MARINE HEATWAVES (Syllabus: GS Paper 3– Env & Eco)

Context: Study finds fish surprisingly resistant to marine heatwaves.

• Some marine heatwaves caused biomass declines, but these were exceptions, not the rule, say researchers.
• Prolonged periods of unusually warm ocean temperatures or marine heatwaves can have devastating effects on marine ecosystems, but the extent of the impact on fish was not known.

Key Points of Study

• Marine heatwaves can lead to decay and bleaching of sponges and corals, seabirds dying in large numbers, waterbodies witnessing harmful algal blooms, decimation of seaweeds and increased marine mammal strandings. 
• The study relied on data from long-term scientific trawl surveys of continental shelf ecosystems in North America and Europe conducted between 1993 and 2019.
• Although some marine heatwaves caused biomass declines, the researchers said these were the exception rather than the rule. 
• Marine heatwaves can drive local change. 
• The scientists also considered whether marine heatwaves were causing changes in the composition of fish communities, looking for losses of species associated with cold water and an increase in species associated with warm water (known as “tropicalisation”).

Heatwaves: Heatwaves are prolonged periods of abnormally high temperatures relative to the local climate conditions. They typically last for several days or even weeks. IMD recognises it as when the maximum temperature is 40°C or higher in the plains and 30°C or higher in hilly regions and the departure from normal temperature is 4.5°C to 6.4°C.