Signs of Summer 16: HAB’s on The Plains!

Cyanobacteria bloom. Photo by C.Fischer, Wikimedia Commons

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I have written about Harmful Algae Blooms (HAB’s) a number of times before. These HAB’s include the noxious red tides on the Florida coast ( Signs of Winter 2, December 13, 2018), the explosive growth of sargassum seaweed out in the Atlantic and in the Gulf of Mexico (Signs of Winter 3, December 20, 2018) and the once occasional but now seemingly seasonally occurring “blue green algae” infestations of the western sections of Lake Erie (Signs of Summer 11, August 29, 2019). It turns out that moving away from these oceans, coastlines and large lakes doesn’t guarantee that HAB’s will stay far away. There are HAB’s happening all over the state of Colorado!

All of these different types of algal blooms essentially follow the same causal sequence. They each involve the inflow primarily of phosphate-rich fertilizers into surface water that has been significantly warmed during a long, summer season. Shallow waters will warm faster, so bodies of water like Lake Erie (the shallowest of the five Great Lakes with an overall average depth of only 62 feet including a particularly shallow western basin (average depths there are between 25 and 32 feet)) will warm relatively quickly. Shallow ocean water on the coasts especially if they are being fed by currents that have been warmed as a result of ongoing Climate Change  will also reach the critical temperature threshold for rapid algal growth.  If the requisite nutrients are then added algae species will grow at a very rapid rate.

Some of the stimulated algae species are green algae which serve as the foundation for the robust food chains in both freshwater and also marine ecosystems. The stimulation of these green algae, within limits, can be overall beneficial to the productivity of the aquatic ecosystem.

Red tide. Photo by NOAA, Public Domain

Unfortunately, though, these phosphate-fed, summer-warmed algal blooms do not just involve the green algae. In coastal marine ecosystems dinoflagellate algae are important components of the phytoplankton base of the marine food chain. Some of these dinoflagellate species, like Karina brevis, explode in numbers in these marine ecosystems when excessive phosphate nutrients are combined with warm water temperatures and favorable winds and currents. These dinoflagellates have very complex pigments that are associated with their photosynthetic metabolic pathways. When their numbers are overstimulated, these pigments build up in the ecosystem and can reach toxic levels. This generates the ocean shoreline phenomenon called a “red tide” which can lead to significant mortality in marine invertebrates and fish and render a coastal area unusable for food gathering or recreation.

In warmed, fresh bodies of water, the influx of nutrients can stimulate the growth of cyanobacteria (also called “blue-green algae”). Cyanobacteria are found typically in small numbers in the complex bacterial community of almost all freshwater ecosystems. Cyanobacteria can also synthesize complex protein toxins. These proteins are probably weapons used by the cyanobacteria in the intense, on-going chemical battles with other bacteria in their crowded, resource limited, aquatic habitats. The cyanobacteria have existed for nearly three billion years and so, as a result of competition and evolution, have generated an incredibly diverse array of these survival tools. As a result they can synthesize three to four hundred different, toxic peptides.

Cyanobacteria bloom. Photo by ECTran71,, Wikimedia Commons

Usually, cyanobacteria are a small, non-threatening part of the freshwater microflora, but they  respond very vigorously to added phosphates! Also, cyanobacteria need water temperatures above 20 degrees C (64 degrees F). Temperatures that warm can be easily generated in small, shallow lakes and ponds and also in larger lakes if summer temperatures have been consistently warm.

There are a few other interesting features of cyanobacteria also come into play during a bloom: 1. Cyanobacterial cells contain gas filled, intracellular vacuoles (therefore they float!),  2. Cyanobacteria require high levels of sunlight to run their photosynthesis (therefore they NEED to be on the top of the water),  3. Cyanobacteria are not very high quality food sources for zooplankton (so they tend to get left behind after feeding and grazing … maybe the peptides have something to do with this, too?), 4. Cyanobacteria clump together into large colonies (which may be too large for most zooplankton to easily consume), and 5. Cyanobacteria can obtain the nitrogen they need to grow directly from the nitrogen gas of the atmosphere (they are “nitrogen fixers”).

Cyanobacteria. Photo from Piclist.

So, the floating, clumped together masses of cyanobacteria when they get their population boost from the phosphates and the warm temperatures of the water and since they are already making the nitrogen that they need, tend to survive and accumulate in their ecosystems and crank out their hundreds of different toxic peptides! These toxins then can sicken and/or kill fish, waterfowl, livestock, dogs, and even people! There is also a concern that chronic, low level ingestion of these toxins can lead to liver damage and even liver cancer! Drinking water taken from surface water sources needs to be checked for these dangerous bacteria!

So far this summer there have been numerous cyanobacterial blooms across the state of Colorado. The expected peak of cyanobacteria activity typically occurs in August and September and, so, we are just in the middle of the potential peak of activity. Cherry Creek Reservoir in Denver, Prospect Lake and Pikeview Reservoir  in Colorado Springs, Bear Creek Reservoir in Lakewood, Barr Lake near Brighton and Steamboat Lake near Clark and a large number of smaller lakes and ponds have all reported the presence of cyanobacteria.  Almost all of these sites also had significant cyanobacteria blooms last year, too. Closer to home here in Greeley, the Cache de Poudre River last year had significant cyanobacteria blooms especially in its attached wetlands and ponds, and the reservoir in nearby Windsor was closed for a week last July because of a cyanobacteria bloom.

The reports of these cyanobacteria explosions are getting more numerous and more widely spread with each passing year. Increased summer temperatures and increased human population densities around the bodies of surface waters are all suggested to be contributors to this rise. More people means more pollution not only from agricultural and municipal waste sources but also from unregulated fertilizer use on lawns and uncollected pet waste from around the ponds and reservoirs. The abundant, shallow reservoirs all across the state are used for both drinking water and also for recreation. The growing presence of cyanobacteria in them represents a significant ecological, economic and public health hazard.

 

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One Response to Signs of Summer 16: HAB’s on The Plains!

  1. Jim Sampson says:

    I am Don Wicks brother-in-law. Please add me to your distribution list. I enjoy seeing these and keep learning.

    Jim Sampson

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