In his talk, ‘The Hidden Diversity, Behavior and Life Histories of Atlantic Deep-Sea Cephalopods’ Henk-Jan showed us why samples from nets don’t give us the full picture of deep-sea life. In all the nets deployed in the deep by 1977, the biggest cephalopod beak recovered suggested a deep-sea cephalopod no bigger than 10 cm. Whereas, the biggest beaks found in the stomachs of sperm whales by the same time suggested regular consumption of deep-sea cephalopods ten times that. And of course, we know there are giant squids even 10x bigger than that.

I enjoyed digesting this slice of humble pie — that humans are at least 10x worse than whales at catching squids. I also enjoyed pondering its follow-up: what else is in the deep, dark ocean that we’re useless at finding?

Diva Amon spoke thoughtfully on the long-standing problems of colonial science, wherein institutes of developed countries arrive to small islands and other developing countries to do science, check out and then (“Ta Da!”) get credit for all the data. More institutes and funding programs like Horizon Europe are recognizing the importance of integrating local scientists into the research process, but often under the label ‘Capacity Building’. Dr. Amon reminded us of the power of word choice and how ‘Capacity Building’ implies a unidirectional supply of knowledge. Instead, and recognizing the wealth of information and valuable perspectives from local communities, she proposed ‘Capacity Sharing’ as a new model of strengthening science around the world. We like it and we’re already using it for TWILIGHTED!

This jovial quote from jellyfish expert Gerlien Verhaegen was given in a bid to inspire more people to care about pelagic species. I saw its truth extend throughout the conference. All in all, there is very little data about the ocean’s 300 million cubic miles of water between the shallows and the seafloor and the species within them. Amelia Bridges demonstrated this with an analysis of global data repository OBIS, showing a strong bias in that 50% of global biodiversity data covers only 0.98% of the ocean’s depths. 

Such a focus on benthic life could be skewing our perception of risks, such as those from deep-sea mining. Out of 17 talks on deep-sea mining impacts at DSBS, and with the exception of a micronekton biodiversity talk by Jeffery Drazen, there was a striking lack of research at DSBS on the potential impact on midwater species from deep-sea mining plumes. Yet, it’s in the midwater where many of the fish we eat live and spawn, where many of our fisheries operate. If experiments suggest that toxic mining plumes can kill coral larvae within hours and adults within days (MAD-Deep podcast and Carreiro-Silva et al, 2022), shouldn’t we be asking what could happen to one of the world’s major food sources under similar conditions? We already know tuna and other top predators concentrate heavy metals like mercury up the food chain…and now there’s a threat of more heavy metals floating around? Spreading up to 40km from each mining discharge site? Hopefully by the next DSBS we’ll have more research on what deep-sea mining foretells for global fish stocks and human health.

A ‘wow’ moment for me shone through by listening to Eva Stewart’s and Adrian Glover’s talks. Since 1970, there have been thirteen studies on the impacts of deep-sea mining on abyssal nodule ecosystems and one study on the impact of deep-sea mining to hydrothermal vents and seamounts. Compare this to almost 700 published studies into the effect of deforestation – on soil alone (Mgelwa et al, 2025).

Due to the nature of most deep-sea research (done aboard vessels in month-long expeditions), there is very little time-lapse data for the deep sea. There are also limited opportunities for repeating experiments, to get results we can really trust. The large, overlapping error bars and confidence intervals of much of the data presented did not, in fact, inspire confidence. This is an area we hope Madeira and other volcanic islands not on continental shelves can contribute to. We hope to create a hub for deep-sea research where scientists can join us in time-lapse studies, long-term monitoring and replicable experiments, taking advantage of our easy, year-round access to the deep sea.

Aistė Klimašauskaitė showed a compelling example of how science can be warped to suit political agendas. She and collaborators compared an impact report for a European government reviewing deep-sea mining, which said that benthic community impacts of mining would be ‘small’. This summary was based on a scientific paper that said ‘not enough knowledge to know’. How governments or the public interpret scientific uncertainty can have real-life consequences and we, the scientists, should pay closer attention to the policies and impact reports being written based on our science. 

Images of deep-sea life never fail to amaze. My personal favorites are plankton (aliens are real!) and anything with lights (more on this soon). But I learned some new deep-sea party-tricks at DSBS, too:

• There are deep-sea microbes that can metabolize pesticides and insecticides (Liu et al, 2024)
• There are over 100 genera of deep-sea fungi from hydrothermal vents that can degrade oil (a critter you want on-side if you accidentally spill 5 million barrels of oil into the ocean — take notes, BP)
• Some primary producers at hydrothermal vents metabolize electricity (termed electrophy; Yamamoto et al, 2024)

The cold temperatures and limited food supplies in the deep slow down metabolism, growth and reproduction rates. Case in point:

• If you’ve ever been frustrated by how long it takes for your bones to knit back together after breaking a toe, imagine how much more frustrated you’d be as a black coral – their exoskeletons grow at 0.05 mm per year. (While their shallow water cousins shoot past at a rapid 6.4 mm/yr)
• One type of deep-sea octopus takes TWO YEARS after fertilization to incubate its eggs, over which time Mamma Octopus starves herself, giving all her body’s nutrition to the eggs. (Don’t try this diet at home.) In comparison, the common octopus in shallow, warmer waters only needs 50 days for its eggs to hatch. 

Deep-sea coral and a deep-sea cephalopod for you (not the species mentioned, sorry!). Bobtail, NOAA Office of Ocean Exploration and Research, Windows to the Deep 2018; Sibelius Seamount, NOAA Office of Ocean Exploration and Research, Deep-Sea Symphony: Exploring the Musicians Seamounts. 

Sylvia Earle in the documentary ‘Mission Blue’ shares what it was like to descend in a deep-sea suit (very cool) and said the deep-sea wasn’t dark at all, but filled with sparkling lights. I learned more about this bioluminescence at DSBS:

• 75% of organisms in the ocean have bioluminescence
• There are two types of deep-sea light: photophores (also used by fireflies) and luminescent spew (a marvellous reimagining of vomit used to distract predators)
• Bioluminescence has evolved 94 times since the dawn of time, now found across bacteria, fungi, plants and animals.

Which just makes the rest of us look bad. While our ancestors were sitting around picking lice off each other, the rest of the tree of life was learning how to glow. And, okay, I know we should be grateful for the opposable thumbs — but were sparkly earlobes really that much to ask?

Maybe I’m late to the party on this one, but I don’t hear about this very much: the environmental impacts of renewable infrastructure. Namely, and because of having substantially less power per square meter of infrastructure compared to oil and gas, renewable infrastructure will likely interfere with a lot more habitats to achieve our climate goals. In numbers, and with current technologies, Lucy Harris from the National Oceanography Centre revealed that, to produce the same energy as one oil rig, it will take 2,000 offshore wind turbines! What will be the environmental consequences of that? Can we improve the efficiency of renewable infrastructure 2,000x?! …Like, now? 

And saving the best for last:

You don’t have to have the latest technology to make a reliable seafloor map! In his talk, Daniel O B Jones shared how his team was able to find an old test mining site using the hand-drawn map of a 1970’s expedition (which, at the time, had used single-beam sonar). When they scanned the same site with today’s latest multi-beam sonar technology, the overlay was …well, let’s let the picture do the talking! 

If you enjoyed this list and would like to learn more about the deep sea, head on over to our ‘Resources‘ page for some inspiration!