Royal Netherlands Institute for Sea Research
Phone number
+31 (0)222 36 9380
Ocean Systems (OCS)
Research Leader
  • Biomineralization
  • Foraminiferal shell geochemistry
  • Paleoceanographic proxy development
  • Bioerosion

Dr. Lennart de Nooijer

Research Leader

‘There’s a complex balance between calcium carbonate, acid and CO2

Biologist Lennart de Nooijer studies the formation of calcium carbonate in relation to CO2, and does this in various organisms that live in the ocean. ‘Shellfish, corals and certain species of algae are a vital part of the global CO2 bookkeeping and consequently our climate. Generally speaking, animals like these find it harder to form calcium carbonate as more CO2 is dissolved in the oceans. That is because, just like a fizzy drink, the water becomes more acidic and calcium carbonate dissolves more easily. Nevertheless, the actual marine situation is more complex still. Naturally, more CO2 also means more carbon, which is one of the primary building blocks of calcium carbonate. Certain organisms may well benefit from this and produce more calcium carbonate when a modest increase in the quantity of CO2 in the water occurs. We study that by adding different CO2 concentrations to water tanks and examining what this does to their calcium carbonate formation.’

Destructive sponges

‘Besides calcium carbonate producers, the oceans also contain “calcium carbonate degraders”. In the Caribbean Sea, for example, we study certain sponges that produce some acid to dissolve the inside of coral skeletons and then live in the cavities they create. When seawater becomes slightly more acidic due to the rising amount of CO2, these “bio-eroding sponges” benefit and are able to dissolve more of the coral’s skeleton. For example, we have already found locations around Curaçao and Sint Eustatius where these sponges have caused considerable damage to the coral colonies.’

Inhibiting CO2

‘A good understanding of the relationship between CO2 and calcium carbonate producers in the seas and oceans is important for several reasons. Firstly, all of those calcium-carbonate-producing organisms actually inhibit the amount of CO2 that can dissolve in the seawater from the atmosphere. That is because during the formation of calcium carbonate, additional CO2 dissolves in the water, which makes the transfer of that greenhouse gas from the atmosphere to the oceans slightly harder. If all the algae, shellfish and corals were to stop producing calcium carbonate today, then its concentration in the atmosphere would decrease. That is exactly why it is so important to investigate whether calcium carbonate producers do better or worse in a changing climate. At the same time, the acidification of the oceans can significantly harm the biodiversity around coral reefs, for example. However, we can only gain a more precise understanding of how that works if we better comprehend the complex relationship between calcium carbonate, CO2 and calcium-carbonate- producing organisms.’

Read more +

Research interests & personal motivation

My research focusses on the underlying mechanisms of shell formation in foraminifera. These unicellular organisms produce a shell consisting of calcium carbonate for which they take up ions from the surrounding seawater. This process and the resulting chemical composition of their shells is influenced by the conditions (temperature, pH, etc.) in which these organisms live. Quantifying these relationships (for example Mg-incorporation as a function of seawater temperature) and application to fossil foraminifera allows reconstructing past changes in seawater conditions and thereby, past climates. I collect and culture foraminifera under a range of pCO2’s, salinities, etc to develop new tools to reconstruct the history of our earth. At the same time, I use these specimens to look at their biological controls on calcification. This will help to predict their response to current changes in ocean chemistry (like ongoing acidification and warming) and their ability to calcify in the near future.

It is surprising how little we understand of such a fundamental and ubiquitous process. Despite the geological relevance, abundance, evolutionary longevity and value for understanding Earth’s climate, very little is known about the fundamental process by which they form their shells. I find biomineralization in foraminifera a highly challenging research subject since it requires bringing together geology, chemistry and biology.


10 februari 2017 - NRC Handelsblad - Schelpdiertje houdt stand in verzurende zee

Sampling for seawater chemistry around the island of Saba (Dutch Antilles) to quantify calcification in the field.

Linked news

Thursday 16 November 2023
Calciferous organisms are a good tool in climate research (but you should know how to operate it!)
The fossil calciferous skeletons of single-celled foraminifers are a beautiful history book with information on CO2-levels in the oceans of the distant past. "But if you want to fully understand that history, you must first understand exactly how…
Monday 09 October 2023
The changing climate creates more noise in the oceans
Due to the changing climate, the underwater world is getting ever noisier. That is the main conclusion of a study that was published today in the scientific journal PeerJ. "In some places, by the end of this century, the sound of ships, for example,…
Friday 18 August 2023
Calcifying algae as key players in climate models
Over the past 500 million years, different single-celled organisms in the oceans have discovered at different times and also under very different conditions how to build a ‘shell’ around their single cell. “Six different strategies under just as many…
Thursday 07 January 2021
€ 3,5 million awarded for Dutch Caribbean coral reef research
We know that coral reefs worldwide are in decline; remarkably little is known about how exactly this happens. That is why a major multidisciplinary research project will start in the coming years within the NWO's Caribbean Research programme under…
Friday 06 December 2019
Met kleine fossiele kalkskeletjes klimaatverandering reconstrueren
In de zee leven talloos veel ééncelligen die een schaaltje van kalk maken: deze organismen heten foraminiferen. De samenstelling van deze schaaltjes wordt beïnvloed door de omgeving en precies daarom zijn de fossielen van deze schaaltjes bruikbaar…
Friday 27 September 2019
Are sponges threatening Caribbean Reefs?
For coral reefs to persist, constructive processes must be greater than the destructive ones to enable positive growth. Due to global change (ocean acidification and warming) and local stressors (pollution, overfishing), opportunistic organisms such…
Friday 26 April 2019
Onafhankelijke methode voor klimaatreconstructies
Promovenda Eveline Mezger ontwikkelde een nieuwe, onafhankelijke manier om het zoutgehalte van de zee in het verleden te reconstrueren. Deze informatie is van belang voor klimaatvoorspellingen.
Thursday 08 November 2018
NWO lanceert innovatief onderzoek naar energie zuiniger zeetransport
Ruim 75 Nederlandse wetenschappers werken vanaf vandaag aan nieuwe innovaties, samen met het bedrijfsleven en maatschappelijke organisaties. Dat gebeurt binnen zes grote onderzoeksprogramma’s, waarvoor de Nederlandse Organisatie voor…
Thursday 04 October 2018
OCW-minister bij samenwerkingsverklaring Koninklijk NIOZ en JAMSTEC in Tokio
Op vrijdag 5 oktober bevestigen het Koninklijk Nederlands Instituut voor Onderzoek der Zee (NIOZ) en Japan Agency for Marine-Earth Science and Technology (JAMSTEC) hun nauwe samenwerking met een samenwerkingsverklaring. Minister van OCW Ingrid van…

Linked blogs

Tuesday 09 January 2024
Between the 4th and 23rd of January, a team of scientists are on board the RV Pelagia to collect a second set of data and samples for the SEALINK project. This is a large, interdisciplinary project running from 2021 to 2025 in which Dutch and…
Thursday 12 January 2023
Is the ocean getting noisier? The AQUA expedition
Climate change will likely make the oceans noisier. Not only does increased ship traffic add noise, the ongoing dissolution of CO2 into the ocean makes seawater more acidic and that, in turn, makes sound travel further underwater. Various studies…
Friday 09 July 2021
NIOZ@SEA | AQUA expedition from Azores to Iceland
Has water chemistry an effect on the propagation of sound in the ocean? The sound emitted in the ocean decreases exponentially with distance. One of the components contributing to this decrease is the absorption of sound by the seawater chemical…
Thursday 21 January 2021
NIOZ Podcast Van Delta tot Diepzee aflevering 7 De zee als opslagplek voor CO2
Het geluid van een wandeling langs de vloedlijn: schelpen onder je schoenzolen, krakend kalk. De zee waar die schelpendieren hun huizen bouwen verzuurt. Dat komt doordat het oceaanwater CO2 opneemt. En van dat CO2, daar komt alleen maar meer van.…

NIOZ publications

Linked projects

UUNIOZ_Extreme midlatitude seasonality in a hothouse climate?
Rob Witbaard
Utrecht University
Project duration
1 Jan 2021 - 31 Dec 2025
UUNIOZ_Calcification: Global Impact of a Microscopic Process
Lennart de Nooijer
Utrecht University
Project duration
1 Jan 2021 - 31 Dec 2025
PASODOBLE_Production of Shells under Ocean acidification: DOes calcification Become more or Less Energy-efficient?
Lennart de Nooijer
Netherlands Organization for Scientific Research
Project duration
1 Dec 2016 - 28 Feb 2021
Rates and mechanisms of coral dissolution by bioeroding sponges
Lennart de Nooijer
Netherlands Organization for Scientific Research
Project duration
1 Jan 2014 - 31 Jan 2019
UUNIOZ_Calcification: Global Impact of a Microscopic Process
Lennart de Nooijer
Utrecht University
Project duration
1 Jan 2021 - 31 Dec 2025