Aquatic Invasive Species

Since its appearance in Texas in the early 1990’s, the invasive aquatic species Daphnia lumholtzi has been successful in colonizing in many aquatic regions of North America. Studies have yet to be done linking the reproductive strategy of the Daphnia to its success in invading new territories.  Most rotifers, especially Cladocerans, have the ability of changing between asexual reproduction via clonal reproduction and budding, as well as sexual reproduction in which resting eggs are used to avoid an overcrowded environment.

Scientists have been trying to find a link between nutrient supply, light availability, and algae content with the reproductive capacity of the spiny water flea.

Through rigorous experimentation, scientists found a direct correlation between low Phosphorous levels and the Daphnia population’s growth rates. The effects of overcrowding in aquatic systems were also noted in the growth rates of the water flea. It was shown that low levels of phosphorus, coupled with high quantities of Daphnia, effectively reduced the growth rates for the water flea.

References:

Hydrobiologia (2009) 618:47–56 DOI 10.1007/s10750-008-9546-2

Overcrowding, food and phosphorus limitation effects on ephipphia production and population dynamics in the invasive species Daphnia lumholtzi

Allison S. Smith Æ Kumud Acharya Æ Jeffrey Jack

The gowth and reproduction of Daphnia lumholei, an an invasive species in the Southern United States, is highly influenced by temperature and abundance of food. In the absence of predators, Daphnia is faced with a trade off. They can either live in the epilimnion where development in the

warm water is fast, but food shortage causes low egg production, or in the hypolimnion, where food availability is high but development is slow because of low temperatures.

In this study, Kessler and Lampert test whether Daphnia is affected by light to choose the best depth of the water for reproductive or growth purposes. They also tested the depth preferences of varying Daphnia size classes and egg-bearing females . However, they found no direct correlation between light and Daphnia’s physical necessities. In fact, large and egg-bearing females, being forced into deeper layers by the residual light response during the day , experienced a lower average temperature during day than juveniles.

Kessler, K., and Lampert, W. 2004. Depth distribution of Daphnia in response to a deep-water algal maximum: The effect of body size and temperature gradient. Freshwater Biology 49(4): 392-401.

Daphnia lumholtzi most notable characteristics are its pointed helmet and large spines.  2 features that make the D. lumholtzi difficult to feed on allowing it to prosper as an aquatic invasive species. It was first introduced in 1990 in Texas and can now be found throughout southeastern USA.

Philip W. Lienesch and Moshe Gophen of the University of Oklahoma’s department of Zoology and Biological Station, are interested if inland silverside (Menidia beryllina) are size-selective predators of D. lumholtzi. By placing 3 various sizes of  inland silversides in tanks with various sizes of D. lumholtzi, Lienesch and Gophen were able to determine inland silverside’s feeding habits. Smaller inland silversides preferred smaller D. lumholtzi, while the larger fish ate the large D. lumholtzi. Next Lienesch and Moshe tested their results in Lake Texcoma, comparing D. lumholtzi to native Daphnia, results were similar to labratory experiment, suggesting that when zooplankton is scarce, D. lumholtzi could become a food source for juvenile silversides.

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.

The water flea (Daphnia lumholtzi) is a cladoceran native to Eastern Africa, Australia and the Asian subcontinent of India and was first reported in 1991 in an Eastern Texas.

Dagram Frisch and Lawrence Weider of the University of Oklahoma are examining the ecological genetics of D. lumholtzi in Lake Texoma, Texas, USA. As no spatial and or temporal survey of the genetic variation of the specie was ever conducted in this lake, they took a combined approach of field surveys and controlled lab experiments to examine the seasonal variation of in the Lake Texcoma population.

The population genetic structure of the D. lumholtzi was observed on 22 dates for a three year period along with temperature and salinity gradient. A two-allele polymorphism at the PGI locius was discovered. Frisch and Weider concluded that the rapid expansion and micro evolutionary dynamics of D. lumholtzi throughout North America might be a result of the genetic and environmental interactions. [156]
Sources: Freshwater Biology 2010, 55:1327-1336 DOI: 10.1111/j.1365-2427.2009.02356.x

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.

The April lab group swiftly counted their very dense sub-samples this afternoon.  Jordan Lake surface water was 17 degrees Celsius today (pretty warm!), but Daphnia lumholtzi is still not present in our samples.  But the seasonal shifts in the densities of the two main taxonomic groups are striking!  I’ve included both linear and log plots of the Jordan Lake zooplankton trends:

Our final group project – a research note on Daphnia lumholtzi in Jordan Lake – is coming up!  D. lumholtzi is an exotic water flea that forms long tail, head, and neck spines, which may reduce its edibility for juvenile fish.  Its ecological impacts have been found to vary in different ecosystems, however, and very little is known about its effects in Jordan Lake (a reservoir near Apex, NC), not to mention its seasonal abundance.  The top figure are the D. lumholtzi and other zooplankton data collected by last semester’s Aquatic Invasive Species students, and the bottom figure are the updated data, with the final data point provided by students from our class. How do you think our research notes will compare to those from last semester?

I was very impressed with Tran-Phu’s article not only for subject matter and topic, but his ability to articulate and provide a strong argument using his sources. He also did more than merely cite his sources, but was fluently weaved them into this prose to form a very interesting and strong argument that intelligence, an abstract concept, can and has been commodified by the  market activities just as other tangible goods such as dairy have been. What I enjoyed about the article was the use of examples to help explain and introduce the reader to the concept of the abstract concepts being marketable, such as the commercialization of organ transplants and surrogate motherhood

Bran-Phu argues that intelligence can be commodified within a market just as any tangible good. One of his strongest points was that knowledge has a discrete exchange value and can have a quantitative economic value expressible in monetary units.  He presented an argument which included economic concepts such as supply demand, opportunity cost and incentive as he discussed how intelligence in our modern world has been commercialized. One of the major components of Tran-Phu’s article was a relationship between intelligence, educational level, certification, and career opportunity. The article goes on to further analyze the correlation between wage and intelligence in which he argued that wage disparity remains because access to knowledge and enterprise is protected to prevent devaluation.  He provided an example of a farmer and electrical engineer to show this disparity. One of Phu’s strong po9nt was using Marxian theory to solidify his argument an I found this very entertaining as he showed that products and services such as Adderall, Ritalin and tutoring all aid in the commodification (commercializing) our intelligence and these false incentives we use actual detract from the pure essence and value of intelligence.

In addition he believes that the commodification of intelligence can lead to a loss of freedom.

While Tran-Phu’s writing seems to fit under the category of social science, but in regards to my MWP1 assignments has a lot of similar context. For instance the opening the introduction was, while short was written in a professional, non-fictional tone which was similar many science related-jargon. In addition, he provided much quantitative evidence for his argument, quite suitable for the context of his paper, and natural science papers.  

While the tones in our paper s are similar to an extent, there is also a difference. Tran-Phu’s tone is more targeted to a general audience, while my writing tone for MWP1 was more focused on both the scientific and general community.

Wei’s “Gaining Access to Myanmar” is a press article about the aftermath of the 2008 cyclone that ripped through the country, killing almost 135,000. The article describes the ruins that are left behind by the cyclone, as well as the difficulties that the people of Myanmar face in rebuilding their country. It is also clear that the local militaristic government is reluctant to grant access to foreign aid, an action which may further hinder the rebuilding of Myanmar. Even a month after the cyclone struck, foreign aid to Myanmar was still limited by the government. The local relief efforts were led by Buddhist monks.

Because the article is written in a journalistic style, it is a bit different from the pieces that I have become accustomed to reading. However, I really liked how clear the author’s point of view was, even though it was very well contained and politically neutral. I also thought the author’s use of photos and figures was well done. The pictures really add another dimension to the article when the reader is able to see bits of what is actually going on after the cyclone, and the chart that puts together the timeline of events that took place after the cyclone further intensifies the fact that government action is not fast enough in providing aid for displaced families. Labeling the sections was also effective in organizing the essay in a way that allowed readers to easily follow the flow of events. I did notice that some of the sections were short and not very elaborate. I do not know if this is part of the writing style but it seems that having such short sections can leave the reader with more questions than before they read anything about the topic.

Because the targeted audience of my MWP1 and “Gaining Access to Myanmar” is so different, it is hard to say what would have worked in both essays and what would not have. I too, used subheadings, which seems to be a good tool for organizing written works in many fields. But in a literature review, it is necessary to add suggestions and insights that are gained through analysis of the written works, while in a journalistic approach, the author only has to report on what has happened and spin it into an interesting article that people will want to read. This makes the approach when writing a literature analysis different from when reporting in a journalistic style. Journalistic essays also have to stay unbiased, which can sometimes be difficult and is not as much of a concern in literature review.

Overall, it was very interesting to read an essay written from a journalistic approach, even though the techniques employed are not the same as those I used in writing my literature review.

Recent studies have discovered a higher alien richness in the Curonian lagoon than in the benthic zones of the Baltic Sea.  Through their research, scientists have postulated what allows an ecosystem to be invaded, and for that matter, why is the invader invading?

There are two general hypotheses concerning species diversity and the “invisibility” of a habitat. Stachowicz et al.(1999) argues that the diversity of an ecosystem  increases is resistance, amd protects it from foreign invasion Stohlgren et al.(2003), on the other hand, believes that invasive species are “invisible” and undetectable under such a huge lens of a marine ecosystem.

Research concluded that systems have already been modified by man, through dams or embankments, or have already been invaded by a species, such as the zebra mussel, are high susceptible to further invasion. For instance, when a concrete construction is made in the Klaipeda strait, it provides the zebra mussel a hard substrate to bind to. The mussels then provide foreign invaders with nutrients and thus create a positive feedback system that may never be stopped.  The correlation between debth range and inasice species richness is explained by the decline in oxygen and thus yielding more vigorous conditions (Leppakoski and Olenin 2000). Species tend to approach less diverse ecosystems that have less competition and more of their particular nutrients of interest. It’s important for biological control to focus on these hot spots of lagoons and swamps, even if they aren’t directly related to the fishing trade; an abundance of invasive species can clog or poison entire water channels that deposit  into our water reserves.

http://www.glerl.noaa.gov/pubs/fulltext/2006/20060037.pdf

Biol Invasions- DOI 10.1007