Given the important role that organisms (including man) play in ecosystem processes, it is surprising that little work has examined how man-made environmental changes affect the way organisms evolve and adapt. In a planned 36-month project, the PIs will use an integrated approach involving genetic/genomic, physiological, and 'resurrection ecology' methods to examine how cultural eutrophication (i.e., enrichment of freshwater systems with nutrients such as phosphorus) influences evolutionary changes in organisms. The waterflea, Daphnia pulex, which plays a major role in freshwater food webs (i.e. it eats algae/bacteria and in turn is fed upon by fish), will serve as the model organism. Daphnia are ideal for such studies because they produce resting eggs that can lay dormant in lake sediments for long periods of time. Decades-old eggs can be induced to hatch (i.e. 'resurrection ecology') and viable DNA can be extracted from eggs that are centuries old. Moreover, the D. pulex genome has been sequenced and genetic/genomic methods (i.e. gene expression) are in place to study how changes in eutrophication (phosphorus-level) patterns over the past century have influenced how an organism like a daphniid can respond to ecosystem/environmental change. The PIs expect to find distinct changes in the genetic structure and physiological mechanisms of different populations 'resurrected' from different sediment (time) layers in the resting egg bank from lakes that differ in eutrophication history. Results from this cross-disciplinary study will provide an excellent example of how man-made environmental changes (via eutrophication) influence natural (freshwater) ecosystems. Academic (i.e. university) researchers, applied researchers (e.g., lake managers), and members of the general public (i.e. recreational users) should be keenly interested in the results from this project. Educational training opportunities will include Native American high school interns as research assistants. Results will be published in peer-reviewed journals, while presentations to both scholarly and general-public audiences are planned.
Collaborative Research: Funded by the U.S. National Science Foundation (NSF) Using water fleas to track long-term environmental changes in freshwater ecosystems Co-Principal Investigators: Prof. Lawrence J. Weider, Dept. of Biology, U. of Oklahoma Prof. Punidan D. Jeyasingh, Dept. of Zoology, Oklahoma State. U. As part of our NSF-funded research, we want to gain a better understanding of how organisms adapt to changing environments. Therefore, we study the small freshwater organism called Daphnia (common name is water flea – but it is not a real flea – they are more "shrimp-like"). Daphnia are key species living in ponds and lakes around the world, and they play an important role because they feed on algae (small aquatic plants) resulting in improved water quality/clarity. In turn, many fish species eat Daphnia, so they play an important central role in aquatic "food webs". Historically, different Daphnia species have been used in laboratories around the world to test for water quality (i.e. chemical pollutants) because these "critters" are very sensitive (like a "canary-in-a-coal-mine") to toxic chemicals. So, they play an important role in making sure that drinking water is safe for human consumption. Another important feature of Daphnia is that it is primarily asexual – that is, mothers produce genetically identical (clonal) daughters. This allows for easier culturing and use in the laboratory for all types of experiments because you can have jars and jars containing genetically distinct clones. However, Daphnia also has a sexual phase, where they produce both sons and daughters. When mating occurs, the result is the production of dormant (resting) eggs in a protective casing (ephippium) that can sink and become buried in the mud in the bottom of ponds and lakes. Think of peas (eggs) in a pea pod (ephippium). This dormant "egg bank" builds up over decades and centuries (even thousands of years). We can "travel back in time" by taking mud/sediment cores from the lake/pond bottom, slicing the cores into hockey-puck-sized sections (that are time-dated using special methods), sifting out the eggs from the mud (almost like prospecting for gold), and then hatching the eggs in the laboratory, and establishing individual Daphnia clones from each egg. With our NSF-funded research, we have been looking at lakes in Minnesota that have been experiencing different levels of nutrient (i.e., phosphorus) pollution through time. Note: phosphorus is a critical nutrient that is used world-wide in fertilizers for both agricultural and home-owner use. When too much phosphorus washes into lakes and ponds, it can cause algal blooms – i.e. "pond scum" – which impact water quality for human consumption as well as recreational use, and can lead to degradation of aquatic ecosystems. In these Minnesota lakes, we have successfully hatched out Daphnia eggs that are decades to even centuries-old (perhaps as old as ~600-700 years). This means that, to date, these ancient hatched Daphnia clones are among the oldest (if not THE oldest) animals brought back to life from a dormant life stage. We have been looking at how these Daphnia clones from different time periods over hundreds of years (i.e. before and after European settlers came to Minnesota) respond to changing environmental conditions such as phosphorus pollution. Our results indicate that these clones show distinct differences in how they respond genetically and physiologically to changes in their nutrient environment. This provides critical information for trying to understand how other species can adapt to environmental changes. Further work will continue to examine how using an organism like Daphnia can help us better track environmental changes and protect water quality for future generations. Our results should prove useful in assisting lake managers, natural resource stakeholders and private land owners in protecting our freshwater ecosystems - one of our most precious resources!
