Toxic Algae
Overview
Algae are photosynthetic organisms that are critical to aquatic food webs. An algal bloom is the overgrowth of microscopic algae or algae-like bacteria in fresh, salt, or brackish waters. Depending on the type of algae or bacteria, a bloom may produce bad-smelling scum, foam, froth, or a paint like slick and impede activities like swimming and fishing and cause oxygen depletion. Algal blooms can be many colors, including blue-green, yellow, brown, pink, and red.
Not all agal blooms are toxic but research indicates that a growing number of blooms can produce toxins that are dangerous to humans and other organisms.
Blue-green algae, known as Cyanobacteria, are bacteria that perform photosynthesis like algae. The most frequently reported type of bloom-forming cyanobacteria is Microcystis which can produce dangerous cyanotoxins. Microcystis blooms which accumulate and dry on the shores of lakes can contain high concentrations of microcystin that last several months after the blooms go away. Cyanobacterial toxins can also bioaccumulate in common aquatic vertebrates and invertebrates such as fish, mussels, and zooplankton. Microcystins primarily affect the liver (hepatotoxin), but can also affect the kidney and reproductive system. There is some evidence of an association between liver and colorectal cancers in humans. Other toxic algaes/bacterias are cylindrospermopsin, anatoxins and saxitoxins.
Extent and Impact Of Infestation
Harmful algae blooms occur naturally and as a result of human activities. Human activates have vastly increasied the frequency, prevalence, and toxicity of harmful algae blooms. Algae blooms cause lakes, reservoirs, and rivers to become unsightly and at times dangerous, reducing tourism, recreation, commercial fishing, and property values and increasing water quality monitoring, management, and treatment costs. Estimates have suggested freshwater blooms may cost the nation $4.6 billion annually.
Various reasons for the increase in algae blooms are as follows. Nitrogen and phosphorus from agricultural and urban runoff into rivers, lakes, ponds, and reservoirs act like fertilizer to promote the growth of algae and bacteria. According to the U.S. Environmental Protection Agency’s most recent surveys on national water quality, nutrient pollution in the United States is a problem in more than one-third of lakes and about half of all rivers and streams.
Warming water also contributes to increased frequency as it gives cyanobacteria a competitive advantage. These bacteria grow faster than more benign algae in higher temperatures and once a bloom forms, the dark surfaces of the algae mats absorb more sunlight, which leads to warmer water and more algal growth. Climate change is both increasing the frequency and duration of droughts in many parts of the country and intensifying extreme storms. Periods of drought interspersed with strong precipitation increase runoff from agricultural lands, lawns, and other sources, leading to higher nitrogen levels in rivers—and therefore harmful algal blooms. Burning fossil fuels, deforestation, and land development are increasing the amount of carbon dioxide in the atmosphere. This fuels harmful algal blooms because cyanobacteria can feed on the carbon dioxide not only present at the surface of a water body but also dissolved in the water. And when algae die and sink to the bottom of a freshwater body, they decompose and release carbon that was once sequestered, providing more fuel for cyanobacteria growth. Climate change and more severe droughts also modify the flow regime in freshwater bodies and can increase competition for ever-scarcer freshwater supplies. Reduced flows in waterways means the remaining water will be warmer and more stagnant, creating conditions ripe for algal blooms.
People can be exposed to algae toxins by swallowing or swimming in affected waters, eating poisoned fish or shellfish), or inhaling airborne droplets of affected water. Pets are vulnerable to toxic algae too—dogs in particular, because they’re most likely to swim in or drink the water. A recent paper published in the journal Toxins found 63 dog deaths associated with HABs in 13 states.
It is estimated that some 30 to 48 million Americans get their drinking water from lakes and reservoirs that could be periodically contaminated by algal toxins. Boiling algae contaminated water does not destroy toxins, but can in fact increase their concentration. Drinking water treatment facilities can remove algae toxins but must be up to date and well maintained or the bacteria can remain in the water. In 2014, for example, a major algae bloom in Lake Erie prompted the city of Toledo, Ohio, to issue a “do not drink” order for tap water that affected nearly 500,000 people for three days and sickened more than 100.
The toxins released from algae blooms can cause large-scale fish kills, impacting mammals, birds, and other wildlife that feed on grasses, shellfish, or fish tainted with toxins. Texas recently experienced a major fish kill that devastated Lake Texoma, a reservoir on the Oklahoma-Texas border. Approximately 157,000 fish died in just three days due to a golden algae bloom. Fish kills in Lake Texoma have been reported since 2004 when almost half of the reservoir’s one million fish died. Statewide, from 2001 to 2010, golden algae blooms caused more than 130 major fish kills and resulted in the loss of more than 34 million fish, costing the Texas economy more than $14 million in revenue.
Even nontoxic algae blooms can have a detrimental impact on aquatic ecosystems in the form of dead zones, areas in a water body with so little oxygen that aquatic life can’t survive. According to the EPA, more than 166 dead zones have been reported nationwide. The largest, which happens every year in the northern Gulf of Mexico at the mouth of the Mississippi River, is estimated to occupy more than 8,500 square miles, an area the size of Massachusetts.
Algae blooms can also create a turbid (cloudy) underwater environment, one that prevents much of the sun’s light from reaching bottom-dwelling organisms, including plants. Underwater plants are a critical source of food and shelter for other organisms, and without them entire aquatic food webs and ecosystems can suffer. For example, algal blooms killed off much of the eelgrass in the Chesapeake Bay area leading to the decimation of blue crab population, which plummeted by nearly 70 percent between the early 1990s and 2007.
Status Of A Solution
We are in negotiations for five candidate microbes that could potential be suitable algaecides but they require further research, proof-of-concept, toxicology and manufacturing feasibility studies before being offered to third parties for commercialization.
