Return of the Natives

From May, 1996 (Update #27)

Water plants that had not been seen in more than 30 years may be staging a comeback in Lake Erie due to improved water clarity resulting from the presence of zebra mussels, Ohio State University researchers have reported. Researchers located nine plant species that have either returned to the lake or appeared for the first time, said Ronald L. Stuckey, professor emeritus of plant biology at Ohio State. Stuckey and David Moore, a former Ohio State graduate student, reported their findings in the June issue of the Ohio Journal of Science. The inventories were conducted at Put-in-Bay Harbor, part of an island group in western Lake Erie. Fourteen plant species have survived since zebra mussels were first detected in the lake in 1988, the researchers noted. One plant, Vallisneria americana, or tape grass, has grown in such abundance that it covers most of the bottom of Put-in-Bay Harbor, Stuckey said. One cause for the resurgence of these plants, scientists believe, may be improved water clarity caused by zebra mussels, which consume algae and other organisms on rocks and on the bottom of the lake. Clearer water allows for more photosynthesis and increased growth of certain plant species, Stuckey said. "Before the presence of the mussels, the water was very turbid," he said. "Many of the plants received little or no sunlight. Now it's clearer, and the lake flora seems to have returned to a condition similar to what it was like 100 years ago." Stuckey's plant research in Put-in-Bay Harbor began in the summer of 1967. Since that time, he has noted declines in certain plant species and increases in others. Following the 1988 zebra mussel invasion, Stuckey noticed a significant rise in the abundance of many of the plant species. He also noted the return of some species that had not been reported in decades. One of those, Potamogeton pusillus, or small pondweed, had not been seen in more than 30 years. "It's apparent that the seeds for this plant and other annuals have been able to survive on the lake bottom for 30 or 40 years," he said. Species new to Lake Erie have also been identified. Specimens of Najas minor, commonly called minor naiad, were obtained in 1994 near the docks at Gibraltar Island. Lake Erie's clearing has not been good for all aquatic plants. Five species of low-light plants, such as Sago pondweed, a submersed species, aren't as abundant as they were a few years ago. "Plants have a tolerance to certain conditions," Stuckey said. "Some plants are quite tolerant to turbid water conditions, and some flourish under those conditions. Others are intolerant to turbid conditions. These are the ones that are returning." Although the studies were done in Put-in-Bay Harbor, Stuckey said conditions should be similar in other western Lake Erie harbors. "Aquatic plant growth of this type can be beneficial to certain aquatic animals," he said. "These plants can serve as a food source, and they also can increase the level of oxygen in the water. Plant growth may also cause an increase in the zebra mussel population. It's really too soon to tell."

Kelli Whitlock, Ohio State University Communications.

ID: 199605-10.

The Zebra Mussel Update was a 4- to 8-page quarterly national newsletter published by the University of Wisconsin Sea Grant Institute from May 1990 through May 1997. The ZMU documented the spread of the zebra mussel -- an exotic nuisance mussel -- through North America's freshwater environments, especially the Great Lakes, and on efforts to control it.