Illinois Natural History Survey - University of Illinois

Status and Distribution of Daphnia lumholtzi Sars in Illinois

 

The exotic cladoceran, Daphnia lumholtzi Sars, was first discovered in North America in 1990 from a small lake in Texas. Since then, D. lumholtzihas spread extensively throughout the southeastern U.S. The native range of D. lumholtzi includes Australia, central Asia, and Africa. North American populations are believed to have originated from Africa since genetic studies revealed close similarities between these populations. Because of their inland distribution, it is unlikely that the species was introduced as a result of ballast-water discharge. Rather, D. lumholtzi appear to have `hitchhiked' with the intentional introduction of other exotic species, such as Nile perch, Lates niloticus, and the cichlid, Tilapia mossambica. Unlike other exotic cladocerans (e.g., Bythotrephes cederstroemi), the expansion of D. lumholtzi in North America seems to have occurred in less time and over a larger geographic range. It has been postulated that their expansion may be due to transfer of ephippia via waterfowl, fishermen, or introduction of aquatic species and plants.

Successful establishment of D. lumholtzi has been linked to a variety of physical factors. In general, D. lumholtzi colonize in relatively small, unconnected bodies of water and then spread to other locations, a pattern opposite of that for Bythotrephes and Dreissena, which typically colonize large lakes and expand to smaller, connected water bodies. For example, Bythotrephes and Dreissena generally spread outwards from the Great Lakes, whereas D. lumholtzi has the potential to spread into the Great Lakes through smaller, connected water bodies, such as the Illinois River and Chicago area waterways. In the Southeast, D. lumholtzi are typically found in reservoirs greater than 225 ha, with mean August water temperatures greater than 25deg.C. Moreover, reservoirs containing D. lumholtzi typically have high conductivities and high concentrations of nitrite and nitrate.

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The seasonal occurrence of D. lumholtzi differs from most native Daphnia in North America. Daphnia lumholtziabundance typically peaks in late summer (August), when water temperatures exceed 25deg.C. Because their temporal distribution does not overlap with many common daphnids, the effect of D. lumholtzi on native cladoceran populations is unclear. Moreover, because their seasonal timing generally follows peaks in zooplanktivory by larval fishes, no effects have been observed in systems that have been studied. However, because of their large spines and helmets, predation rates onD. lumholtzi by planktivorous fishes is reduced compared to other Daphnia, implying that D. lumholtzi may affect foraging success of native fishes.

In Illinois, D. lumholtzi was first collected in July 1992 from Lake Springfield. Additional sampling in 1993 and 1994 revealed D. lumholtzi in 10 additional reservoirs: Carlyle Lake, Clinton Lake, Dutchman Lake, Lake Bloomington, Lake Decatur, Lake Kinkaid, Lake Shelbyville, Lake Taylorville, Rend Lake, and Sangchris Lake. They have also been collected in the Illinois River since 1995, but probably occurred in the river as far back as 1991. Recent studies have shown that the establishment of D. lumholtzi in Illinois has affected zooplankton composition and size structure. Since the establishment of D. lumholtzi in Lake Springfield, the zooplankton community has shifted from greater than 75% cladocerans to greater than 75% copepods. It has been postulated that these shifts could result from direct or indirect mechanisms associated with competitive interactions among zooplankton or differential predation pressure on daphnids.

At present, research efforts are focused on evaluating zooplankton communities in Illinois lakes with and without D. lumholtzi. Using time-series data from a variety of lakes, we are addressing questions related to effects of the establishment of D. lumholtzi on native zooplankton populations in Illinois. This information is being coupled to data on fish diets to help elucidate the role D. lumholtzi plays as a potential competitor or as a prey resource in Illinois reservoirs. Preliminary findings suggest that D. lumholtzi are a common diet item in stomachs of brook silversides, Labidesthes sicculus, but occur less frequently among other native zooplanktivorous fishes. Additional understanding of the potential effects of D. lumholtzi on Illinois ecosystems will assist in the development of management options.

Steven R. Chipps, David H. Wahl, Cynthia S. Kolar, Kaskaskia Biological Station, Center for Aquatic Ecology; and James A. Stoeckel, La Grange Reach LTRMP Field Station, Center for Aquatic Ecology.



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