Study Finds Phosphorus Level That Leads to Declines in Stream Water Quality

The study, which is the first to utilize the new Baylor Experimental Aquatic Research (BEAR) stream facility, demonstrates with certainty that an amount of phosphorus over a certain level does indeed cause negative changes observed in many Texas streams.

“This study is the first to really link nutrient field observations to controlled experiments and allows water managers to use the research as the scientific basis for water management strategies,” said Dr. Ryan King, associate professor of biology at Baylor, who led the study. “We were able to link cause and effect and show that the ecology of the streams is very sensitive to phosphorus.”

According the scientific literature, nutrient pollution – specifically phosphorus – is the most common cause of poor water quality in lakes, streams and wetlands in the United States. For instance, one of the most noticeable consequences of nutrient pollution is the accelerated growth of aquatic vegetation, like algae, which produces an undesirable disturbance to the balance of organisms present in the water. Explosive growths of nuisance algae can taint drinking water, cause foul odors and can result in dissolved oxygen shortages that kill fish and other aquatic organisms.

In Texas, phosphorus has been identified by the Texas Commission on Environmental Quality as the nutrient that would have the most effect in limiting algal and plant growth. However, until now, numerical nutrient criteria to control phosphorus levels have largely been developed subjectively and without experimental evidence to support them.

The Baylor researchers collected water nutrient samples and measured algae and aquatic vegetation growth over a two-year period from 26 different streams in Texas. They compared phosphorus levels to how much algae and aquatic vegetation was present. The researchers then conducted controlled experiments at the BEAR facility by dosing the streams with various phosphorus levels.

In both field observations and BEAR experiments, King and his team found that concentrations of phosphorus above 20 ppb are linked to declines in water quality and aquatic plant and animal life. They found filamentous algae levels dramatically increased with higher phosphorus levels, while the thickness of periphyton, which are algae attached to rocks, and the amount of aquatic plans declined. King and his team also found the level of dissolved oxygen, which is important for fish survival, plummeted when phosphorus levels were higher than 20 ppb and the stream’s water flow was low.

Dr. Bryan Brooks, associate professor of environmental sciences at Baylor, and several Baylor graduate students also collaborated on the project.

About BEAR

The only one of its kind at an academic institution in the United States and one of a few in the world, the Baylor Experimental Aquatic Research (BEAR) stream facility is outfitted with 12 miniature “real life” streams, which can be manipulated to look and act like streams found across central Texas and in other regions. The streams measure 60 feet in length and allow researchers to test aquatic contaminants in a controlled setting. In addition to the model streams, the research facility is outfitted with 24 model wetlands and is located near the Waco Wetlands west of the city limits.