Reviving Dead Zone Laurence Mee Summary

The Scientific American article, “Reviving Dead Zones” by Laurence Mee focuses on answering the essential question, “How can we restore coastal seas ravaged by runaway plant and algae growth caused by human activities?” The article writes about eutrophication. Eutrophication is where an influx of nutrients that are normally limiting such as nitrogen and phosphorus overwhelms an aquatic ecosystem. These nutrients allow for the rapid growth of phytoplankton (floating algae). When these organisms die, they undergo decomposition. In order to decompose these dead phytoplankton, bacteria need oxygen. As they consume oxygen, they create ‘dead zones,’ or zones devoid of oxygen—and non-bacterial life. It is not the excess nutrients that directly causes the death of ecosystems, rather it is the resulting deprivation of oxygen that does them in.
In a process called ‘trophic cascading,’ the removal of apex predators allows for populations of smaller fish species to increase because the top-down selective pressures on them are weakened. These fish consume zooplankton and the decreased amount of zooplankton results in an increase in phytoplankton populations because they now have less predators. The increase in phytoplankton population then also results in the formation of dead zones as they die and decompose. Oftentimes, such as in the Black Sea, nutrient runoff and overfishing occur in tandem. Additionally, the species composition of the ecosystem will change, with the growth of “highly tolerant gelatinous organisms such as Noctiluca (responsible for nighttime phosphorescence)” often increasing. Species such as these are referred to as “dead-end species” because they are not eaten by many organisms. This results in the food chain being less