Ocean acidification in the Mediterranean is already affecting the calcification of marine plankton

The Impact of Ocean Acidification on Marine Plankton Shells in the Mediterranean Sea

Introduction

The acidification of the oceans caused by human activity is already altering the production of marine plankton shells in the Mediterranean Sea. This is the worrying conclusion of a study led by the Institute of Environmental Science and Technology of the Universitat Autònoma de Barcelona (ICTA-UAB), which alerts of the impact the decrease in pH of the surface ocean has on the production of calcium carbonate by marine plankton, with negative consequences for marine ecosystems.

Sustainable Development Goals (SDGs)

• SDG 14: Life Below Water
• SDG 13: Climate Action

Background

Anthropogenic carbon dioxide (CO₂) emissions have increased alarmingly in recent decades. Since the Industrial Revolution, about 25% of anthropogenic CO₂ has entered the ocean, changing water chemistry and lowering pH, a phenomenon known as ocean acidification.

Methodology

The study, carried out in collaboration with researchers from the University of St Andrews (UK), the Max Planck Institute of Chemistry (MPIC) in Mainz (Germany) and the Spanish Council for Scientific Research (CSIC) in Barcelona (Spain) and published in the Nature Portfolio journal Communications Earth & Environment, assessed the impact of CO₂ -induced changes in the Mediterranean Sea on foraminifera, a particular group of calcifying planktonic organisms.

To do this, they studied records from different Mediterranean sites: the Alboran Sea, off the coast of Barcelona, and the Strait of Sicily, spanning the past two thousand years. The researchers chose to study the western Mediterranean Sea because it is a region particularly affected by anthropogenic pressures and climate change. Due to the high alkalinity and the fast circulation of water masses in the basin, Mediterranean waters are susceptible to the uptake of anthropogenic carbon, which has led to a pH drop of 0.08 units since the Industrial Revolution, affecting the biogenic calcification of marine plankton.

Findings

Foraminifera are a common type of marine calcifying zooplankton that live in the upper ocean and are very sensitive to climatic and environmental changes. These single-celled organisms build a shell, several hundred micrometers in size, which is made of calcium carbonate. Albeit the shell’s extreme robustness, these calcite structures are highly sensitive to changes in seawater chemistry, which makes them an ideal tool for studying the long-term impacts of carbon perturbations on marine ecosystems. This is reflected in an accelerated decrease in shell weight during the 20th century. In contrast, before the Industrial Revolution, the shells of planktonic foraminifera were heavier without showing much variability in weight over time. The study also shows that the anthropogenic carbon dioxide signature has already been transferred to the shell chemistry of the planktonic calcifiers” explains Sven Pallacks, lead researcher of the study.

The researchers found that ocean acidification caused by anthropogenic emissions is the main driver of the decline in foraminiferal calcite mass, while ocean warming may be mitigating this effect.

“This demonstrates the basin-wide change in marine calcite production under increased atmospheric CO₂ concentrations and acidification of surface waters in the Mediterranean Sea,” explains Patrizia Ziveri, oceanographer at ICTA-UAB.

Implications

By reconstructing the records, the researchers were able to assess the impact of acidification on the calcification of planktonic foraminifera. The results can also be applied to other calcifying planktic organisms living in Mediterranean surface waters, such as coccolithophores or pteropods, which play an important role in the modulations of atmospheric CO₂.

The results indicate that anthropogenic ocean acidification at the Mediterranean Sea surface has affected foraminiferal calcification during the 20^th century. As calcifying plankton are an important component of both the marine food web architecture and biogeochemical cycles, continued ocean acidification would have a negative impact on marine ecosystem services, including climate regulation, ocean’s ecosystem functioning and food security, reiterating the importance of mitigating climate change by drastically reducing CO₂ emissions.

Conclusion

The study highlights the detrimental effects of ocean acidification on marine plankton shells in the Mediterranean Sea. The findings emphasize the need to address climate change and reduce CO₂ emissions to protect marine ecosystems and achieve the Sustainable Development Goals (SDGs), particularly SDG 14 (Life Below Water) and SDG 13 (Climate Action).

Journal Details

• Journal: Communications Earth & Environment
• Method of Research: Experimental study
• Subject of Research: Not applicable
• Article Title: Anthropogenic acidification of surface waters drives decreased biogenic calcification in the Mediterranean Sea
• Article Publication Date: 28-Aug-2023

SDGs, Targets, and Indicators

1. Which SDGs are addressed or connected to the issues highlighted in the article?

• SDG 14: Life Below Water – Conserve and sustainably use the oceans, seas, and marine resources for sustainable development.
• SDG 13: Climate Action – Take urgent action to combat climate change and its impacts.

2. What specific targets under those SDGs can be identified based on the article’s content?

• SDG 14.3: Minimize and address the impacts of ocean acidification.
• SDG 13.3: Improve education, awareness-raising, and human and institutional capacity on climate change mitigation, adaptation, impact reduction, and early warning.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

Yes, the article mentions indicators that can be used to measure progress towards the identified targets:

• Calcite mass of foraminiferal shells: The decline in calcite mass indicates the impact of ocean acidification on marine ecosystems.
• Anthropogenic carbon dioxide (CO₂) emissions: The increase in CO₂ emissions is causing ocean acidification and impacting marine plankton.

Table: SDGs, Targets, and Indicators

The article highlights the issue of ocean acidification caused by human activity, which is connected to SDG 14: Life Below Water. The decline in calcite mass of foraminiferal shells indicates the impact of ocean acidification on marine ecosystems, aligning with target 14.3 of SDG 14. Additionally, the article mentions the increase in anthropogenic carbon dioxide (CO₂) emissions as a driver of ocean acidification, which is also relevant to SDG 13: Climate Action. This aligns with target 13.3 of SDG 13, which focuses on improving education and awareness on climate change mitigation. The indicators mentioned in the article, such as the calcite mass of foraminiferal shells and anthropogenic CO₂ emissions, can be used to measure progress towards these targets.

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Source: eurekalert.org

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