Biological Implication of Prolonged Darkness

Prolonged darkness would have had a profound effect on the marine food chain

Phytoplankton are microscopic floating plants which need sunlight. They are the producers of the ocean. Zooplankton are microscopic animals that feed on the phytoplankton. Small fish feed on the zooplankton which are then fed upon by larger fish.

As the darkness set in, the phytoplankton abundance would have decreased rapidly. Not only would phytoplankton be dying due to loss of light, they would also be fed upon by zooplankton. It is assumed that their feeding rate remains constant through this prolonged darkness (Milne and McKay, 1980). According to Milne and McKay, the zooplankton would have suffered starvation in the first 10-30 days of darkness.

Recall : Toon and others concluded that light would be insufficient for photosynthesis for 2 months to 1 year. (See Prolonged Darkness)

Milne and Mc Kay concluded that if the darkness were to persist for appoximately 1 year, all marine life would be exterminated in tropical waters.

In 1980 Alvarez theorized that his impact scenario would cause an absence of light that would cause a collapse of both the marine and terrestrial food chain. According to Toon and others this would likely not occur. The biomass on land is much larger than that in the oceans (Toon and others, 1980). Also plants (unlike phytoplankton or zooplankton) have a better chance of surviving as they have strategies like hibernation and encystment ( an organism forming a protective capsule around itself).

Large land animals like the dinosaurs would have been affected by this prolonged darkness. Some are carnivorous and therefore hunt smaller prey. This would be very difficult as the prolonged darkness would have made vision impossible (Toon and others, 1980). Also because of the environmental crisis, it is likely that most of the smaller animals took refuge in hybernaculas (areas where small animals can hibernate such as caves, cracks and under rocks). This would make them even more difficult to catch.

Back to Main Page
Go To Bio. Implications of Temp. Change