Zebra Mussels Invade the Hudson River
The Hudson River is home to the invasive Zebra mussels. Credit: Greta Stuckey ‘23
Zigzagging yellow and brown colors on a wedge-shaped bivalve mollusk identify the small, but mighty zebra mussel that sits at the bottom of the Hudson River, actively damaging and altering the aquatic ecosystem. These fingernail-sized mussels, usually ranging from one-quarter to one and a half-quarter in size, use their byssal threads and tiny fibers to stick to vessels, power plants, aquatic plants and rocks where they claim their territory and populate like rabbits.
Classified as invasive, these freshwater shellfish initially showed up in 1991 in the Hudson and in under two years “the weight of the zebra mussels in the river was greater than the combined weight of all the fish, all the water birds, all the invertebrates, all the other bivalves, all the eels, all the insects in the river,” David Strayer, freshwater ecologist and researcher at the Cary Institute Ecosystems Studies in Millbrook, New York, said. "Each female can have 1 million eggs a year.”
One may think that cleaner and more visible water is better, however, this can indicate other imbalances in the aquatic food web. These invasive mussels are filter feeders or, in other words, these mollusks can draw in water and particles as their source of food. Their efficiency at this can eliminate many floating particles in the water. This essentially decreases the abundance of food for other native species and makes it easier for predators to see their prey.
Microzooplankton populations have significantly decreased by 70% and a little more for the phytoplankton population. Fish species such as Shad and redbreasted sunfish are struggling to survive from other sources of food. Oxygen levels are decreasing and food supply is decreasing which all in all creates a domino effect in the food chain of the Hudson.
Classified as invasive, these freshwater shellfish initially showed up in 1991 in the Hudson. Photo courtesy of Riverkeeper
“In Lake Erie, it was attributed with helping to clear the lake of excessive algae,” Dr. Richard Feldman, the environmental chair at Marist, said.
The clear waters are allowing sunlight to sneak in and allow additional growth of aquatic plants for other fish species and native mussels to feed on, but once again, “With almost all invasion cases," said Stuart Findlay, Strayer’s colleague at the Cary Institute Ecosystems Studies in Millbrook, New York. "There are winners and there are losers.”
This is a dynamic shift caused by their abundant population and behavior is detrimental because of their instinct to outcompete native species for food and their suffocation of about 70% of native mussels because of their ability to attach to various surfaces.
"They've just completely transformed the ecology of the river,'' Strayer said.
Humans could be blamed for the spread of this invasive species because of the constant transport across different water locations. The invasive bivalves expel veligers, larvae, into the water that can stick to traveling boats to increase their population. The unintended instigation of these mussels in the river is a “fascinating transcontinental story,” Feldman said.
It is difficult to eliminate the species, but some of the best ways to decline the spread include: cleaning the boat surfaces, letting it dry and spreading awareness to others.
It appears that the zebra mussels are reaching younger ages than in the past and the presence of older mussels is less common, giving more ability for other species to survive. The Hudson ecosystem is presently different than it was pre invasion.
“If we don’t do anything,” Nick Phelps, co-director of the Minnesota Aquatic Invasive Species Research Center (MAISRC) said, “everything that can be invaded, will be.”