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Water Today Title December 15, 2017

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Why a lake near you might start glowing and why you should worry

New study finds that algae blooms create their own favorable conditions

By Kelly Broom
Fact Checked by U of Darthmouth, Kathryn L. Cottingham


Cyanobacteria, also called Blue-Green Algae and 'pond scum', can produce Harmful Algal Blooms containing toxins that can kill fish, mammals, and birds, and may cause human illness. This is what happened on July 19, 2014, when microcystin toxins slipped through Toledo's Collins Park eight-phase Water Treatment Plant, triggering a 'do not use' warning for over 400,000 Toledo residents, and a state of emergency declaration. Microcystin toxins are heat stable which means cooking won't destroy them. The toxins can be inhaled, absorbed, and ingested, which is why Toledo residents were told not to bathe or wash in it.
There are over 1100 different species of Cyanobacteria which are ubiquitous in our environment. They can be found on earth in the biosphere (areas occupied by living organisms), cryosphere (cold or frost areas), hydrosphere (all waters including lakes, rivers, seas, and airborne clouds), and the lithosphere (the crust and upper mantle of earth). Some species can produce multiple types and variants of cyanotoxins at the same time.
According to Health Canada, "Microcystins are extremely stable in water because of their chemical structure, which means they can survive in both warm and cold water and can tolerate radical changes in water chemistry, including pH. So far, scientists have found about 50 different kinds of microcystins. One of them, microcystin-LR, appears to be one of the microcystins most commonly found in water supplies around the world. For this reason, most research in this area has focused on this particular toxin."
It was long thought that the primary sources of cyanobacteria are runoff of fertilizers, animal manure, sewage treatment plant discharges, storm water runoff, car and power plant emissions and failing septic tanks. Now, a new multi-institution study shows the aquatic microbes themselves can drive nitrogen and phosphorus cycling in a combined one-two punch in lakes.

Algae Blooms set up a "positive feedback loop", creating their own favorable conditions

Cyanobacteria as biological drivers of lake nitrogen (N) and phosphorus (P) cycling, published in January 2105 and headed by U of Darthmouth professor, Kathryn L. Cottingham, shows the aquatic microbes themselves can drive nitrogen and phosphorus cycling in a combined one-two punch in lakes.

The study demonstrates that blooms of cyanobacteria in low-nutrient conditions can cause a shift to the high-nutrient state by reducing the resilience of the low-nutrient state" and cause fresh water dead zones (from lack of oxygen) and "eutrophication by bringing both nitrogen and phosphorus into the water column."

Human actions such as phosphate mining are altering the global phosphorus cycle and causing phosphorus to accumulate in some of the world's soil. Increasing phosphorus levels in the soil elevate the potential phosphorus runoff to our aquatic systems. Scientists estimate the increase in phosphorus storage in terrestrial and freshwater ecosystems to be at least 75% greater than preindustrial levels of storage. Professor Kathryn Cottingham says "this is the main problem causing cyanobacterial blooms".

According to the study, "Blooms are reported to be increasing in many areas due to warmer temperatures and stronger stratification" and soil erosion "due in part to global climate change" When cyanobacteria get a toe-hold in healthy, pristine (oligotrophic) lakes they can set up a "positive feedback loop" (called biogeochemical cycling) that amplify the effects of pollutants and climate change and make conditions more favourable for algal blooms which threaten water resources worldwide.

Biogeochemical cycling is the natural movement of nutrients between living organisms and the atmosphere, land, and water. The researchers found that cyanobacteria can change the amount of nutrients and oxygen in a lake "by tapping into sources of phosphorus and nitrogen not usually accessible to phytoplankton,"possibly by unlocking the electrons that bind oxygen to iron (Fe) and aluminum (Al). The ability of many cyanobacterial organisms to fix dissolved nitrogen gas is a well-known potential source of nitrogen, but some organisms can also access pools of phosphorus in sediments and bottom waters. Both phosphorus and nitrogen nutrients "can then be released" by cyanobacteria "into the water column via cellular leakage or decomposing organisms, thereby increasing nutrient availability for other phytoplankton and microbes."

The study demonstrates how cyanobacteria can affect phosphorus recycling:
"Cyanobacteria can "overwinter on or near lake sediments, access sediment phosphorus, and then transport it upward during seasonal recruitment;

"In stratified lakes, cyanobacteria sink to the hypolimnion (bottom of the lake), acquire phosphorus, and then rise back to the surface during diel vertical migrations" (of organisms); and

"Benthic cyanobacteria enhance phosphorus release from sediments, increasing near-sediment phosphorus and also storing it in bodies."

Inorganic phosphorus is negatively charged in most soils. Because of its particular chemistry, phosphorus reacts readily with positively charged iron (Fe), aluminum (Al), and calcium (Ca) ions to form relatively insoluble substances. When this happens, phosphorus is considered fixed or tied up. Cyanobacteria can break those electron bonds and "increase access to phosphorus in the water that would not normally be available in surface waters, especially in the well-oxygenated, low-nutrient systems in which redox-mediated recycling of sediment phosphorus occurs rarely, if at all."

Nitrogen fixation happens during dark periods with non-photosynthetic cells, and photosynthesis happens during light periods with the outer green cells. These actions all help "cyanobacteria fix nitrogen and release fixed nitrogen into the water column in biologically available forms, such as ammonium." "Cyanobacteria have the potential to provide both nitrogen and phosphorus to the water column - nutrients that can then be released to the rest of the lake system by cellular leakage or viral lysis (death)."

If there are too many nutrients in the water, phytoplankton can become excessive, die, and sink to the bottom. Rapid decomposition of the phytoplankton can cause oxygen depletion (anoxia) and fish to die from lake eutrophication which then affects drinking water quality.

The study was funded by the National Science Foundation and co-authored by freshwater ecologist Kathryn Cottingham at Dartmouth, ecosystem ecologist Holly Ewing and mathematician Meredith Greer at Bates, freshwater ecologist Cayelan Carey at Virginia Tech and biogeochemist Kathleen Weathers at the Cary Institute of Ecosystem Studies.

More info
Lake stratification is the separation of lakes into 3 layers: Epilimnion - top of the lake; Metalimnion (or thermocline) - middle layer that may change depth throughout the day; and the Hypolimnion - the bottom layer.
Diel vertical migration is movement by an organism to the surface of the lake or ocean at night and returns to the middle of the lake or ocean during the day.
Cyanobacteria toxins include: anatoxin, anatoxin-a, cylindrospermopsin, LPS endotoxins, microcystins, nodularin, and saxitoxins.

More about Cyanobacteria:

There are currently over 1123 different species, genuses, families, orders, and classes of Cyanobacteria with 60 assigned genera names

In 2004, 36 countries at the VIth International Conference on Toxic Cyanobacteria stated substantial gaps remain in the understanding ahd recognition of the hazards and risks of cyanobacterial cells and their toxins

The World Health Organization (WHO) Working Group on Protection and Control of Drinking-Water Quality identified cyanobacteria as one of the most urgent areas in which guidance was required. During the development by WHO of the Guidelines for Safe Recreational-water Environments, it became clear that health concerns related to cyanobacteria should be considered and were an area of increasing public and professional interest

As of 2010, the WHO only has guideline values or standards for Cyanobacterial Microcystin toxins in drinking water

A cyanobacteria bloom developed in Australia's Warragamba Dam in August 2007, and persisted over three months. The cell count of Microcystis exceeded 100,000 cells/mL in the first week of September 2007, and reached 700,000 cells/mL near the dam wall in October 2007. More than 120 water samples were tested for toxins, and all but four detected no toxins. On the four occasions where toxins were detected, the toxin levels were well below the guideline values, and immediate re-sampling of the same sites detected no toxins

In 1996 in Brazil 131 dialysis patients were exposed to microcystins from the water used for dialysis, 56 died.

Phosphorous (P) is used in fertilizers, animal feeds, agricultural crops, and other products (such as: flame retardants, paper, glass, plastics, rubber, pharmaceuticals, petroleum products, foods, toothpaste, baking soda, matches, pesticides, nerve gases, soda pops, detergents, water softeners)

Nitrogen (N) is used: in ammonia, in steel, as a refrigerant to keep things cold, to refine oil, make gasoline, over 78% of air is made up of nitrogen, and to help plants grow.

Carbon dioxide (CO2) is used in: Food & Beverages: Carbonation, CO2 Snowing, Flour & Dough cooling, Freezing & chilling, Greenhouse growing, Meat mixing;
Healthcare: Respiratory Therapy & Pulmonary Function Testing;
Oil & Gas: Enhanced oil recovery, Well hydraulic fracturing;
Pulp & Paper: Screening, Washing;
Waste & Wastewater Treatment: for pH Control;
Welding & Metal Fabrication;
Other Industries in: Chemicals, Electronics, and Pharmaceutical & Biottechnology.

Other well-known Biogeochemical Cycles include the: carbon cycle, nitrogen cycle, oxygen cycle, phosphorus cycle, sulphur cycle, water cycle, and the rock cycle

Cyanobacteria, through the Calvin cycle process, turn carbon dioxide from the air into sugar, the food autotrophs need to grow.

The Calvin cycle is a process that plants and algae use to turn carbon dioxide from the air into sugar, the food autotrophs need to grow.

Aquatic ecosystems include: rivers, streams, lakes, wetlands, and the groundwater systems that are linked to them.

Terrestrial ecosystems include: tundra, taiga, temperate deciduous forests, tropical rain forests, grasslands, and deserts.

Freshwater ecosystems include: lakes, ponds, rivers, streams, springs, and wetlands compared with marine ecosystems which have a larger salt content.


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