What is Algae? A unicellular plant that produces oxygen and plays and important role in the aquatic food web.

• The Good...
  A good diversity of algae is important to the ecosystem of a natural water body. It provides food and habitat/cover for the macroinvertebrates and fish living in the pool, provides ozygen, and consumes nutrients.
• The Bad...
  Filamentous Blue Green and Green algae can form large nuisance mats that reduce diversity. In more stagnant waters, these "blooms" could increase to the point where their decomposition would rob the water of oxygen and cause fish kills. This would probably not happen in Barton Springs unless flow was extremely low.
• The Ugly...
  Though primarily a nuisance that poses no health risks to humans, algae produce oxygen "bubbles" when sunlight hits them. This lifts the broken pieces to the surface of the water. This normally happens in the afternoon when there are more swimmers causing increased turbulence.

CAUSES

• Rainwater. Rainwater washes nutrients and other pollutants from the land into the caves and sinkholes that recharge the aquifer. The pollutants then discharge at Barton Springs.
• Nutrients. Algae naturally results from a combination of the nutrients, nitrogen and phosphorus. The most common source of excess nutrients is fertilizer, but there are many others, such as phosphate detergents and wastewater leaks.
• Summer Heat. As the summer days get longer and hotter, the increased sunlight and surface water temperatures result in an increase in nuisance algae growth in the pool.
• Drought. This summer's drought has reduced the amount of water flowing into the springs in half -- from an average of 32 million gallons a day to around 16. This slows down movement of water through the pool and prevents much of the algae from being flushed out.

What is the City Doing to Help?

• Clearing the floating algae daily with a large skimmer net
• Increasing turbulence with an underwater fire hose during weekly cleaning to scour the algae and wash it downstream
• Opening the adjustable gate on cleaning day to release algae from the pool
• Cleaning the shallow end several days a week as attendance allows
• Testing the benefits of leaf litter bags to inhibit algae growth
• Testing a gutter system near the diving area to siphon off surface algae downstream of the pool
• Reintroducing native vegetation in the pool (August) to compete with the algae for nutrients. Native vegetation also provides habitat for invertebrates and fishes which feed on the algae

Investigations: Algae Growth and Control

• Investigate other unique algae control technology. Ultrasound involves inaudible sound waves that vibrate at a frequency above human hearing. When ultrasounds are applied to the water, the waves produce cavitation, a phenomenon that damages the cells of algae. Because we are unsure how the ultrasonic waves affect beneficial algae or the Barton Springs Salamanders, we will be experimenting with underwater ultrasound algae inhibition devices to determine if they are safe to use in Baron Springs Pool. If they are safe, we can deploy them in limited areas of the shallow end during drought conditions.
• Research possible causes for algae growth. A periphytometer is an apparatus that helps identify the nutrient dynamics of a body of water. The apparatus will be placed in Barton Springs Pool and Bear Creek from July 6, 2006 - July 20, 2006. By the end of July, after additional field and lab experiments using the collected samples, we will have greatly furthered our understanding of which nutrients in Barton Springs Pool are controlling algal productivity. Most importantly, this information will assist the City in protests to the TCEQ regarding additional nutrient threats to the aquifer in the form of proposed wasterwater effluent discharges.
• Research impacts of fertilizer on water quality. The Water Quality Protection Section is partnering with the LBJ Wildflower Center to study the impacts of fertilizer on leachate to the aquifer. Working with three major fertilizer companies (Scotts, Lebanon, and Purcells), the project will identify low impact fertilizers and will test the long-term viability of unfertilized turf and native grasses that have the potential to replace lawns.
• Review current City of Austin erosion/sedimentation control guidelines. Nutrients absorbed to sediment particles may be increasing algae problems in the pool as well as increasing turbidity. Recent innovations in erosion control techniques will be reviewed for inclusion in the City's Criteria Manual.

How Can YOU Help?
Ask for your copy of the Green Neighbor booklet at the Pool Office, for a comprehensive and practical guide to water quality protection or ask if you can borrow a skimmer to help clean the pool!