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Research Reveals Threats to Bay of Bengal’s Marine Life Due to Monsoon Changes

Recent findings from a collaborative study involving Rutgers University professors highlight concerns regarding the impact of extreme fluctuations in India’s summer monsoon on the Bay of Bengal’s marine ecosystem, a vital part of the region’s food resources.

This study, published in Nature Geoscience, was conducted by researchers from Rutgers, the University of Arizona, and international collaborators from India, China, and Europe. The team analyzed how historical variations in the monsoon, which brings substantial rainfall to the Indian subcontinent, have affected marine productivity in the Bay of Bengal over the last 22,000 years.

Despite comprising less than 1% of the Earth’s oceans, the Bay of Bengal contributes approximately 8% to global fishery production. Coastal populations heavily depend on these marine resources for their food and livelihoods.

“Millions are reliant on the sea for protein, particularly from fisheries,” noted Yair Rosenthal, a Distinguished Professor in Marine and Coastal Sciences at Rutgers and a co-author of the study. He emphasized that the ocean’s productivity—the capacity to foster plankton growth—is essential to the marine food web. A decline in this productivity could severely threaten both fish stocks and food security for communities along the coast.

While the monsoon is crucial for supplying freshwater to the region, the study uncovered that both extreme highs and lows in monsoon activity over time have led to considerable disruptions, resulting in up to a 50% decrease in available food for marine life. The research indicated that these extreme conditions hinder the mixing of nutrient-rich waters, essential for sustaining populations of marine organisms.

Considering the potential intensification and variability of future monsoon patterns due to climate change, the researchers warn that the food supply from the Bay of Bengal could be jeopardized.

To investigate the historical interactions between the Indian summer monsoon and ocean productivity, the team studied fossilized foraminifera, a type of plankton that builds calcium carbonate shells. These shells retain evidence of their historical environment, providing insights into past ocean and climate conditions.

“By examining their chemical composition and the prevalence of certain species linked to productive waters, we were able to reconstruct long-term variations in rainfall, ocean temperatures, and marine life in the Bay of Bengal,” explained Kaustubh Thirumalai, the study’s lead author from the University of Arizona.

These chemical signals reveal how both monsoon activity and ocean conditions have reacted to larger global climate changes over millennia. Analysis of sediments collected from the ocean floor by the research vessel JOIDES Resolution, as part of the International Ocean Discovery Program, focused on key periods of weak and strong monsoon activity, such as Heinrich Stadial 1 and the early Holocene.

Furthermore, the amount of monsoon rainfall significantly influences the flow of rivers into the Bay of Bengal, altering oceanographic conditions and impacting the feeding cycles of both fish and plankton. Excessively heavy rain can create a surface layer of freshwater that obstructs nutrient delivery from deeper waters. Conversely, weaker monsoons diminish ocean circulation, leading to nutrient scarcity.

“Both extremes pose risks to the availability of marine resources,” stated Thirumalai.

Comparisons between ancient patterns and modern oceanographic data suggest worrying trends: future projections indicate warmer surface waters and greater freshwater influx, closely resembling periods of historical marine productivity declines. Additionally, future wind patterns may not suffice to rectify the ocean layering that prevents nutrient mixing.

Understanding past climate patterns is vital for comprehending how various elements of the Earth’s system—including the atmosphere and biosphere—interact over extended timescales.

“The connections we have identified between monsoon activity and marine ecosystems in the Bay of Bengal provide concrete evidence of how these systems have responded to previous warming events and may do so again,” noted Rosenthal. “These insights could refine future projections and help in the sustainable management of fisheries and coastal resources as climate change impacts escalate.”

More information: Extreme Indian summer monsoon states stifled Bay of Bengal productivity across the last deglaciation, Nature Geoscience (2025). DOI: 10.1038/s41561-025-01684-6

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phys.org