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