Tales of the ocean

After others have gone to bed at night, Eva Meyers is still found swimming through the pitch-black water off Playa de Las Teresitas in Tenerife. Equipped with an underwater lamp and hand net, she keeps her eyes peeled for the pairs of eyes gleaming in the beam of her light every now and then. Meyers and her team are on the hunt for the angel shark, one of the world’s most endangered marine animals.
With their flat bodies and widely spread pectoral fins, angel sharks are more reminiscent of rays than of sharks. While they populated all of the North Atlantic and the Mediterranean for 150 million years and well into the 20^th century, they are now under threat of extinction with just a few sites in the Mediterranean and around the Canary Islands still housing significant populations.
Meyers and her team come at night to measure, weigh, and tag the young animals, about a foot in length, near San Andrés in Tenerife three times a year. Adult animals receive coloured tags to enable researchers to determine whether they are territorial or wander between the islands.
“The ocean is full of underdogs,” says Meyers. There are plenty of species that barely anyone is familiar with but that are crucial for the balance of the seas. Angel sharks are only one of them. Silent ambush predators, buried in the sand by day, they hunt by night and were all but unheard of even a decade ago, Meyers says. She herself immediately fell in love with these animals.

Meyers is the founder and project manager of the Angel Shark Project, an international collaboration between the LIB, the Zoological Society of London, and the University of Las Palmas de Gran Canaria. Launched as a citizen science initiative in 2013, it strives to document sightings and develop effective conservation measures. A lack of data held by local authorities such as the regional government of the Canary Islands and the Spanish Ministry of the Environment led to the decision to involve recreational divers as research partners.
Meyers considered the search for the nurseries – the angel sharks’ breeding grounds – to be particularly important. They are crucial for protection and long-term survival of the species. The artificially created beach of Las Teresitas, protected by breakwaters, has become one of the most important nurseries in the Canary Islands by now.
Acoustic telemetry in the form of small transmitters that record the animals’ movements is the method of choice for Meyers and her team to reconstruct migration patterns and habitats. Genetic analyses document the relative isolation of individual population groups. At least three genetically separate island populations have been found. “Based on this, we need to adapt our conservation measures locally. We cannot just transfer our findings between groups.”
Rather than aiming to forbid anything, the project tries to establish a dialogue. The negative effects of fishing, a major point of conflict in some other regions, seem to be rather limited in the Canary Islands. “We never wanted to act as some kind of marine protection police. Our approach includes listening, explaining, and cooperating, just as it always has,” says Meyers. This collaboration is key for her. Extinction of species and the climate crisis are problems that are just too complex for simple solutions. Effective protection can only be achieved together.
The Angel Shark Project has far outgrown the status of a local conservation project in the meantime. Much rather, the Canary Islands have turned into a natural laboratory that allows us to assess the effectiveness of conservation measures virtually in real time. Meyers and her team are now sharing their knowledge with Ireland, Corsica, Wales, Croatia, Libya, and Greece.
The same principle that Eva Meyers demonstrates with the angel shark applies to the research of Dr Nancy Mercado Salas as well: Many treasures of our oceans live hidden from view. Many of them require close attention.

Mercado Salas has tracked down these tiny creatures on three continents and has collected her first freshwater species in her native Mexico. Later, she moved her research to the rainforests of South America, before coming to Germany in 2014, where she studies, amongst other things, deep-sea species in the Clarion-Clipperton Zone of the Northeast Pacific. Examining an area of no more than 300 x 300 metres, she and her colleagues have already discovered more than 500 copepod species, most of which were not previously scientifically described.
Here, at depths of about 5,000 metres, is the place where a new danger looms in the form of deep-sea mining, however. “Most deep-sea creatures live in the uppermost three centimetres of sediment,” she explains. “Disturbing this layer by drilling or underwater vehicles will cause all life there to disappear. The consequences are almost unimaginable.”

It’s not just the sea that holds some secrets, however. Copepods occur virtually everywhere, be it in saltwater, in freshwater springs, and even in isolated caves. Mercado Salas finds the species that live in water-filled bromeliads—funnel-shaped tropical plants—particularly fascinating. “Copepods can’t fly and need a constant supply of moisture,” Mercado Salas says. “We have no idea how they move from plant to plant.”
When Mercado Salas isn’t out on her expeditions, her workplace is in the Museum of Nature in Hamburg, which belongs to the LIB and where she acts as curator managing the museum’s crustacean department. With about one million animals and 7,200 described species, her workplace is the home of one of the world’s most important collections of marine microorganisms. “It’s approaching 15 percent of all known crustacean species worldwide,” she says proudly.
Many of these species can no longer be collected today because their habitats have been destroyed or become inaccessible. Collections like the one in Hamburg frequently become the only way to access the past. Mercado Salas and her team digitise samples, record metadata, and take photographs to let even researchers in Madagascar or South America access their collection in the Hanseatic city.
We need this if we are to learn about the future from the past. Old samples show us how biodiversity has changed over decades.
The oceans feed billions of people, decelerate global warming, and protect coastlines from storms. Coral reefs, seagrass meadows, and mangroves form both habitats and vital buffers against the climate crisis by storing carbon, filtering water, and dampening storm surges. Even medicines often originate from marine organisms. Every single species we lose kills off part of this protective function as well, which harms us all.

An early warning system for corals

We cannot limit our view of biodiversity to retrospective analysis, but we need to look ahead in order to protect it. This is the aim of Dr Sarah Lemer’s research.
She is looking for warning signals in the genetic code of corals long before a reef starts to fade. At the helm of the LIB’s molecular laboratory in Hamburg, she wants to build a molecular early warning system for reef health.
Born in France, Lemer was raised in Indonesia and the Caribbean. The sea was a constant presence in her youth, and she developed a curiosity about it early on. Why is water salty? Why is it blue? When she learned that such questions could be explored professionally, she knew that she was going to be a scientist when she grew up.
She first encountered a destroyed reef while snorkelling while studying for her master’s degree. “That was the moment that showed me that coral bleaching and climate change are real.” She had never planned to go into corals, a field that was already overcrowded, but originally was going to focus on the smaller, less-studied species. The reef had a firm hold on her mind, however.

Not only are coral reefs hotspots of biodiversity, they also are extremely sensitive. They depend on light and warmth, but they cannot be too exposed to them. Small temperature increases are enough to trigger bleaching or disease. Lemer has spent two decades investigating the genetic diversity of reefs and their inhabitants along with its effects on resilience.
She has found reefs with virtually identical genetic makeups off the coast of some islands in the Mariana Archipelago in Micronesia. “This does have some positive aspects. It shows us that these genotypes have survived several heat waves. However, they are now vulnerable to new threats.” Diseases can wreck entire reefs if all the corals are equally susceptible to them.
“Genetic diversity equals resilience. That is why we need as much as possible of it,” says Lemer. Evolution takes its own sweet time, however, and that is exactly what we don’t have anymore. Lemer and her team are developing a molecular early warning system to facilitate early responses by analysing how particular genes react to environmental stress even before the first visible symptoms become evident in the corals. “We have since been able to identify about half a dozen genes that react weeks in advance.”
At this point, they still need to take tissue samples, or specifically coral pieces to achieve this. However, the team is now working on a gentler method that involves a swab that is as harmless as the cheek swabs used in humans. It nevertheless stresses the animal measurably.
Lemer is also developing methods to extract genetic material from old collections at LIB: “Understanding how species used to react to past environmental changes helps us to better predict what they lack today and what might help them tomorrow.”

The work of Eva Meyers, Nancy Mercado Salas, and Sarah Lemer demonstrates the multifaceted nature of marine biodiversity conservation. In this context, we can see particularly well how long-standing knowledge can be combined with modern technologies to make the invisible visible before it can disappear.