The blitzkrieg advance of two closely related species of mussels—the zebra and quagga—is stripping the lakes of their life-supporting algae, resulting in a remarkable ecological transformation and threatening the multibillion-dollar U.S. commercial and recreational Great Lakes fisheries.
Previous studies have linked the mussels to far-reaching changes in Lake Michigan's southern basin. Now a paper by two University of Michigan ecologists and a colleague shows that the same dramatic changes are occurring in northern Lake Michigan and throughout Lake Huron, as well.
"These are astounding changes, a tremendous shifting of the very base of the food web in those lakes into a state that has not been seen in the recorded history of the lakes," said Mary Anne Evans, lead author of a paper scheduled for publication in the April 15 edition of the journal Environmental Science & Technology. "We're talking about massive, ecosystem-wide changes."
Evans is a research fellow at the U-M School of Natural Resources and Environment. The other authors are Donald Scavia, director of U-M's Graham Environmental Sustainability Institute, and Gary Fahnenstiel, senior ecologist at the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Laboratory.
Because the changes are so profound and are happening so rapidly, the authors recommend that Great Lakes management agencies review and perhaps revise their policies so they can respond more quickly.
"New strategies for managing the lakes are urgently needed. Ecological changes that formerly occurred over decades are now happening in just a few years, so we need to adapt our management policies to this new reality," Scavia said.
This recommendation is especially relevant in the context of the current review of the Great Lakes Water Quality Agreement by the International Joint Commission, Scavia said. Through the IJC, the United States and Canada jointly manage the Great Lakes.
Though the zebra mussel is better known to the public, over the past decade it has largely been overshadowed by the quagga mussel, which can thrive far from shore in deep, mud-bottomed waters. Each of the fingernail-size quagga mussels filter about a quart of water a day, and billions of them now blanket the bottoms of lakes Michigan and Huron down to depths of nearly 400 feet.
They feed on algae, including single-celled plants called diatoms that are encased in glass-like shells made of silica, which the diatoms extract from lake water. Until recently, the diatoms "bloomed" each spring in the Great Lakes, and the level of silica in upper lake waters dropped as diatoms built their protective shells, then sank to the lake bottom, taking the silica with them.
The drop in silica levels due to the spring diatom bloom, known as the seasonal drawdown, has long been used as an indicator of overall algal production in the Great Lakes.
Reviewing records of silica levels in lakes Michigan and Huron collected over the past 30 years by the Environmental Protection Agency, Evans and her colleagues found that algal production throughout the two lakes was about 80 percent lower in 2008 than it had been in the 1980s.
In Lake Michigan, the decrease in the seasonal drawdown coincided with an explosion in the quagga mussel population and its expansion to greater depths, which began in 2004. The same changes occurred a few years earlier in Lake Huron, where quagga mussels greatly increased in abundance between 2000 and 2003.
"For years, all the talk was about the zebra mussels. And then its close cousin comes in, the little quagga mussel, and wreaks even more havoc on these huge offshore systems," said NOAA's Fahnenstiel.
"These changes are unprecedented," he said. "In terms of algal abundance and water clarity, lakes Michigan and Huron are now similar to Lake Superior."
By filtering out the algae, the mussels are robbing other organisms of the food they need to survive. Of particular concern is the plight of Diporeia, a tiny shrimplike creature that was one of the pillars supporting the base of the Great Lakes food web.
Nearly every fish species in the Great Lakes relies on Diporeia at some point in its life cycle. But Diporiea populations have crashed in lakes Michigan and Huron, and the change is already impacting Great Lakes commercial fisheries and the sport-fishing enterprise.
"The big question now is how large the quagga mussel population will get," Evans said. "And when it gets as big as it can get, will it stay at that level or will it die back because it has decimated its own food supply? We don't really know what to expect at this point."
Jim Erickson | EurekAlert!
Upcycling 'fast fashion' to reduce waste and pollution
03.04.2017 | American Chemical Society
Litter is present throughout the world’s oceans: 1,220 species affected
27.03.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
26.04.2017 | Life Sciences
26.04.2017 | Physics and Astronomy
26.04.2017 | Earth Sciences