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J. Great Lakes Res. 30(4):538-544.
Internat. Assoc. Great Lakes Res., 2004
Type: Article

Exotic Marine Macroalga (Enteromorpha flexuosa) Reaches Bloom Proportions in a Coastal Lake of Lake Michigan

Vanessa L. Lougheed and R. Jan Stevenson, Michigan State University, Department of Zoology, East Lansing, Michigan, 48824-1115

ABSTRACT: The exotic marine algae Enteromorpha flexuosa subsp. flexuosa and subsp. paradoxa were first observed in Muskegon Lake during autumn 2003. In September 2003, the littoral zone had between 10 and 80% cover of macroalgae, which grew largely on submerged macrophytes, and was composed almost entirely of Enteromorpha. Enteromorpha formed dense mats, fouled the boat motor and was found washed up in large quantities on the shoreline. Eleven other waterbodies in the region were surveyed: two others had Enteromorpha composing 5 to 20% of the macroalgal community, four had no apparent macroalgae and the remaining five were dominated by Cladophora. Possible reasons for the success of Enteromorpha in these coastal lakes include nutrient enrichment, a history of industrial activity resulting in increased salinity of the water, as well as an absence of grazing pressure. Potential effects on littoral zone food webs are uncertain; however, we found low epiphytic diatom densities on Enteromorpha, which is a concern in these systems where epiphytic diatoms are important components of the food web. Currently, this new macroalgal invader has been found in only three coastal waterbodies of Lake Michigan; however, it is possible that Enteromorpha could spread beyond its current range, if it has not already done so. Given its ability to form nuisance blooms in a coastal lake of Lake Michigan and its reported impacts in marine systems, it is imperative that the possible impacts of this invasive marine macroalga on the Great Lakes ecosystem be determined.

KEYWORDS: Exotic species, macroalgae, Enteromorpha flexuosa, epiphytes.

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