According to a new study by Smithsonian Institution researchers published yesterday in the journal Global Change Biology, global warming is playing a potentially larger role than previously thought in dead zones in lakes, oceans and rivers across the globe and it’s only going to get worse.
The research team examined over 400 ocean dead zones worldwide. A dead zone is what happens in the summer when the temperature of the water rises to a degree at which some species of wildlife die. Generally speaking, this results in the death of crab, fish, oyster and shrimp—which all require oxygenated water.
As the temperature of the water rises, so too does the body temperature of the water-dwellers’ bodies, which increases metabolism. They eat more—notably algae that create oxygen—which then results in smaller amounts of oxygen in the water. According to the data this effect “could quickly cause stress and mortality and, at larger scales, drive an ecosystem to collapse.”
Furthermore, “(c)limate change will drive expansion of dead zones, and has likely contributed to the observed spread of dead zones over recent decades. Temperature is perhaps the climate-related factor that most broadly affects dead zones.”
Less oxygenated warmer water not only adds to the problem from runoff but it also adversely affects dead zones by preventing oxygen-poor deep water from mixing. Andrew H. Altieri of the Smithsonian Tropical Research Institute in Panama and co-author of the study explained: “It’s like Italian dressing that you haven’t shaken, where you have the oil and water separate.”
Keryn B. Gedan, co-director of a conservation program through the University of Maryland and Smithsonian Environmental Research Center researcher and co-author said: “Over 40 percent of the world’s population lives in coastal areas. We depend on these resources. No one wants to see a fish kill or harmful algal bloom at their local beach.”
The study revealed that the number of dead zone events worldwide “have doubled since the middle of the last century.” Additionally, Gedan suggests that humans are probably responsible for the increase in intensity and size.
She concluded: “We just don’t know how much of this (dead zone) doubling is due to climate change or nutrient runoff.” Gedan admits that they require more “sophisticated modeling” to keep current on the changes so that they can make those determinations.
Dead Zones Dangerously Doubling