Decline in plankton and stock biomass

The challenge

Warming of the ocean’s uppermost layers tends to increase the thermal stratification of the water column. This can limit access to nutrients and affect the primary production of marine ecosystems. Lower ocean productivity can also have very important implications for climate regulation.

The solution

AZTI estimates the effect of warming on marine biomass using its own studies and published global projections (Chust et al., 2014; Lotze et al., 2019). It also took part in the Malaspina expedition (2010), which studied deep-sea animal life and its role in carbon sequestration.

The results

• Estimated reductions in phytoplankton and zooplankton biomass of 6% and 11% respectively by the end of this century.
• The biomass of animal species in the oceans could fall by 5% to 17% by the end of the century, amplifying the climate signal through the food web.
• The Malaspina expedition showed that deep-sea animal life, which is responsible for sequestering large tonnages of CO₂ that would otherwise end up in the atmosphere, is far more abundant than previously thought.
• This means its role in mitigating climate change is much more important than was believed.