A recent study highlights the potential for significant declines in sea fish catch due to increasingly extreme monsoon patterns, driven by global warming. The research, published in Nature, warns of disruptions to marine ecosystems and a potential crash in marine productivity, particularly in the Bay of Bengal.

The study combined historical data with climate projections to reach its conclusions. Researchers analyzed fossilized foraminifera, microscopic zooplankton, from the Bay of Bengal seabed, dating back 22,000 years, to reconstruct the history of the Indian summer monsoon. These shells hold records of environmental conditions, allowing scientists to understand how past monsoon variations impacted ocean ecosystems. The team found that both extremely strong and weak monsoons led to collapses in marine productivity.

Kaustubh Thirumalai, the study's lead author and a scientist at the University of Arizona, explained that stronger and more variable monsoons lead to a collapse in marine productivity. This is particularly concerning because the Bay of Bengal, while covering less than 1% of the ocean area, accounts for approximately 8% of global fishery production. The hilsa fishery, in particular, is crucial for sustaining the protein needs of densely populated regions.

The study indicates that extreme monsoon conditions, whether excessively wet or unusually dry, can cause ocean stratification in the Bay of Bengal. Stratification refers to the separation of ocean layers, preventing the mixing of nutrient-rich deep waters with the sunlit surface layer. Phytoplankton, the base of the marine food web, reside in this surface layer and require nutrients to photosynthesize. Without the mixing of waters, the nutrient supply is cut off, leading to a decline in phytoplankton and, subsequently, a collapse in the food web. Furthermore, warmer ocean temperatures exacerbate this stratification, hindering nutrient replenishment. Changes in river runoff due to intense monsoons also contribute to stratification.

These findings have significant implications for food security and the livelihoods of millions who depend on the Bay of Bengal's fisheries. A reduction in fish stocks could trigger a major food security crisis in the region. Additionally, the study's authors suggest that climate projections indicate stronger monsoon rainfall, warmer surface waters, and weaker winds in the future, mirroring the conditions that led to past ecosystem collapses.

The research underscores the complex interplay between climate change, monsoon patterns, and marine ecosystems. It highlights the need for a deeper understanding of these interactions to mitigate the potential impacts on fisheries and food security in the region.