Thank you so much for your beautiful art. You really captured how humanity has challenged the oceans, while also providing hope for future flourishing seas through recovery and restoration.

🌊

🔗 doi.org/10.1098/rstb.2024.0026

Thank you to all the amazing authors who trusted us with their research. Not to mention our wonderful artists Jacek Matysiak (www.instagram.com/big.hippo.art/) and Maddy Dall (www.instagram.com/maddydall/) who brought the issue to life with their beautiful illustrations.

Contributions use bones 🦴, shells 🐚, old catch records 📜, logbooks 📖, marine sediments 🧪 & more to reach before monitoring began. Using stable isotopes 🧬, ancient DNA 🧫, ecosystem models 🌍 & other tools, they reveal fresh insights into our impact on the seas 🌊.

My amazing co-guest editors @ruththurstan.bsky.social @kbohmann.bsky.social @mikkelwp.bsky.social @tangeolsen.bsky.social & non-Bskyers Ol Craig, David Orton, James Scourse and I found only enthusiasm and interest from our networks - the amazing research rolled in!

There wasn’t an obvious place to bring together data from archaeology 🏺, ecology 🌿, and marine geology 🌊…

Then I saw a call from @royalsocietypublishing.org 📣 for theme issues — and suddenly, everything clicked! 💡🧩

A couple of years ago we were beginning to see exciting interdisciplinary datasets coming out of @erc.europa.eu 🌍 @seachange-erc.bsky.social 🌊. It was amazing to begin to understand the complex dance of climate 🌡️, humans 🧍‍♂️🧍‍♀️, and marine biodiversity 🐟🪸 across centuries! ⏳✨

🙌 Thanks to amazing co-authors @kbohmann.bsky.social sky.social, @mikkelwp.bsky.social @seachange-erc.bsky.social, many others not on 💙☁️, & our funders @erc.europa.eu.

Dive into the full study here: doi.org/10.1111/1755...

Lots more detail in the supplements!

💡 Some takeaways:

Different eDNA methods give us different snapshots of ancient biodiversity. Interpret ancient records with care —methodological biases can shape ecological conclusions.

When your material crosses 2-4k years BP be careful interpreting alpha diversity changes.📝

📊 Consistent beta diversity

Despite the richness differences, both methods produced similar beta diversity patterns, highlighting consistent shifts in community composition over time.

Phew!

📉 Very different richness across methods!📉

Our results showed opposing alpha diversity trends:

• Metabarcoding = lower ASV richness in older sediments

• Metagenomics = lower genus richness in younger sediments

A clear reminder that the method truly matters! 🎯

🔍 What taxa overlapped? 🔍

We found that only 3 metazoan genera overlapped between methods:

• Oikopleura (larvacean)
• Gadus (cod)
• Clupea (herring)
(+ 🌿seagrass🌿)

Interestingly we found that only metagenomics provided reliable detections beyond 4k years for all taxa.

🔬 What did we do?🔬

We sampled a long (30m+), old (20y+) marine sediment core from the Skagerrak, North Sea, performing 18S(v9) metabarcoding and shotgun-metagenomic sequencing to see what these very different techniques tell us about ancient oceans.

We have so much more to do to support women in STEM! 👩‍🔬 Here at GLOBE, across Danish academia🇩🇰, and around the 🌍

🚀 Follow these great women, read & cite their work, and stay aware of the biases that can make us miss out on talented researchers & amazing collaborators! 💙 #WomenInSTEM #EquityInScience

Finally, the super talented Lene Bruhn Pedersen! 🧪✨ Her lab skills are crucial to keeping our projects running. 🔬💡

Lene is looking for new opportunities in Copenhagen as our project wraps up. If you need the best lab tech in town, reach out! 👀📢

🔗 More about Lene: seachange-erc.eu/people/lene_...