Heat waves are a major public health concern, but you might be a little less aware of marine heat waves. A recent study illuminates the danger of these phenomena on an important species at the bottom of the food chain.

What's happening?

Brazilian researchers simulated how increased temperatures might affect the Atlantic mangrove fiddler crab, Leptuca thayeri. They published their findings in the journal Estuarine, Coastal, and Shelf Science. 

A marine heat wave is defined as a period of at least five days with temperatures on the water measuring at 90% greater than the historical average. The occurrence of marine heat waves is projected to increase by 35% by 2100 in the area of study off the coast of São Paulo state, Brazil. 

The researchers uncovered that rising water temperatures posed severe dangers to the Atlantic mangrove fiddler crab.

"A rise of 2 degrees Celsius (3.6 degrees Fahrenheit) in sea surface temperature during the first three to four days of their lives led to a 15% drop in the survival rate compared with larvae at the average temperature for the region," Murilo Zanetti Marochi revealed in a news release. "A rise of 4 degrees Celsius (7.2 degrees Fahrenheit) led to a 34% rise in mortality."

Why is the Atlantic mangrove fiddler crab's survival important?

While fiddler crabs may not seem crucial compared to the flashier ocean creatures we all know, every species plays a role in its ecosystem. These crabs are a food source for marine and land animals alike, so their decline could disrupt food chains. 

The researchers also suggested that the development could be detrimental to commercial fisheries as well. Other studies reveal they might be valuable allies in taking on plastic pollution.

So few fiddler crabs typically make it as is. The crabs lay their eggs in mangrove forests and head to the ocean after a few days. Under 1% complete the life cycle, which shows just how consistent a food source the creature is in their ecosystem.

What's being done about marine heat waves and the fiddler crabs?

The researchers pointed out that despite the rising numbers of marine heat waves, the creature had so far been resilient. They theorized that it's possible that warmer sea temperatures speed up their larvae developments, or boost the production of the microorganisms they feed on.

It's likely we can't bank on those dynamics forever as sea temperatures rise. Innovations in Blue Tech to improve ocean health can stave off the rise in marine heat waves. Cleaner energy adoption could also help slow rising sea temperatures that result in elevated ocean temperatures.

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