Unveiling Historical Marine Ecology: 800-Year-Old Ice Core Challenges Assumptions

A recent University of Washington study, delving into an 800-year-old ice core, has revealed that phytoplankton populations in the North Atlantic have remained consistent since the industrial revolution. Contrary to prior beliefs of a substantial decline, this research underscores the influence of industrial pollutants on atmospheric chemistry. Source: SciTechPost.com

Recent findings have shown that phytoplankton populations in the North Atlantic have not fluctuated significantly since the onset of the industrial era, challenging earlier beliefs of their decline.

Echoing the sentiments of Mark Twain, the idea of a decrease in North Atlantic phytoplankton may have been overstated. A notable 2019 study, using ice cores from Antarctica, indicated a 10% reduction in marine productivity in the North Atlantic during the industrial era, raising concerns about a continuing downward trend.

However, newer research spearheaded by the University of Washington suggests a different scenario. The investigation into an 800-year-old ice core indicates that phytoplankton in the North Atlantic – vital for the broader marine ecosystem – have been more resilient than previously thought. This complex atmospheric process could explain the observed trends.

The findings were published in the Proceedings of the National Academy of Sciences.

Satellite imagery can detect chlorophyll reflections, indicative of photosynthetic organisms like phytoplankton. Images from the North Atlantic show these reflections, mingling with ocean currents. While previous studies based on ice core analysis reported a 10% decrease in North Atlantic phytoplankton since the mid-19th century, recent research suggests these populations might be more stable. Credit: NASA

Exploring Phytoplankton’s Importance

Phytoplankton, minuscule photosynthetic organisms, form the foundation of the marine food web. They play a crucial role globally, producing approximately half of the oxygen in Earth’s atmosphere.

Due to their small size, direct counting of phytoplankton is challenging. Scientists have developed alternative methods to estimate their numbers. One such method involves tracking dimethyl sulfide emissions, a gas responsible for the distinct smell of beaches. Once released, it transforms into methanesulfonic acid (MSA) and sulfate, which are eventually deposited on land or snow. Ice cores can thus be used to infer historical phytoplankton populations.

Becky Alexander, at the University of Washington’s IsoLab, examines an ice core extracted from Greenland. Her team’s analysis of this core suggests that emissions from photosynthetic marine organisms have been consistent since the mid-1800s. Credit: Mark Stone/University of Washington

Insights from Greenland’s Ice Cores

“Analysis of Greenland ice cores indicated a decrease in MSA concentrations over the industrial era, initially interpreted as a sign of reduced primary productivity in the North Atlantic,” explains Ursula Jongebloed, a doctoral student at the university. “However, our research, which also examined sulfate in a Greenland ice core, demonstrates that MSA levels alone do not provide a complete picture of primary productivity.”

Since the mid-19th century, industrial activities have released sulfur gases into the atmosphere. These gases contain distinct sulfur isotopes, allowing differentiation between marine and terrestrial sources in ice cores.

Broader Historical Context

This study delves deeper than previous research by examining various sulfur-containing molecules in a Greenland ice core, covering the period from 1200 to 2006. The findings suggest that human-made pollutants altered atmospheric chemistry, affecting the gases released by phytoplankton.

“Our findings from the ice cores show an increase in sulfate from phytoplankton during the industrial era,” Jongebloed notes. “This implies that the decline in MSA is balanced by an increase in phytoplankton-derived sulfate, suggesting overall stability in phytoplankton sulfur emissions.”

Ursula Jongebloed utilizes a stable isotope mass spectrometer in the university’s IsoLab to analyze sulfur isotopes in the Greenland ice core. These isotopes help trace changes in sulfate sources over the centuries, including marine phytoplankton, fossil fuel emissions, and volcanic activity. Credit: Mark Stone/University of Washington

Conclusions and Future Directions

Considering this balance, phytoplankton populations appear to have remained stable since the mid-19th century. However, the researchers caution that marine ecosystems still face multiple threats.

“Analyzing both MSA and phytoplankton-derived sulfate offers a more comprehensive view of changes in emissions from marine primary producers over time,” states senior author Becky Alexander, a professor at the university.

Combining ice core measurements with other independent estimates of phytoplankton abundance, such as chlorophyll data, and integrating modeling studies, can enhance our understanding of historical changes in marine productivity and predict future trends.

The study, “Industrial-era decline in Arctic methanesulfonic acid is offset by increased biogenic sulfate aerosol” by Ursula A. Jongebloed and colleagues, was published on 17 November 2023 in

Frequently Asked Questions (FAQs) about North Atlantic phytoplankton stability

More about North Atlantic phytoplankton stability

• University of Washington Research Findings
• Proceedings of the National Academy of Sciences Publication
• SciTechPost.com Original Article
• NASA Satellite Imagery of Phytoplankton
• 2019 Antarctic Ice Core Study Report
• Marine Biology and Climate Change Research
• Environmental Impact of Industrial Pollutants