The stench of thousands of dead, bloated fish hung over the beaches of western Florida for months in 2018. The fish were casualties of an algae bloom — an uncontrolled growth of small organisms. Such blooms hit the Gulf of Mexico’s coastlines almost every year.
Called a red tide, this year's bloom has been particularly intense — and toxic. The algae that turn the water a murky reddish tint also emit a poison. It can cause breathing problems for people — and kill sea creatures. Dolphins and endangered sea turtles may turn up among the dead.
“Algae” is a catch-all term used for a variety of water dwellers that use photosynthesis to make energy from the sun. They can range in size from bacteria and other single-celled organisms to larger algae, such as kelp.
Not all algae are bad. But harmful algae blooms — abbreviated HABs — can be sickening, even deadly. That's why scientists are at work to better predict when and where blooms might emerge. Many systems are being developed to forecast blooms. Most can predict such toxic tides only three to seven days off.
Climate change could further worsen toxic tides, the U.S. Environmental Protection Agency warns. Those changes could include warmer water temperatures, growing salinity and higher sea levels of carbon dioxide.
And Florida’s red tide is not the only bloom plaguing U.S. waters. Other types of toxic tides are also appearing ever more frequently. They also are popping up in more places and lasting longer.
Scientists are working on ways to predict blooms of toxic algae using satellite data, computer analyses and knowledge about the species involved. Take a look at the different microscopic organisms that threaten U.S. waters.
Tap or click circles to explore.
Breathing in Florida’s red tides
The best known toxic tides are caused by Karenia brevis (Kaa-REN-ee-uh BREV-iss). These fragile, single-celled algae create red tides. When their cells die or become damaged by waves, they release poisons. These are called brevetoxins (BREV-eh-tox-ins).
During a bloom, the algae’s poisons can enter the air. People walking along an affected beach “might cough or sneeze or have itchy eyes,” notes Tracy Fanara. She’s a research scientist at Mote Marine Laboratory & Aquarium in Sarasota, Fla. A red tide’s effects can be worse for people already struggling with lung issues, such as asthma.
In September 2017, Mote began testing a program called HABScope. It trained 20 volunteers to sample waters daily at various beaches affected by a red tide. These citizen scientists placed three drops of seawater under a microscope, then recorded a 30-second video of the algae swimming around.
A computer program can analyze these videos to count the algae in each sample. Those data, along with information on winds and water currents, then go into a computer model. It was created by the National Oceanic and Atmospheric Administration (NOAA). This computer program can then predict red-tide threats to breathing over the next few days at each beach.
Across the Gulf of Mexico, the University of Texas Rio Grande Valley is running a similar program. It’s called Red Tide Rangers.
Counting K. brevis cells in a water sample used to take an expert an entire day. The new program “allows a volunteer to do this within five minutes,” Fanara says. “Hopefully with this real-time data that we’re providing, we can get better and more accurate” forecasts.
Seafood can turn toxic
The Gulf of Maine is home to another nasty algal species. People who eat shellfish tainted with this Alexandrium catenella (Al-ex-AN-dree-um Kaa-tuh-NEL-uh) may become paralyzed — even die.
The single-celled organism paddles around using two whip-shaped “oars” known as flagella. Blooms of this alga are “incredibly toxic,” notes Richard Stumpf. He’s a NOAA oceanographer based in Silver Spring, Md. Between 2007 and 2009, A. catenella left eight people in Maine with paralytic shellfish poisoning. All had eaten shellfish from closed areas.
These algae flourish in the warm waters off Maine from July through September. Blooms of the species will consume available nutrients until they run out. Then the algae reproduce. Their offspring clump, forming cysts that sink to the ocean floor. There they’ll rest until the next warm season.
For about 12 years, scientists have been gathering seafloor samples each October and November at some 50 affected sites. The cysts in each sample are counted. These data then go into a computer model to forecast how big next year’s bloom might be, explains Stumpf. He leads the forecasting project.
But his team can’t predict exactly which areas will be most affected. For that, the team produces another, shorter-term forecast. It relies on wind conditions and estimates of local conditions for three to seven days out.
Neither forecast can tell how toxic a bloom might become. That’s a goal for Dennis McGillicuddy. He’s an oceanographer at the Woods Hole Oceanographic Institution in Massachusetts. “Shellfish are basically little bio-accumulators of the toxin,” he says. They can hold onto the poison long after the algae are gone.
McGillicuddy’s team is working on a computer model to predict how many toxic algal cells shellfish might be exposed to over a summer. That should help the researchers figure out how long it will take those shellfish to flush the toxins from their bodies. And shedding those toxins isn’t quick. It may take months — even years.
The blue-green blooms of Lake Erie
Over the past several years, a thick, slimy foe has been plaguing Lake Erie. It’s a cyanobacterium, a type of blue-green algae. And it “is gross,” Stumpf says. “There’s no other way to describe it.”
These algae live in open waters of all U.S. states. Scientists are now working to predict when they may bloom into toxic tides. That way officials can figure out how much to treat tainted waters. Cyanobacteria produce toxins known as microcystins. These produce skin rashes, vomiting and diarrhea.
Erie, the fourth-largest U.S. lake, provides drinking water to roughly 11 million people. During its warmest months, this lake also hosts the nation’s biggest cyanobacteria blooms. Communities treat the water that will be used for drinking. But when a bloom’s toxicity has been underestimated, the water may not be treated enough.
In 2014, 110 people were sickened after drinking undertreated water.
The intensity of a bloom is directly related to how much phosphorus enters a lake after running off of farm fields. That mineral is a fertilizer of crops (and these algae). Heidelberg University in Tiffin, Ohio, runs a river monitoring program that samples waters flowing into Lake Erie. It measures phosphorus levels several times a day, Stumpf notes. Researchers use the data to predict seasonal blooms.
Stumpf and other researchers also produce a short-term forecast for a toxic tide of this alga. It’s based on satellite images of the bright green blooms together with data on phosphorus levels and winds. That forecast can point to where within the lake a bloom will likely emerge during the next few days.
Some blooms can poison your memories
Another type of toxic tide often hits the West Coast of North America. Blooms of this Pseudo-nitzschia (Sue-doh NIT-zhee-uh) can show up anywhere from Alaska down to southern California. Some species of the rod-shaped algae secrete a poison known as domoic acid. People who eat fish or shellfish tainted with the toxin may develop permanent brain damage.
A primary symptom: People no longer can make short-term memories. High doses of the poison can bring death. And humans aren’t the only ones at risk. Each year, dozens of marine mammals suffer brain damage after blooms poison them with domoic acid.
Today “is a really pivotal moment” for developing ways to forecast toxic blooms, says Clarissa Anderson. She’s an oceanographer at the Scripps Institution of Oceanography in La Jolla, Calif. She has spent the past decade developing a way to predict Pseudo-nitzschia’s domoic-acid levels. Those forecasts should work for locations up to 1,000 kilometers (620 miles) off the Oregon and California coasts.
Called C-HARM, the three-day forecasts rely on satellite photos that show chlorophyll patterns, ocean temperatures and sea-salinity levels. Three different computer models integrate these data to forecast the toxic tides.
Anderson also puts out a monthly bulletin. It estimates the likelihood of a Pseudo-nitzschia bloom showing up at various sites.
As toxic tides become more common, it becomes ever more important to predict which beaches and coastal areas may get hit. Only then can communities and workers safely work, play and enjoy the bounty of their coastal waters.
algae Single-celled organisms, once considered plants (they aren’t). As aquatic organisms, they grow in water. Like green plants, they depend on sunlight to make their food.
app Short for application, or a computer program designed for a specific task.
asthma A disease affecting the body’s airways, which are the tubes through which animals breathe. Asthma obstructs these airways through swelling, the production of too much mucus or a tightening of the tubes. As a result, the body can expand to breathe in air, but loses the ability to exhale appropriately. The most common cause of asthma is an allergy. Asthma is a leading cause of hospitalization and the top chronic disease responsible for kids missing school.
bacteria (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals).
biology The study of living things. The scientists who study them are known as biologists.
bloom (in microbiology) The rapid and largely uncontrolled growth of a species, such as algae in waterways enriched with nutrients.
carbon dioxide (or CO2) A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. Carbon dioxide also is released when organic matter burns (including fossil fuels like oil or gas). Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food.
cell The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.
chlorophyll Any of several green pigments found in plants that perform photosynthesis — creating sugars (foods) from carbon dioxide and water.
colleague Someone who works with another; a co-worker or team member.
computer model A program that runs on a computer that creates a model, or simulation, of a real-world feature, phenomenon or event.
computer program A set of instructions that a computer uses to perform some analysis or computation. The writing of these instructions is known as computer programming.
cyanobacteria A type of bacteria that can convert carbon dioxide into other molecules, including oxygen.
cyst A group of cells that form a type of bubble-like shell or sac. Some cysts develop as a result of disease or tissue damage. Others may develop as a normal, protective during certain phases of a parasite’s maturation.
diarrhea (adj. diarrheal) Loose, watery stool (feces) that can be a symptom of many types of microbial infections affecting the gut.
dolphins A highly intelligent group of marine mammals that belong to the toothed-whale family. Members of this group include orcas (killer whales), pilot whales and bottlenose dolphins.
domoic acid A toxin produced by some algae. If ingested by humans or other animals, it can cause brain damage, seizures and memory problems.
endangered An adjective used to describe species at risk of going extinct.
environment The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of components in some electronics system or product).
Environmental Protection Agency (or EPA) A national government agency charged with helping create a cleaner, safer and healthier environment in the United States. Created on Dec. 2, 1970, it reviews data on the possible toxicity of new chemicals (other than foods or drugs, which are regulated by other agencies) before they are approved for sale and use. Where such chemicals may be toxic, it sets limits or guidelines on how much of them may be released into (or allowed to build up in) the air, water or soil.
flagella (sing. flagellum) A thread-like structure that comes out of certain types of cells. The term derives from the Latin word for whip. And that's because the structures serve like oars to help these cells travel.
freshwater A noun or adjective that describes bodies of water with very low concentrations of salt. It’s the type of water used for drinking and making up most inland lakes, ponds, rivers and streams, as well as groundwater.
global warming The gradual increase in the overall temperature of Earth’s atmosphere due to the greenhouse effect. This effect is caused by increased levels of carbon dioxide, chlorofluorocarbons and other gases in the air, many of them released by human activity.
kelp A type of large seaweed that is usually a type of brown algae. They grow underwater and form large forests, providing habitat for many organisms. Some kelp forests are so large they can be seen from space.
marine mammal Any of many types of mammals that spend most of its life in the ocean environment. These include whales and dolphins, walruses and sea lions, seals and sea otters, manatees and dugongs — even polar bears.
microcystins A class of toxins produced by some freshwater algae that are also known as cyanobacteria. Most of these toxins work by poisoning the liver.
microscope An instrument used to view objects, like bacteria, or the single cells of plants or animals, that are too small to be visible to the unaided eye.
National Oceanic and Atmospheric Administration (or NOAA) A science agency of the U.S. Department of Commerce. Initially established in 1807 under another name (The Survey of the Coast), this agency focuses on understanding and preserving ocean resources, including fisheries, protecting marine mammals (from seals to whales), studying the seafloor and probing the upper atmosphere.
nutrient A vitamin, mineral, fat, carbohydrate or protein that a plant, animal or other organism requires as part of its food in order to survive.
oceanography (adj. oceanographic ) The branch of science that deals with the physical and biological properties and phenomena of the oceans. People who work in this field are known as oceanographers.
organism Any living thing, from elephants and plants to bacteria and other types of single-celled life.
paralysis (adj. paralytic) The inability to willfully move muscles in one or more parts of the body. In some cases, nerves that carry the signal to move may have been severed or damaged. In other cases, the brain may be the source of the problem: It may fail to understand or act on a nerve’s signal to move.
phosphorus A highly reactive, nonmetallic element occurring naturally in phosphates. Its scientific symbol is P. It is an important part of many chemicals and structures that are found in cells, such as membranes, and DNA.
risk The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)
satellite A moon orbiting a planet or a vehicle or other manufactured object that orbits some celestial body in space.
sea An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.
seawater The salty water found in oceans.
secrete (noun: secretion) The natural release of some liquid substance — such as hormones, an oil or saliva — often by an organ of the body.
short-term memory (also known as primary memory) The small amount of memory held actively in the mind for a short period of time, such as the series of digits in a telephone number.
species A group of similar organisms capable of producing offspring that can survive and reproduce.
toxic Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.
toxin A poison produced by living organisms, such as germs, bees, spiders, poison ivy and snakes.
Journal: K. M. Benedict et al. Surveillance for waterborne disease outbreaks associated with drinking water—United States, 2013-2014. Morbidity and Mortality Weekly Report. Published online November 10, 2017.
Journal: T. Goldstein et al. Novel symptomatology and changing epidemiology of domoic acid toxicosis in California sea lions (Zalophus californianus): an increasing risk to marine mammal health. Proceedings of the Royal Society B. Vol. 275, February 7, 2008, p.267. doi: 10.1098/rspb.2007.1221.
Journal: S. M. McKibben et al. Climatic regulation of the neurotoxin domoic acid. Proceedings of the National Academy of Sciences. Vol 144, January 10, 2017, p. 239. doi: 10.1073/pnas.1606798114.