Climate-Driven Monsoon Extremes Threaten Bay of Bengal’s Vital Marine Resources.

The Bay of Bengal’s critical role in supporting marine life—and by extension, millions of livelihoods—is facing serious threats from increasingly extreme monsoon patterns, according to new research led by Rutgers University scientists and international collaborators. Published in Nature Geoscience, the study highlights how projected changes in India's summer monsoon could dramatically diminish the region’s ocean productivity.

Although the Bay of Bengal accounts for less than 1% of the global ocean area, it remarkably produces nearly 8% of the world's fisheries. The bay's nutrient-rich waters underpin food security for densely populated coastal communities, making its stability vital. However, researchers caution that the future of this ecosystem is uncertain.

"Millions living along the Bay depend on it for protein, mainly through fisheries," said Yair Rosenthal, Distinguished Professor at Rutgers’ Departments of Marine and Coastal Sciences and Earth and Planetary Sciences. "Marine productivity—especially the growth of plankton—is the foundation of the oceanic food web. A decline would ripple through the ecosystem, threatening fish stocks and regional food supplies."

By analyzing sediment cores from the seafloor—collected by the research vessel JOIDES Resolution during the International Ocean Discovery Program—the team reconstructed 22,000 years of monsoon and ocean productivity history. Central to their analysis were the fossilized shells of foraminifera, tiny plankton that serve as historical indicators of past marine conditions through their chemical compositions.

"We examined the chemistry of these microscopic shells and tracked species that thrive in nutrient-rich environments," explained Kaustubh Thirumalai, an assistant professor at the University of Arizona and lead author of the study. "This allowed us to map long-term changes in rainfall patterns, sea temperatures, and marine productivity in the Bay of Bengal."

Their findings reveal that both unusually weak and excessively strong monsoon periods in the past led to sharp declines—up to 50%—in marine food availability. During weak monsoons, reduced river discharge and weaker ocean mixing limited nutrient transport to surface waters. Conversely, extremely strong monsoons created a thick freshwater layer that capped the ocean surface, also restricting nutrient upwelling essential for plankton growth.

The study highlights two historical periods of collapse: Heinrich Stadial 1, a cold event between 17,500 and 15,500 years ago, and the early Holocene, a warmer era around 10,500 to 9,500 years ago marked by rapid glacier melt and rising sea levels.

"The monsoon's strength dictates river flow into the Bay, significantly altering ocean conditions critical to the marine food chain," Thirumalai noted. "Both extremes—too weak or too strong—disrupt the system, threatening marine resources."

When comparing ancient records with modern climate models, the researchers found disturbing similarities. Future projections suggest surface waters will warm and freshwater influx will increase, creating conditions that historically triggered sharp drops in marine productivity. Adding to the concern, future wind patterns may not be sufficient to counteract the ocean's stratification, further stifling nutrient mixing.

"Understanding past climate and ocean interactions helps us predict future challenges," said Rosenthal. "Our work shows how marine ecosystems have responded to warming and monsoon variability in the past and what might happen moving forward."

The insights from this study underscore the urgent need for sustainable management of the Bay of Bengal’s marine resources as climate change accelerates. Kaixuan Bu, an assistant research professor at Rutgers-New Brunswick’s Department of Marine and Coastal Sciences, also contributed to the research.

Source:https://phys.org/news/2025-04-extreme-monsoon-threaten-bay-bengal.html

This is non-financial/medical advice and made using AI so could be wrong.