The Spread of Freshwater Harmful Algal Blooms
 |
| Harmful algal bloom (Planktothrix agardhii) on Grand Lake St. Marys in Ohio |
Cyanobacteria were among the first photosynthetic organisms
on earth, and are hypothesized to have been the organisms that eventually
became chloroplasts in eukaryotic plants through an endosymbiotic relationship.
Despite their importance in generating oxygen in earth’s atmosphere as life
first evolved, they’ve become quite a problem in water bodies throughout the
world today.
Cyanobacteria are found in both fresh and salt water and their
excessive growth can lead to harmful algal blooms. They can sequester nutrients
faster than other types of algae and often grow at higher temperatures than
other algae. They also can regulate their position in the water column,
allowing them to outcompete other types of algae for light and nutrients. They
can often dominate warm, nutrient-rich bodies of water in the summer. If they
outgrow their nutrient supply or conditions change, the cells may die,
resulting in an unsightly surface scum.
Not only are the blooms unsightly, but they also have
wide-ranging impacts on wildlife, people, and society as a whole. Cyanobacteria
consume oxygen as they respire at night, and in high abundance they can deplete
oxygen levels in the water, resulting in fish kills. Additionally,
cyanobacteria are poor quality food for zooplankton and fish compared to other
types of algae due to their low nutritional value, and the dominance of
cyanobacteria in the water column may result in reduced fish populations.
Cyanobacteria impact humans as well. Some species also create toxins, which are
harmful to humans and wildlife, as they can cause problems with the skin,
liver, and brain. Many also produce chemicals that cause a bad taste and smell
in the water. Blooms that occur in water bodies used for drinking water can be
extremely costly, as advanced water treatment techniques are required to make
the water safe for consumption.
 |
| Bloom on Grand Lake St. Marys, Ohio (Credit: EPA) |
What’s being done to stop the spread of harmful algal
blooms? Many solutions have been proposed for mitigating cyanobacteria growth,
and thus harmful algal bloom occurrences, in water bodies, of which the primary
goal is almost always to reduce nutrient concentrations. With lower nutrient
concentrations, faster-growing algae can outcompete cyanobacteria, which have
slow growth and reproduction rates. Using grassy “buffer strips” along creeks
adjacent to farmland has been shown to reduce nutrient loading and subsequently
the occurrence of harmful algal blooms, as has the construction of wetlands in
lakes near incoming streams high in nitrogen and phosphorus. In private ponds,
cyanobacteria are much more manageable. Barley straw has been shown to inhibit
cyanobacteria and other algal growth. Blue dyes can limit the amount of light
available to algae and inhibit growth as well. Additionally, as with large
lakes, the construction of wetlands can reduce nutrient concentrations in the
water column.
While water bodies may be managed to reduce the possibility
of harmful algal blooms occurring, it may not be enough. Blooms continue to
increase in frequency and range worldwide with increasing water temperatures
from climate change, as well as increased nutrient loading to water bodies from
industrial and agricultural runoff. As harmful algal blooms spread across the
globe and their impacts are realized first-hand, we may only hope that
continuing research and water management will eventually yield a solution to
this growing problem.
Links for additional information:
:)
ReplyDelete