The oldest known fossil
Rarely does blue-green algae make the news for something positive.
Recent reports of blooms in other parts of the state have piqued the interest of many who like to visit
waterways with their children and pets.
But what are blue-green algae?
For one thing, it’s not actually algae. When it was first discovered and described, it looked very much like
the green algae in that it was microscopic, free-floating and grew in colonies. And, of course, it had a
blue-green color. But under closer inspection, it does not have the special cell parts that plants and algae
have. Because of this, blue-green algae are considered a type of bacteria and are more properly termed cyanobacteria.
These cyanobacteria are aquatic – they live in the water and are photosynthetic, meaning they can make their
own food. And they are microscopic.
"But I’ve seen a blue-green algae bloom," you say.
Correct. Enough microscopic bacteria grown in colonies can create a mass so large it can be seen. This
mass is called a bloom.
Cyanobacteria have been in the news recently for causing what is called a harmful algal bloom. Because cyanobacteria
are found naturally in all types of water, under the right conditions, a bloom, or in the worst-case scenario a
harmful algal bloom, can happen on just about any body of water. Conditions that promote a bloom are waters that
are warm, slow-moving and nutrient-rich (high in phosphorus and nitrogen). Typical sources of nutrient enrichment
are from point sources such as fertilizer runoff and septic tank overflows. Under these conditions, cyanobacteria
can multiply quickly, creating visible blooms. There also may be blooms that you can’t see. Blooms sometimes stay
below the water surface, or they may float to the surface. The blooms are typically blue, bright green or brown
and sometimes look like paint floating on the water. Cyanobacteria blooms can look like foam, scum, or mats also.
Cyanobacteria aren’t all bad all the time.
Cyanobacteria are actually the oldest known fossils, more than 3.5 billion years old. Many of the oil deposits
from the Proterozoic period (between 2.5 billion to 541 million years ago) are attributed to the activity of
cyanobacteria. And their photosynthesis during this period and before generated the oxygen needed for Earth’s
atmosphere and oceans to become suitable for life as we know it today.
Cyanobacteria make up the oldest fossil record, helped create oil deposits, generated oxygen for the atmosphere
and oceans, and were instrumental in creating photosynthetic plants. The chloroplast with which plants photosynthesize
and make food for themselves, and is a distinguishing feature of plants, is a cyanobacterium that was taken up by
a green algae plant ancestor.
But what about cyanobacteria in today’s world?
Cyanobacteria are photosynthetic, so they do still provide oxygen to the atmosphere. They are also important in the
nitrogen cycle. They are one of the few groups of organisms that are “nitrogen-fixers.” This means they convert
nitrogen from the atmosphere into a form such as nitrate or ammonia that plants use for food. They provide a natural
fertilizer for plants. They are primary producers, providing food for higher trophic level organisms such as fish and
invertebrates. Some cyanobacteria are also used as a food source for humans. The cyanobacterium Spirulina, for
instance, which is high in protein, is consumed as a health food supplement and is sold in stores, usually as a
But beware, not all cyanobacteria are the same.
There are other species of cyanobacteria that produce toxins that are harmful to humans and animals.
Cyanobacteria blooms can cause water quality concerns, including decreased sunlight penetration, oxygen and nutrient
depletion. The blooms can also be potent enough to poison animals and humans. Not every bloom, though, produces
toxins, and you cannot tell by looking if a bloom is harmful or contains toxins. Cyanotoxins must be tested in a
laboratory. This can be difficult as blooms can disappear as quickly as they appear, which means many times the
bloom has passed before testing can be performed.
Specialized laboratories can typically detect the cyanotoxins found to cause illness in humans and animals,
including microcystin, cylindrospermopsin, anatoxin, and saxitoxin.
So, what do you do if you can’t tell whether the bloom is harmful?
Out of precaution, to protect yourself, your family, and your pets from harmful algae blooms, do not recreate in
areas where the water is discolored or where you see foam, scum, or mats of algae. Do not allow children or pets
to play in or drink suspicious-looking or smelling water. And, if you, your children, or your pet does happen to
swim in water that might contain harmful cyanobacteria, rinse off with fresh water as soon as possible.
Cyanobacteria has a long history and can provide benefits to humans and the natural environment. However, when
conditions become unbalanced, and water quality is poor, cyanobacteria can also worsen water issues and cause
harm to humans and animals.
By Jenna Olson
Brazos River Authority Environmental Programs Coordinator