Johan Viljoen

Impact of Rising Carbon Dioxide on Human Health and Cognitive Performance This blog post and the “Deep Dive” podcast, created by NotebookLM, are based on “Direct human health risks of increased atmospheric carbon dioxide.” by Jacobson et al. (2019) and three other studie…

The atmospheric CO2 level has increased by 30% since the early 1970s. This blog post discusses the multifaceted impacts of rising CO2 levels on human health, and cognitive performance: 🌊🧪 ocean2climate.org/2025/12/24/i...

Survey region showing a transect across the Polar Front

Most surveys of Southern Ocean biogeochemistry occur in summer. Viljoen et al., explore the winter dynamics of phytoplankton and micronutrients, finding that phytoplankton continue to influence trace metal distribution 🌊

agupubs.onlinelibrary.wiley.com/doi/10.1029/...

Ocean stratification in a warming climate - Nature Reviews Earth & Environment Ocean stratification — density-related layering of seawater — influences oceanographic and climatic processes. This Review outlines observed and projected changes in stratification, noting a 0.8% dec−1 increase in 0–2,000 m stratification from 1960–2024, and a further 1.4% dec−1 increase by 2100 under SSP2-4.5.

"Ocean stratification in a warming climate" | Our ( Lijing Cheng et al) new review article in @nature.com Reviews Earth & Environment: www.nature.com/articles/s43...

Unexpected decline in the ocean carbon sink under record-high sea surface temperatures in 2023 - Nature Climate Change The ocean carbon sink strengthened in previous warm El Niño years due to reduced CO2 outgassing in the tropics. Here the authors show that the ocean carbon sink declined in 2023 despite record-high se...

🌊 In 2023, the ocean carbon sink weakened for the first time in a record-hot year 🌡️🌎
Our new study in Nature Climate Change quantifies this unexpected decline and explains how it came about. 👇
doi.org/10.1038/s415...

Nitrogen status exerts dynamic control over phosphorus sensing and acquisition via PSR1 in colimited marine diatoms Diatoms exert reciprocal, fine-scale control of P acquisition by N availability, depending on the immediate needs of the cell.

How do diatoms cope with nitrogen and phosphorus colimitation? — Happy to share our new paper:

"Nitrogen status exerts dynamic control over phosphorus sensing and acquisition via PSR1 in colimited marine diatoms"
🔗 doi.org/10.1126/scia...

@exetermarine.bsky.social @thembauk.bsky.social

Emerging evidence of abrupt changes in the Antarctic environment Nature - Abrupt changes are developing across Antarctica’s ice, ocean and biological systems; some of these changes are intensifying faster than equivalent Arctic changes, potentially...

3️⃣ 'Emerging evidence of abrupt changes in the Antarctic environment' is published in nature.com today, led by @climatenerilie.bsky.social with authors from @antarcticsciaus.bsky.social, @arcsaef.bsky.social, AAD, @imas-utas.bsky.social, @ccrc.bsky.social & other key research groups.

▶️ rdcu.be/eBCJA

Monitoring the Ocean’s Green Pulse: A New Global Dataset for Phytoplankton Phenology Phytoplankton are tiny, single-celled organisms mainly found in the ocean’s sunlit surface, where they grow through photosynthesis, forming the marine food web’s base and regulating Earth’s climate by...

🌊 blogs.egu.eu/divisions/os...

Anthropogenic iron alters the spring phytoplankton bloom in the North Pacific transition zone | PNAS Industrial activities have increased the supply of iron to the ocean, but the magnitude of anthropogenic input and its ecological consequences are ...

New paper out lead by Nick Hawco and many other amazing co-authors on how iron inputs alter the position of the transition zone in the North Pacific ocean. Amazing collaborative effort funded by @simonsfoundation.org www.pnas.org/doi/10.1073/...

OCEAN DARKENING ON CNN: PML's Prof Tim Smyth speaking to @cnn.com this morning about his new study with Dr Thomas Davies of @plymuni.bsky.social / @plymbiomarsci.bsky.social that revealed a 21% reduction in sunlight zones vital for life in the sea. More: pml.ac.uk/news/new-stu...

🌊 Pre-registration is open for GEOTRACES Summer School 2025!

📅 17–21 Nov | 📍 Cape Town
🎓 Training in marine biogeochemistry of trace elements & isotopes for 36 students.

Apply by 30 June 2025 👉 geotraces-2025.sciencesconf.org

#MarineScience #Biogeochemistry #SummerSchool
@scor-int.bsky.social

Satellite-derived global-ocean phytoplankton phenology indices Abstract. Phytoplankton bloom phenology is an important indicator for the monitoring and management of marine resources and the assessment of climate change impacts on ocean ecosystems. Despite its re...

🌊 New paper led by @sarahnicholson.bsky.social, myself and others. We generated a multi-year, multi-algorithm data product of global phytoplankton bloom phenology. The data is provided at 3 different spatial resolutions depending upon your study requirements.

essd.copernicus.org/articles/17/...

The distribution of subsurface microplastics in the ocean Nature - Global data collected between 2014 and 2024 provide insights into the distribution and potential transport mechanisms of subsurface microplastics throughout the oceanic water column.

Microplastics are now found at high concentrations throughout the deep ocean rdcu.be/ej7Cx 🌊🧪 #plasticpollution

Is ocean circulation the ultimate driver of biological carbon storage in the ocean? at University of Liverpool on FindAPhD.com PhD Project - Is ocean circulation the ultimate driver of biological carbon storage in the ocean? at University of Liverpool, listed on FindAPhD.com

Fully funded PhD project through @ukri.org future leaders fellowship to Jamie Wilson @livuniresearch.bsky.social on whether ocean circulation the ultimate driver of biological carbon storage in the ocean 🌊🧪⚒️

www.findaphd.com/phds/project...

Phytoplankton in peril, global ocean productivity plummets, study warns New research led by the CSIR has uncovered a troubling global trend – a significant decline in ocean productivity over the past 26 years, with consequences for marine biodiversity, fisheries, and the ...

Media release going at full speed now:

www.dailymaverick.co.za/article/2025...

Why scientists are counting tiny Antarctic krill from Space Differences in seawater colour could reveal how tiny Antarctic creatures are faring in a warming world.

Tiny animals with a huge impact.... total weight of krill in the world exceeds the total weight of humans or cows... and they play vital roles in ecosystems and climate.

We need to know what fishing and climate change are doing to them! 🌊🧪🥼❄️

www.bbc.co.uk/news/article...

Application Process-Youth - SOI Foundation The SOI Foundation inspires and empowers leadership for a sustainable future by connecting youth to nature, and to the knowledge, people, and resources to make a difference.

🧪📍🌊 🦑🍎 Last call - Applications open for all of the expeditions and you only need to fill out one to be considered for all of the work this season. Note there is a Scholarship Application version - this is the one you want to apply for 💙. Open to ages 14-35. soifoundation.org/en/youth/exp...

High metabolic zinc demand within native Amundsen and Ross sea phytoplankton communities determined by stable isotope uptake rate measurements Abstract. Zinc (Zn) is an essential micronutrient for most eukaryotic phytoplankton. Zn uptake by phytoplankton within the euphotic zone results in nutrient-like dissolved Zn (dZn) profiles with a lar...

Hello bluesky! I am so happy to share that some of my Antarctic work was published today in BG: bg.copernicus.org/articles/21/.... This paper is seven (!) years in the making! Zinc is an essential micronutrient for phytoplankton, and is uptaken rapidly (biogeochem modelers please take note!)

Southern Ocean carbon pump vulnerability to changing iron supply - Yorkshire Environmental Sciences • Doctoral Training Network Using your results, you will be able to test assumptions and make predictions about iron-mediated impacts of climate change on the biological carbon pump.

PhD opportunity at the University of Leeds, UK with myself, @willhomoky.bsky.social @altagliabue.bsky.social @marmite-usf.bsky.social S.Ussher & A. Milne studying how natural iron fertilisation shapes phytoplankton growth and impacts our climate. Deadline 8th Jan. yes-dtn.ac.uk/research/sou...

Frontiers | Revisiting the relationship between surface and column-integrated chlorophyll-a concentrations in the Biogeochemical-Argo and satellite era

🌊Well done Ella & team @exetermarine.bsky.social on paper out: Revisiting the relationship between surface and column-integrated chlorophyll-a concentrations in the Biogeochemical-Argo and satellite era. #RemoteSensing doi.org/10.3389/frse...

Applications for both positions are now open! Deadline for both is January 3, 2025. Please get in touch if you have questions.

🎉 argopy turns 5! 🎉
Join us as we celebrate this milestone with exciting activities:
🚀 Coding Challenges
🎮 Online Game Contest
📋 User Survey
📚 Free Training Camp
Get involved and help shape the future of Argo data! 🌊
👉 euroargodev.github.io/argopy-5years #argopy #argofloat #oneargo
1/5

Thanks for this! Could I be added?

Thanks for this! Could I be added?

Rectangular transparent perspex shape glued onto driver mounts of 2 stepper motors with wires attached to motor ends on a anti-static solder mat. Will be used later as a sample stage within a DIY microscope setup to adjust the focus of images.

Pieces of laser cut transparent and white perspex shapes on an anti-static solder mat. The larger piece have a PCB electronics board fitted onto it that will be used later to control stepper motors in a DIY microscope.

Long time coming, but finally making steady progress on my side project to build a DIY #PlanktoScope.

The Times view on BP’s U-turn on oil and gas: Profit and the Planet In sensibly scaling back its environmental targets, the oil major offers a salutary example to politicians of the need to balance climate-friendly policies against short-term costs

The UK Times yesterday published a misinformation-strewn leader that implies decarbonisation is optional and subordinate to the needs of finance, and celebrates BP's decision to dump output reductions.

Global Estimates of Particulate Organic Carbon Concentration From the Surface Ocean to the Base of the Mesopelagic agupubs.onlinelibrary.wiley.com/doi/10.1029/... #jcampubs 🌊

Thanks! Note though that Chl doesn’t always directly represent biomass, as it can vary with photoacclimation & community shifts. We noted a decline in Chl, but not in phytoplankton carbon, during recent warming. Light, nutrients, & top-down controls play a role—we're keen to explore this further!

Photo of a CTD rosette under water. It is an oceanographic device equipped with sensors and bottles, used to collect water samples and measure different properties of the ocean, like temperature and phytoplankton abundance, at various depths.

We used 33 years of data from the Bermuda Atlantic Time-series Study (BATS) 📊and highlight the implications for and importance of monitoring phytoplankton below the ocean surface. #ClimateChange #Phytoplankton #MarineScience
Photo Credit: Bob Brewin
SharedIt link here: rdcu.be/dU3Ja

Climate variability shifts the vertical structure of phytoplankton in the Sargasso Sea - Nature Climate Change The authors reveal distinct trends in surface and subsurface phytoplankton dynamics, highlighting the need for subsurface monitoring. Whereas subsurface phytoplankton respond to recent warming with bi...

🎉 Excited to share paper out today in @natureportfolio.bsky.social Climate Change with Bob Brewin & Xuerong Sun @uniofexeter.bsky.social. We show that surface & subsurface phytoplankton have contrasting seasonality & respond to climate variability differently. 🌊
www.nature.com/articles/s41...

Happy to share that I will be joining the newest cohort of BioGeoSCAPES @biogeoscapes.bsky.social fellows!
Excited to collaborate with this amazing group of ECRs and others
👉See more here biogeoscapes.org/fellows/
🌊