NASA has created new maps showing the grim reality of marine dead zones.  These areas of deep water where oxygen levels are too low for marine life to survive have grown at a staggering pace since the middle of the 20th century.

The dead zones are created when fertilizer run off from crops makes it into the ocean, creating massive algae blooms.  When the algae dies, it sinks to the bottom where microbes decompose the matter, which consumes oxygen and creates a suffocating environment for marine life.

NASA was able to located the areas where this was occurring by using satellites that detect high concentrations of particulate organic matter.  Those high concentrations are a signal of extra fertile areas that lead to dead zones.

The dead zones are mainly located along the coasts of large population centers, with the east coast of the U.S. and the coasts of Northern Europe having the largest numbers of these zones.

Since the 1960's, the creation of dead zones has snowballed, with the total amount of area occupied by dead zones now equaling 152,000 square miles and 400 different ecosystems being affected.

via Yale e360

Climate change is having a dramatic affect on the oceans -- rising sea levels, warming temperatures, increased acidity -- all of which will take its toll on sea life.  The clownfish will have a particularly hard time surviving, as scientists have discovered that rising CO2 levels in the oceans alter their sense of smell, preventing them from evading predators and finding shelter.

Researchers at James Cook University simulated CO2 levels within the range predicted for the end of the century with clownfish larvae.  The experiments tested their behavior at increasing concentrations.   At 550 ppm of CO2, the current concentration, larvae were able to detect a predator and swim in the opposite direction, but as the concentrations rose to 700 ppm, only half the larvae swam away, with the other half swimming toward a predator.

At the highest concentration, 850 ppm, their sense of smell was completely askew and all larvae swam toward the predator.

The same researchers carried out experiments last year that showed that rising CO2 levels also prevented baby clownfish from being able to find their way home.

The researchers think that the CO2 could be affecting the fishes' neurons and confusing how they perceive threats and interpret smells and that other fish will likely be similarly affected.

via Discover Magazine