Biologie | Environnement


Sebastian Leser, 2003 | Bretigny-sur-Morrens, VD


With ever-increasing pollution and record-breaking temperatures, corals are increasingly under threat. Therefore, conservation efforts have risen in popularity, but their real effectiveness remains uncertain. The coral conservation strategies fall into four categories: (i) coral restoration which tries to rebuild damaged reefs; (ii) helping corals adapt to warmer temperatures through assisted evolution; (iii) reducing the light and heat that reaches them with the help of geo-engineering; or (iv) reducing the threats through systemic changes that aim to do so. The goal of this study was to investigate the effectiveness of these different strategies. To do this, a literature review followed by three expert interviews were conducted. The chemical bases and efficacy of one of the restoration strategies, Mineral Accretion Technology (MAT), were also tested out in lab experiments. MAT is a method using electrolysis to assist the corals in the production of their CaCO3 structures, so that they can save energy. This experimental study demonstrated that MAT may aid the corals less in future, more acidic, ocean conditions. In conclusion, most of the strategies (i-iii) are short-term oriented and don’t tackle the root threat: climate change. It is therefore essential to diminish CO2 emissions for the survival of the reefs in the long term.


Corals nowadays are under serious stress from environmental threats, most notably from anthropogenic climate change. The world has already lost 50% of its corals over the past 30 years, and the Intergovernmental Panel on Climate Change predicts that all reefs could be gone by 2070. Corals are essential for the functioning of the whole reef ecosystem since they provide shelter for a plethora of marine animals. Their disappearance would have a detrimental impact on the more than 400 million people who depend on them directly for food and income. The goal of this extended project was to get an overview of the different restoration and conservation strategies that exist, with a focus on their utility in the short and long-term.


To better understand the science underlying the different methods for coral reef conservation, a scientific literature search was done. Then, three experts in the field were contacted to gather their opinion and analysis of the current situation and future development paths. Finally, the chemical bases of one of the restoration strategies, the Mineral Accretion Technology (MAT), were tested in laboratory experiments, in present and future, more acidic ocean water conditions. To do this, a standard electrolysis montage was used with a salt bridge connecting 2×200 mL of collected water from the North Sea. A 5V DC current passed through the system for 2 hours. To simulate future, more acidic environments, CO2 was bubbled into the water with the help of a balloon attached to a Pasteur pipette. The pH was constantly measured with a pH meter.


The results of the experiments showed that the more CO2 was bubbled, the more acidic the environment was, and the less CaCO3 was produced. For waters with three different starting pHs: 8.6/6.2/5.3, the pH rose by 1.4/1.3/0.9 units and 56/33/11 mg accreted to the cathodes respectively. A linear regression between the initial pH and the amount of accretion was observed with a correlation of 0.95. The control group of pH 8.8, decreased by 0.04 pH units and gained 5 mg of mass. The increase in mass of the cathodes corresponded well to the amount of visible accretion.


The experimental results correspond to the theory. The more CO2 there is, the more H+ is formed, which reacts with and dissolves CaCO3 structures. They demonstrate that MAT is a useful method today and could still facilitate the creation of coral exoskeletons in future, more acidic seawater, but probably to a lesser degree. The literature review and the interviews reveal that most of the present restoration and conservation strategies are only effective in the short to mid-term. None of them represent a “magical solution” that would solve the underlying problem.


Different conservation strategies can have different benefits and could be used in synergy. However, their utility relies on the reduction of the threats corals face, most notably climate change. We therefore need to act together to achieve systemic changes that aim to reduce anthropogenic emissions of CO2, as well as other local stressors such as local pollution and overfishing.



Appréciation de l’experte

PhD Gaëlle Toullec

Dans son travail, Sebastian Leser s’intéresse aux stratégies de conservation des coraux et discute leur efficacité face au changement climatique. Il offre une présentation exhaustive et organisée de la problématique, révélant sa curiosité, son travail, et son esprit de synthèse. En testant une des stratégies en laboratoire, il a fait preuve de créativité, de sens critique et a su relier ses résultats à la thématique globale. Avec une discussion enrichie par l’interview de 3 spécialistes internationaux, ce travail scientifique et ses conclusions reflètent tout à fait la problématique actuelle.


très bien

Prix spécial Fondation Gamil – Sail & Explore




Gymnase cantonal de BEAULIEU, Lausanne
Enseignant: Matteo Pluchinotta