That's a pretty significant number.
If I were to lose 40% of my body weight, I would be 25 kg, or 55 lbs. Basically, I'd be dead.
So how can we flippantly dismiss this fact:
Phytoplankton, the basis of the entire marine food chain, and an important player in the global carbon cycle, have declined by 40% since 1950. (probably in response to ocean warming)
The average global phytoplankton concentration in the upper ocean currently declines by around 1% per year and this rate is increasing. [Boris Worm]
Why should you care?
Phytoplankton, through photosynthesis, produce around half of the oxygen in Earth's atmosphere and drive the 'biological pump' that fixes 100 million tonnes of atmospheric carbon dioxide a day into organic material.
Open-ocean fish will also be severely affected by the drastic decline in phytoplankton.
The Little Mermaid is one of my favorite movies and I want us to be able to tell our future children that Flounder (Ariel's best friend) is a real animal and not just a figment of my imagination, or a thing of the past. OKAY?