A recent study suggests that drought is the primary factor that results in dead zones in Lake Erie. For years, the lake has been plagued by algal blooms. More recently, however, drought has also caused the emergence of a massive dead zone.
Lead authors of the study Yuntao Zhou and Anna Michalak of the Carnegie Institution for Science at Stanford University revealed that the research involved studying hypoxic events in Lake Erie from 1985 to 2012.
Michalak explained that dead zones are areas of a water body where oxygen levels are very low. These dead zones are usually caused by the influx of nitrogen and phosphorus from fertilizers that run off from agricultural lands.
The researchers reported that each year the size of the dead zone observed at Lake Erie in summer varies. The study measured the size of the dead zones for 28 years and identified the factors that affect the size of the dead zones yearly.
The study found that the drought in 2012 resulted in rivers, which bring water to the lake, to run low. This accounted for the worst dead zone ever recorded.
The researchers cited previous studies that focused primarily on the inflow of phosphorous due to the washing of fertilizers from farms as the driver of the dead zones.
New research is suggesting that the inflow of fertilizers is definitely a cause of dead zones, but the water from rivers that flow into the lake is the primary factor of dead zones in the case of Lake Erie.
The researchers believed that the water flow from river tributaries in 2012, which was at a record low, led to the biggest dead zone observed in Lake Erie. The algal boom was, however, mild in 2012. The study also highlighted that 2011 witnessed a record high algal boom in Lake Erie, but it did not cause a record high dead zone.
Michalak claimed that increased water flow from river tributaries resulted in small dead zones but increased algal blooms.
"In fact, water inflow from rivers alone explains over a third of the year-to-year variability in the size of dead zone, and the mechanisms behind this require further investigation," said Michalak.
The study also found that other factors, such as northwesterly winds that blow in June and wind speeds in July, are also responsible for dead zones and algal blooms in Lake Erie.
The study was published in the journal Environmental Science & Technology.
