Algae and Nutrient Sourcing

Stringy, bright-green algae underwater.

NPS

Algae is a natural part of any aquatic environment. Though it often makes swimmers, anglers, and paddlers go, “Ick!,” algae performs important ecological services like oxygen production and nutrient cycling. It also provides food and habitat for a host of organisms. Factors like air/water temperature, sunlight, nutrients, foraging pressure, and rainfall amounts can lead to algal growth. At Buffalo National River, algal growth is most apparent in the summertime, when weather conditions are hot and dry and the river’s current slows.

In high concentrations, algae can harm water quality and aquatic life. As it grows, the oxygen it produces gets trapped within its stringy, “filamentous” texture . This trapped oxygen causes the algae to float to the surface of the water. As algae starts to die off, it is consumed by decomposers that produce carbon dioxide. As a result, the river’s increased carbon dioxide levels and decreased oxygen levels can create unhealthy conditions for aquatic life. In excess, algae may indicate that a waterway contains too many nutrients, possibly caused by sedimentation, human or livestock waste, excess fertilizer, or other factors.

What You Should Know

• People and pets should avoid ingesting or swimming in water near algal blooms
• Too much algae in waterways can lead to dead zones, where aquatic life cannot survive due to low oxygen levels
• 70 80% of the oxygen we breathe comes from algae

A park scientist wearing brown waders and blue gloves collects a water quality sample in the Buffalo River.

NPS

The United States Geological Survey, Arkansas Game and Fish Commission, Arkansas Department of Environmental Quality, and National Park Service are studying the growth of filamentous algae on the Buffalo River. Previous studies suggest that filamentous algae covered an estimated 25 river miles in the summer of 2016, 70 river miles in 2017, and 95 river miles in 2018.

To find the sources of nutrients that lead to excess algae, researchers are collecting samples and monitoring the growth of algae from 25 locations that include springs, shallow wells, and the main channel of the Buffalo. Although it may take years to completely understand the sources and pathways of these nutrients, research suggests that the springs that feed into the Buffalo have relatively high nitrogen levels with low phosphorous levels, gravel bars have high concentrations of phosphorus, and the main channel has concentrations that appear to be uniquely low during the agricultural growing season compared to other times of the year.

As the study continues, researchers are focused on how the nutrients in the river and gravel bars change seasonally in regards to human use and storm patterns. Learn more at: https://www.nps.gov/buff/learn/nature/waterquality.htm

How You Can Help

• Maintain septic systems.
• Reduce fertilizer use near waterways.
• Maintain vegetated streambank buffer.
• Never go to the bathroom in the river or on a gravel bar! “Go” at least 200 ft. away from the water. Bury or pack out solid human waste.
• Support research and efforts to effectively manage the nation’s water resources.