Corals have been a part of Earth’s oceans for millions of years now. In fact, they can be categorized as primitive beings that laid the foundation for modern life to develop in our oceans. They are at least 500 million years old and date back to the late Cambrian period, during the Paleozoic era when complex multi-cellular life first developed. 

They have witnessed the rise and fall of thousands of species and have withstood the evolutionary demands that 500 million years of existence brings. A new study shows that 

Corals could hold the secret to understanding 1,000 years of seasonal changes in the Arabian Sea and the impact global warming could have on marine life. 

Scientists from Japan, Taiwan, and Germany, including coral reef scientists from Hokkaido University, have uncovered evidence from corals off the coast of Oman that show how sudden changes in temperature (like the effects of global warming) could impact the climate, ecosystems and socioeconomics of the densely populated areas surrounding the Indian Ocean. The findings were published in the journal Geophysical Research Letters.

The scientists studied fossiled corals from the Indian ocean to understand and document the changes corals underwent in the past to gauge the extent of modern-day climate change. They achieved this because, every year, the Arabian Sea upwells, allowing cold water from the deep sea to rise to the surface, enriching the coastal life with nutrition. 

“The Indian summer monsoon and the Arabian Sea upwelling were expected to intensify with global warming, following the hypothesis that the Eurasian landmass would warm faster than the Indian Ocean,” said a media release by Hokkaido University.  But, the team found that the northern Indian Ocean currently warms faster than the Indian subcontinent. The reported weakening of the Indian monsoon in the past few weather cycles is possibly weakening the Arabian Sea upwelling, a huge indicator of climate change.  

By studying fossilized corals found in the area, they established a correlation between coral seawater temperature changes and salinity changes in the water that is affected by temperature. The four fossil corals they used dated to approximately 1167 CE, 1624 CE, 1703 CE and 1968 CE, respectively. They then analyzed the ratio of strontium to calcium in the samples, as well as the amounts of oxygen and carbon isotopes. This told them about the coral growth rate (much like the rings of a tree that indicated its approximate age). While the corals grew at a steady rate throughout modern history, the strontium-to-calcium ratio and isotope oxygen-18 in coral decreased with an increase in oceanic temperature.

The results of the study showed the team that previous temperature spikes in the recent past did not affect the upwelling. In fact, the ocean mineral concentration and salinity remained stable through the warmer period of the medieval climate anomaly in the 12th century; the cooler little ice age, which extended between the 14th and 19th centuries AD; and up until the mid-20th century. This clearly shows the immense ability of coral to adapt and also reflect the conditions of their surroundings. 

But the study of corals from more recent times paints a different picture. The team observed a clear weakening of the Arabian Sea’s upwelling. The team subsequently came to the realization that this could only be a direct impact of human-driven warming of the oceans, which is sudden, unnatural, and does not give marine species enough time to adapt. Global warming, driven by the metric spike in greenhouse gases which is slowly but surely causing fluctuations and sudden spikes in temperatures across the Indian subcontinent. This is primarily due to the heavy increase in aerosol emissions across southeast Asia. This absorbs the heat, weakening the monsoon s gradually. 

Across the Indian subcontinent, there are reports of dry monsoons, leading to a severe impact in crop production, decreasing cool monsoon winds, and the Arabian Sea upwelling, which the corals clearly show. 

“The seasonal upwelling is vital for commercial fishing and has significant impacts on the regional climate, ecosystems, and socioeconomics,” says Tsuyoshi Watanabe. “Our findings imply that weakening of the Arabian Sea upwelling is likely to continue along with global warming, impacting monsoon rainfalls, sea levels, fisheries, and even agricultural production.”

What does this mean? 

This is a clear indicator that man-made global warming is not the same as drastic climate change events of the past. This has long been the argument of the deniers of global warming. The ice age and other warming or cooling events were a direct result of natural geological and environmental processes that plants and animals could adapt to. But man-made global warming is cutting out the ability of species to adapt, leading to widescale extinction that is reported today. 

This also severely affects different thriving ecosystems and weather cycles we all depend on for food and maintaining the normal chain of heat and cold. After nearly 250,000 years on Earth, humans suddenly feel a drastic change in how seasons impact our daily lives. Summers are hotter, leading to large forest fires and sudden heatstroke-related deaths. Recently, temperatures in Canada rose to never-seen-before highs, causing several hundred people to die.

In the Indian subcontinent, rain is very unpredictable. Several areas flood while other areas remain barren. Agricultural production is dropping across large swathes of previously fertile land and cities are flooding drastically, impacting human settlements increasingly. 

The case of the polar ice caps has been discussed a lot. But rising oceans are threatening coastal regions, with reported riser in sea levels, ocean-driven typhoons, hurricanes, and other disastrous storms plaguing the North American continent. And all this is visible through the study of the outer layer of corals alone, showing us how important these amazing creatures are and how the study of corals gives us important clues about possible conservation efforts.