Daphnia lumholtzi, an exotic zooplankton, has invaded freshwater systems throughout the southern and midwestern United States. A study done by Dzialowski et al 2000 conducted regional surveys of eastern Kansas reservoirs to document the range of expansion of D. lumholtzi. It was found in five out of 35 reservoirs sampled in 1994, and 11 out of the 35 reservoirs when re-sampled in 1997. In addition, 40 small ponds inaccessible to recreational boats were sampled, where no D. lumholtzi was found. This suggests that non-human dispersal mechanisms play an insignificant role in the spread of the species.
This study suggests that further experimentation is needed to determine if the absence of D. lumholtzi from these ponds is due to insufficient dispersal mechanisms or the species’ inability to colonize in this environment.
Dzialowski A.R., O’Brien W.J., and Swaffar S.M. 2000. Range expansion and potential dispersal mechanisms of the exotic cladoceran Daphnia lumholtzi. Journal of Plankton Research. Volume 22. Issue 12: 2205-2223.
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Daphnia lumholtzi, commonly known as the spiny waterflea, is an invader to many aquatic ecosystems. After they establish themselves in a foreign environment, they often become a prominent member of the local zooplankton community. Currently, not all of the reasons they are such successful invaders are known, but scientists are working to better undertand them.
J.T. Lennon, V.H. Smith and K. Williams of Dartmouth College department of Biological Sciences and the department of Ecology and Evolutionary Biology of the University of Kansas have been working to determine the temperature tolerance of D. lumholtzi. They measured this through observing fluctuations in D. lumholtzi’s reproductive rate, survivorship and molting rates. All these traits demonstrated that D. lumholtzi has a large temperature tolerance ranging from about 20 to 30oC, and that they do not proliferate well when water temperatures fall below 10oC. This suggests that D. lumholtzi may be limited to spreading through only the southern United States.
Lennon JT, Smith VH and Williams K. Influence of temperature on exotic Daphnia lumholtzi and implications for invasion success. Journal of Plankton Research. 425-434. 2001.
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Water heating has been determined to be an effective ballast water treatment method; however the method has major limitations one in particular being the heating time required for efficiency. Laboratory results have showed that conventional water heating requires a temperature of at least 35 ⁰C for 20-80 hours to be effective. However a novel technique, short-time technique, only requires temperatures between (40- 65 ⁰ C ) for 15 hours has been effective.
Quilez-Badia from the University of Newcastle upon Tyne, et al.(2008) conducted a field study short-time high temperature under operational conditions, with the aim of monitoring the method’s effectiveness at removing bacteria, phytoplankton and zooplankton.
According to Badia et al.(2008) the results indicate that running the water through the pump system installed in the short-time method increased the mortality rate of the microorganisms, but increasing the temperature above 55⁰C did not improve the efficiency of the short-time heat treatment.
Source: Marine Poll Bull 2008, 56(09) 1093-1097 DOI: 10.1016/j.marpolbul.1037.2007.09.036