News Flash

Urban Biologist

Posted on: July 7, 2017

Algae in Dallas Park and Recreation Lake


Summer is the time of year where we start seeing various shades of green, blue, red and brown in Dallas area water bodies.

These different colors are typically associated with different types of algae. Algae is a generic term that covers many different organisms from single cell bacteria to large, multi-celled organisms. Algae may appear as pond scum, long fibers, or cause the water color to  suddenly change.  

What ties them all together?  They all get their energy from the sun through photosynthesis and get their nutrients from the water.

What is an algae bloom?  Algae is always present in Dallas area waters.  They are a critical ecosystem component, in that they provide food and through photosynthesis, help with oxygen in the water.  However, through the process of eutrophication (enrichment of a water body with excessive nutrients), some species of algae can flourish to nuisance and dangerous levels.  How fast this happens is driven by nutrient levels, ph of the water, increased water temperature, the amount of sunlight hitting the water, mixing by the wind, and area water/land management practices.  In other words, during a Texas summer, it can happen very rapidly.  As the algae starts to use up the nutrients, it begins to turn brown and die.  When algae starts to die, combined with warmer water temperatures, the dissolved oxygen content of the water drops quickly. This is the oxygen available to fish, and as the level drops, we start to see fish kills.  

What is a cyanobacterial bloom?  Cyanobacteria is also known as blue-green algae.  With the right combination of nutrients (nitrogen and phosphorus), water temperature and sunlight, a “cyanobacteria bloom” can occur. Some species of cyanobacteria, like Microcystis sp., can produce what is known as a cyanotoxin.  This toxin can make humans sick, but is potentially VERY dangerous to dogs that may drink or swim in the water.  This is the type of algae bloom currently (June/July 2017) being seen in Lake Cliff Park. The bright neon green, and general pea soup appearance of the water is characteristic of this type of blooming event. 

Where do the nutrients come from?  The main nutrients in question are nitrogen and phosphorus.  Nitrogen can get into the parks’ lakes from many sources, and not just close to the lakes. The lakes in Dallas parks are often the recipient of large amounts of stormwater runoff.  That runoff may contain leaves and grass clippings which can decompose, dog and wildlife fecal matter, and fertilizer.  All of these add to the nitrogen getting into the water. Phosphorus tends to bind tightly to soil.  This is why sediment from erosion becomes a major water quality issue.  As the soil settles into a water body, the phosphorus slowly leaches off of the soil and into the water.  Algae blooms are often driven by the amount of phosphorus that has gotten into a water body.  A particularly rainy Spring/Summer, with high volume rain (ie flooding) events may help trigger algae blooms as the water heats up in the summer.

How does the Dallas Park and Recreation Department minimize the potential for algae blooms?  The Dallas Park and Recreation Department takes several steps to help minimize and the react to algae blooms if necessary.

  • Through Integrated Pest Management (IPM) practices, the department works to minimize the amount of fertilizer and other chemicals that are used on park properties.
  • Where practical, a 5-7 foot vegetated buffer strip is maintained along shorelines to help act as a filter for nutrients and help control erosion.
  • Ponds and lakes are chemically treated as part of routine maintenance, with EPA approved chemicals that help keep nutrient levels in check.  This does not prevent algae from occurring, but minimizes the chances of a nuisance or harmful algal bloom (HAB).  It is important to note that following large amounts of rain, the nutrient load may exceed what is normally taken care of through routine maintenance.
  • Park Department staff monitor park ponds and lakes for the presence of algae, and will report to and work with other city and state agencies when an issue is noted. This may lead to additional and/or more extensive water quality testing, and additional water treatment if needed.
  • Encouraging park users to pick up dog waste.  Dog waste can be a significant contributor to nitrogen levels.  This is extremely important around dog park areas and near bodies of water.
  • Where appropriate, water display fountains are installed.  These fountains help circulate the water and keep the dissolved oxygen content up in the water.
  • If a potentially hazardous condition occurs, the department will take steps to minimize the hazard to the general public.  

How can YOU help with minimizing algae blooms in Dallas?  There are multiple ways you can help minimize algae issues in Dallas.

  • Work to maximize the efficiency of fertilizer in your yard.  That means the fertilizer stays in your yard.  Test your soil so you only put the nutrients your yard needs. Make sure whatever fertilizer you may use is carefully watered in so that it does not end up getting washed away in a big rain event.
  • Do not sweep your yard clippings into the street.  As much as possible, mulch your grass.
  • PICK UP YOUR DOG’S WASTE and properly dispose of it.  This is especially important around the dog parks.
    DO NOT FEED THE WATERFOWL AROUND THE LAKE.  This tends to concentrate the ducks and geese to one small area, and significantly increases the nutrient load in that area.  They will find food without you feeding them.
  • Watch for significant soil in runoff water, especially around construction projects. Soil is a major contributor to phosphorus levels.  If you see significant amounts of soil leaving a specific site, please submit a report to 311.
  • If reports and signs are put up regarding HAB conditions at a particular pond or lake, please avoid contact through swimming (not allowed anyway), fishing or allowing your dogs to have contact with the water until otherwise notified.

We can never completely stop an algae bloom from happening in an ecologically responsible manner. However, we can take steps to minimize the chances of them occurring.  If an algae bloom does occur, there are steps that can be taken to minimize potential health and ecological hazards.  Also remember, most algae blooms are more of a nuisance and not a health hazard.

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