Johan Viljoen
@johanviljoen.bsky.social
Postdoc, @uniofexeter Cornwall. Marine Phytoplankton vertical structure response to Climate Change. Previously Stellenbosch Uni (South Africa), Phytoplankton & Trace Metals in the Southern Ocean. BioGeoSCAPES Fellow.
academic.link/johannesjviljoen
academic.link/johannesjviljoen
Pinned
Johan Viljoen
@johanviljoen.bsky.social
· Sep 25
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...
www.nature.com
🎉 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...
www.nature.com/articles/s41...
Reposted by Johan Viljoen
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/...
agupubs.onlinelibrary.wiley.com/doi/10.1029/...
October 11, 2025 at 6:08 AM
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/...
agupubs.onlinelibrary.wiley.com/doi/10.1029/...
Reposted by Johan Viljoen
"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...
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.
www.nature.com
September 30, 2025 at 12:38 PM
"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...
Reposted by Johan Viljoen
🌊 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...
Our new study in Nature Climate Change quantifies this unexpected decline and explains how it came about. 👇
doi.org/10.1038/s415...
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...
doi.org
September 2, 2025 at 11:59 AM
🌊 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...
Our new study in Nature Climate Change quantifies this unexpected decline and explains how it came about. 👇
doi.org/10.1038/s415...
Reposted by Johan Viljoen
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
"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
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.
doi.org
September 2, 2025 at 8:58 AM
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
"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
Reposted by Johan Viljoen
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
▶️ rdcu.be/eBCJA
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...
rdcu.be
August 21, 2025 at 5:04 AM
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
▶️ rdcu.be/eBCJA
Reposted by Johan Viljoen
Reposted by Johan Viljoen
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/...
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 ...
www.pnas.org
June 2, 2025 at 9:56 PM
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/...
Reposted by Johan Viljoen
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...
May 30, 2025 at 9:07 AM
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...
Reposted by Johan Viljoen
🌊 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
📅 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
May 27, 2025 at 1:43 PM
🌊 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
📅 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
Reposted by Johan Viljoen
🌊 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/...
essd.copernicus.org/articles/17/...
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...
essd.copernicus.org
May 12, 2025 at 10:36 AM
🌊 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/...
essd.copernicus.org/articles/17/...
Reposted by Johan Viljoen
Microplastics are now found at high concentrations throughout the deep ocean rdcu.be/ej7Cx 🌊🧪 #plasticpollution
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.
rdcu.be
April 30, 2025 at 4:15 PM
Microplastics are now found at high concentrations throughout the deep ocean rdcu.be/ej7Cx 🌊🧪 #plasticpollution
Reposted by Johan Viljoen
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...
www.findaphd.com/phds/project...
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
www.findaphd.com
February 24, 2025 at 7:15 PM
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...
www.findaphd.com/phds/project...
Reposted by Johan Viljoen
Reposted by Johan Viljoen
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...
We need to know what fishing and climate change are doing to them! 🌊🧪🥼❄️
www.bbc.co.uk/news/article...
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.
www.bbc.co.uk
February 4, 2025 at 8:51 AM
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...
We need to know what fishing and climate change are doing to them! 🌊🧪🥼❄️
www.bbc.co.uk/news/article...
Reposted by Johan Viljoen
🧪📍🌊 🦑🍎 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...
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.
soifoundation.org
January 30, 2025 at 12:40 AM
🧪📍🌊 🦑🍎 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...
Reposted by Johan Viljoen
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!)
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...
bg.copernicus.org
December 20, 2024 at 1:24 AM
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!)
Reposted by Johan Viljoen
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...
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.
yes-dtn.ac.uk
December 18, 2024 at 12:53 PM
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...
🌊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...
Frontiers | Revisiting the relationship between surface and column-integrated chlorophyll-a concentrations in the Biogeochemical-Argo and satellite era
doi.org
December 12, 2024 at 11:25 AM
🌊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...
Reposted by Johan Viljoen
Applications for both positions are now open! Deadline for both is January 3, 2025. Please get in touch if you have questions.
Two postdoc positions in my group are opening: First is part of SOCCOM3 (3 years, NSF funded, S. Ocean carbon/oxygen/nutrient budgets), Second is part of InMOS (4.25 yrs, Schmidt Sciences / OBVI funded, long-term oxygen/carbon flux and inventory constraints). More info: bushinskyoceanlab.org/people/
People
Looking for two postdocs (SOCCOM and InMOS), details below. I am not currently planning to take on new students in Fall 2025. HI Cycles group at the 10th annual SOCCOM meeting at Princeton Universi…
bushinskyoceanlab.org
December 10, 2024 at 7:02 PM
Applications for both positions are now open! Deadline for both is January 3, 2025. Please get in touch if you have questions.
Reposted by Johan Viljoen
🎉 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
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
Celebrating argopy 5 years anniversary ! — Celebrating argopy 5 years anniversary !
euroargodev.github.io
November 27, 2024 at 9:16 AM
🎉 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
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
Long time coming, but finally making steady progress on my side project to build a DIY #PlanktoScope.
November 5, 2024 at 12:03 PM
Long time coming, but finally making steady progress on my side project to build a DIY #PlanktoScope.
Reposted by Johan Viljoen
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.
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
www.thetimes.com
October 9, 2024 at 2:29 PM
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.
Reposted by Johan Viljoen
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 🌊
October 3, 2024 at 1:04 PM
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 🌊
🎉 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...
www.nature.com/articles/s41...
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...
www.nature.com
September 25, 2024 at 10:24 AM
🎉 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...
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/
🌊
Excited to collaborate with this amazing group of ECRs and others
👉See more here biogeoscapes.org/fellows/
🌊
Fellows - BioGeoSCAPES
BioGeoSCAPES Fellows This program brings together an international, interdisciplinary cohort of early career researchers (postdocs and senior graduate students) working in experimental and modeling ba...
biogeoscapes.org
September 19, 2024 at 4:17 PM
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/
🌊
Excited to collaborate with this amazing group of ECRs and others
👉See more here biogeoscapes.org/fellows/
🌊