A Blooming Problem
Toxic algae, killer bacteria. Is it safe to swim in the Bay?
by Brennen Jensen
It began with cormorants acting drunk on the beach. In early October 2017, concerned residents and visitors started delivering Double-crested Cormorants to an animal rehabilitation center in Sanibel Island, Florida. The water birds, they reported, appeared to be disoriented. Staff at the center quickly determined that it wasn’t alcohol that was making them behave this way: it was exposure to Karenia brevis, a toxin-creating alga called a dinoflagellate—a single-celled creature possessing the attributes of both plant and animal.
Under the right conditions, these microalgae, or phytoplankton, can experience population explosions called blooms. When the plankton display toxic properties, as do K. brevis, scientists classify these events as harmful algal blooms (HABs), which have the potential to disrupt ecosystems and threaten wildlife and humans.
K. brevis blooms are a common occurrence along Florida’s Gulf Coast. Almost every year, they cause the ocean surface to turn a deep red, inspiring the nickname “red tide.” The cormorants, it turned out, had encountered an algal bloom in the Gulf of Mexico not yet visible from shore. The water birds were the canaries in the coal mine, harbingers of the largest and longest-lasting HAB in more than a decade. By the time the bloom cleared, more than a year later, wildlife casualties included some 150 manatees, 400 sea turtles, and at least a hundred tons of fish.
Florida Sea Grant estimates that the state suffered $20 million in tourism-related losses, as bloom-besieged beaches from Tampa to Fort Myers closed and visitors shunned coastal resorts. Sarasota alone lost an estimated $4 million in one month when dead fish piled up on the city’s sandy beaches, patrolled by lifeguards wearing surgical masks. Hits to local fisheries have not yet been tabulated, but HABs in 2015 and 2016 cost the shellfish industry more than $1 million.
Florida reported no human fatalities as a result of exposure to the particular neurotoxins produced by K. brevis, called brevotoxins, but many people were hospitalized after inhaling them. The pounding surf aerosolizes the toxins, launching them into the air, where winds may carry them as far as 10 miles inland—and cause symptoms like painful and difficult breathing, especially for individuals having compromised respiratory systems.
To date K. brevis has not appeared in the Chesapeake Bay; however, the Bay has its own resident phytoplankton that could create a harmful algal bloom with the right combination of water temperature, salinity, pH, and nutrients. If a bloom occurred, what would happen? And how could resource managers and scientists control it?
A Bloom Boom
A bloom of
Prorocentrum minimum, commonly called a mahogany tide, appeared in Spa Creek in Annapolis, Md., on October 28, 2009.
Photo , Alicia Pimental / Chesapeake Bay Program
Algal blooms can happen when excessive amounts of nitrogen and phosphorus accumulate in bodies of water. These nutrients come from fertilizers, sewage treatment plants, air pollution, storm water, and other sources. When phytoplankton in the water take up these nutrients, they reproduce, then die off. As the dead organisms sink to the sea bottom and decompose, oxygen in the water is consumed in the process, creating dead zones with little or no oxygen that cause fish kills. This is what happened in 2012, when a toxic bloom of Prorocentrum minimum killed an estimated 100,000 fish in Baltimore’s Inner Harbor.
A growing phenomenon in both saltwater and fresh, harmful algal blooms pose a challenge to scientists working to control them.
“Globally the algal bloom problem is expanding,” says professor Patricia Glibert of the University of Maryland Center for Environmental Science (UMCES) Horn Point Lab. She’s a phytoplankton ecologist who spent part of last spring in China researching bloom threats there. “We have new and different species—and new and different toxins appearing throughout the world.”
The reason, she says, is the rise of nutrients in the water, particularly nitrogen and phosphorus from fertilizers and human and animal waste. Climate change may be playing a contributing role, expanding the range of HAB species, many of which thrive in warmer waters.
“The Bay has a long list of toxic or potentially toxic or harmful species,” Glibert says. “A shopping list of species resides here, some of which are not problematic. They may just be present in low numbers as part of the ecosystem and have never really exploded.”
Perhaps the Bay’s most infamous bloom occurred in 1997. Maryland made national headlines after the dinoflagellate Pfiesteria piscicida—dubbed the “cell from hell”—was blamed for large fish kills in the Pocomoke River. Many affected fish developed ugly, festering lesions. The event cost the seafood industry more than $40 million. More problematic, however, was the fact that approximately 35 people exposed to the bloom suffered a host of health problems, including fatigue, headaches, and temporary short-term memory loss.
Some scientists in the region, including Allen Place, a biochemist based at the UMCES Institute of Marine and Environmental Technology in Baltimore, believe that another dinoflagellate—Karlodinium veneficum—may actually have been the primary cause of the fish kill. What caused the human symptoms, however, remains a medical mystery.
Place believes that Pfiesteria was framed during the 1997 fish kills. P. piscicida, he says, were simply opportunists that showed up in the bloom to feed on fish killed by Karlodinium. He helped isolate a toxin from K. veneficum, which kills fish by essentially dissolving their gills, a process he captured in footage of a zebrafish succumbing to it.
Pfiesteria may have different strains, not all of which may produce toxins or which may do so only under specific conditions. Because the organism was rarely detected after 1997, Maryland stopped DNA-based water testing for it in 2010. Organisms resembling Pfiesteria do show up occasionally, but only in low numbers, during routine algae counts. Meanwhile fish kills linked to K. veneficum have been documented in the Chesapeake eight times since 2005.
“That first cell that gets exposed to [Karlodinium] may die, but that’s only one of 10 trillion cells in the human body,” Place says. “It may cause skin irritation, but it’s not going to find its way beyond the local exposure site. Bottom line: we injected it inside mice and it did not kill them. Brevotoxins kill mice.”
Science has made great strides in understanding the habits and life cycles of various toxic phytoplankton since “Pfiesteria hysteria” gripped the region. State and local governments have expanded and improved methods for routine monitoring of Bay waters. And new technologies, such as Maryland Healthy Beaches, a free app, can keep the public apprised of rainfall amounts and advisories based on indicator bacteria levels at more than 180 beaches and recreational areas.
In 2014 Maryland Sea Grant and the National Oceanic and Atmospheric Administration’s (NOAA) National Centers for Coastal Ocean Science cosponsored a workshop on remote sensing of harmful algal blooms in the Chesapeake and coastal bays that explored available technologies to detect blooms and identify research gaps. That work helped determine what Bay communities need to know regarding human health and environmental impacts, and how quickly officials could identify blooms and warn the public.
Technology may be key in early detection of HABs. NOAA is experimenting with analyzing slight color changes in satellite imagery of the Bay that might indicate the start of a bloom.
Scientists Heidi Sosik, Robert Olson, and Joe Futrelle of the Woods Hole Oceanographic Institution have developed an underwater device called an Imaging FlowCytobot (IFCB) to perform real-time analysis of phytoplankton in coastal waters. The IFCB uses a combination of video and flow technology to capture images of organisms for classification, allowing researchers to determine when levels of potentially toxic ones increase significantly.
But is it enough to predict, or prevent, a bloom of Florida-level disruption?
Good and bad algae
The Chesapeake contains some 700 species of algae. Many are important low-rung components of the food web. Most don’t bloom, and the vast majority don’t create toxins—fewer than 2 percent, according to the Maryland Department of Natural Resources (DNR).
“The spring usually brings Prorocentrum, which some people call the “mahogany tide,” in that it turns the water a reddish brown, but it’s perfectly fine to swim in and doesn’t have any harmful impacts to people,” says Cathy Wazniak, DNR’s program manager. “It does cause ecosystem issues, because its large biomass can contribute to lowering dissolved oxygen levels and [creating] dead zones.”
The state performs a variety of water quality analyses—including monthly algae-specific monitoring at 34 locations in the Bay and 13 locations in coastal bays—to measure algal density in cells per milliliter. A species will be noted as present if as few as two cells per milliliter are detected. Each species has a different density threshold that denotes a bloom; some thresholds exceed hundreds of thousands of cells per milliliter. A mahogany tide’s Prorocentrum minimum, for example, are considered blooming when the density exceeds 3,000 cells per milliliter.
People are encouraged to report discolored water so it can be tested as soon as possible. You can call the Maryland DNR or go online and fill out the Algae Bloom Sighting Report at eyesonthebay.dnr.maryland.gov. (See “Healthy Waters 411”).
Occasionally Chesapeake Bay beaches are impacted by algal blooms, although these are not the only reason for beach closures. Not infrequently the culprit is high fecal coliform counts, often resulting from heavy rains that wash animal waste into waterways or cause sewage and storm water overflows (See “To Swim or Not to Swim”).
In 2003 the state issued a no-contact advisory for Kent County’s Betterton Beach when a bloom of Microcystis aeruginosa, a cyanobacterium, caused some swimmers to report itching and rashes. Commonly referred to as blue-green algae, cyanobacteria actually are not algae but photosynthetic bacteria whose toxins commonly cause skin irritations and can also affect the liver or nervous system. Largely a freshwater menace, cyanobacteria blooms increasingly threaten drinking water supplies around the world. A 2014 bloom in Lake Erie forced the city of Toledo, Ohio, to shut down its water system for three days; in Maryland, blooms have forced the closing of popular recreational lakes. But cyanobacteria have also bloomed in the Bay’s brackish waters and tributaries, including the Potomac and Sassafras rivers.
Even if there’s no swimming advisory, you probably wouldn’t want to dive into the middle of a cyanobacteria bloom. “It’s sort of common sense that you shouldn’t go swimming if the water is bright green,” says Judy O’Neil, an associate research professor at the UMCES Horn Point Lab. “It’s repulsive looking, and it would be like swimming in Shrek’s lagoon.”
Alas, dogs are not so discriminatory, and several have died from cyanobacteria poisoning, as have water birds.
Compared to cyanobacteria, the Bay’s problematic dinoflagellates—K. veneficum, Pfiesteria—are complex creatures. They can convert light energy into chemical energy like photosynthetic algae; they can also hunt like an animal with their flagella, the tiny appendages that enable mobility. Some are even bioluminescent, such as Alexandrium monilatum, which sometimes blooms, and glows, in the Bay’s southern reaches.
“We call them the Venus flytraps of the microbial world,” Glibert says of dinoflagellates. “They can capture other phytoplankton and small bacteria, they can capture bits of fish tissue.”
They can also create toxins to stun prey as an aid to hunting and eating, to keep competitors at bay, or simply as metabolic byproducts. “They create an array of compounds that have lots of different effects, but metabolically, there are still a lot of questions about how and why they’re produced,” Glibert adds.
Karenia have not yet been found in the Bay, but they have been detected along the Mid-Atlantic coast and in Delaware Bay. The worry, O’Neil says, is that HAB organisms that prefer warmer water, such as Karenia and Dinophysis, will thrive as temperatures rise, flourishing in warmer waters during summer months. Dinophysis, more common on the West Coast, has bloomed in waters as far north as New York State, and it has been observed in the Chesapeake in moderate salinities. It is possible that both of these dinoflagellates will get into the Gulf Stream and come right up the Atlantic coast.
“Things are warm enough now that, on a seasonal basis, they can come in and potentially cause trouble,” O’Neil says. “We’re working with Maryland DNR and the National Park Service on a research project going offshore to monitor what’s out there. We generally haven’t been looking offshore much, so we want to have a baseline so we can detect changes over time.”
During a monitoring trip offshore in May, O’Neil and DNR colleagues identified Dinophysis acuminata, a dinoflagellate whose toxins can accumulate in shellfish.
Maryland and Virginia’s shallow coastal bays, popular destinations for recreational fishing and water sports, are also home to a growing shellfish industry. These bays may be at the greatest risk from these potential invaders.
“The environment selects”
The Bay doesn’t have a lot in common with the Gulf of Mexico, but what it does share is the seasonal formation of dead zones. This spring’s above average rainfall, following the state’s wettest year on record, in 2018, led to blooms of P. minimum and other organisms creating one of the largest dead zones in the Chesapeake Bay for the summer of 2019. At its peak, the dead zone in the Maryland portion of the Bay was about two cubic miles, according to Maryland DNR’s 2019 Hypoxia Report.
The hypoxia volumes were the third largest since 1985 for the early August time period, and that was after a slight drop in the dead zone from the peak in July. Scientists had predicted the largest dead zones because they were watching the precipitation, particularly in the Susquehanna River watershed, which is responsible for about half of the nutrient loads to the Bay.
“We’re just getting record amounts of rainfall persisting throughout the state,” says Jeremy Testa, a biological oceanographer with UMCES.
Assessing the increased presence of phytoplankton and photosynthetic bacteria—more blooms in more locations—O’Neil quotes the late Dutch botanist Lourens Baas Becking: “Everything is everywhere, but the environment selects.”
As climate change warms waters and higher pollution levels make nutrients more plentiful, these environmental “selections” can be increasingly problematic.
“We’ve got these oceans with lots of different species of phytoplankton, and the environment selects the ones that can grow well in a particular environment,” O’Neil says. “It just so happens that the harmful algal bloom species are the ones that like our sewage and the things that we’re polluting the waterways [with], so that’s why we have to work on cutting those back.”
Writer Brennen Jensen lives in Baltimore.