Department
of Fisheries
and Aquatic Sciences
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Department
of Fisheries |
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Karl
E. Havens
Professor and Chair B.A. Biology, State University of New York at Buffalo, 1979 M.S. Biology, West Virginia University, 1981 Ph.D. Biology, West Virginia University, 1984 |
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Karl Havens is Chair of the Department of Fisheries and Aquatic Sciences, where he provides program leadership for research, education, and extension activities that support the missions of the Department, IFAS, and the University. He is an applied limnologist whose research focus is on trophic interactions in lake plankton communities, interactions between aquatic plants, plankton and fish, and the ecology and management of shallow eutrophic lakes. He has conducted collaborative research projects with scientists in Brazil, Canada, China, Denmark, Italy, Japan and the Netherlands, and is actively involved in the application of science in the management of Florida lakes. Phone: 352-392-9617 ext 232 Curriculum Vitae - includes all publications Dr. Havens has a website on Zooplankton Ecology: http://planktonweb.ifas.ufl.edu Courses Taught: FAS 6932 (Special Topics) credits, lecture, discussion, and field experiences (no formal laboratory component). This course provides graduate students with a comprehensive overview of classical and contemporary aspects of the biology and ecology of freshwater plankton, with particular consideration of how zooplankton structure and function relates to fisheries and water quality. The course includes both classroom and field experiences, critical evaluation of methods used to sample and analyze zooplankton data, and discussion of important papers from the contemporary peer-reviewed literature. Emphasis is on freshwater plankton, however, selected marine literature is covered and most basic principles apply across the freshwater marine continuum. For more information: (download - MS Word) Power Point Presentations: |
Selected
Publications |
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The role of freshwater zooplankton (microscopic animals) in lake food webs is a focal area of Dr. Havens' research. He has examined how zooplankton feed on different types of algae, how they respond to various chemical stressors, and how they are affected by predators, including fish. These photo-micrographs show two different species of zooplankton commonly found in Florida lakes Diaptomus dorsalis, a copepod (on the left), and Eubosmina coregoni, a cladoceran (on the right). These animals feed on bacteria, algae, and protozoa. Each animal is less than a millimeter long, yet a liter of lake water may contain hundreds of individuals. Some fish depend on zooplankton as a food source during early stages of their life cycle, so information about the dynamics of zooplankton in a lake can be critical to understanding the population dynamics of fish. |
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Phytoplankton (suspended algae) experience blooms in Florida lakes, rivers, and coastal waters when there are high concentrations of nutrients and adequate light for net algal growth. Blue-green algae (cyanobacteria) often are the dominant species during blooms in fresh water. Drs. Havens and Phlips have conducted research to examine how dissolved nutrients and light influence biomass and taxonomic composition of phytoplankton, as well as the factors that cause them to bloom in shallow Florida lakes. This photograph shows a cyanobacteria bloom in Lake Okeechobee. |
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Research conducted by Dr. Havens and his colleagues has shown that submerged plants play a critical role in shallow Florida lakes, providing habitat for fish and other wildlife, and also maintaining clear water by a variety of mechanisms. The plants provide a substrate for periphyton that removes nutrients from the water, thereby indirectly reducing the biomass of phytoplankton. Plants also stabilize sediments, reduce shearing stress on the lake bed from wind-driven waves, and when they carry out intense photosynthesis, result in co-precipitation of phosphorus with calcium at high pH. This photograph shows clear water over a dense bed of submerged plants. |
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Sandy substrate and a diverse aquatic plant community provide good conditions for foraging and nesting by fish such as largemouth bass. Dr. Havens and colleagues at the Florida Fish and Wildlife Conservation Commission have studied how variations in water level affect aquatic plants and largemouth bass recruitment in Lake Okeechobee. This photograph shows a fish bed in a shallow shoreline area of that lake. |
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The two photographs to the right were taken during summer 2006 at Lago Trasimeno, a shallow 125 square kilometer lake in Umbria, Italy. This lake is home to the Italian Institute of Hydrobiology (University of Perugia), where aquatic scientists including Baldi, Vollenweider, and Margalef conducted classical studies of lakes in the early to mid 1900s. The Department of Fisheries and Aquatic Sciences recently established a formal cooperative agreement with the University of Perugia to provide opportunities for faculty and students to conduct collaborative research on freshwater ecosystems in Florida and Italy. Contact Dr. Havens for details if you are a student interested in an international opportunity as part of your graduate studies in FAS. |
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Page revised January 14, 2008
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