Avian Botulism puzzles Great Lakes scientists

It’s a horror story: fish and birds wash up dead on the beach, invaders change the environment, poison lurks in the sand.

Avian botulism causes wildlife deaths in the Great Lakes. Photo: Barb Montgomery

But it’s no story. It’s avian botulism, a toxin that has shown up on Great Lakes shorelines repeatedly over the past 13 years.

“It is by far the most toxic substance on earth,” said Stephen Riley, a research biologist at the U.S. Geological Survey’s Great Lakes Science Center in Ann Arbor, Mich.

Botulism occurs after exposure to the toxin produced by Clostridium botulinum bacterium. It grows in warm environments without oxygen and is so toxic that one gram of the stuff, if dispersed evenly, could wipe out 1 million people.

But the type-e botulism found in the Great Lakes isn’t a human threat. A creature has to ingest the toxin to get botulism, so as long as people avoid eating dead fish and birds gathered from the shoreline, botulism is a wildlife problem.

It is a problem that  first emerged in the Great Lakes in the 1960s when there were excess nutrients in the lakes. Once pollution controls were strengthened by the Clean Water Act, it went away. But in the 1990s it returned when animals like carp, sea gulls and smallmouth bass began washing up on shore.

Why the toxin has resurfaced and how it gets through the food web are mysteries Riley and researchers from the U.S. Geological Survey and the National Park Service are trying to solve. They are studying whether invasive species like zebra mussels, quagga mussels and round gobies play a role.

Toxin tracking

To find the best places to test for the toxin, the Upper Midwest Environmental Sciences Center in La Crosse, Wisc. tracks the migration and feeding habits of common loons which are often affected by it.

Researchers are studying common loons to find out where to test for avian botulism. Photo: Jackanapes (Flickr)

“They’re hit very hard, so consequently that’s a bird we wanted to focus on,” said Kevin Kenow, a wildlife biologist for the center and principal investigator on the study.

Kenow and other researchers put tags and satellite transmitters on common loons to document where they summer in Minnesota, Wisconsin and Michigan’s Upper Peninsula before flying south for the winter.

The transmitters feed information into a map that tracks the daily migration of each loon throughout the year.

The tags record temperature and pressure so researchers can track how deep loons dive for food. That helps them speculate what they eat and helps decide where to test for avian botulism.

Kenow was surprised that the birds dive to the same depth, meaning they probably feed at the bottom of lakes.

“We know that species like round goby inhabit the bottom, so that might be a tie into that,” Kenow said.

Invasive species could play a role

Round gobies, a fish from Eastern Europe, were first spotted in the Great Lakes in 1990 and are just one of the potential links between avian botulism outbreaks and invasive species. Invasive freshwater mussels, like zebra and quagga mussels, may be another.

“Botulism seems to occur when the lake levels are low and the water temperatures are high,” Riley said.

Mussels help create these conditions. They filter water, allowing in more light that heats water and promotes algae. The mussels’ feces concentrated in the bottom of the lake also provide nutrients to the algae. The algae use up oxygen after they die and decompose.

All the better for botulism growth. But how did the bacterium get here in the first place?

“It’s everywhere,” Riley said. “It’s in the dirt, the sand, the mud in the bottom of the lake.”

Riley said botulism outbreaks happen in every aquatic environment because the bacterium is naturally occurring in the sand and sediment. The bacterium is not harmful on its own, but when it gets in the right warm, oxygen-free environment the toxin starts to grow.

How it spreads through the food chain is what Riley and other researchers are trying to find.

One hypothesis is that mussels promote conditions for toxin growth on the lake floor and that invertebrates ingest the toxins from the mud. Then fish eat the invertebrates and die before washing up on the shore. A bird eats the fish, dies and becomes ridden by maggots, which are eaten by another bird. The cycle continues until someone buries the carcass.

Volunteers help stem the tide

AMBLE volunteer Patrick Sullivan surveys the Lake Michigan shoreline in Door County, Wisc. Photo: Paula Sullivan

The U.S. Geological Survey’s Avian Monitoring for Botulism Lakeshore Events, or AMBLE, encourages people to walk segments of the Lake Michigan beach in Door County, Wisc., every seven to 10 days. They track what birds, algae, fish and weather they see.

“What AMBLE does is provide them a way to supply data to us about what they’re seeing with regards to bird health and beach condition,” said Jenny Chipault, AMBLE coordinator.

When volunteers come across a “fresh” bird carcass – one that doesn’t smell, isn’t filled with maggots and has intact feathers – they bag it and send it to Madison for testing.

“We have found avian botulism, but that’s different than saying that every bird that washes ashore has died from avian botulism,” Chipault said.

Because the toxin can grow in dead birds and fish, finding avian botulism in a carcass isn’t conclusive.

“The older carcasses might have the toxin, but it might not have been what killed the bird,” Chipault said.

AMBLE data helps researchers look at the transmission of the toxin through the food web. Until they nail down how it works, large-scale prevention methods will have to wait.

“At this point, it’s kind of getting a foothold, getting a good understanding on mechanisms that seem to be driving [avian botulism], and from there devising potential management strategies.” Kenow said.

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About Carol Thompson

Carol graduated from Michigan State University with a degree in journalism and environmental studies. She reported for Great Lakes Echo from 2011 to 2012, and now works for the Peninsula Pulse in Door County, Wis. She was an intern at the Leelanau Enterprise and The Daily Green and contributed to EJ Magazine. Contact Carol through email at thomp872@gmail.com or Twitter @thompsoncarolk.

  • Harold

    George, you bring up some good points…but if you want people to read what you write, please learn to turn off your “ALL CAPS” button.

  • GEORGE

    WE STUPIDLY BELIEVE THAT SEWAGE IS JUST FROM HUMAN OFFAL. IN THE 20TH CENTURY WE INVENTED SOME 1000 HOUSEHOLD CHEMICALS, MANY BASED ON PETROLEUM THAT ARE FOUND IN HOUSEHOLD PRODUCTS. THIS INCLUDES MANY PHARMACEUTICALS THAT PASS THROUGH OUR BODIES.

    NO SEWAGE PLANT REMOVES ALL OF THE CHEMICALS THAT OUR SEWAGE PRODUCE. ONLY ONE PER CENT OF THE WATER IN LAKE HURON GOES DOWN THE ST CLAIR RIVER TO LAKE ERIE. THE REST EVAPORATES LEAVING BEHIND THE CHEMICALS THAT BUILD UP.

    IF YOU PUT ONE GRAIN OF SUGAR INTO COFFEE NO ONE NOTICES, BUT DO IT OVER AND OVER AND THE COFFEE BECOMES LIKE SYRUP.SIMILARLY, THE CHEMICALS WE FLUSH INTO THE LAKES AND RIVERS HAS BUILT UP OVER THE LAST CENTURY. IT TAKES ONLY ONE PART PER 10 BILLION OF ESTROGEN TO CHANGE MALE FISH INTO FEMALES. WHAT EFFECT DO THESE CHEMICALS HAVE ON PLANTS AND RESULTING BOTULISM. WHY ARE WE DUMPING THIS MESS INTO OUR MOST VALUABLE RESOURCE CREATING EVENTUALLY DEAD SEAS. THERE ARE ALTERNATIVE MODERN TOILETS THAT KEEP SEWAGE DISPOSAL AT SOURCE. THESE CONVERT IT INTO POWDER THAT CAN BE COLLECTED PURIFIED AND KEPT FROM LAND AND OUR WATERS

    IT COSTS ONLY 10 PERCENT OF PRESENT SYSTEMS WITH LESS WATER PRODUCTION AND SEWAGE PLANT OPERATIONS.

    CHECK IT OUT IN YOUR COMPUTER SEARCH ENGINES

    OH WHAT DAMNED FOOLS WE MORTALS BE

  • Eleodore

    The botulism outbreaks of the 1960′s occurred before zebra mussels or round gobies invaded the Great Lakes. Native species can transfer botulism as well as exotic species. However, what is different is that temperatures in the lakes are higher and warm temperatures trigger higher decomposition. Just the thing that the botulism bacteria love. Under those conditions they proliferate. So, yes, invasive species play a role, but the widespread botulism events that we are experiencing are more likely being triggered by higher temperatures in the first place.

  • Thomas

    Let’s blame everything on Global Warming it is the cool thing to do. Give me a break… I wonder what the montra was before the last Ice Age… “you know if all the carnivours eat all the herbavoirs the earth is going to turn into and ice cube!”.

    Don’t make any assumptions on what is causing botulism out breakes collect data see what it tells you. If it is global warming the data will tell you that. However, it is a very complex system undergoing great changes due to invasive species introductions. I hypothesize that these have a greater contribution to the botulism outbreaks than global warming.

  • don

    one more reason technology needed to steriltze ballast water being moved from one location to another in the Great Lakes is needed. Currently the only protection that dose not follow an International diverse group of politically different governments including communist and foreign economic interest (IMO) is the state of New York. Hopefully Governor Coumo will remain strong after spending the states money to create the type of protection needed that will force the shipping industry which is mostly foreign ships to do the right thing.

  • Stephanie

    Just a wildlife clarification coming from a Fisheries and Wildlife Major at MSU, it is just Gulls. Unfortunately there is no such thing as a “sea gull”.

  • Nelda

    Please send me a copy of this article.
    Nelda B. Ikenberry

    Thank you!

  • Gail

    The primary cause in this chain of events certainly seems to be climate change. Rising water temperatures along with fewer and less deep freezes has given rise to the proliferation of many species (including bacterium, algae, beetles, ticks, jelly fish, etc) that are able to take full advantage of their expanding ecological niches.

    I think it’s vital to look deeper than blaming the invasive species. The general health of the environment has been drastically altered by pollution, rising temps, and less oxygen in the water. The mussels are and gobis are basically minor players in the larger scheme of things.