In recent years, the U.S. has seen a higher severity of algal bloom activity, a natural occurring event observed here since the 1700's.

There has been a drastic increase in algal blooms, also known as red tide, especially in Florida. Red tides occur when there is an abundance of red dinoflagellates and other algae blooms in the ocean, creating a discoloration of the water off the coast. The algae blooms can have harmful effects on both wildlife and humans. The Algae causes a lack of oxygen and/or releases harmful toxins into the water killing fish and other wildlife. Humans are at risk when consuming shellfish and other seafood due to the potential exposure to toxins. Red tides have become more frequent in the last 40 years and have been seen to occur in Argentina, Australia, Brazil, Canada, Chile, Denmark, England, France, Guatemala, Hong Kong, India, Ireland, Italy, Japan, the Netherlands, New Zealand, Norway, New Guinea, Peru, the Philippines, Romania, Russia, Scotland, Spain, Sweden, Thailand, the United States, and Venezuela (WHOI, 2007CDC, 2012).

There are a few species of algae that can be harmful which include:

  • Alexandrium fundyense – found along the Atlantic coast from the Canadian Maritimes to southern New England
  • Alexandrium catenella– found along the Pacific coast from California to Alaska
  • Karenia brevis– found in the Gulf of Mexico along the west coast of Florida

Algae blooms are caused when the right combination of sunlight, temperature and nutrients provide boosted growth.

There are several factors that lead to the bloom and spread of red tides. These include; warm ocean surface temperatures, higher nutrient content, low salinity, calm currents, and warmer weather after rain in the summer. Warming ocean surface temperatures can be attributed to higher amounts of CO2 in the atmosphere. Higher nutrient content comes from the run-off of pesticides, fertilizers and other human-made chemicals.  These conditions create the ideal environment for an algae bloom. Once this has been initiated, the red tides can be carried and spread by winds, currents and storms.

Krill and shellfish are unaffected by the toxins from algae, but the concentration of toxins increase and become dangerous for the larger fish and mammals further up the food chain. The impacts of red tides go beyond life in the ocean. The water can also be harmful to humans in and near the areas. Swimming in contaminated water may cause skin and eye irritation. Even being on the beach by the water may cause respiratory irritation from the aerosols produced by the algae. (NOAA, 2018) There are economic consequences due to the decrease in tourism and recreation for impacted areas. Local economies may suffer, and this becomes a problem the more often and more time red tides are present.

Scientists have been able to use satellite imagery to track and monitor algae blooms. This allows them to predict the tides and warn against eating shellfish. Nearby communities can also plan for economic and recreational impacts. Scientists have been researching an antidote to the algae toxins. This would help to alleviate any threat to fish and humans consuming shellfish. Not all algae are toxic so it’s important that mitigation is focused on preventing the harmful toxins as opposed to all algae species.

Human mismanagement of water flow is suggested to be linked to more severe algal blooms in waterways.

In Florida, where red tides are most prevalent, the natural flow of water has been modified by agriculture, infrastructure, housing, and more as the state population has steadily increased. Lee County used to contain 50% wetlands, now it only has 10% remaining. In the past, rainwater would flow slowly through estuaries and aquifers, which help filter byproducts and excessive nutrients. Now, water flow is rushed and filtration is diminished, which provides greater food sources like nitrogen for the algae to flourish.

Last September after Hurricane Irma, high amounts of nutrient-laden water were released from Lake Okeechobee to prevent the overflow of the Hoover Dike. It is believed that these nutrient-dense waters catalyzed the unusually persistent Red Tide as they flowed through the Caloosahatchee River and into the shallows of the Gulf Coast.

Unfortunately, Florida is not the only one experiencing the increasing severity of algal blooms. Earlier this year, Oregon experienced algae toxin contamination in their drinking water supply. However, there is hope! Scientists have made recent progress on the genetic basis for toxic algal blooms that could allow us to determine what environmental or biological factors trigger these events. With climate change already influencing marine patterns, it is important that we properly manage our waterways in the future to prevent an overabundance of nutrients from creating more long-lasting algal blooms.