasite is dormant under 13.5 °C so the water is kept cold, reducing the periske’sannual growth to a miniscule 1 centimetre per year. The lack of genetic diversity due to few reproducing populations is clear, but its consequences are not. The Brijuni archipelago seems to be the best area to find young periske in Croatia. There, the numbers are sobering: fifteen last year, thirty the year before. This is many fewer than the colony of dead periske on just one of the beaches that I regularly swim at.

The response to the mass mortality event relied on “citizen science:” locating live individuals depends on people diving, snorkelling, studying, and living with, and in, the sea. In 2020, the Očuvanje plemenite periske u Jadranskom moru, a multi-stakeholder project intended to both monitor developments and experiment with solutions was launched. Periske were individualised, filmed, named, and rooted for. Some died, others resist—like Nova Nada (New Hope), which was just visited by a whole conference of scientists after it survived three long hot summers. Periske are in the news, in schools, and in government offices. But even those most committed to their survival, like the Pula Aquarium, maintain that “no one can discover the origin of the parasite, and no one can stop it.”

Protecting Nova Nada near Omiš. Photos courtesy of Očuvanje plemenite periske u Jadranskom moru FB page.

It is difficult to not root for the periske: Morana from Krk, Luce from Mali Lošinj, Nova Nada from Omiš. The magical appearance, the long history, the feeling that it is part of our love story with the Adriatic. The Have you seen it?campaign further invites the public to join the science project: we can download apps, open eyes, report, and hope. Morana from Krk is named after the woman who found it. But the way these personal relations fold into larger ecological systems is less empowering. Even biologists have no idea whether any of this will ultimately preserve the species. The entire Adriatic now has fewer than thirty live individuals. Yet, these people move forward, invent, believe, and act.

Have you seen it? campaign Photo courtesy of Očuvanje plemenite periske u Jadranskom moru FB page.

Potato bag collectors used for attracting larvae that can be transferred to the sanctuary. Photo courtesy of Očuvanje plemenite periske u Jadranskom moru FB page.

Even if they succeed, we are still left with a warming sea increasingly vulnerable to invasive species. To stop the Adriatic from heating and attracting species from warmer waters, we would need a global reduction of greenhouse gasses. It would also probably help to think of its heating not only as ruining holidays for German and British tourists, but as an existential threat to the life that exists here year-round. To protect Adriatic species, we would need a new vision of (economic) development that does not depend on cruise ships that bring invasive species in their ballast waters, does not encourage the growth of marine tourism and the increasing number of anchors that will tear, injure, crush, and kill. We would need to see the Adriatic not as something to protect or exploit, but as life, a web of companions experiencing life and death. So, I also turn to periske as companions: I am hopeful that they will shape more childhood holidays, curious about the many different ways in which they intersect with the lives of humans that go on above them, and humbled by the existential threat they are currently facing.

One of the many mysteries in the story of my first (possible) extinction event is the somewhat irrational behaviour of the parasite. It is headed for the complete destruction of its host. Parasites usually take out weaker individuals, leaving enough of a future for both their hosts and themselves. Despite the risk of falling into an easily available comparison, it seems that the parasite might be like us, humans. Heading toward extinction with enthusiasm and gusto.

But I don’t wish to tell you that the world is ending. I don’t want you to imagine the Adriatic dying. Even if I wanted to, heartbreak is difficult to convey. But I do wish to tell you that when I think of periske, I am still in love. When I think of periske, I feel the magic of that first contact, when the breaking of the shiny surface chills and surprises me, when I first open my eyes to weeds, urchins, and fish, when I first kick my fins to set off and love the sea—curiously, problematically, ignorantly, and carefully. Maybe I’ll find a periska alive, perhaps I’ll visit sea cucumbers who I hope are safe from being individually named. When I think of periske, I think of extinction, and I think of joy.  

My mum and nephew fishing in the Adriatic. Photo by Paul Blamire.