Human Activities Trigger Hypoxia in Freshwaters Around the Globe
A new study shows that the increase in human activities and nutrient release have led to the current rise in the number of hypoxic lakes worldwide.
This is an underwater view of a lake bed and varved sediment core. Credit: Nordic Moonlight
This finding has just been released in the journal Global Change Biology. The international research team has found out that the onset of lacustrine hypoxia is mainly due to direct and local anthropogenic impacts rather than to recent climate change. The study also showed that aquatic rehabilitation programs have failed so far to return lake bottoms to their original well-oxygenated status.
Dissolved oxygen is fundamental to the health of lakes and streams, and the recent oxygen depletion of bottom waters (hypoxia) is a major threat to freshwater resources. Both eutrophication (caused by an excess of nutrients) and climate change can deplete bottom-water oxygen. But it is difficult to identify the main forcing factor between these two since they have confounding effects. Moreover, hypoxia can also have a natural origin. Continuous long-term monitoring of lake-water oxygenation would be required to clearly determine the cause of hypoxia, but these records are rarely available.
http://www.sciencenewsline.com/news/2016010620010032.html