Thinking beyond the data: When the sea went dark

摘要

Five mass extinction events in earth's history each resulted in major oceanic species loss. All of these appear to be associated with significant atmospheric aerosol loading and a reduction in sunlight intensity at the surface. Importantly for marine species, it is not only the intensity of the incident light, but also its colour that is important as, within the ocean, only light with wavelengths less than about 550 nm penetrate to significant depths. However, it is these shorter wavelengths that are preferentially absorbed by atmospheric aerosol, with this effect thereby amplifying any reduction of light within the sea. This was modelled for various aerosol loadings, and it is shown that the amount of light in the sea, required for photosynthesis and visual predation, is especially sensitive to the aerosol loading and type.