Great Lakes loons dying in record numbers from botulism outbreak spurred by ecological disturbance
(Editor's note: This story was originally published on Aug. 5, 2013, but received limited visibility on AnnArbor.com and MLive.com.)
The Common Loon, arguable one of the most beautiful birds that grace our Great Lakes, is dying at an alarming rate. The fact that they’re dying is troubling, but the cause is downright scary. Most readers are familiar with the loon, but here’s a brief description for those who are unfamiliar with these gorgeous diving birds.
The loon is about the size of a small goose and has black and white plumage with piercing red eyes and can be found throughout the Great Lakes and other northern waters. Not only is their beauty unmatched, their eerie calls echo across waters they inhabit that make them one of the most unforgettable birds you’ll ever see or hear.
Recently, the Great Lakes Science Center - a Division of the United States Geological Survey - has discovered that the Common Loon can dive down to 150 deep catching fish with their beaks.
The loons are diving down to 150 feet to eat fish to survive. Loons only reside in the Great Lakes for a brief period in the late summer and fall on their way from their northern breeding lakes to their wintering grounds in the Gulf of Mexico and the Atlantic Ocean, but they feed heavily on highly concentrated schools of fish that occur in the deeper waters of the Great Lakes.
photos courtesy of USGS
Believe it or not, the goby itself is not the problem as to why the diving birds are dying. The problem is Botulism E. “Botulism E.,” you say? How and why do the Great Lakes have such a terrifying disease?
Dr. Kurt Newman with the GLSC stated the following: “Botulism E. toxin is the most toxic substance known to man. One gram of purified toxin could kill hundreds of thousands of people.”
We have to go back in time to set the stage for this situation that affects us all. It started with the invasive Zebra Mussel and then the introduction of another invasive mussel called the Quagga Mussel.
Both mussel species have the ability to filter Great Lakes water at an alarmingly fast rate, in turn, clearing up the water. Most people would think clear water in the Great Lakes is a good thing. Unfortunately, that wouldn’t be the case.
The mussels are taking away food for tiny fish to eat; they’re upsetting the food chain making its way up to the predators including the sturgeon, salmon and trout species. The salmon and trout numbers are dwindling but that’s not the point of this story; at least for now anyway.
The greater problem is the water is getting clearer, allowing the sun to penetrate to the bottom of the Great Lakes; in particular Lake Michigan.
The sunlight reaching down more than 50 feet is allowing algae mats to grow along the bottom of the lakes, especially Lake Michigan where its most hit. Algae mats are growing very fast and they’re many feet thick. The top layer of algae is getting sunlight, but the lower layers begin to decay, and large amounts of algae are sloughed off the algal beds, sometimes by storms. This results in tons of algae being washed off and decomposing on the lake bottom, and that’s where the Botulism E. bacteria grows and produces toxin.
The Goby swims through these piles of decomposing algae and eat worms and bugs that have eaten up the toxin from the rotting algae, and diving birds like the Common loon and Cormorants dive down to eat the Goby and other deep swimming bait fish.
The Gobies carrying the Botulism E. toxin are now infecting the birds that eat them. So, now we know how the birds are getting the Botulism E., but how do they ultimately die?
Simply put, Botulism E. carries a neurotoxin that affects the central nervous system of the infected birds. This neurotoxin causes paralysis and the birds often drown because they can’t perform the simple task of keeping their head above water.
Scientists with the GLSC are working with the USGS National Wildlife Health Center and the National Park Service, and they have estimated that we’ve lost more than 100,000 birds to date and the numbers are expected to get worse until scientists find a way to intervene.
It was estimated that around 3000 loons died from botulism in Lake Michigan in 2012. This could have a significant effect on loon populations if it occurs often, as there are only 20,000 adult loons in the Great Lake states.
These scientists have also found that botulism outbreaks are more likely to occur when lake levels are low and water temperatures are high. These are exactly the conditions predicted under climate change, so we can probably expect the problem to get worse.
This is a relatively new problem because it affects us all. We’re dealing with a highly toxic substance that is increasing its territory on our Great Lakes. Furthermore, it’s killing our diving birds, the majestic Lake Sturgeon and the deep diving duck populations.
If you thought the Great Lakes were doing okay, then it’s time to reconsider. I’ll stay on this story and give updates in a timely manner.
Rick Taylor warmly welcomes your comments and story ideas. Feel free to email him at email@example.com.