Aquatic Invasive Species

Daphnia lumholtzi is an invasive cladoceran native to Asia and Africa that has been found in the South-Eastern United states only in last twenty years. A study lead by J.E. Havel of Southwest Missouri State University conducted population counts of this invader in 119 reservoirs in Southwest Missouri during the years 1992-1993. The counts were structured to take place each month over the two year period in order to determine any fluctuations in seasonal populations of D. lumholtzi.

Havel found that D. lumholtzi populations were not constant year round, and instead were highest during the summer and fall, with very small during the winter and spring. Havel also found that during the periods of highest population density of the native Daphnia, D. lumholtzi experienced a period of lower population density.

In addition to population details, Havel discovered that D. lumholtzi was more likely to invade larger reservoirs than smaller ones and warmer reservoirs rather than colder ones. The studies findings are consistent with the predicted behavior of D. lumholtzi.

Canadian Journal of Fisheries and Aquatic Sciences, Volume 52, Pages 151-160, Published JAN 1995, “Invasion of the exotic cladoceran daphnia-lumholtzi in North American reservoirs.”

Native to the regions of Asia, Africa, and Australia, Daphnia lumholtzi has become successful in establishing their presence throughout the southern region of the United States within the past decades. Previous experiments conducted on other Daphnia species and theoir change in morphology has prompted Peder M. Yurista of Murray State University to conduct his own experiment on Daphnia lumholtzi and their undergoing of cyclomorphosis (changing of helmet and spine length).

Several scientists have claim that Daphnia’s undergo a change in their helmet or spine length because of higher survival rates from predation. Yurista believed that higher temperatures affect body changes and cyclomorphosis features are found to be more of an advantage to the D.lumholtzi swimming abilities, consequently indirectly increasing their survival rates.

After conducting his experiment with D. lumholtzi from Kentucky Lake in a diverse range of temperatures, Yurista discovered the D. lumholtzi that had the longest spines and helmets were those who were contained in an aquarium at 31 C’. Those who possess the smallest helmet and spine length were those who were contained in temperatures of 21- 28 C’.

Yurita, Peder M. Cyclomorphosis in Daphnia lumholtzi induced by temperature. Freshwater Biology. 2000 Issue 43:207-213

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 30^oC, and that they do not proliferate well when water temperatures fall below 10^oC. 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.

Daphnia lumholtzi is a spiny water flea that has been invading freshwater lakes and reservoirs in the southern United States since the early 1990s. Though it has become established in many ecosystems, its full environmental effects, positive or negative, have not yet been determined.

To explore the predation of inland silversides (Menidia beryllina) on D. lumholtzi, Lienesch and Gophen from the University of Oklahoma measured the size of D. lumholtzi consumed by several different size classes of silversides. Placing hungry silversides of a particular size in a tank with a mix of D. lumholtzi sizes, they correlated the each silverside size to its preferred D. lumholtzi size. They found smaller silversides most commonly preyed on smaller daphnia, though they did not lack the capacity to consume larger water fleas. Similarly, large silversides preferred to consume large D. lumholtzi. These results suggest that D. lumholtzi could become an important food source for juvenile silversides when native zooplankton is scarce.

Lienesch, P.W., and M. Gopen. 2005. Size-selective predation by inland silversides on an exotic cladoceran, Daphnia lumholtzi. The Southwestern Naturalist 50, 158-165.

Scientists currently have contrasting views on the correlation between a biome’s diversity and its vulnerability to invasive species.  Some believe that an environment with many species has higher competition for resources and will discourage invaders, while others believe that if many species can already share a niche in the environment an invasive one will logically be able to as well.  Dzialowski (2010) tested these theories with the invasive plankton, Daphnia lumholtzi.

D. lumholtzi is invasive to North American lakes and rivers, so three native Daphnia species were raised both separately and in combination, then D. Lumholtzi was introduced to each test.  While the number of species in the test did not directly correlate to the population of D. lumholtzi, one of the native species, D. magna, lowered the D. lumholtzi populations significantly in all tests where it was present.  Dzialowski concludes that certain native species are more capable of outcompeting exotics, and that species-rich environments are more likely to contain such a species.

Dzialowski, A.R., 2010.  Experimental effect of consumer identity on the invasion success of a non-native cladoceran.  Hydrobiologia 652: 139-148.

Elser from Arizona State University and his team conducted a study examining the distribution and competitive effects of the invasive zooplankton Daphnia lumholtzi in Arizona. First detected in Texas in 1990, this species indigenous to Africa, Australia, and India has spread throughout the midwestern and southern United States.

Elser conducted a field sampling of 12 reservoirs in central Arizona and a competition experiment involving water from Canyon Lake. The samplings demonstrated that D lumholtzi was dispersed across central Arizona in various watersheds, some with a greater percentage of the exotic zooplankton than others (ranging from none to more than the native species). This proves the persistence of this specie’s invasion in Arizona. The competition experiments found that the production of both species (D lumholtzi and native D pulex) decreased when both were present at the lake. Also, D lumholtzi reduced total zooplankton production. Therefore, communities dominated by D lumholtzi are expected to be less fertile and retain lower biomass.

Research on this detrimental species will continue because it impacts plankton communities and fish production since their spination renders them inedible.

Resource: Journal of the Arizona-Nevada Academy of Science Vol. 34(2): pp 89-94. (2002)