top of page

Harmful Algal Blooms

Harmful algae bloom off the coast of San Diego County, California. Photo by NOAA, Kai Schumann.

June 17, 1793 Seaman John Carter on George Vancouver’s voyage of discovery along the coast of British Columbia died. A few days earlier Seaman Carter and some others ate fresh mussels that they collected in a cove along the coast. Within a few minutes, their lips and fingers became numb. The numbness progressed to paralysis. All but Carter recovered ( Years later it was determined that Seaman Carter had become the first recorded European to die from exposure to ‘the Red Tide” in the new world.

The Red Tide is an example of a phenomenon now known as a harmful algae bloom, or HAB for short. Algae are an essential component of the aquatic community forming the base of the aquatic food chain. Normally algae are not a serious problem in a water body, or at worst, a nuisance. But under certain conditions some algae blooms can produce toxic compounds. Scientists don’t fully understand the conditions that create HABs. But there are lots of factors to be considered.

The National Oceanic and Atmospheric Administration (NOAA) describes a HAB as occurring ‘when colonies of algae — simple plants that live in the sea and freshwater — grow out of control and produce toxic or harmful effects on people, fish, shellfish, marine mammals and birds’ (learn more here). The Red Tide is likely the best known of the HABs. The State of Florida is currently, as I write this in mid-August 2018, experiencing a severe Red Tide along its west coast. This August 13th the Governor of Florida issued an emergency order for the Red Tide. The order covers 7 coastal counties. The local economy as well as wildlife are suffering because of the event.

Florida’s Red Tide is a coastal event. HABs can also occur inland in freshwater. August 2, 2014, the city of Toledo, Ohio issued an advisory warning residents to not use water from the city’s water system ( The toxins were said to come from a growing algae bloom on Lake Erie and concentrations were found to be higher than the 1 part per billion that the State’s standards allowed. Lake Erie is the source of drinking water and residents were warned that consuming the water could lead to a series of health complications, including "abnormal liver function, diarrhea, vomiting, nausea numbness or dizziness." Attempting to boil and drink the water would only worsen those health effects because it would "increase the concentration of the toxins.". The event lasted three days. Imagine three days without tap water!

Right here in Arkansas that same year swim beaches in Lake Nimrod were closed because of a HAB. That closure was also a result of a bloom of cyanobacteria. The closure lasted for several days.

Most HABs in freshwater systems are the result of cyanobacteria. Cyanobacteria tend to grow best when the temperature is above 77 degrees Fahrenheit with intermittent exposure to intense sunlight, in stable or sluggish water with low turbidity, and when the nutrients nitrogen and phosphorus are present (

Most of these conditions occur naturally and we cannot do much about them. But, increased nutrient loading into a body of water can exacerbate the situation. Extreme storm events may also wash nutrients into the water contributing to the problem, especially if the storm is followed by an extended drought. Stagnant water can then lead to retention of nutrients in the water ( Well, that kind of sounds like late summer in Arkansas.

So, what can a person do to help manage HABs or to avoid the negative impacts? Here are a few suggestions:

• When a severe algae bloom is present in a stream or lake, avoid contact with the water, • Keep pets and livestock away from water with severe algae blooms, • Learn how to manage fertilizer (nitrogen and phosphorus) to keep it on the land and not washing off of your property, Support local watershed management and source water protection efforts.

1 view0 comments

Recent Posts

See All


bottom of page